High Performance Concrete 1993

3426
ACI Committee 211
"GUIDE FOR SELECTING PROPORTIONS FOR HIGH-STRENGTH CONCRETE WITH PORTLAND CEMENT AND FLY ASH"
ACI Materials Journal, May-Jun 1993, Vol. 90, No. 3, pp 272-283.

This guide presents a generally applicable method for selecting mixture proportions for high strength concrete and optimizing these mixture proportions on the basis of trial batches. The method is limited to high-strength concrete produced using conventional materials and production techniques. Recommendations and tables are based on current practice and information provided by contractors, concrete suppliers, and engineers who have been involved in projects dealing with high-strength concrete.

3427
Aitcin, P-C. and Neville, A.
"HIGH-PERFORMANCE CONCRETE DEMYSTIFIED"
Concrete International, Jan 1993, Vol. 15, No. 1, pp 21-26.

In the last 15 years, concretes of very high strength have entered the field of construction of high-rise buildings and bridges, i.e., concretes with strengths of 90, 100 and 110 MPa (13,000, 14,500 and 16,000 psi), with an occasional 120 MPa (17,000 psi). All of these strengths have been achieved consistently and on a routine basis. This type of concrete is perceived by some engineers, owners and specifiers as a material fundamentally different from the concrete we have all grown up with. They suspect that there is some mystery about the manufacture of such concrete, and possibly even a secret recipe. It is the purpose of this article to destroy this myth and to show that high-strength concrete is just concrete. High-strength concrete differs from normal-strength concrete in that it invariably contains a high-range water reducer (or superplasticizer), while normal-strength concrete contains it only sometimes. All the other basic ingredients are the same -- namely, portland cement, aggregate, water and admixture. As far as other ingredients are concerned, such as retarders, fly ash, blast furnace slag and silica fume, they may or may not be present in either type of concrete.

3428
Al-Qadi, I. L., Prowel, B. D., Weyers, R. E., Dutta, T., Gouru, H., and Berke, N., "CONCRETE BRIDGE PROTECTION AND REHABILITATION: CHEMICAL AND PHYSICAL TECHNIQUES: CORROSION INHIBITORS AND POLYMERS"
Virginia Polytechnic Institute and State University, Blacksburg, VA, 1993, xvii, 248 pp. (SHRP-S-666; PB94-186491)

This report deals with the improvement of existing non-electrochemical methods for protecting and rehabilitating chloride-contaminated concrete with and without concrete removal and with the development of new methods. Existing methods include deep impregnation of the concrete with a polymer or with calcium nitrite, and the new methods include corrosion inhibitor application processes and a resin concrete asphalt composite material. Field data suggest that the deep polymer impregnation can increase the service life of corrosion deteriorating decks by at least 30 years. Two methods of impregnating calcium nitrite were examined in the field. In the laboratory polymer impregnated concrete was compared to other protection techniques. Five corrosion inhibitors were evaluated in the laboratory. Asphalt Portland Cement Concrete Composite (APCCC) material was designed and evaluated for physical properties and durability characteristics for different moist and dry curing periods. APCCC showed higher strength properties and resistance to freeze thaw and stripping than hot mix asphalts. It also was more resistant to chloride intrusion than portland cement concrete. It is suggested that this material be used to rehabilitate existing bridge decks with hot mix asphalt preformed membrane protection systems.

3429
Andersen, P. J. and Johansen, V.
"A GUIDE TO DETERMINING THE OPTIMAL GRADATION OF CONCRETE AGGREGATES"
Idorn (G. M.) Consult A/S, Birkeroed, Denmark, 1993, vii, 200 pp. (SHRP-C-334; PB93-191245)

The proportioning of fine and coarse aggregates in the concrete mix has an important effect on the properties of both fresh and hardened concrete. This guide provides a means of determining the optimal gradation of fine and coarse aggregates for use in the concrete mix using a set of tables. The tables are based on a computer model for the theoretical packing of spherical particles which takes into account their size and specific gravity. Use of these tables in conjunction with the American Concrete Institute's ACI Standard Practice 211.1 should help produce a more workable mix, and a better consolidated hardened concrete with decreased permeability and improved durability.

3430
Armaghani, J. M.
"TESTING OF CONCRETE PERMEABILITY FOR DURABILITY EVALUATION"
Structural Engineering in Natural Hazards Mitigation, Proceedings of Papers Presented at the Structures Congress '93, April 19-21, 1993, Irvine, CA; Ed. by A. H-S. Ang and R. Villaverde; ASCE, NewYork, 1993, pp 989-995.

Field and laboratory permeability tests are being performed to evaluate the durability of concrete in Florida. These tests are part of an extensive research program to develop a durability specification for concrete mixtures and a durability rating system for concrete structure. This paper describes the permeability tests being utilized in the research and their benefits. Also included is an overview of the research program and a discussion of the main findings.

3431
Atzeni, C., Massida, L., and Sanna, U.
"DIMENSIONAL VARIATIONS, CAPILLARY ABSORPTION AND FREEZE-THAW RESISTANCE OF REPAIR MORTARS ADMIXED WITH POLYMERS"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 301-308.

The results are presented of an investigation aimed at determining the properties required by cement mortars admixed with polymers to be used as overlays in the repair of concrete structures. Tests were conducted using acrylic latex and epoxy resin as polymer admixtures. The adhesion of the modified mortars to different cement bases was tested under stresses induced by dimensional variations (ageing, thermal cycles), capillary absorption and freeze-thaw resistance.

3432
Ayano, T., Sakata, K., Ogawa, A., and Kaneko, T.
"STUDY ON THE MIX PROPORTION OF HIGHLY FLOWABLE CONCRETE WITH LIMESTONE POWDER"
Transactions of the Japan Concrete Institute, 1993, Vol. 15, pp 1-6.

The highly flowable concrete of enhanced deformability without any segregation contributes to improve the work efficiency in placing of concrete. But the quantity of the powder ingredient involved in such concrete is larger than that of ordinary concrete. In order to minimize the effects such as high heat of hydration or high shrinkage, there is a need to substitute low reactive material for a part of the powder ingredient. The flowability of concrete with limestone powder, which is low reactive material, is investigated and the method of how to mix highly flowable concrete with limestone powder is proposed.

3433
Azizinamini, A., Kuska, S. S. B., and Brungardt, P.
"SEISMIC BEHAVIOR OF HIGH STRENGTH CONCRETE COLUMNS"
Structural Engineering in Natural Hazards Mitigation, Proceedings of Papers Presented at the Structures Congress '93, held April 19-21, 1993, Irvine, CA; Ed. by A. H-S. Ang and R. Villaverde; ASCE, New York, 1993, pp 610-615.

Information on the ductility of high strength columns in seismic areas has been scarce. The available information is based mainly on small test columns subjected to monotonic concentric axial load only. This investigation develops design and detailing criteria for transverse reinforcement in high strength (compressive strength exceeding 15,000 psi) rectangular reinforced concrete columns for seismic resistant structures.

3434
Azizinamini, A., Stark, M., Roller, J. J., and Ghosh, S. K.
"BOND PERFORMANCE OF REINFORCING BARS EMBEDDED IN HIGH-STRENGTH CONCRETE"
ACI Structural Journal, Sep-Oct 1993, Vol. 90, No. 5, pp 554-561.

Because of the lack of test data, ACI-318-89 building code requirements imposed an arbitrary upper limit of 10,000 psi (69 MPa) on specified compressive strength of concrete that may be used in calculating tension development length and tension splice length. A research study was conducted to evaluate the bond performance of reinforcing bars embedded in high-strength concrete. Twelve beam splice specimens using No. 11 reinforcing bars and concrete with compressive strengths exceeding 14,000 psi were tested. The effect of several variables on bond capacity in high strength concrete is discussed and a failure hypothesis explaining the observed behavior during the experimental phase of the study is presented. Additionally, it is concluded that the current trend in ACI of making the splice length longer to compensate for having small cover and spacing may not be an effective approach. A better approach would be to provide a minimum amount of transverse reinforcement.

3435
Baalbaki, M., Sarker, S. L., Aitcin, P-C., and Isabelle, H.
"PROPERTIES AND MICROSTRUCTURE OF HIGH-PERFORMANCE CONCRETES CONTAINING SILICA FUME, SLAG, AND FLY ASH"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 921-942. (ACI SP-132)

This paper presents the compositions and properties of several high-performance concretes in their fresh and hardened state made with a reground Type 50 (ASTM Type V) cement of Blaine fineness 650 m sq/kg and silica fume, slag and fly ash at W/C 0.30 ratio or lower. All these high-performance concretes present long slump retention, combined with high elastic modulus, modulus of rupture and splitting tensile strength. The actual compressive strength can be as high as 124 to 136 MPa at 1 year. These results are compared with a reference concrete made with the same cement at the same W/C ratio, but without any mineral admixtures. The microstructural characteristics of these concretes and their relationship to mechanical properties are discussed.

3436
Balayssac, J.-P., Detriche, Ch. H., and Grandet, J.
"VALIDITY OF THE WATER ABSORPTION TEST FOR CHARACTERIZING COVER CONCRETE"
Materials and Structures/Materiaux et Constructions, May 1993, Vol. 26, No. 158, pp 226-230.

The authors justify their choice concerning the water absorption test for assessing both cover concrete porosity and largest capillary size, which are significant factors for concrete durability. In this way they extend to concrete an existing model used for terra cotta. The criterion used is the amount of water absorbed after one hour. This value is sufficiently representative of the mean radius of the largest capillaries. The results show that the absorption test can assess the effects of cement content on cover concrete porosity. Relating to these same results, the absorption test makes it possible also to take into account the beneficial effects of curing on capillary size. Correlations between carbonation depth and amount of water absorbed after one hour confirm the validity of these tests to assess the resistance of concrete to carbonation. In French.

3437
Ballim, Y.
"CURING AND THE DURABILITY OF OPC, FLY ASH AND BLAST-FURNACE SLAG CONCRETES"
Materials and Structures/Materiaux et Constructions, May 1993, Vol. 26, No. 158, pp 238-244.

This paper presents preliminary results of a research project into the influence of moist curing on the potential durability of concrete. Durability is characterized by measuring the oxygen permeability and water absorption at various depths in the covercrete. Concretes containing plain OPC, an OPC-FA blend and an OPC-GGBS blend were used. A range of strength grades was tested for each of these binder types. Concretes were exposed to moist curing conditions for 1, 3, 7 and 28 days before being tested at 28 days after casting. The main conclusions are: (i) moist curing has a marked influence on the potential durability of concrete and (ii) a relatively greater influence on durability can be effected by extending the duration of early-age moist curing rather than decreasing the binder/water ratio.

3438
Basheer, P. A. M.
"A BRIEF REVIEW OF METHODS FOR MEASURING THE PERMEATION PROPERTIES OF CONCRETE IN SITU"
Proceedings of the Institution of Civil Engineers: Structures and Buildings, Feb 1993, Vol. 99, No. 1, pp 74-83.

Numerous methods are available to measure the permeation properties of concrete, which can be classified in terms of the diffusion, absorption and permeability properties. The results from these tests are generally used to infer 'quality' or relative durability. Some of these tests involve the laboratory assessment of a sample of concrete extracted from the structure. However, this technical note concentrates on the alternative methods appropriate for use on site. Guidance is given on the choice of an appropriate test method, which in most practical situations depends on the predominant mechanism acting on the concrete under consideration.

3439
Basheer, P.A. M., Long, A. E., and Montgomery, F. R.
"THE AUTOCLAM PERMEABILITY SYSTEM FOR MEASURING THE IN-SITU PERMEATION PROPERTIES OF CONCRETE"
in NDT in Civil Engineering, Proceedings of the British Institute of Non-Destructive Testing International Conference, April 14-16, 1993, University of Liverpool, UK; Ed. by J. H. Bungey; British Institute of NDT, Northampton, 1993, Vol. 1, pp 235-260.

The Autoclam permeability system has been designed and developed to measure the air and water permeability and the sorptivity of concrete near the surface. Using this equipment, the rate of decay of air pressure is recorded for the air permeability test, whereas the volume of water penetrating into the concrete, at a constant pressure of 0.01 bar and 1.5 bar are recorded for the sorptivity and the water permeability tests respectively. These tests, which can be carried out quickly and effectively on site without prior planning, are essentially non-destructive in nature and a skilled operator is not needed. It has been found that statistically satisfactory results can be obtained from a mean of three tests and as the flow lines are largely concentrated within 40 mm from the surface, reliable data can be collected by drying the surface even if the surface under test is initially wet. This paper describes the features of this invention and presents results of a laboratory investigation with water-cement ratio, aggregate cement ratio and number of days of wet curing as the variables. A study of these data has indicated that the Autoclam can serve to bridge the gap between the specification of durability and compliance with it in practice.

3440
Basheer, P. A. M., Long, A. E., and Montgomery, F. R.
"A REVIEW OF MEASUREMENT OF PERMEATION PROPERTIES OF CONCRETE ON SITE"
in NDT in Civil Engineering, Proceedings of the British Institute of Non-Destructive Testing International Conference, April 14-16, 1993, University of Liverpool, UK; Ed. by J. H. Bungey; British Institute of NDT, Northampton, 1993, Vol. 1, pp 273-300.

In this review permeation tests which are appropriate for use on site are described and a general guidance to the selection of these methods is provided. Based on this, the necessity of a joint effort of many of research organisations and individuals involved in permeability/durability research to develop appropriate criteria for various exposure conditions encountered in practice to specify the performance of concrete on site with respect to the durability is indicated.

3441
Batrakov, V. G., Kaprielov, S. S., and Sheinfeld, A. V.
"INFLUENCE OF DIFFERENT TYPES OF SILICA FUME HAVING VARYING SILICA CONTENT ON THE MICROSTRUCTURE AND PROPERTIES OF CONCRETE"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 943-963. (ACI SP-132)

This paper gives the results of an investigation of cement paste structure, and strength, permeability, and frost resistance of concrete with admixtures of silica fume. The admixtures are waste materials from metallic silicon, low-grade ferrosilicon, and ferrosiliconchrome production. The influence of the admixtures on the cement paste microstructure results in an increase of gel porosity volume, decrease of capillary porosity and an increase of strength. Thus concrete strength increases and its permeability decreases. The physical and chemical properties of the admixtures and the frost resistance aspects are covered.

3442
Bazant, Z. P. and Schell, W. F.
"FATIGUE FRACTURE OF HIGH-STRENGTH CONCRETE AND SIZE EFFECT"
ACI Materials Journal, Sep-Oct 1993, Vol. 90, No. 5, pp 472-478.

The results of an experimental study of fatigue fracture of geometrically similar high-strength concrete specimens of very different sizes are reported and analyzed. Three-point bend notched beams were subjected to cyclic loading. The number of cycles to failure ranged from 200 to 41,000. It was found that Paris law for the crack length increment per cycle as a function of the stress intensity factor, which was previously verified for normal concrete, is also applicable to high-strength concrete. However, for specimens of different sizes, an adjustment for the size effect needs to be introduced, of a similar type as previously introduced for normal concrete. A linear regression plot estimating the size-adjustment parameters is derived. An LEFM (linear elastic fracture mechanics)-type calculation of the deflections under cyclic loading on the basis of the size-adjusted Paris law yields correct values for the terminal phase but grossly underpredicts the initial deflections. Overall, the results underscore the importance of considering fatigue fracture growth in the case of high-strength concrete structures subjected to large, repeated loads, and taking into account the very high brittleness under fatigue loading.

3443
Beaupre, D., Mindess, S., and Morgan, D. R.
"DEVELOPMENT OF HIGH PERFORMANCE SHOTCRETE (THEORETICAL CONSIDERATIONS)"
in Shotcrete for Underground Support, VI, Proceedings of the Engineering Foundation Conference May 2-6, 1993, Niagara-on-the-Lake, Ontario, Can.; ASCE, New York, 1993, pp. 1-8.

This paper presents some theoretical considerations for studies on high performance wet-mix shotcrete. A new laboratory shotcrete pump and rheometer are being developed to study the effects of aggregate gradation, cement type, air content, silica fume, superplasticiser and fibers on the rheological properties of wet-mix shotcrete.

3444
Belanger, P. R. and Shirlaw, M. R.
"TEMPERATURE CONTROL IN HIGH-STRENGTH, MASSIVE CONCRETE GIRDERS"
Concrete International, Nov 1993, Vol. 15, No. 11, pp 30-32.

This paper describes the procedures which were incorporated in the construction of massive high-strength, reinforced concrete transfer girders in a recent Toronto, Canada, high-rise project. After initial testing, control specifications were revised to permit thermal gradients in the girders beyond traditionally accepted limits. The girders are described, and the control measures are detailed. Details of the construction are given, and temperature readings are discussed. Taking into consideration the influence of cement type and content as well as aggregate characteristics, it appears that a suitable specification for thermal gradient should be a function of concrete thickness, i.e., the gradient could be specified in terms of temperature differential per unit of concrete thickness. The results indicate that a predictable isothermal distribution of a cross-section can be plotted to indicate a possible variation in allowable thermal gradient expressed in terms of degrees per unit of lineal dimension.

3445
Bickley, J. A.
"PREQUALIFICATION REQUIREMENTS FOR THE SUPPLY AND TESTING OF VERY HIGH STRENGTH CONCRETE"
Concrete International, Feb 1993, Vol. 15, No. 2, pp 62-64.

The strength of a concrete mix is affected by the level of control exercised by the supplier, and the reliability of the quality assurance tests made on behalf of the owner. In the field of testing, improved plant and techniques are seen to be necessary. The Canadian Standards Association is reviewing the latter, and this paper describes practices used in Ontario. It is noted that very high strength concrete (VHSC) should preferably be produced at pre-mix plants. Specifications for VHSC should place the responsibility for the quality of the mixed concrete and all its ingredients on the supplier. Concrete testing services are discussed, as well as testing procedures. Guidelines for prequalification are spelled out.

3446
Bjerkell, L., Jensen, J. J., and Lenschow, R.
"STRAIN DEVELOPMENT AND STATIC COMPRESSIVE STRENGTH CONCRETE EXPOSED TO WATER PRESSURE LOADING"
ACI Structural Journal, May-Jun 1993, Vol. 90, No. 3, pp 310-315.

An experimental investigation was conducted to study the strain development and static compressive strength of concrete cylinders exposed to high water pressure loading. The experimental program included one low and one high-strength concrete, and one lightweight aggregate concrete. The cylinders were exposed to water pressure loading in pressure vessels for periods of up to 144 days. The test results show that pore pressure developed in the concrete specimens. The presence of the pore pressure did not reduce the compressive strength of the concrete.

3447
Boulay, C. and de Larrard, F.
"THE SAND-BOX"
Concrete International, Apr 1993, Vol. 15, No. 4, pp 63-66.

High performance concrete (HPC) is being increasingly used for many applications, and it is necessary to have a reliable and easy method of testing cylinders, suitable for any small laboratory, with minimal initial investment. Various methods for doing this are discussed. The lapping process remains the best for results but it entails expensive investment. Methods based on the use of bonded caps are questionable. As the strength of confined sand seems to have no limits, the sand-box method is theoretically more reliable. The practical suitability of the sandbox process has been demonstrated in round-robin tests.

3448
Burieke, F. and Hilsdorf, H. K.
"METHOD TO DETERMINE THE DURABILITY POTENTIAL OF CONCRETE"
" Beton-und Stahlbetonbau, Nov 1993, Vol. 88, No. 11, pp 306-308.

In this paper a simple test method to determine the air-permeability of concrete is presented. A correlation exists between the coefficient of permeability and carbonation of concrete under laboratory conditions which is independent of water-cement-ratio and duration of curing.

3449
" Buyukozturk, O. and Lee, K-M.
"ASSESSMENT OF INTERFACIAL FRACTURE TOUGHNESS IN CONCRETE COMPOSITES"
Cement & Concrete Composites, 1993, Vol. 15, No. 3, pp 143-151.

Interfaces, such as mortar-aggregate interfaces and cement paste-fiber interfaces, affect the mechanical behavior of concrete composites. Characterization of interfacial behavior is needed to study the role of the interfaces on the global behavior of concrete composites as a basis for the development of high-performance cementitious materials. In this paper, an interface fracture mechanics-based methodology is presented to assess the fracture toughness of mortar-aggregate interfaces. Sandwich specimens used to develop the fracture toughness curves of mortar-aggregate interfaces are described.

3450
Campbell, G. M. and Detwiler, R. J.
"DEVELOPMENT OF MIX DESIGNS FOR STRENGTH AND DURABILITY OF STEAM-CURED CONCRETE"
Concrete International, July 1993, Vol. 15, No. 7, pp 37-39.

The importance of strength and durability for the satisfactory performance of concrete is noted, and the article describes a study of the optimization of mix designs for concretes subjected to an 18-hour steam curing regime. In all cases, the water-to-cementitious-materials ratio was 0.45, the maximum allowed for a Class A exposure. The details of the materials and mix designs, curing, chloride ion penetration and compressive strength findings are presented. The test results indicated that concretes with such a water/cement ratio can perform very differently, particularly in their resistance to chloride ion intrusion. In the case of steam-cured concretes, silica fume and slag can be used to improve strength and durability. These and other findings are discussed.

3451
Carette, G. G., Bilodeau, A., Chevrier, R. L., and Malhotra, V. M.
"MECHANICAL PROPERTIES OF CONCRETE INCORPORATING HIGH VOLUMES OF FLY ASH FROM SOURCES IN THE U.S."
ACI Materials Journal, Nov-Dec 1993, Vol. 90, No. 6, pp 535-544.

This paper presents the results of studies to determine the properties of fresh and hardened high volume fly ash concretes using 8 fly ashes and 2 portland cements from the U.S. The details of the studies are described. The analysis of the test results leads to the conclusion that high performance air entrained high volume fly ash concrete can be produced with the fly ashes and cements used in this investigation. The concretes so produced have low bleeding, satisfactory slump and setting characteristics and low autogenous temperature rise. These concretes also have excellent mechanical properties at both early and late ages with compressive strengths reaching as high as 50 MPa at 91 days. The creep and drying shrinkage of the concretes investigated are relatively low.

3452
"CHEMICAL ADMIXTURES"
" Compilation 23, American Concrete Institute, Detroit, MI, 1993, 88 pp.

This booklet is a compilation of selected articles on chemical admixtures including a general discussion of new admixtures on the market, antifreeze admixtures, corrosion inhibitors, accelerators, high range water reducers, waterproofing admixtures, antiwashout admixtures, and a case history of admixture-cement incompatibility. The articles were previously published in the Institute's periodicals.

3453
Clarke, J. L.
"HIGH STRENGTH CONCRETE. AN ECONOMIC SOLUTION"
Materials World, Feb 1993, Vol. 1, No. 2, pp 98-100.

Improvements in the strength of concrete to over 80 MNm-2 have led to weight savings, simpler and faster construction, as well as significant economic benefits despite the higher cost of the material itself. In Europe, Norway is leading the way with the use of high grade concrete in Condeep oil production platforms. The most significant variable influencing the strength, and the long-term quality of concrete is the ratio of the weight of water to the weight of cement. Thus the most important developments have been superplasticizers and water reducing agents.

3454
Clarke, J. L.
"THE NEED FOR DURABLE REINFORCEMENT"
in Alternative Materials for the Reinforcement and Prestressing of Concrete, Ed. by J. L. Clarke, Blackie Academic & Professional, London, 1993, pp 1-33.

This article describes the various types of concrete damage or deterioration which can cause corrosion. These include carbonation and chloride ingress. Methods of avoiding corrosion are also discussed, as are the various relevant UK, Japanese, European and American codes and standards. The latter rely on specifying a minimum cement content. Other methods discussed include the use of superplasticisers, or corrosion inhibitors, and the addition of microsilica. Surface treatments include the grouting of prestressed tendons. Cathodic protection methods and the use of fusion bonded epoxy resin coated reinforcement is also discussed, as is the use of both galvanised and stainless steel reinforcement. The use of non-ferrous reinforcement as an alternative to the conventional steel in traditional structures is presented in the final section. Brief details are provided of its design criteria and serviceability.

3455
Collins, M. P., Mitchell, D., and MacGregor, J. G.
"STRUCTURAL DESIGN CONSIDERATIONS FOR HIGH-STRENGTH CONCRETE"
Concrete International, May 1993, Vol. 15, No. 5, pp 27-34.

This paper highlights aspects of structural design in which traditional procedures may need to be modified to account for the different characteristics of high- strength concrete. The stress-strain response of such concretes is considered, as well as the capacity of columns and the minimum reinforcement and ductility in tension and flexural members. The shear strength of beams is also considered.

3456
"CONCRETE DURABILITY: CORROSION PROTECTION"
Compilation 25, American Concrete Institute, Detroit, MI, 1993, 84 pp.

This booklet is comprised of selected articles on the subject of concrete durability including protection against chloride-induced corrosion, corrosion inhibitors in concrete, evaluation of bridge deck protective strategies, concrete cracking in coastal areas - problems and solutions, sealing to improve durability of bridge infrastructure concrete, mesh-based cathodic deck protection, durability of post-tensioned prestressed concrete structures, structural system performance in parking structures, site investigation of reinforcement placement on buildings and bridges, cathodic protection of new high-rise buildings in Abu Dhabi, preventing reinforced concrete deterioration in the Arabian Gulf, HPI concrete, and durability of concrete treated with silanes. The articles were previously published in the Institute's periodicals.

3457
Cox, B. E.
"PRODUCTS OF SHRP"
Highways and Transportation, June 1993, Vol. 40, No. 6, pp 11-13.

The United States Strategic Highway Research Program (SHRP) has been a five year, $150m research effort directed at achieving substantial progress in specific areas. The prime objective was to improve the performance of bituminous and concrete road making materials, the durability of the pavement and highway structures, and the cost-effectiveness of maintenance operations throughout the year. This paper describes the unique way in which the research has been conducted and is being implemented, and discusses some products of SHRP that are likely to be of particular interest to the UK highway engineering community.

3458
Cramer, S. M. and Bakke, P. M.
"PILOT STUDY ON THE EFFECT OF CHANGES IN TOTAL AGGREGATE GRADATION ON PORTLAND CEMENT CONCRETE PERFORMANCE", Final Report, Applied Research Section, Office of Construction, Division of Highways, Wisconsin Department of Transportation, Madison, WI, 1993, 26 pp.

The primary objective of this study was to initially quantify the effect of changes in total aggregate gradation on concrete performance. The effect of total gradation was studied by monitoring for different mixes: ease of placement; unit weight of fresh PCC; change in w/c at constant slump; change in slump for constant w/c ratio; compressive strength; shrinkage; and possible segregation under vibration. These effects were assessed for bridge deck mix and pavement mix by field and laboratory investigation. Briefly, it was found that optimized gradations can result in the following: modest increases in compressive strength (10 to 20%); air content can be achieved with reduced amounts of air entraining agent (20 to 30%); potentially reduced water demand (up to 15%) as indicated by field results; potentially higher spacing factors in the air void system of hardened concrete; and reduced segregation and higher density surfaces following extended vibration (from 1 to 3 minutes). Some mixed findings and uncertainty continue to cloud the picture, however. Further testing is needed to confirm the trends observed and to establish the effect of gradation optimization on concrete freeze-thaw durability.

3459
Daerga, P. A. and Pontinen, D.
"A FATIGUE FAILURE CRITERION FOR CONCRETE BASED ON DEFORMATION"
Nordic Concrete Research, 1993, Publication No. 13, pp 6-20.

A hypothesis is presented for fatigue failure of concrete structures. It is based on a deformation formulation, and utilizes the monotonic F - delta curve and the fatigue creep curve. The hypothesis is applied to flexural fatigue tests on notched beams of a plain high performance concrete. The experimental part comprises monotonic loading in deformation control and constant amplitude loading at three different load levels in flexural tension. The hypothesis is in all essentials consistent with the experimental findings. Furthermore, it provides a deformation formulation for accumulated damage estimation and remaining service life prediction, which takes account for the nonlinear nature of damage development in contrast to the linear Palmgren-Miner hypothesis.

3460
de Ceukelaire, L. and Van Nieuwenburg, D.
"ACCELERATED CARBONATION OF A BLAST-FURNACE CEMENT CONCRETE"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 442-452.

By means of an accelerated test using an atmosphere containing 10% CO2, the evolution of some parameters of concrete caused by the carbonation processes at different levels of relative humidity is studied. In the first place, the carbonation depth is measured and it is related to the results of short term and long term reference carbonation tests using an atmosphere containing 0.03% CO2. An extrapolation between the two tests can be made. The short time test reveals a carbonation depth that can be compared with the one reached after about two years in a normal atmosphere. Measurements of the compressive strength, a water absorption test and a permeability test after the exposure of the samples lead to surprising observations. The accelerated carbonation of a shortly cured blast-furnace cement concrete does not seem to improve its durability.

3461
de Larrard, F. and Le Roy, R.
"THE INFLUENCE OF MIX COMPOSITION ON MECHANICAL PROPERTIES OF HIGH-PERFORMANCE SILICA-FUME CONCRETE"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 965-986. (ACI SP-132)

This paper discusses the relationship between the composition and the mechanical properties of high-strength concretes (HSC) in the range 50-100 MPa. The models proposed for each of these properties are based on an analysis of the hardened concrete as a composite material, making it possible to go from the properties of the concrete to those of its matrix. The properties of the matrix are related to the two main parameters of composition by empirical models obtained by smoothing the experimental data. The study found that the models, which sum up current knowledge of the material, can be useful in designing HSCs according to specifications.

3462
de Larrard, F., Schaller, I., and Fuchs, J.
"EFFECT OF BAR DIAMETER ON THE BOND STRENGTH OF PASSIVE REINFORCEMENT IN HIGH-PERFORMANCE CONCRETE"
ACI Materials Journal, Jul-Aug 1993, Vol. 90, No. 4, pp 333-339.

The paper discusses the bond strength between a high-performance concrete (HPC having a 28-day strength of 95 MPa) and reinforcing bars. This was measured in a series of beam tests in which the concrete type (HPC and ordinary concrete), reinforcement diameter (between 10 and 25 mm), and reinforcement surface condition (smooth and deformed bars) were varied. In general, concrete- reinforcement bond strength increases with the tensile strength of the concrete, and at a higher rate with smaller reinforcement (a more marked scale effect).

3463
Dhir, R. K. and Byars, E. A.
"PFA CONCRETE: PERMEATION PROPERTIES OF COVER TO STEEL REINFORCEMENT"
Cement and Concrete Research, May 1993, Vol. 23, No. 3, pp 554-566.

The effect of PFA, at up to 30% replacement, on the water absorption and air permeability properties of cover concrete to reinforcement is described. PFA concrete designed for 25 to 50N/mm2 and cured under different conditions of relative humidity and temperature and tested at the age of 28 and 180 days is shown to give better resistance to fluid permeation properties than the corresponding series of OPC concrete.

3464
Dhir, R. K. and Byars, E. A.
"PULVERIZED FUEL-ASH CONCRETE: INTRINSIC PERMEABILITY"
ACI Materials Journal, Nov-Dec 1993, Vol. 90, No. 6, pp 571-580.

This study, which is part of a major international research program into the durability of concrete incorporating pulverized fuel ash (PFA) concrete, deals with the effect of PFA on the intrinsic permeability. Permeability measurements were made using both air and water flows. The concrete mixtures, made with ordinary and rapid hardening portland cements (OPC and RHPC), were designed with 0.15, and 30 % cement replacement with PFA for equivalent strength of 25, 35, 50, and 60 MPa, with a workability of 75 mm slump. The test specimens were subjected to different curings and tested at the age of 28 and 180 days. Concrete is shown to have progressively lower intrinsic permeability with increasing PFA content. The effect is more marked with water permeability. RHPC/PFA blends perform better than OPC/PFA blends with poor curing.

3465
Dhir, R. K., Byars, E. A., Chan, Y. N., and Shaaban, I. G.
"ISAT PREDICTION OF CONCRETE DURABILITY"
in NDT in Civil Engineering, Proceedings of the British Institute of Non-Destructive Testing International Conference, April 14-16, 1993, University of Liverpool, UK; Ed. by J. H. Bungey; British Institute of NDT, Northampton, 1993, Vol. 1, pp 301-314.

This paper deals with the assessment of durability potential of concrete by measurement of its absorption properties. The durability aspects covered were freeze-thaw, carbonation, chloride diffusion and abrasion. The test method for determining the absorptivity was the Initial Surface Absorption Test (ISAT), used essentially as defined in BS 1881, but with several modifications to enhance its application as a laboratory test. The results from accelerated carbonation, freeze-thaw attack, abrasion and chloride diffusion tests are plotted against those of the ISAT, and basic statistical analyses performed to ascertain the certainty with which these aspects of durability may be predicted from the absorption. The results obtained from different concrete types, including varying grade, workability and maximum aggregate sizes and the effect of curing are considered. In addition, the effect of pulverised fuel ash (PFA) on coefficient of chloride diffusion rate is discussed.

3466
Dhir, R. K., Jones, M. R., and Elghaly, A. E.
"PFA CONCRETE: EXPOSURE TEMPERATURE EFFECTS ON CHLORIDE DIFFUSION"
Cement and Concrete Research, Sep 1993, Vol. 23, No. 5, pp 1105-1114.

The results are discussed of a study into the effect of exposure temperature on the coefficient of chloride diffusion (D) of concrete, with PFA contents varying from 0 to 50%, strengths from 20 to 60 N/mm2 and initial curing being in either water 20 degree C or in air 20 degree C 55% RH. The effect of PFA in reducing D is shown to increase with exposure temperature. This effect is greater than the effect of design strength and is more marked where the initial curing has been poor. The work shows that the diffusion test conditions must be chosen to reflect the exposure environment of the concrete structure, as it is possible to greatly over or underestimate the durability of concrete using the standard temperature of 20 degree C.

3467
Do, M-T., Chaallal, O., and Aitcin, P-C.
"FATIGUE BEHAVIOR OF HIGH-PERFORMANCE CONCRETE"
Journal of Materials in Civil Engineering, Feb 1993, Vol. 5, No. 1, pp 96-111.

This study attempts to provide data on the response of high-strength concrete (HSC) to cyclic loading. The study results are compared with those on normal concrete and also with those obtained in other studies with HSC. It was found that fatigue life results are scattered, but may be predicted reasonably well using a probabilistic approach based on the McCall model and assuming a probability of failure. Longitudinal strain development in high-strength concrete is similar to normal strength concrete. These and other findings are presented and discussed.

3468
Dolan, C. W., Ballinger, C. A., and LaFraugh, R. W.
"HIGH STRENGTH PRESTRESSED CONCRETE BRIDGE GIRDER PERFORMANCE"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 88-97.

This paper reviews the evolution of prestressed concrete girders in North America and correlates historical behavior to the development and application of high strength concrete for bridge girders. Institutional and production issues affecting the use of high strength concrete are discussed and design strategies to further utilize high strength concrete are presented. The paper concludes that high strength concrete girders offer excellent opportunities for extending the effectiveness of these bridge members. Many prestressing plants already have the capacity to produce high strength concrete girders or can readily develop the high strength mix designs. Lastly, modern mix designs with high cement factors and admixtures are likely to retain the high performance characteristics of older girders.

3469
Dolan, C. W. and LaFraugh, R. W.
"HIGH STRENGTH CONCRETE IN THE PRECAST CONCRETE INDUSTRY"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 16-19.

The precast concrete industry has, since its inception, been a recognized leader in the development and use of high strength concrete. Yet in recent years, whereas concrete strength in building applications has increased from 6000-8000 psi to 12,000-16,000 psi, there has not been a corresponding trend in the strength of precast concrete. As part of its continuing mission, the PCI Committee on High Strength Concrete conducted a survey of producer members in 1990 to determine the use, benefits and liabilities of high strength concrete in the industry.

3470
Dunstan, M. R. H., Thomas, M. D. A., Cripwell, J. B., and Harrison, D. J.
"INVESTIGATION INTO THE LONG-TERM IN-SITU PERFORMANCE OF HIGH FLY ASH CONTENT CONCRETE USED FOR STRUCTURAL APPLICATIONS." Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. I, pp 1-20. (ACI SP-132)

The paper presents results of investigations carried out on high fly ash content concrete (HFCC) cores removed from a number of structures constructed in the United Kingdom since 1979. The structures investigated were a road pavement, a major road viaduct, water-retaining and industrial structures, and a spillway subjected to marine exposure. The concrete properties measured after ten years include compressive strength, depth of carbonation, permeability and chloride and sulphate penetration profiles. Petrographic analysis of thin sections was also made. The results show a durable concrete with increases in compressive strength beyond 28 days, little evidence of carbonation, low to average permeability and resistance to chloride penetration.

3471
"DURABLE CONCRETE"
Compilation 24, American Concrete Institute, Detroit, MI, 1993, 71 pp.

This booklet is a compilation of selected articles on concrete durability including long service life of concrete, design considerations for service life, research innovations for durable concrete, the use of fly ash, economic considerations, water and its role in concrete, concrete in a sulfate environment, the use of superplasticizers, effective curing on durability, shotcrete durability, and exposed aggregate concrete. The articles were previously published in the Institute's periodicals.

3472
"DURABLE CONCRETE IN HOT CLIMATES"
Proceedings of the International Symposium on How to Produce Durable Concrete in Hot Climates, held in Oct. 1992 at the ACI Fall Convention in San Juan, Puerto Rico; Ed. by Cameron MacInnis; American Concrete Institute, Detroit, MI, 1993, vi, 188 pp. (ACI SP-139)

The papers presented at the Symposium are as follows: Effect of Hot Weather Conditions on the Microcracking and Corrosion Cracking Potential of Reinforced Concrete, Rasheeduzzafar and S. M. A. Al-Kurdi; Effect of Temperature on Cathodic Protection Criterion for Reinforced Concrete Structures, Rasheeduzzafar and M. G. Ali; Electron-Optical Evaluation of Concrete Cured at Elevated Temperatures, B. A. Clark, E. A. Draper, R. J. Lee, J. Skalny, M. Ben-Bassat, and A. Bentur; The Effect of Curing Temperature on the Chloride Ion Diffusion of Superplasticised Cement and Fly Ash Cement Pastes, J. G. Cabrera, T. A. H. Dodd, and S. O. Nwaubani; Properties of Pozzolanic Mortars Cured in Hot Dry Environments, J. G. Cabrera, P. J. Wainwright, and A. M. Alamri; The Influence of Controlled Permeability Formwork Liner on the Quality of the Cover Concrete, A. A. Sha'at, A. E. Long, F. R. Montgomery, and P. A. M. Basheer; Research on Concrete in Hot Environments at the National Building Research Institute, Haifa, Israel, D. Ravina and I. Soroka; Concrete Problems Associated with Hot Climates, J. M. Scanlon; Concreting of Thick Sections in the Tropics, C. T. Tam, S. Swaddiwudhipong, A. C. Mani, and S. L. Lee; and Strength of Concrete Cured under Various Conditions in Tropical Climates, R. Huyke-Luigi. An Index is provided.

3473
Durning, T. A. and Rear, K. B.
"BRAKER LANE BRIDGE - HIGH STRENGTH CONCRETE IN PRESTRESSED BRIDGE GIRDERS"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 46-51.

A bridge over Interstate I-35 at Austin, Texas, was designed and built using Texas Type C girders fabricated with high strength concrete. Compressive strengths required were 7400 psi (51 MPa) within 17 hours and 9600 psi (66MPa) at 28 days, which allowed a design with fewer girders and increased girder spacing compared to a design with normal strength concrete. Test results on production quality high strength concrete containing microsilica are presented.

3474
Ewertson, C. and Petersson, P. E.
"INFLUENCE OF CURING CONDITIONS ON THE PERMEABILITY AND DURABILITY OF CONCRETE. RESULTS FROM A FIELD EXPOSURE TEST"
Cement and Concrete Research, May 1993, Vol. 23, No. 3, pp 683-692.

Two concrete qualities were subjected to different curing conditions and then exposed to three different climates; outdoors exposed to rainfall, outdoors protected from rainfall and indoors. After one or two years of exposure the water impermeability and the carbonation depth were determined. The test results show that the differences between different curing conditions becomes more pronounced the drier the climate. This means that laboratory tests cannot always be used for predicting the concrete behaviour of a real structure. Field exposure tests are to be preferred. According to the results from the carbonation tests, it seems that wet curing and covering with plastic foil are equally efficient. This is relevant for Swedish field conditions, and other climatic conditions probably give other results.

3475
Fang, I-K., Yen, S-T., Wang, C-S., and Hong, K-L.
"CYCLIC BEHAVIOR OF MODERATELY DEEP HSC BEAMS"
Journal of Structural Engineering, Sep 1993, Vol. 119, No. 9, pp 2573-2592.

The experimental investigations of moderately deep high-strength concrete beams subjected to various imposed inelastic cyclic deformations are presented. Fifteen cantilever beams having cross section of 200 x 400 mm were reinforced in accordance with the seismic design provisions of the current building code (ACI 318-89). An additional two normal-strength concrete beams were tested as reference specimens. The test variables included: (1) Shear span-to-depth ratio; (2) ratio of longitudinal reinforcement at top and bottom; and (3) loading histories. The cyclic performances of beams were evaluated in terms of the characteristics of strength and stiffness degradation and energy-dissipation capacity. The behavior of plastic hinges was also studied. Test results revealed that moderately deep HSC beams were able to resist the various cyclic loads to a displacement ductility factor of 3 to 4. For the loading histories considered in this study, the specimens exhibited pronounced decay in both strength and flexural stiffness when they were loaded beyond a displacement ductility factor of 3. Under cyclic loads, moderately deep HSC beams exhibited less spalling in the plastic-hinge zone, which led to slower strength degradation and better energy-dissipation capability than did the normal-strength concrete beams.

3476
Fidjestol, P.
"APPLIED SILICA FUME CONCRETE"
Concrete International, Nov 1993, Vol. 15, No. 11, pp 33-36.

The article describes how silica fume concrete has gained increasing acceptance for use in high-performance concrete. The benefits of silica fume in shotcrete include strength increase and improved durability, a reduction in rebound by 50-70% and the ability to build layers of 2-300 mm in one pass. Silica fume can be used in dry and wet shotcrete with the same success, and both processes can use both the dry and wet (slurry) product. Recent uses of slurry in dry shotcrete are described in the article. The Frasdorf sewage tunnel project in Bavaria is described, as well as the Schonrain tunnel (currently under construction for the German High Speed Train), a 47-floor high-rise in Frankfurt, Germany, the Boknasundet Bridge in Norway, and the Bergoysundet Bridge.

3477
French, C. W. and Mokhtarzadeh, A.
"HIGH STRENGTH CONCRETE: EFFECTS OF MATERIALS, CURING AND TEST PROCEDURES ON SHORT-TERM COMPRESSIVE STRENGTH"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 76-87.

As part of a multiyear study on applications of high strength concrete to the precast, prestressed concrete industry, a laboratory investigation was conducted to determine the effect of various parameters on uniaxial compressive strength. Parameters investigated included mold size, mold material, aggregate type, type of curing, age and specimen end condition. More than 650 specimens for strength evaluation were cast from 10 high strength concrete mixes having 28-day compressive strengths ranging from 9000 to 15,000 psi (62 to 103 MPa). In this study, Type III Portland cement concrete as well as Type III Portland cement concrete incorporating fly ash, microsilica and their combination were used.

3478
Fukudome, K., Miyano, K., Taniguchi, H., and Kita, T.
"RESISTANCE TO FREEZING AND THAWING AND CHLORIDE DIFFUSION OF ANTI-WASHOUT UNDERWATER CONCRETE CONTAINING BLAST-FURNACE SLAG"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1565-1582. (ACI SP-132)

The resistance to freezing and thawing and chloride diffusion of anti-washout underwater concrete were investigated. In this study, 2 types of cement were used. Two types of blast furnace slag were used as a cement replacement. The results show that anti-washout underwater concrete without blast furnace slag shows poor resistance to freezing and thawing compared with normal concrete. But the freezing and thawing resistance can be improved by blast furnace slag. Also, chloride diffusion becomes smaller with blast furnace slag.

3479
Giaccio, G., Rocco, C., and Zerbino, R.
"FRACTURE ENERGY (GF) OF HIGH-STRENGTH CONCRETES"
Materials and Structures/Materiaux et Constructions, Aug-Sep 1993, Vol. 26, No. 161, pp 381-386.

This paper presents results for the fracture energy of concrete (GF) obtained from a wide range of high- strength concretes. Strength levels up to 100 MPa, aggregate type and aggregate surface texture were included as variables. The determination of GF was performed according to the recommendation of the RILEM 50-FMC Committee. Compressive and tensile strengths and the modulus of elasticity are also presented. Measured values of GF are compared with those proposed in the last CEB Model Code.

3480
Gifford, P. M., Lanfan, B. W., and Ward, M. A.
"USE OF FLY ASH IN HEAT-CURED CONCRETE AND THE EFFECT OF POST-CURING STORAGE REGIMES ON STRENGTH, MODULUS OF ELASTICITY, AND FREEZING-THAWING DURABILITY"
Cement, Concrete, and Aggregates, Summer 1993, Vol. 15, No. 1, pp 14-23.

This is a study of the use of ASTM Type C fly ash from two western Canadian sources with a Type III cement and a slump-extending superplasticizer. The details of the study are described in the paper. It was found that fly ash, when used with a slump-extending superplasticizer, can be incorporated at a low to moderate level of cement replacement in heat-cured precast, prestressed concrete. The fly ash concretes met adequate release and 28-day strengths, and possessed very high scaling resistance and could provide high durability in a freezing and thawing environment. The compressive strength, elasticity modulus, and durability of fly ash heat-cured concrete was not more affected by post-heat-curing storage regimes than proven concrete containing fly ash.

3481
Glavind, M., Olsen, G. S., and Munch-Petersen C.
"PACKING CALCULATIONS AND CONCRETE MIX DESIGN"
Nordic Concrete Research, 1993, Publication No. 13, pp. 21-34.

This article deals with computer-based calculations of packing of the aggregates as an aid when choosing a concrete mix design. The packing theory and the developed computer program are presented. Furthermore, an investigation relating packing of the aggregates and the properties of the fresh concrete is described. Finally, application of the packing calculations and practical experience are discussed.

3482
Goldman, A. and Bentur, A.
"INFLUENCE OF MICROFILLERS ON ENHANCE-MENT OF CONCRETE STRENGTH"
Cement and Concrete Research, Jul 1993, Vol. 23, No. 4, pp 962-972.

The research presented in this paper was intended to clarify the nature of concrete strengthening in the presence of silica fume. For this purpose, compressive strength development of high strength concrete and its paste-matrix was investigated. Carbon black was introduced as an alternative microfiller to silica fume. The results indicated that carbon black was effective in modifying the basic concrete-matrix strength relationship to an extent similar to that obtained by silica fume. It is suggested that the mechanism by which silica fume affects the concrete behavior is of a physical origin and is based on microfiller effect, prior to its action as a pozzolanic material. The microfiller effect is of greater significance to strength enhancement.

3483
Goltermann, P.
"PERFORMANCE TAILORING OF STRUCTURAL CONCRETE"
Nordic Concrete Research, 1993, Publication No. 13, pp 35-42.

This paper presents the acquired knowledge from the development and use of an expert system for the performance tailoring of concrete. The expert system combines a shell in the Windows-environment with a number of programs and applications, in an optimal constellation where the most suitable program, shell or application can be used for solving the problem. The system can design concretes according to Danish, Spanish, and French codes for a specific strength, workability and durability according to the national codes. The system uses the local aggregates and cements, documented with the different national codes. The facilities enable a fast and optimal use of aggregates and cement, thus leading to a better use of the available types of aggregates and a reduced cost.

3484
Hammons, M. I. and Neeley, B. D.
"TRIAXIAL CHARACTERIZATION OF HIGH-STRENGTH PORTLAND CEMENT CONCRETE"
Transportation Research Record, 1993, No 1382, pp 73-77.

Triaxial characterization tests were conducted on a high-strength portland cement concrete proportioned from readily available materials. The objective was to develop mechanical response data for this high-strength concrete along selected stress and strain paths in multiaxial stress space. The concrete chosen for testing had a water-cement ratio of 0.23 and an unconfined compressive strength at 56 days of 105 MPa. The triaxial test specimens were 50-mm nominal diameter right circular cylinders. All tests were performed in a 276-MPa-capacity cylindrical triaxial cell in conjunction with a 1340 kN-capacity servohydraulic materials testing system. Confining pressure was generated by an external 600-MPa-capacity, air driven hydraulic pumping system. Active measurements attempted for each test included vertical and horizontal strain, testing machine displacement, axial load, and confining pressure. Triaxial shear tests were conducted at confining pressures of 50, 100, 150, and 200 MPa, and uniaxial strain tests were conducted to a principal stress difference of 350 MPa. These stress-strain data were plotted, and a failure envelope was developed. The test data show that high-strength portland cement concrete is capable of large plastic strains and ductile flow under states of high confinement. The material exhibited strain-softening behavior at the 50-MPa level; thus, it appears that the brittle-ductile transition for the material lies between the 50- and 100-MPa confining stress levels. At confining stresses of 100 MPa and greater, the material behavior is characterized by a strain-hardening ductile behavior to axial strains of 10% or greater.

3485
Hansen, M. R., Leming, M. L., Zia, P., and Ahmad, S. H.
"CHLORIDE PERMEABILITY AND AC IMPEDANCE OF HIGH PERFORMANCE CONCRETE"
in Proceedings of the Symposium on High Performance Concrete in Severe Environments, held Nov 9, 1993 at the ACI Fall Convention, Minneapolis, MN; Ed. by Paul Zia; American Concrete Institute, Detroit, MI, 1993, pp. 121-145. (ACI SP-140)

Three types of high performance concrete (HPC) for highway applications were investigated: Very Early Strength (VES), High Early Strength (HES), and Very High Strength (VHS). The objectives of the research were to measure the chloride permeability of these concretes and explore an alternate method using AC impedance. Many of the concretes had coulomb values of 4,000 and higher, placing them in the "high permeability" category as specified by AASHTO T 277 - Rapid Chloride Permeability Test (RCPT). Coulomb values were also found to decrease with concrete age and with increased silica fume content. Coulomb values were found not to vary significantly with dosage of calcium nitrite used as accelerator, up to 6 gallons/cubic yard (29.7 liters/cubic meter). The AC impedance test results (ohms) were found to correlate well with the RCPT results (coulombs) and were sufficiently accurate to place the concretes in the proper chloride permeability category. The advantages of the AC impedance test are that it is faster and less expensive than RCPT and it avoids the potential heating problem sometimes encountered in RCPT. AC impedance was found to increase with concrete age and with increased silica fume content and decrease with increased calcium nitrite dosage.

3486
"HIGH PERFORMANCE CONCRETE IN SEVERE ENVIRONMENTS"
Proceedings of the Symposium held Nov 9, 1993 at the ACI Fall Convention, Minneapolis, MN; Ed. by Paul Zia; American Concrete Institute, Detroit, MI, 1993, vi, 310 pp. (ACI SP-140)

This publication contains 14 papers, of which 13 were presented at the Symposium held at the ACI Fall Convention in 1993. The papers are as follows: High Performance Concrete in Florida Bridges, J. Armaghani, D. Romano, M. Bergin, and J. Moxley; Development and Utilization of High Performance Concrete Employed in the Akashi Kaikyo Bridge, K. Tanaka, K. Sato, S. Watanabe, I. Arima, and K. Suenaga; The Use of a High Performance Air Entrained Concrete for the Construction of the Portneuf Bridge, P-C. Aitcin, G. Ballivy, D. Mitchell, M. Pigeon, and L. G. Coulombe; High Performance Concretes in the "Elorn" Bridge, J. Le Bris, P. Redoulez, V. Augustin, J. M. Torrenti, and F. de Larrard; High Performance Concrete for Highway Applications: Field Results, J. J. Schemmel and M. L. Leming; Chloride Permeability and AC Impedance of High Performance Concrete, M. R. Hansen, M. L. Leming, P. Zia, and S. H. Ahmad; Application of Super Workable Concrete to Construction of a 20-Story Building, S. Kuroiwa, Y. Matsuoka, M. Hayakawa, and T. Shindoh; Application of Super Workable Concrete to Reinforced Concrete Structures with Difficult Construction Conditions, N. Miura, N. Takeda, R. Chikamatsu, and S. Sogo; Advances in Underwater Concreting: St. Lucie Plant Intake Velocity Cap Rehabilitation, N. Hasan, E. Faerman, and D. Berner; High Performance Concrete to Plug the Flooding of the Chicago Tunnels, J. Moreno and G. Detwiler; HPC for the Improvement of Tightness of Nuclear Reactor Containments in Case of Severe Accidents, G. J. B. Ithurralde and J. L. Costaz; Salt Saturated Mass Concrete Under Chemical Attack, L. D. Wakeley, T. S. Poole, J. J. Ernzen, and B. D. Neeley; Development of Very Low Heat Mass Concrete Mixtures for the Modification of Theodore Roosevelt Dam, W. F. Kepler and K. F. von Fay; and High Performance Concrete Mixtures for Durability, J. M. Shilstone, Sr, and J. M. Shilstone, Jr. An Index is provided.

3487
"HIGH-PERFORMANCE CONSTRUCTION MATERIALS AND SYSTEMS: AN ESSENTIAL PROGRAM FOR AMERICA AND ITS INFRASTRUCTURE -- TECHNICAL REPORT"
Prepared by the Civil Engineering Research Foundation (CERF) and the Planning Committee for the Nationally-Coordinated Program on High-Performance Concrete and Steel, ASCE, New York, 1993, 220 pp.

This report outlines a program for a concerted effort to return the United States to the forefront of construction materials technology. The two main materials addressed in this report, the first of a series, are high performance concrete and steel. These two technologies are examined in parallel, first addressing the need for a unified, national program, then detailing a proposed national program plan, and a concomitant technical plan, management plan, and budget summary. The need for these programs is surveyed, in terms of the importance of these technologies, recent advances in materials science, potential benefits from the technology, and a vision of the future. The report then defines the goals of the nationally coordinated program. The technical plan describes mechanisms for improving technology transfer, as well as proposed research and development on high performance concrete and steel. The management plan discusses the requirements for a coordinated effort, including the establishment of several coordinating bodies made up of representatives from industry, government, and academia. Finally, the report presents a proposed budget and time schedule for converting the plan into reality. The report also contains three appendices: Appendix A - Technology Transfer; Appendix B - High-Performance Concrete; and Appendix C - High-Performance Steel. Appendix A depicts a number of methods for collecting and disseminating technical knowledge to the design and construction industry as well as means for accelerating the acceptance of new technology. Appendix B provides a detailed examination of the state-of-the-art of materials and techniques relative to high-performance concrete. Appendix C provides a similar examination of the state-of-the-art of materials and techniques relative to high-performance steel.

3488
"HIGH-PERFORMANCE CONSTRUCTION MATERIALS AND SYSTEMS: AN ESSENTIAL PROGRAM FOR AMERICA AND ITS INFRASTRUCTURE -- EXECUTIVE REPORT"
Prepared by the Civil Engineering Research Foundation (CERF) and the Planning Committee for the Nationally-Coordinated Program on High-Performance Concrete and Steel, ASCE, New York, 1993, 40 pp.

This report provides a high-level, policy-oriented summary of the findings detailed in its companion volume, the Technical Report (Report No. 93-5011). As evident in the introductory letter addressed to President Clinton, the intended audience is the Administration and Congress, other national policy makers, and government and industry leaders. Initiated as a result of the 1991 National Civil Engineering Research Needs Forum organized by the Civil Engineering Research Foundation (CERF), this report builds a case for a national program aimed at exploiting the potential of high-performance concrete and steel for improving the competitiveness and quality of U.S. construction. While the report includes a synopsis of conclusions contained in the companion Technical Report, its main emphasis is on the potential benefits to be realized from such a national program. The report concludes with a call for active support, participation, and funding from government, industry, and academia in order to realize this critical national priority.

3489
"HIGH STRENGTH PRESTRESSED CONCRETE: RESEARCH - DESIGN - APPLICATION"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, 160 pp.

This special issue of PCI Journal presents a series of papers on high strength concrete and the goals of the PCI High Strength Concrete Committee. The following papers are included: High Strength Concrete in the Precast Concrete Industry; The Federal Outlook for High Strength Concrete Bridges; Performance of Prestressed High Strength Concrete Bridge Girders; Braker Lane Bridge - High Strength Concrete in Prestressed Bridge Girders; Influence of High Strength Concrete on Transfer and Development Length of Pretensioning Strand; Feasibility Study of 14,000 psi Pretensioned Concrete for a Navigational Structure; High Strength Concrete - Effects of Materials, Curing and Test Procedures; High Strength Prestressed Concrete Bridge Girder Performance; Prestress Losses in Partially Prestressed High Strength Concrete Beams; Static and Fatigue Behavior of Pretensioned Composite Bridge Girders Made with High Strength Concrete; and, High Strength Concrete Bibliography.

3490
Idorn, G. M.
"FIT-FOR-PURPOSE CONCRETE"
Concrete International, Jul 1993, Vol. 15, No. 7, pp 53-54.

The concept of high-performance concrete (HPC) has received much attention in recent years within institutional research in North America and Europe. The promotional literature for the ACI International Conference on High-Performance Concrete, to be held in Singapore in November 1994, mentions that "a number of countries, including Canada, France, Japan, Norway, and the U.S.A., have recently embarked on major research programs in the area of HPC. I believe that the primary commitment for ACI in view of the current economic and social conditions should be a broad promotion and research strategy for what might well be designated "Fit-for-Purpose Concrete", while preserving the current efforts for the development of HPC as an exciting niche of narrower fields off profitable applications for many years to come.

3491
Ipatti, A.
"EFFECT OF SPECIMEN SIZE AND CAPPING METHOD ON APPARENT COMPRESSIVE STRENGTH OF HIGH-STRENGTH CONCRETE"
Nordic Concrete Research, 1993, Publication No. 13, pp 56-69.

Compressive testing of high-strength concrete is a critical issue on which no consensus has yet been reached. Among the many factors that are often under discussion are the effects of specimen size, shape and capping method on the compressive strength results. The main objectives of the present investigation were to conduct a well designed and statistically analyzed experiment to investigate effects of the abovementioned factors, and possible interactions of these on compressive strength of high-strength concrete. A 3 x 4 x 3 factorial experimental design was adopted with three levels of specimen sizes, three methods of specimen capping and four levels of concrete strength grades. To properly evaluate the test result, two and three way analyses of variance and procedures for pairwise comparison of factor main effects were used.

3492
Jiafen, J.
"HIGH-STRENGTH CONCRETE IN CHINA"
Concrete International, Jan 1993, Vol. 15, No. 1, pp 43-45.

The development of high-strength concrete (HSC) in China occurred in two stages. The initial stage began in the 1950s, when HSC was studied and applied to prestressed concrete structures. At the time, HSC could be prepared in two ways: using high-grade cement with a 28-day compressive strength of 70 to 80 MPa (10,150 to 11,600 psi), or using ordinary portland cement with a low water-cement ratio and a low sand percentage. Compressive strengths of 90 to 100 MPa (13,050 to 14,500 psi) could be achieved using high-grade cement. Due to low rates of production of high-grade cement, use of HSC in this early period was limited because of the difficulties in placing concrete with a low water content. Rapid progress in China in the 1980s in research and development with concrete admixtures and supplementary cementitious materials has propelled HSC into its second stage of development. Workable concretes with 50 to 80 MPa (7250 to 11,600 psi) compressive strength are now easily manufactured using ordinary portland cement, low water-cement ratios and superplasticizers. During the past ten years, HSCs have been successfully applied in a variety of construction projects.

3493
Johnson, C. D. and Mirza, S. A.
"COMPRESSIVE STRENGTH TESTING OF HPC CYLINDERS UTILIZING CONFINED CAPS"
Department of Civil Engineering, Lakehead University, Ontario, Canada, Civil Engineering Research Series, Report No. CE-93-2, Dec 1993, 26 pp.

The Confined Capping System reported in this paper provides a simple approach for compressive strength testing of high performance concrete cylinders. This method employs standard concrete laboratory testing equipment and an inexpensive customized capping apparatus for preparing the cylinder ends. The method ensures that confinement is provided to the cap without having to place tight controls on cylinder end roughness prior to capping and on the cap thickness itself. This paper explains and documents the use of the method for testing concretes with strengths up to and exceeding 100 MPa.

3494
Johnston, C. D.
"DURABILITY OF HIGH EARLY STRENGTH SILICA FUME CONCRETES SUBJECTED TO ACCELERATED AND NORMAL CURING"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1167-1187. (ACI SP-132)

The short term strength development and long-term durability of silica fume concretes were investigated for mixtures intended to be alternatives to those without silica fume currently used in precast prestressed concrete bridge girder production in Alberta, where accelerated curing at 65 Deg C to obtain specified strength of 28 MPa at 16 hours and 35-42 MPa at 28 days are normal industry practice. The study found that silica fume significantly enhance all aspects of durability relevant to exposure conditions involving freezing and thawing with deicers. Varying degrees of short and long-term strength improvement and reduced cost in terms of cementitious material are also possible as a consequence of using silica fume.

3495
Johnston, C. D.
"SUPERPLASTICIZERS FOR CONCRETE BRIDGE CONSTRUCTION"
Report No. ABTR/RD/RR-93/01, Research and Development Division, Alberta Transport and Utility, Edmonton, Alberta, Canada, 1993, 67 pp.

The primary objective of this project was to determine how the range of superplasticizing and air-entraining admixtures currently available in Alberta can be specified and used to enhance the properties of the different concretes used in bridge construction. Special reference is given to cast-in-place deck and substructure applications. A secondary purpose associated with substructure concretes was to determine the conditions under which Alberta fly ashes can partially replace cement to slow the rate of heat development in large units without adversely affecting concrete performance in other respects. The results of the laboratory test program indicate that there are many advantages and few, if any, major disadvantages associated with using superplasticizers in air-entrained concretes for bridge works. Many aspects of performance in both freshly mixed and hardened states are significantly admixture specific, and should be confirmed from trial mixtures or past job records.

3496
Kakizaki, M., Edahiro, H., Tochigi, T., and Niki, T.
"EFFECT OF MIXING METHOD ON MECHANICAL PROPERTIES AND PORE STRUCTURE OF ULTRA HIGH-STRENGTH CONCRETE"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 997-1015. (ACI SP-132)

High-strength and ultra-high-strength cast-in-place concrete tend to contain excessive unit volumes of cement when compared with normal concrete, and because the improvement of workability relies largely on the efficiency of the air-entraining and high-range water-reducing admixture, the properties of workability are different from normal concrete. With high-strength concrete it was found that the method of mixing concrete influenced flowability, strength properties, and pore structure. The manner in which this occurred is detailed.

3497
Kashima, S., Furuya, N., and Ymaoka, R.
"HIGH-STRENGTH CONCRETE FOR WALL FOUNDATION USING TERNARY BLENDED CEMENT WITH INTERMIXTURE OF BLAST-FURNACE SLAG AND FLY ASH"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1451-1469. (ACI SP-132)

The anchorage of the Akashi, Kaikyo bridge in Japan, the world's longest suspension bridge, will be constructed as a concrete foundation surrounded with underground wall of depth of 75 m. This wall is composed of 46 slender reinforced concrete panels. A high strength, low-heat generating concrete using a ternary blended cement containing large amounts of blast furnace slag and fly ash, and superplasticizer were used. This paper describes the results of tests on basic properties such as workability, strength, heat generation of high strength concrete using ternary blended cement with large amount of blast furnace slag and fly ash, the results of tests performed on experimental models, and the results of actual work.

3498
Kato, K., Shin, H. Y., and Kunishima, M.
"STUDY ON THE CONSTRUCTABILITY OF SELF-PLACEABLE CONCRETE"
" Proceedings of the Japan Society of Civil Engineers, Dec 1993, No. 480, Pt 6-21, pp 117-126.

The objective of this study is to compare the constructability of self-placeable concrete with that of conventional concrete and examine its efficiency. Self-placeable concrete developed at the Concrete Engineering Laboratory of the University of Tokyo could fill everywhere in the formwork without any consolidation procedure. This concrete possesses the flowability and segregation resistance under fresh concrete and durability under hardening stage. This study discusses about the efficiency of the self-placeable concrete which is applied to the usual reinforced concrete structures.

3499
" Khayat, K. H. and Aitcin, P-C.
"SILICA FUME IN CONCRETE - AN OVERVIEW"
" Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 835-872. (ACI SP-132)

An overview of recently published literature on the subject of silica fume in concrete is presented. The various mechanisms of action of silica fume which cause physical and chemical changes in concrete are discussed. The role of silica fume in altering engineering properties of concrete is highlighted. In particular, the effects of silica fume on the following properties of concrete are discussed: rheological properties, mechanical properties, and durability (such as resistance to deterioration by aggressive chemicals, abrasion-erosion, and freezing and thawing cycles).

3500
" Khayat, K. H., Gerwick, B. C., Jr., and Hester, W. T.
"SELF-LEVELING AND STIFF CONSOLIDATED CONCRETES FOR CASTING HIGH-PERFORMANCE FLAT SLABS IN WATER"
Concrete International, Aug 1993, Vol. 15, No. 8, pp 36-43.

Self-leveling concretes suitable for casting high- performance flat reinforced beams and slabs in water are described in this paper. Such concretes should be highly fluid with approximate slump and DIN flow values of 11 and 28 in. respectively. The details are noted of casting self leveling concrete that can be done using an inclined tremie pipe. It is noted that properly cast, self leveling concrete can form flat surfaces and flow at least 12 feet without exhibiting significant reduction in quality. It is pointed out that the casting and consolidation of stiff concrete underwater seems to offer an attractive alternative for repairing shallow scour holes and isolated patch areas, and also for enhancing the wear resistance over existing surfaces. These and other observations are presented.

3501
LaFraugh, R. W.
"FEASIBILITY STUDY OF 14,000 PSI PRETENSIONED CONCRETE FOR A NAVIGATIONAL STRUCTURE"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 68-75.

On a proposed waterway project, an in-depth test program was conducted to develop a mix design that could provide plant-produced, high strength concrete of 14,000 psi (97 MPa) at 28 days. This paper reports the strength data and other physical properties of the concrete which indicate the feasibility to meet the design requirements of the project.

3502
Lane, S. N. and Podolny, W.
"THE FEDERAL OUTLOOK FOR HIGH STRENGTH CONCRETE BRIDGES"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 20-33.

Considerable research has been conducted during the last 20 years on high strength concrete materials, mix proportions and basic properties. Some research has also been conducted during this time span on its capacity for use in bridge members. However, structural questions remain. Also, very little has been done regarding the implementation of high strength concrete bridges. This paper will document the use of high strength concrete in bridges and present bridge design concerns. Additionally, it will present significant research results and ongoing research programs, as well as highlight remaining areas for future research. It should be noted that the contents of this paper reflect the views of the authors and do not necessarily reflect the official views or policies of the Federal Highway Administration or any other federal agency.

3503
Leeming, M. B.
"A SURFACE AIR PERMEABILITY TEST FOR CONCRETE AND SURFACE TREATMENTS ON CONCRETE"
in NDT in Civil Engineering, Proceedings of the British Institute of Non-Destructive Testing International Conference, April 14-16, 1993, University of Liverpool, UK; Ed. by J. H. Bungey; British Institute of NDT, Northampton, 1993, Vol. 1, pp 261-272.

The 'Surface Air Permeability' test provides a simple test for the relative durability of concrete and can also be used on surface coatings. It completes the quartet of tests comprising the Figg Air and Water Permeability tests and the Initial Surface Absorption test. It is much quicker to carry out than the other three tests and requires much simpler equipment. However, in the same way as the above tests it suffers from its sensitivity to the moisture content of the concrete. The paper describes the development of the equipment. The initial results of the test look promising. The test is sensitive enough to differentiate between the sides, top and bottom of a concrete cube and relates in some measure to the carbonation depth. Because of the simplicity of the test and quickness of use the test deserves further consideration. One potential application is the testing of surface coatings for their ability to restrict the carbonation of concrete. Another application may be to test whether the surface of the concrete is sufficiently dry so that silanes will achieve adequate penetration.

3504
Leming, M. L., Schemmel, J. J., Zia, P., and Ahmad, S. H.
"HIGH-PERFORMANCE CONCRETE: NORTH CAROLINA FIELD INSTALLATION RESULTS"
Transportation Research Record, 1993, No. 1382, pp 78-81.

A Strategic Highway Research Program contract included five installations in five states. The objectives of the field installations were to confirm the ability to produce and place certain high-performance concretes and to achieve desired strength-time targets under realistic conditions, with several sources of raw materials. Data obtained from the most extensive field trials, conducted in North Carolina, are presented and examined.

.

3505
Lessard, M., Chaallal, O., and Aitcin, P-C
"TESTING HIGH-STRENGTH CONCRETE COMPRESSIVE STRENGTH"
ACI Materials Journal, Jul-Aug 1993, Vol. 90, No. 4, pp 303-308.

Comparative testing reveals that high strength concrete (HSC) compressive strength values are greater by 5% when measured on 100 x 200 mm specimens. Moreover, the coefficient of variation on one set of three 100 x 200 mm specimens is as small as, or smaller than that for 150 x 300 mm specimens. Furthermore, a high performance capping compound testing 60 to 70 MPa using 50-mm cubes has proved to be effective when used for testing HSC up to 120 MPa due to the confinement of the capping compound between the platen and the specimen, but the capping layer has to be less than 3 mm thick. Under these conditions, the results are similar to those obtained when the ends are faced by grinding. Nevertheless, it is safer to grind the specimen ends when the strength of the concrete exceeds 100 MPa. It is shown that eccentricity of less than 4 mm between the testing machine and specimen axis does not affect the compressive strength values.

3506
Lindgard, J. and Smeplass, S.
"HIGH STRENGTH CONCRETE CONTAINING SILICA FUME - IMPACT OF AGGREGATE TYPE ON COMPRESSIVE STRENGTH AND E-MODULUS"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1061-1074. (ACI SP-132)

A number of aggregate types have been combined with high strength binders in order to evaluate the impact of the aggregate strength on concrete compressive strength. The significance of the aggregate strength has been compared with the effect of the cement type and the use of silica fume. According to the obtained results, the impact of the aggregate strength on the strength of high strength concrete is limited, compared to the impact of the binder type, while the differences in E-moduli between the different aggregate types is fully reflected in the concrete E-moduli. This contradiction is explained by a hypothesis based on stress concentrations due to the difference in rigidity between the binder and the aggregates.

3507
Lloyd, N. A. and Rangan, B. V.
"HIGH STRENGTH CONCRETE: A REVIEW"
Research Report No. 1/93, School of Civil Engineering, Curtin University of Technology, Perth, Western Australia, Jan 1993, 132 pp.

This report covers the constituents of high-strength concrete, properties of the fresh concrete, structural design properties and application of high-strength concrete. In addition, research needs and possible future research are highlighted. Materials for the report has come from recently published research findings throughout the world.

3508
Lopez, W. and Gonzalez, J. A.
"INFLUENCE OF THE DEGREE OF PORE SATURATION ON THE RESISTIVITY OF CONCRETE AND THE CORROSION RATE OF STEEL REINFORCEMENT"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 368-376.

Quantitative relations between the corrosion rate of reinforcements and the degree of pore saturation (PS) and resistivity ( ) of mortars without Cl- and with 2% Cl- were obtained. The mortar specimens were cured in a water for chamber before the final exposure at 50 degree C and 50% relative humidity (RH). The electrolyte supply was found to determine the mortar resistivity which varies over a wide range (5 x 103 - 5 x 107 cm) and this in turn influences the corrosion rate of the reinforcements. There is a critical practical PS value that results in a mortar resistivity of 105 cm, below which the corrosion rate values are too small to pose any durability problems. Below the critical PS value, the resistivity of the mortar prevents active state corrosion of reinforcements as effectively as passivating layers of steel in mortars without Cl-.

3509
Luther, M. D.
"SILICA FUME (MICROSILICA) CONCRETE IN BRIDGES"
Concrete International, Apr 1993, Vol. 15, No. 4, pp 29-33.

It is noted that in the United States, SFC (silica fume concrete) has been used in more than 190 bridges, and is fast becoming an established material for bridge construction in Europe. This article describes the form of silica fume. The performance features of SFC and other silica fume modified materials are tabulated. SFC mix proportions, and its placing, finishing, and curing are described, as well as its performance. The low permeability and high electrical resistivity of SFC make its use desirable in bridges to better protect embedded reinforcing steel from corrosion. Other benefits include improved durability, high strength, high-early strength, abrasion resistance and improved bond. It is noted that best results occur when bonding grouts are used with overlay concrete, when water is prevented from prematurely evaporating from the concrete, and when the concrete is water cured.

3510
MacGregor, J. G.
"CANADIAN NETWORK OF CENTRES OF EXCELLENCE ON HIGH-PERFORMANCE CONCRETE"
Concrete International, Feb 1993, Vol. 15, No. 2, pp 60-61.

The Canadian Network of Centres of Excellence (NCE) on High-Performance Concrete comprises 11 principal researchers from seven universities and two consulting engineering firms spread across Canada from Quebec to British Columbia. The research program is divided into three projects -- namely, the development of a new generation of building materials, the design of high-strength concrete structures, and the development of new products based on HPC and new techniques for construction using it.

3511
Maher, M. H. and Nawy, E. G.
"EVALUATION OF FIBER OPTIC BRAGG GRATING STRAIN SENSOR IN HIGH STRENGTH CONCRETE BEAMS"
in Applications of Fiber Optic Sensors in Engineering Mechanics: a Collection of State-of-the-Art Papers in the Applications of Fiber Optic Technologies to Civil Structures; Ed. by Farhad Ansari; ASCE, New York, 1993, pp 120-133.

Fiber Optic Bragg Grating (FOBG) sensor was tested on large scale concrete beams for measurement of strain due to flexural deformations. The sensor, which has recently been developed at the United Technologies Research Center (UTRC) for monitoring of strain in structural composites, was tested with the objective of direct and quantitative measurement of load induced strain. The experimental results showed that the FOBG sensor can be used for monitoring strain in concrete structures through remote sensing. A number of issues such as sensor bonding to structure, sensor placement, sensor arrangement (embedded or exposed), and instrumentation on large concrete structures were addressed in this study.

3512
Malek, R. I. A. and Roy, D. M.
"EFFECT OF SUPERPLASTICIZERS ON THE WORKABILITY OF CONCRETE AS EVIDENT FROM APPARENT VISCOSITY, YIELD STRESS AND ZETA-POTENTIAL"
Materials Research Society Symposium Proceedings, 1993, Vol. 289, pp 191-197.

Modern concrete technology projections indicate a great expansion in low-cost and time efficient construction. Mixture designers will likely be more concerned with the developments in concrete making materials. Among those is the effective use of chemical admixtures and superplasticizers which will lower the water to cement ratio but will still give a dense workable concrete. An investigation of the workability of fresh concrete and the effect of superplasticizers should, therefore, constitute an essential part of modern concrete durability studies. In this paper we report part of the work on rheological properties of fresh concrete. Various concrete samples covering a range of compositions that are commonly used for highway pavements are prepared. The proportioning parameters are: cement content, aggregate size, gradation and sphericity-roundness, and water and superplasticizer contents. The individual solid ingredients were characterized and the fresh concrete properties were assessed by the slump, two-point workability (Tattersall's) apparatus, air pressure and unit weight methods. The effects of superplasticizer on the apparent viscosity and yield stress of concrete are discussed and the relevance of the findings for field applications (handling of fresh concrete) are discussed. Also discussed are the implications for microstructural development.

3513
Marosszeky, M., Chew, M., Arioka, M., and Peck, P.
"TEXTILE FORM METHOD TO IMPROVE CONCRETE DURABILITY"
Concrete International, Nov 1993, Vol. 15, No. 11, pp 37-42.

The textile form method developed in Japan to reduce air bubbles or blow holes generated on sloping concrete surfaces is described. It uses conventional plywood panels that have been perforated with small holes and are covered with a high tensile strength, high alkaline resistant small ductile synthetic textile. The details of the method are described, and the performance improvements over concrete cast with conventional plywood forms are listed. This study attempted to substantiate overseas research findings concerning the durability, performance and surface quality, using Australian concretes, and whether the extra cost incurred can be offset by the improved durability. The tests and their results are described, and the cost benefit analysis is discussed.

3514
Marzouk, H. and Chen, Z. W.
"NONLINEAR ANALYSIS OF NORMAL- AND HIGH-STRENGTH CONCRETE SLABS"
Canadian Journal of Civil Engineering, Aug 1993, Vol. 20, No. 4, pp 696-707.

Proper simulation of the post-cracking behavior of concrete has a significant effect on the nonlinear finite element response of concrete slabs supported on 4 edges and loaded axially and transversely. Cracking and post-cracking behavior of concrete which includes aggregate interlock, dowel action, and tension-stiffening effects is specially crucial for any nonlinear concrete analysis. The post-cracking behavior and the fracture energy properties of high-strength concrete are different from those of normal-strength concrete. This can be realized by comparing the experimental testing results of plain normal- and high- strength concrete. The experimental results of testing plain high-strength concrete in direct tension indicated that the total area under the stress - crack width curve in tension is different from that of normal-strength concrete. A suitable softening and tension-stiffening model is recommended for high-strength concrete; other existing models suitable for normal-strength concrete are discussed. The proposed post-cracking behavior models are implemented in a nonlinear finite element program in order to check results. Finally, a parametric study was made to provide more insight into the behavior of high-strength concrete slabs subjected to combined uniaxial in-plane loads and lateral loads. The effects of the magnitude of in-plane load and the sequence of loading on the structural behavior of such slabs are examined.

3515
Mather, B.
"CONCRETE IN TRANSPORTATION: DESIRED PERFORMANCE AND SPECIFICATIONS"
Transportation Research Record, 1993, No. 1382, pp 5-10.

To obtain the desired performance of concrete in transportation, it is necessary to decide the tolerable and intolerable levels of imperfection, understand what causes intolerable imperfections, evaluate the environment in which the concrete is to serve, use properly prepared concrete specifications for the environment that they are intended for, and finally to ascertain that both the contractor's quality control and the owner's quality assurance systems work to ensure that the concrete produced is as specified.

3516
Miao, B., Aitcin, P-C., Cook, W. D., and Mitchell, D.
"INFLUENCE OF CONCRETE STRENGTH ON IN SITU PROPERTIES OF LARGE COLUMNS"
ACI Materials Journal, May-Jun 1993, Vol. 90, No. 3, pp 214-219.

This study investigates the influence of concrete strength on the measured core compressive and tensile strengths of 3 large columns. The lower strength concrete had larger variability in strength than the higher strength concretes. Measured compressive and tensile strengths from the core specimens were found to be between those strengths measured on cylinders cured in air and those cured in water. The permeability was found to decrease significantly with the increased matrix densities of the higher strength concretes.

3517
Miao, B., Chaallal, O., Perraton, D., and Aitcin, P-C.
"ON-SITE EARLY-AGE MONITORING OF HIGH-PERFORMANCE CONCRETE COLUMNS"
ACI Materials Journal, Sep-Oct 1993, Vol. 90, No. 5, pp 415-420.

The results are presented of on-site temperature and strain monitoring of columns made with high-performance concrete at an early age. Two pairs of circular reinforced concrete columns made of 80 MPa concrete were instrumented with the aid of vibrating wire extensometers. One of these columns was active. The other was never loaded and was used as a mock column. The strains in the concrete and in the embedded steel along with the internal temperatures as well as the ambient temperature and relative humidity, were recorded. The results show that the concrete is subjected to strains and stresses during the first 3 days due to thermal gradient and different thermal behavior of concrete and steel. It was found also that the coefficient of thermal expansion of early-age concrete is substantially higher than that of hardened concrete.

3518
"MINERAL ADMIXTURES"
Compilation 22, American Concrete Institute, Detroit, MI, 1993, 72 pp.

This American Concrete Institute (ACI) Compilations combine material previously published in ACI periodicals to provide compact and ready reference on the subject of mineral admixtures.

3519
Mitchell, D., Cook, W. D., Khan, A. A., and Tham, T.
"INFLUENCE OF HIGH STRENGTH CONCRETE ON TRANSFER AND DEVELOPMENT LENGTH OF PRETENSIONING STRAND"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 52-66.

Twenty-two precast, pretensioned concrete beam specimens were fabricated and tested to determine the influence of concrete strength on the transfer length and development length of pretensioning strand. The main variables were the concrete compressive strength, varying from 4500 to 12,900 psi (31 to 89 MPa), and the strand diameter, which included 3/8, 1/2 and 0.62 in. (9.5, 12.7 and 15.7 mm) diameters. Expressions are given for the influence of concrete strength on the transfer length and development length of pretensioning strand.

3520
Mokhtarzadeh, A. and French, C. W.
"BIBLIOGRAPHY ON HIGH STRENGTH CONCRETE"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 130-137.

This bibiliography contains 205 unannotated citations on high strength concrete pertaining particularly to precast and prestressed concrete.

3521
Naaman, A. E. and Hamza, A. M.
"PRESTRESS LOSSES IN PARTIALLY PRESTRESSED HIGH STRENGTH CONCRETE BEAMS"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 98-114.

The results of a comprehensive parametric study on prestress losses in prestressed and partially prestressed high strength concrete beams are reported. Attention is focused on the influence of the partial prestressing ratio (from no prestressing to full prestressing) and the compressive strength of concrete, from 6 ksi (41 MPa) up to 10 ksi (69 MPa). Different beam cross sections, representing building and bridge girders with various spans and spacings, were studied. Additional parameters investigated include the strength and type of prestressing steel (stress-relieved of low- relaxation), the yield strength of reinforcing steel, the relative humidity of the environment and curing conditions (steam- or moist-curing). Time-dependent prestress losses were computed through an accurate time-step analysis procedure, which was implemented in a computer program. Conclusions and recommendations are drawn for use in design practice. The results are applicable to pretensioned as well as post-tensioned members. Proposed design recommendations are suggested to replace current lump sum design tables suggested in the AASHTO Specifications and the ACI 343R-88 report on analysis and design of reinforced concrete bridge structures.

3522
Nakamura, N., Sakai, M., and Swamy, R. N.
"EFFECT OF SLAG FINENESS ON THE DEVELOPMENT OF CONCRETE STRENGTH AND MICROSTRUCTURE"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1343-1366.

(ACI SP-132)

This paper presents test data on the development of the microstructural properties of concrete containing 50% replacement of cement by ground granulated blast furnace slag of varying fineness. The following characteristics and properties were investigated: pore structure; hydration and rate of heat evolution; microstructure by scanning electron microscopy and water permeability. It is shown that the use of very fine slag of about 1200 sq m/kg specific surface area results in accelerated hydration, high early strength of 30 to 50 MPa at 3 days, high 28-day cylinder compressive strength of 100 to 110 MPa, very low total pore volume and fine pore sizes, a highly densified microstructure and very low water permeability diffusion coefficient.

3523
Nasser, K. W. and Lai, P. S. H.
"RESISTANCE OF FLY ASH CONCRETE TO FREEZING AND THAWING"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 1, pp 205-226. (ACI SP-132)

A study was made of the effects of Saskatchewan lignite fly ash on the resistance of concrete to freezing and thawing. The results show that the use of high percentages of fly ash in concrete reduced its resistance to freezing and thawing even though it contained about 6% air and was cured in water for 80 days. Concrete containing 20% fly ash gave satisfactory performance provided its air content and strength were comparable to control concrete which contained no fly ash. The decrease in resistance of fly ash concrete to freezing and thawing may be due to the slow migration of portlandite and ettringite crystals from the dense C-S-H zones to the air voids. Concrete with fly ash was less susceptible to the migration of portlandite, but its air voids contained more fibrous hydrates which may have led to an increase in the paste porosity.

3524
"NON-DESTRUCTIVE TESTING IN CIVIL ENGINEERING"
Proceedings of an International Conference, Organised by the British Institute of Non-Destructive Testing, and Others, held 14-16 April 1993, University of Liverpool; Ed. by J. H. Bungey; Northampton, The British Institute of NDT, 1993, 2 vols.

Non-destructive testing (NDT) is widely used in civil engineering as part of routine quality control and maintenance procedures. NDT in this conference applies to buildings, bridges and similar structures made from concrete and masory, and to highway pavements. The papers reflect current concerns relating to the integrity of construction and durability performance, and encompass recent research into the use of non-destructive techniques to assist assessment of these properties. The major subject areas covered include sub-surface radar, concrete permeability and durability assessment, and corrosion assessment of reinforcing steel in concrete. Other subjects covered include concrete strength assessment, integrity and ultrasonic testing of structural concrete and masonry as well as testing of roads and pavements. Cover measurement of steel embedded in concrete is also included, together with recent developments in the use of thermography.

3525
Ozyildirim, C.
"DURABILITY OF CONCRETE BRIDGES IN VIRGINIA"
Structural Engineering in Natural Hazards Mitigation, Proceedings of Papers Presented at the Structures Congress '93, held April 19-21, 1993, Irvine, CA; Ed. by A. H-S. Ang and R. Villaverde; ASCE, New York, 1993, pp 996-1001.

This paper discusses four major types of deterioration found in concrete bridges: corrosion of the reinforcement, alkali-aggregate reactivity, freeze-thaw deterioration, and attack by sulfates. These types of deterioration are caused by improper matching of ingredients and environmental conditions and poor construction practices. For each type, the mechanism of deterioration and the measures taken to prevent the deterioration are discussed.

3526
Ozyildirim, C.
"A FIELD INVESTIGATION OF A CONCRETE OVERLAY CONTAINING SILICA FUME ON ROUTE 50 OVER OPEQUON CREEK"
Final Report, Virginia Transportation Research Council, Charlottesville, VA, 1993, 22 pp. (FHWA-VA-93/R15; VTRC-93-R15; PB94-113412)

This study evaluated concretes containing silica fume for use in overlays as a suitable alternative to the widely used latex-modified concrete (LMC). A two-lane, four-span bridge deck was overlaid with concrete containing silica fume at 7% or 10% by mass of the portland cement as an additional cementitious material. The results of laboratory tests on field concretes containing silica fume were satisfactory. Silica fume concrete (SFC) bonds well with the base concrete and has very low permeability, high strength, and satisfactory freeze-thaw resistance. In the field, over the 5-year evaluation period, cracking and increases in half-cell potentials and chloride content indicated a tendency to corrosion. However, such increases are also evidenced with LMC overlays. Thus, the results indicate that SFC can be effectively used in thin overlays as an alternative to LMC. SFC, as LMC, is prone to plastic shrinkage; therefore, immediate and proper curing must be provided to avoid the shrinkage cracking that can occur under adverse curing conditions.

3527
Ozyildirim, C.
"HIGH-PERFORMANCE CONCRETE FOR TRANSPORTATION STRUCTURES"
Concrete International, Jan 1993, Vol. 15, No. 1, pp 33-38.

When bridges and pavements are repaired or rebuilt, lane closure time should be minimized to increase safety and reduce costs and inconvenience for the traveling public. To provide a short lane closure time, special concretes are needed that attain an appropriate strength more rapidly than is possible with conventional concretes. The research reviewed in this paper demonstrates the usefulness of special concretes to provide performance and placement advantages not attainable with conventional concretes. The special concretes discussed are those containing slag, those with pozzolanic additions (silica fume or fly ash), latex-modified concrete, concretes made with Pyrament-blended cement, and portland cement with a low water-cement ratio for fast-track construction. Field applications and supporting laboratory investigations are reported that document the characteristics and superior performance levels of these special concretes.

3528
Patel, N. P. and Brach, J. R.
"ATLANTA TRANSIT STRUCTURES"
Concrete International, Feb 1993, Vol. 15, No. 2, pp 40-44.

The Metropolitan Atlanta Rapid Transit Authority's (MARTA) policy is to have a unique design for each station on its 32-mile, 29-station transit system. The policy has provided challenge and opportunity for designers to choose the material that best satisfies the requirements of durability, economy, and ease of maintenance, as well as aesthetic appearance. This article describes some notable examples of concrete use in the aerial structures, stations, special applications and artwork in MARTA. The aerial structures of MARTA over Lee Street had to satisfy alignment constraints and resulted in a 5-span, continuous structure with span lengths varying from 83 ft to 119 ft-6 in. The station roof at the Five Points Station, the hub of the MARTA system is described, as well as the Dorville Station roof canopy. Special applications described here include the in-service replacement of 3 piers of the East Line aerial structure. MARTA's policy to provide an art program in every station is noted.

3529
Petersen, C. G., Dahlblom, O., and Worters, P.
"BOND-TEST OF CONCRETE AND OVERLAYS"
in NDT in Civil Engineering, Proceedings of the British Institute of Non-Destructive Testing International Conference, April 14-16, 1993, University of Liverpool, UK; Ed. by J. H. Bungey; British Institute of NDT, Northampton, 1993, Vol. 1, pp 367-378.

The Bond-Test system developed in Denmark is presented. A testing case illustrates its use compared to incorrect testing of the adhesion strength. A finite element analysis is applied for a normal and a high strength concrete to compare the theoretical uniaxial tensile strength with the strength measured by the Bond-Test performed at the surface and with a drill depth of the partial coring at 75 mm. The effect of the drill depth is further investigated in an experimental program for two types of concrete mixes. The Bond-Tests are compared to tensile strength of drilled-out cores and to compressive strength measured by the Lok-Test and the Capo-Test. The results are compared to other experimental findings.

3530
Pigeon, M., Garnier, F., Pleau, R., and Aitcin, P-C.
"INFLUENCE OF DRYING ON THE CHLORIDE ION PERMEABILITY OF HPC"
Concrete International, Feb 1993, Vol. 15, No. 2, pp 65-69.

Tests are described that were performed to obtain basic information on the influence of drying on the resistance of HPC (high performance concrete) to the penetration of chloride ions. To analyze the performance of a wide range of concretes from very high performance to normal concretes, 13 basic mixtures were prepared using 4 different hydraulic binders at 3 water-cementitious material ratios. The specimens prepared from the 13 basic mixtures were dried at 3 different temperatures. The details of the tests are described, and the results are presented and analyzed. It was found that it was possible with the use of silica fume and water- cementitious material ratios of 0.25 or less, to make high-performance concretes that are extremely resistant to the internal damage that can result from drying, even at 110 deg C. It is thus most probable that, under natural exposure conditions, the resistance to the penetration of chloride ions of these concretes will decrease significantly with time, unless they are not adequately protected against the effect of freezing and thawing cycles.

3531
Pistilli, M. F. and Willems, T.
"EVALUATION OF CYLINDER SIZE AND CAPPING METHOD IN COMPRESSION STRENGTH TESTING OF CONCRETE"
Cement, Concrete and Aggregates, Summer 1993, Vol. 15, No. 1, pp 59-69.

Sulfur caps were compared with unbonded polymer pads in compressive strength testing of concrete within the strength range 3,000 to 18,000 psi (20.7 to 124.2 MPa). A less extensive study, still in progress, compares polymer pads with ground surfaces and lapped surfaces within the range of 13,000 to nearly 20,000 psi (89.7 to 138.0 MPa).

3532
"PUTTING NEW HIGHWAY TECHNOLOGY ON THE ROAD: SHRP IMPLEMENTATION PROGRAM"
U. S. Dept. of Transportation, Federal Highway Administration, Washington, D. C., 1993, 16 pp. (FHWA/SA-93-081)

This booklet briefly describes the Strategic Highway Research Program (SHRP) Implementation Program, then describes the following SHRP products: high-performance asphalt; chloride corrosion of bridges - diagnostic tools and repair manuals; technical guidance, tests, and equipment for producing better-performance concrete; spin-off products to help improve pavement management; improved maintenance equipment and techniques, including preventive maintenance treatments, methods for surveying subsurface conditions, and manuals for surface repair; winter weather operations management techniques and improved snowplows and snow fences; and work zone safety devices. The booklet concludes with comments on the challenge to put these products to use.

3533
Rocole, L.
"SILICA-FUME CONCRETE PROVES TO BE AN ECONOMICAL ALTERNATIVE"
Aberdeen's Concrete Construction, Jun 1993, Vol. 38, No. 6, pp 441-442.

When Milwaukee's General Mitchell Airport Authority decided to build a 600,000 sq. ft., 2300-car parking structure, one of the bid requirements called for separate proposals for silica-fume concrete and a traffic membrane. In a bid submitted by a Milwaukee contractor, silica-fume concrete was less than half the cost of a traffic membrane and offered several advantages. One of the main benefits of silica fume is increased strength. Silica fume is 100 times finer than the cement grains in conventional concrete. This allows it to react more efficiently and make further products of hydration, which fill the capillaries between cement grains, making the concrete more dense. This increased density not only makes concrete stronger but also makes it less susceptible to chloride-induced corrosion.

3534
Rogers, C. A.
"ALKALI-AGGREGATE REACTIVITY IN CANADA"
Cement and Concrete Composites, 1993, Vol. 15, No. 1-2, pp 13-19.

In Canada, three types of alkali-aggregate reaction in Portland cement concrete are recognized. Each type is evaluated using different tests. Corrective measures such as the use of low-alkali cement, lower cement contents, or pozzolans are seldom used with reactive aggregates. Beneficiation or selective extraction is used with some reactive aggregates. Work is being conducted on multilaboratory study of existing tests and new, rapid tests.

3535
Roller, J. J., Martin, B. T., Russell, H. G., and Bruce, R. N., Jr.
"PERFORMANCE OF PRESTRESSED HIGH STRENGTH CONCRETE BRIDGE GIRDERS"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 34-45.

An experimental evaluation of pretensioned, prestressed bridge girders manufactured using high strength concrete was conducted. Three 70 ft (21.3 m) long, 54 in. (1372 mm) deep bulb-tee girders were fabricated and tested. The design concrete compressive strength for the girders was 10,000 psi (69 MPa). A deck slab was cast on two of the three bridge girder test specimens. One of the two girders with a deck slab and the girder without a deck slab were tested to evaluate flexure and shear strength. The second girder with a deck slab was used to determine long-term behavior under full design dead load over an 18-month period. Results of this experimental evaluation indicate that use of high strength concrete for prestressed bridge girders is both feasible and beneficial. The two girders tested in flexure and shear performed adequately with respect to both design and specification requirements. Interim results from the girder currently being monitored to determine long-term behavior have indicated prestress losses that are significantly less than expected. Measured camber correlated well with deflections calculated using the measured prestress losses and conventional analyses.

3536
Roy, D. M. and Idorn, G. M.
"CONCRETE MICROSTRUCTURE"
Final Report, Materials Research Laboratory, Pennsylvania State University,1993, xv, 179 pp. (SHRP-C-340; PB94-182581)

-

Durability of concrete in highway systems is a problem of national concern. To understand better the mechanisms which intrinsically control durability in highway concrete, it is necessary to define and understand those factors which impact concrete microstructure which is a consequence of both its formulation and the processes taking place during mixing, placing and curing. This report documents an investigation of those variables which control cement hydration and consequent microstructural development.

3537
Russell, B. W. and Burns, N. H.
"STATIC AND FATIGUE BEHAVIOR OF PRETENSIONED COMPOSITE BRIDGE GIRDERS MADE WITH HIGH STRENGTH CONCRETE"
PCI Journal, May-Jun 1993, Vol. 38, No. 3, pp 116-128.

Three full-sized Texas Type C pretensioned concrete girders with 10,000 psi (69 MPa) concrete formed composite girders by the addition of deck slabs with 6000 psi (41 MPa) concrete. Each girder was tested in flexure by a combination of static overloads and repeated service loads. The number of repeated loads varied from a minimum of 225,000 cycles to a maximum of 700,000 cycles. Two of the pretensioned girders contained debonded strands at the ends of the 48 ft (14.6 m) simple span while the third companion girder contained draped strands. The tests were performed with two objectives: 1) to observe the behavior of pretensioned girders made with high strength concrete, and 2) to compare the behavior of pretensioned girders made with debonded strands to behavior of girders containing strands. Special attention was given to the adverse effect of cracking on the anchorage of pretensioned strands. Both horizontal and vertical mild shear reinforcement was placed within the webs at the end regions of the girders, which prevented the propagation of web shear cracks, thereby ensuring the integrity of strand anchorages. Based on these tests, the behavior of pretensioned girders made with high strength concrete is shown to be adequately predicted by current design procedures, and the design and use of pretensioned high strength concrete can be considered safe and reliable. Additionally, the design of girders with debonded strands is shown to be a viable alternative to using fully bonded strands.

3538
Russell, H. G.
"LONG-TERM PROPERTIES OF HIGH-STRENGTH CONCRETES"
Concrete Technology Today, Portland Cement Association, Skokie, IL, November 1993, Vol. 14, No. 3, pp 1-4.

In 1975 when Chicago's Water Tower Place was built, high strength concrete with design compressive strengths in excess of 6000 psi (41 MPa) was used in the columns and shear walls of the building up to 55th level. As part of a research project sponsored by the National Science Foundation and the Portland Cement Association, samples of concrete were obtained at the site and used for measurements of material properties. A similar but smaller project was undertaken during the casting of two experimental columns in the Chicago Mercantile Exchange. These columns represented the first usage in the Chicago area of concrete with a design compressive strength of 14,000 psi (97 MPa). Measurement of creep and shrinkage of the concrete taken from the Mercantile Exchange was also conducted. After eighteen years of measurements, it was decided to terminate the measurement program and use the specimens to determine other properties of the concretes and compare the test results with previously reported results. The test results on the 18-year old specimens have confirmed the properties of the concretes measured at earlier ages.

3539
Saetta, A. V., Schrefler, B. A., and Vitaliani, R. V.
"CARBONATION OF CONCRETE AND THE MECHANISM OF MOISTURE, HEAT AND CARBON DIOXIDE FLOW THROUGH POROUS MATERIALS"
Cement and Concrete Research, Jul 1993, Vol. 23, No. 4, pp 761-772.

The governing equations of moisture, heat and carbon dioxide flows through concrete within the framework of a distributed parameter model are described. The coupling terms and non-linearity of the problem are taken into account and a numerical procedure based on the finite element method is developed to solve the set of equations. The influence of relative humidity and temperature is investigated and typical results are presented. Comparisons with experimental tests are also carried out and one example is presented in detail in order to show the reliability and the effectiveness of the proposed numerical model.

3540
Sanjayan, G. and Stocks, L. J.
"SPALLING OF HIGH-STRENGTH SILICA FUME CONCRETE IN FIRE"
ACI Materials Journal, Mar-Apr 1993, Vol. 90, No. 2, pp 170-173.

A fire test was conducted on 2 specimens, one of high strength concrete and the other of normal strength concrete. At the time of test, specimen strengths were 27 and 105 MPa respectively. Details of the beam slabs and the specimens are described. The specimens were tested after 3.5 months of drying in an indoor environment. Explosive spalling was observed in high strength concrete while no spalling occurred in the normal strength concrete. However, spalling in the high strength concrete was confined to a region with 75 mm cover to steel. It was also found that the length of the path for moisture to escape also has a significant influence on the spalling of high-strength concrete.

3541
Sarkar, S. L.
"PERFORMANCE OF A HIGH-STRENGTH FIELD CONCRETE AT 7 YEARS"
Concrete International, Jan 1993, Vol. 15, No. 1, pp 39-42.

In August 1984, two experimental high-performance concrete columns were cast in the basement of a 26-story building in Montreal, Canada. These columns stand out as being among the first examples of high-strength field concrete containing silica fume in North America. Although both columns were identical in geometry, composition and structure, only one was load-bearing. Three investigations over the last seven years have focused on the unloaded or mock column. Compressive strength testing and microstructural examination of the concrete and its aggregates after seven years clearly demonstrate that this column remains in extremely good state. The paste has retained the dense C-S-H. Only a small development of CH crystals and ettringite needles was noticed. Paste-aggregate bonding is as strong as it was at two and four years. Chloride permeability remains very low. Crack width and frequency have remained static since 1988.

3542
Sarkar, S. L. and Beaulieu, J.
"MICROSTRUCTURAL EVALUATION OF A CONCRETE OVERPASS SYSTEM DURING REHABILITATION"
Cement and Concrete Research, Jul 1993, Vol. 23, No. 4, pp 874-884.

Concrete durability and deterioration are so closely related that they must be considered together. Microstructural characterization, which has received limited attention in determining concrete durability, is used to determine the parameters of concrete overpass deterioration in a major highway in Montreal, Canada. The highway crosses an important urban area and has been subjected to high concentrations of deicer salts for 25 years. Samples of both concrete and rebar corrosion were examined by SEM/EDXA, XRDA, mercury porosimetry, and optical microscopy. A number of interesting features were noted, including a high ettringite content at the paste-aggregate interface and the presence of unusual deterioration products, such as thenardite and trona. Deicer salts and sulfates from vehicle exhaust are suggested as possible sources.

3543
Schemmel, J. J. and Leming, M. L.
"USE OF HIGH-PERFORMANCE CONCRETE FOR RAPID HIGHWAY PAVEMENT REPAIRS: AN OVERVIEW OF FIVE FIELD INSTALLATIONS"
Transportation Research Record, 1993, No. 1382, pp 20-25.

The Strategic Highway Research Program awarded a contract to investigate the use of high-performance concrete in highway pavements and bridge structures. One of the primary objectives of this research effort was "to provide recommendations and guidelines for using these concretes in highway applications." As a result, the research program included an examination of the field performance of high-performance concrete. Field test sections were constructed in Arkansas, Illinois, Nebraska, New York, and North Carolina. Except in North Carolina, the installations consisted of full-depth and lane-width patches. Traffic and environmental exposure conditions differ for all locations. Each batch of concrete brought to a site was tested for its fresh concrete properties. Specimens were cast for long-term testing too. The field installations will continue to be monitored for at least 18 months after construction. Details about site locations, the type of concrete used, the construction process, and the testing plan are provided, and the most important lessons learned from the field trials are discussed.

3544
Schiessl, P. and Haerdtl, R.
"ACCOUNTABILITY OF HARD COAL FLY ASH IN CONCRETE"
VGB Kraftwerkstechnik, Jul 1993, Vol. 73, No. 7, pp 642-645.

Due to its chemical and physical properties, hard coal fly ash (PFA) makes an active contribution to the properties of concrete. In order to determine quantitatively the level of this contribution and the conversion of the effect of fly ash into practical rules of application, investigations have been undertaken to study the effect of PFA on the compression strength and particularly on the durability of concrete and mortar. A comparison with fly ash free reference concrete shows that it demonstrates equivalent durability properties in respect of carbonization and resistance to frost.

3545
Schlorholtz, S. and Bergeson, K. L.
"EVALUATION OF THE CHEMICAL DURABILITY OF IOWA FLY ASH CONCRETES"
Final Report, Engineering Research Institute, Iowa State University, Ames, IA, 1993, 1 Vol. (various pagings); (ISU-ERI-Ames 93-411)

The major objective of this research project was to investigate how Iowa fly ashes influenced the chemical durability of portland cement based materials. Chemical durability has become an area of uncertainty because of the winter application of deicer salts (rock salts) that contain a significant amount of sulfate impurities. The sulfate durability testing program consisted of monitoring portland cement-fly ash paste, mortar and concrete test specimens that had been subjected to aqueous solutions containing various concentrations of salts (both sulfate and chloride). The paste and mortar specimens were monitored for length as a function of time. The concrete test specimens were monitored for length, relative dynamic modulus and mass as a function of time. The alkali-aggregate reactivity testing program consisted of monitoring the expansion of ASTM C311 mortar bar specimens that contained three different aggregates (Pyrex glass, Oreapolis and standard Ottawa sand). The results of the sulfate durability study indicated that the paste and concrete test specimens tended to exhibit surface spalling but only very slow expansive tendencies. This suggested that the permeability of the test specimens was controlling the rate of deterioration. Concrete specimens are still being monitored because the majority of the test specimens has expanded less than 0.05%; hence, this makes it difficult to estimate the service life of the concrete test specimens or to quantify the performance of the different fly ashes that were used in the study. The results of the mortar bar studies indicated that the chemical composition of the various fly ashes did have an influence on their sulfate resistance. Typically, Clinton and Louisa fly ashes performed the best, followed by the Ottumwa, Neal 4 and then Council Bluffs fly ashes. Council Bluffs fly ash was the only fly ash that consistently reduced the sulfate resistance of the many different mortar specimens that were investigated during this study. None of the trends that were observed in the mortar bar studies have yet become evident in the concrete phase of this project. The results of the alkali-aggregate study indicated that the Oreapolis aggregate is not very sensitive to alkali attack. Two of the fly ashes, Council Bluffs and Ottumwa, tended to increase the expansion of mortar bar specimens that contained the Oreapolis aggregate. However, it was not clear if the additional expansion was due to the alkali content of the fly ash, the periclase content of the fly ash or the cristobalite content of the fly ash, since all three of these factors have been found to influence the test results.

3546
Schlorholtz, S. and Bergeson, K. L.
"INVESTIGATION OF RAPID THERMAL ANALYSIS PROCEDURES FOR PREDICTION OF THE SERVICE LIFE OF PCCP CARBONATE COARSE AGGREGATE"
Final Report, Engineering Research Institute, Iowa State University, Ames, IA, 1993, 1 Vol. (various pagings); (ISU-ERI-Ames 93-412)

The major objective of this research project was to use thermal analysis techniques in conjunction with x-ray analysis methods to identify and explain chemical reactions that promote aggregate related deterioration in portland cement concrete. Twenty-two different carbonate aggregate samples were subjected to a chemical testing scheme that included: bulk chemistry (major, minor and selected trace elements); bulk mineralogy (minor phases concentrated by acid extraction); solid-solution in the major carbonate phases; crystallite size determinations for the major carbonate phases; and a salt treatment study to evaluate the impact of deicer salts. Test results from these different studies were then compared to information that had been obtained using thermogravimetric analysis techniques. Since many of the limestones and dolomites that were used in the study had extensive field service records it was possible to correlate many of the variables with service life. The results of this study have indicated that thermogravimetric analysis can play an important role in categorizing carbonate aggregates. In fact, with modern automated thermal analysis systems it should be possible to utilize such methods on a quality control basis. Strong correlations were found between several of the variables that were monitored in this study. In fact, several of the variables exhibited significant correlations to concrete service life. When the full data set was utilized (n=18), the significant correlations to service life can be summarized as follows (alpha = 5% level): Correlation coefficient, r, = -0.73 for premature TG loss versus service life; Correlation coefficient, r, = 0.74 for relative crystallite size versus service life; Correlation coefficient, r, = 0.53 for ASTM C666 durability factor versus service life; and Correlation coefficient, r, = -0.52 for acid-insoluble residue versus service life. Separation of the carbonate aggregates into their mineralogical categories (i.e., calcites and dolomites) tended to increase the correlation coefficients for some specific variables (r sometimes approached 0.90); however, the reliability of such correlations was questionable because of the small number of samples that were present in this study.

3547
Seehra, S. S., Gupta, S., and Kumar, S.
"RAPID SETTING MAGNESIUM PHOSPHATE CEMENT FOR QUICK REPAIR OF CONCRETE PAVEMENTS - CHARACTERISATION AND DURABILITY ASPECTS"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 254-266.

This paper briefly describes the laboratory and field studies undertaken during the development of Magnesium Phosphate Cement (MPC), and discusses its suitability for use in pavement repair. It also discusses the special considerations that need to be taken into account when using it. Drying shrinkage, abrasion resistance, and durability tests were carried out in the laboratory on mortar cube or bar specimens. Various admixtures were used. The effect of ambient temperature upon setting time was also investigated. The concrete was then used to seal cracks and to repair both shallow and deep potholes in concrete pavements. The results indicate that MPC is a suitable concrete for the speedy repair of highway and airfield pavements. MPC develops 100-200 kg per cubic metre strength within an hour of application. After 4 hours its strength is greater than the 7 day strength of Portland cement concrete. Use of Borax additive increases setting time but reduces early strength. MPC is suitable for use in cold weather and traffic can be allowed over the repaired patches 4-5 hours after the patch has been made.

3548
Sellevold, E. J. and Justnes, H.
"HIGH STRENGTH CONCRETE BINDERS. PART B: NONEVAPORABLE WATER, SELF-DESICCATION AND POROSITY OF CEMENT PASTES WITH AND WITHOUT CONDENSED SILICA FUME"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 891-902. (ACI SP-132)

The decrease in relative humidity during hydration and the chemical shrinkage has been measured for different cement paste compositions. The amount of nonevaporable water per degree of hydration as found by nuclear magnetic resonance (NMR), pore size distribution by mercury intrusion and total porosity to water, have also been determined. The cement pastes were made from portland cement with 0, 8 and 16 % condensed silica fume, and with differing water cement ratios. Details of the study are described, and the results are presented and discussed.

3549
Setunge, S., Attard, M. M., and Darvall, P. Le P.
"ULTIMATE STRENGTH OF CONFINED VERY HIGH-STRENGTH CONCRETES"
ACI Structural Journal, Nov-Dec 1993, Vol. 90, No. 6, pp 632-641.

Results are presented from an experimental investigation into the ultimate strength of concrete under triaxial loading. Several mixes are used with strength ranging from normal strength concrete to very high-strength concrete. Other parameters in the mixes were the use of silica fume and three type of crushed coarse aggregate. A 2-parameter model for the failure envelope for confined concrete was adopted. Empirical expressions for the failure envelope were derived for normal strength concrete and very high-strength concrete with and without silica fume. A simple lower bound expression for the ultimate strength of concrete under confinement is presented for any grade of concrete.

3550
Shin, S-W., Lee, K-S., and Ghosh, S. K.
"HIGH-STRENGTH CONCRETE JOINTS UNDER CYCLIC LOADING"
Structural Engineering in Natural Hazards Mitigation, Proceedings of Papers Presented at the Structures Congress '93, held April 19-21, 1993, Irvine, CA; Ed. by A. H-S. Ang and R. Villaverde; ASCE, New York, 1993, pp 622-627.

This experimental investigation was undertaken to check the validity for high-strength concrete beam-column joints of recommendations made by ACI-ASCE (American Concrete Institute-American Society of Civil Engineers) Committee 352 on Joints and Connections in Monolithic Concrete Structures (1985). The recommendations, concerning the design of joints that are part of the primary system for resisting seismic lateral loads, are based on tests of normal-strength concrete connections with compressive strength fc' ranging between 3500 and 5500 psi (24 and 38 MPa).

3551
Sonebi, M. and Khayat, K. H.
"HIGH PERFORMANCE CONCRETES FOR THE FABRICATION OF PANELS FOR THE REPAIR OF SUBMERGED STRUCTURES"
Canadian Journal of Civil Engineering, Aug 1993, Vol. 20, No. 4, pp 650-659.

The field of repair of submerged hydraulic structures (dams, stilling basins, lock chambers, and so forth) is becoming more and more important given the economic worth of such structures. Damage caused by abrasion can make it difficult to maintain such structures in service. The purpose of the study described in this paper was to develop durable high-performance concretes that can be used for manufacture of board for repair of abrasion-damaged surfaces. The board might also be placed on surfaces already repaired with colloidal concrete poured underwater. Two types of cement (type 30 and type 10) and two high-performance coarse aggregates (granite and dolomitic limestone) were used. The eight concrete mixes developed included a variety of additives and admixtures such as silica fume, steel fibre, latex, and superplasticizer. For precise characterization of the mixes, hydraulic abrasion tests, compressive strength tests, and freeze-thaw cycle resistance tests were performed. In addition, shrinkage, thermal expansion coefficient, and permeability of the concretes were measured; in some cases, the board might be subject to freeze-thaw cycles in structures partially emptied for repair or maintenance. Results show that high- performance concretes with very low water : cement ratio, good workability, and improved freeze-thaw cycle resistance can be manufactured. Concretes made with Type-30 cement, silica fume, and granite or limestone aggregate offer excellent hydraulic abrasion resistance (depth of erosion on the order of 1 mm after 72 h), compressive strength greater than 115 MPa after 91 days, and a freeze-thaw durability factor of more than 100%. In French.

3552
Soroushian, P. and Tlili, A.
"EFFECTS OF LATEX MODIFICATION ON THE FAILURE MECHANISM AND ENGINEERING PROPERTIES OF CONCRETE"
ASTM Special Technical Publication, 1993, No. 1176, pp 104-119.

Effects of styrene-butadiene latex modification on the failure mechanism, mechanical, physical, and durability characteristics of concrete materials were studied. Test results on the impact resistance and flexural strength and toughness to concrete were used to quantify and statistically confirm the positive effects of latex modification on various aspects of the mechanical properties of concrete. Latex modification was also observed to substantially reduce the water absorption capacity of concrete.

3553
Sprinkel, M. M.
"POLYMER CONCRETE BRIDGE OVERLAYS"
Transportation Research Record, 1993, No. 1392, pp 107-116.

The current status of polymer concrete overlays for concrete bridge decks is presented. The physical and mechanical properties of the concretes used, the application methods, and the performance of the overlays are described. The economics, government support, market size, and outlook for overlays are also described. It is shown that polymer overlays constructed with epoxy, methacrylate, and polyester styrene binders and graded silica and basalt aggregates can provide skid resistance and protection against intrusion by chloride ions for 15 to 20 years and are an economical technique for extending the life of concrete decks reinforced with black steel, particularly when overlays must be constructed during off-peak traffic periods to minimize inconvenience to motorists. The outlook for polymer overlays has never been better.

3554
Sprinkel, M. M., Sellars, A. R., and Weyers, R. E.
"CONCRETE BRIDGE PROTECTION AND REHABILITATION: CHEMICAL AND PHYSICAL TECHNIQUES. RAPID CONCRETE BRIDGE DECK PROTECTION, REPAIR AND REHABILITATION"
Final Report, Virginia Transportation Research Council, Charlottesville, VA, 1993, 119 pp. (FHWA/VA-94/R12; VTRC-94-R12; SHRP-S-344; PB94-120300)

This report presents the rapid methods used by state highway agencies for the protection, repair and rehabilitation of bridge decks. The report is based on a review of the literature; the responses to questionnaires sent to state departments of transportation, Canadian provinces, selected turnpike and thruway authorities, technology transfer centers, and material suppliers; and the evaluation of 50 bridge decks located in seven states. Polymer overlays, sealers, high-early strength hydraulic cement concrete overlays, and patches are compared for their performance characteristics and service life.

3555
Sultanov, F. A.
"SUPERPLASTICIZED CEMENT APPLICATIONS IN AZERBAIJAN AND OTHER STATES OF THE FORMER USSR"
Concrete International, Apr 1993, Vol. 15, No. 4, p 48.

The article describes how superplasticized cement products exhibit high strength, rapid strength gain, dense microstructure, and low shrinkage. Powdered or granulated superplasticizers are being used in the states of the former USSR. Superplasticized cements improve grindability, are less sticky, and retain their activity for a relatively long time. They have very low water demand. The latter allows an increase of 1.5 to 2 times in acceptable fineness of the cement. The high activity of such cements permits increased addition of mineral additives during grinding, thus saving up to 30% of clinker. However, it is noted, use of superplasticized cement is not always justified because of its relatively high cost. A more effective use of superplasticized cements is in making coatings on the surface of concrete in hydraulic and land reclamation structures for protection against aggressive environments.

3556
Sun, G-K. and Young, J. F.
"QUANTITATIVE DETERMINATION OF RESIDUAL SILICA FUME IN DSP CEMENT PASTES BY 29-SI NMR"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 480-483.

Silica fume is being increasingly used in concretes to provide high strength and/or durability. Ultra-high strength DSP (densified with fine particles) cement pastes are also attracting greater interest. Since silica fume is an active pozzolan it is of interest to be able to follow its rate of reaction quantitatively. Formerly we have used [1] the dissolution method used by Taylor and Mohan [2] to estimate unreacted fly ash, but the fine particle size of silica fume makes this an unreliable method. More recently 29Si solid state nuclear magnetic resonance (NMR) spectroscopy has been used [3] to portland cement-silica fume combinations. A Q4 peak at- 110 ppm is characteristic of the framework structure of silica fume and should not overlap with other components in the paste. Thus it should be possible to use the area under the peak to quantitatively estimate the amount of unreacted silica fume in the system. Such an analysis was developed [4] using cis (trimethyltriphenylcyclotrisiloxane) as an internal standard. An improved analysis based on this approach using silicon carbide as the internal standard is reported.

3557
Sun, Y. P. and Sakino, K.
"AXIAL BEHAVIOR OF CONFINED HIGH-STRENGTH CONCRETE"
Transactions of the Japan Concrete Insitute, 1993, Vol. 15, pp 463-470.

Experimental study on the axial havior of high-strength concrete confined by circular hoops was carried out. Forty eight circular columns, with diameters of 305 mm and 255 mm, were fabricated and tested under axial loading. High-strength concrete, with compressive strength ranging from 323 kg/cm2 to 1343 kg/cm2, and high-strength circular hoops with yield strength of 11,300 k/cm2 were used to make the test columns. Test results confirmed that the use of high-strength circular hoops can increase the strength and ductility of high-strength concrete. Based on the test results, an empirical model for stress-strain curve of confined high-strength concrete was proposed.

3558
Swamy, R. N. and Wan, R. M.
"USE OF DYNAMIC NONDESTRUCTIVE TEST METHODS TO MONITOR CONCRETE DETERIORATION DUE TO ALKALI-SILICA REACTION"
Cement, Concrete and Aggregates, Summer 1993, Vol. 15, No. 1, pp 32-49.

The use of dynamic nondestructive test methods such as pulse velocity and dynamic modulus to monitor the initiation and progress of concrete deterioration due to alkali-silica reactions (ASR) is described. The tests reported cover a range of parameters: two different types of reactive aggregates: varying environments; concretes without and with mineral admixtures such as fly ash, ground-granulated blast-furnace slag, and silica fume; and concrete beams with and without reinforcement. The results show that both pulse velocity and dynamic modulus are sensitive to material and structural changes arising from ASR and that they can respond reliably to changes prior to first crack, at first crack, and with deterioration over time in concrete both with and without cementitious materials other than portland cement. With engineering judgement, pulse-velocity measurements can be used confidently to assess structural deterioration due to ASR.

3559
Tagnit-Hamou, A. and Aitcin, P-C.
"CEMENT AND SUPERPLASTICIZER COMPATIBILITY"
World Cement, Aug 1993, Vol. 24, No. 8, pp 38-42.

The paper discusses how to select locally the best cement-superplasticizer combination in terms of rheology (slump loss) and strength. It discusses portland cement and water ratios, use of superplasticizers, portland cement reactivity and cement/superplasticizer compatibility. Practical measures are suggested, such as monitoring the quality of the commercial gypsum added, maintenance of the mill's inside temperature within certain norms, and rheological studies with pure water and with admixtures.

3560
Tawfiq, K.
"FATIGUE FRACTURE IN CONCRETE"
Final Report, Department of Civil Engineering, FAMU/FSU College of Engineering,, Tallahassee, FL, 1993, 2 Vols. (FL/DOT/RMC/0623-4068; PB94-188570)

This study investigates the fatigue fracture characteristics of Florida concrete subjected to flexural loading. This type of fatigue loading is very common in concrete pavements and bridge decks. The main objectives of this study were to (1) investigate the effect of several parameters on the fatigue strength of Florida concrete under constant amplitude loading, and (2) obtain a relationship between these parameters and the fatigue life expectancy which was represented by the number of cycles endured. The parameters used in this study included: (1) stress ratio, (2) number of cycles to failure, and (3) material properties depicted by the compressive strength of concrete. Included in the objectives also was the study of the strain accumulation, hysteretic behavior, stiffness degradation, and endurance of concrete mixes subjected to constant amplitude cyclic loading. To facilitate the prediction of the fatigue life expectancy of Florida concrete, four empirical formulas have been suggested. The first three formulas are used for plain concrete elements with pre-existing cracking (notch); the fourth formula can be used to estimate the total fatigue life for uncracked elements (unnotched). Testing results showed that high strength concrete could have about 22% shorter fatigue life than lower strength concrete. This implies that to prolong the fatigue life of a high strength concrete element subjected to 70% loading ratio, the total applied loads should be multiplied by a factor equal to 0.78. The rate of stiffness deterioration at the second stage of cracking was much higher in high strength concrete than in lower strength concrete. This confirms the need for better quality control and assurance when high strength concrete is used in pavement and bridge construction.

3561
Toutlemonde, F.
"DYNAMIC BEHAVIOR OF HIGH PERFORMANCE CONCRETE. STATE OF KNOWLEDGE AND SUGGESTIONS FOR FURTHER RESEARCH"
Bulletin de Liaison des Laboratoires des Ponts et Chaussees, Sep-Oct 1993, No.187, pp 51-60.

Present knowledge of the behaviour of concretes under dynamic stress indicates an increase in strength with rate of stressing; the relationship varying according to whether the rate is intermediate (in which case viscous effects predominate, due to the presence of pore water) or very high (in which case inertial effects predominate and the increase in strength is markedly greater). This analysis can be extended to high performance concretes, thanks to the (very few) tests that have been performed on the latter. The relative increase in strength is generally slight, but the absolute increase seems to be comparable for a given volume of paste. The bonding of high-performance concrete and high adhesion steel appears to be considerably strengthened under dynamic stress. Though many aspects remain to be clarified by further research, it can at least be said that from the point of view of the design of a very high-performance concrete structure which must have high impact strength, what matters most is to avoid brittleness due to failure under shear stress and to take account of a shorter anchorage under dynamic stress. In French.

3562
"THE TRIANON BUILDING, FRANKFURT"
Concrete (London), Mar-Apr 1993, Vol. 27, No. 2, pp 33-34.

The first application of high-strength concrete in Germany to the construction of the 47 story high Trianon building in Frankfurt is described. The building is 186 m high. In section, it has a toothed triangular shape. In fire tests, the proposed 85 N/mm2 concrete samples more than satisfied the 180-minute requirement for high-rise buildings in Germany. A mix was chosen incorporating silica fume and plasticiser.

3563
Ukita, K., Ishii, M., Yamamoto, K., Azuma, K., and Kohno, K.
"PROPERTIES OF HIGH STRENGTH CONCRETE USING CLASSIFIED FLY ASH"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 1, pp 37-52. (ACI SP-132)

This research focuses on the effective utilization of fly ash produced from power plants. Three classes of 'classified fly ash' were studied. Special attention was focused on concrete strength enhancement, and basic properties of fresh concrete and hardened concrete with low water-binder ratio and high strength. It is shown that the classified fly ash is an effective material that contributes to the reduction of superplasticizer requirements that are used in high strength concrete. It also contributes to improvement of workability, and improvement of strength either alone or in combination with granulated blast furnace slag.

3564
Vaysburd, A. M.
"SOME DURABILITY CONSIDERATIONS FOR EVALUATING AND REPAIRING CONCRETE STRUCTURES"
Concrete International, Mar 1993, Vol. 15, No. 3, pp 29-35.

A basic understanding of the various deteriorating processes is needed for assuring high performance and long-term durability of new and repaired reinforced concrete structures. More reliable information is needed on the corrosion of steel in concrete, and specifically on the role of chlorides and the 'chloride threshold.' The relation of chlorides to the corrosion of steel in concrete is considered as well as the effect of cracking and the aggregate-matrix contact zone. Bond with reinforcing steel and design details are also discussed. It is concluded that a combination of factors makes the corrosion of steel and the deterioration of concrete possible. Chloride attack by itself is seldom the cause of progressive deterioration, but in combination with other weaknesses it probably is a contributing factor. These and other findings are discussed.

3565
Watkins, R. A. M. and Jones, A. P. P.
"CARBONATION: A DURABILITY MODEL RELATED TO SITE DATA"
Proceedings of the Institution of Civil Engineers: Structures and Buildings, 1993, Vol. 99, No. 2, pp 155-166.

Carbonation is one of the major factors in the deterioration of reinforced concrete. The ability to predict the rate of carbonation in concrete allows maintenance cycles and redevelopment to be planned for existing structures, and specifications to be derived for new ones. This paper presents empirical data for predicting carbonation depths based on a large body of data collected from over 800 buildings in Hong Kong. The buildings range in age from five years to over 30 years old. The data collected comprise depth of carbonation, strength, cement content, density and age. The carbonation process is discussed, with particular reference to the effect of external and internal influences. Separate data on carbonation of concrete with various surface finishes have allowed the effects of these finishes to be assessed. An analysis of the data produced results which correspond reasonably with theoretical models.

3566
Webb, J.
"HIGH-STRENGTH CONCRETE: ECONOMICS, DESIGN AND DUCTILITY"
Concrete International, Jan 1993, Vol. 15, No. 1, pp 27-32.

High-strength concrete is a construction material that has been used in increasing volumes in recent years. It is popular for two obvious reasons: it is economical purely on the basis of cost to resist a specified load, and it allows the use of smaller columns. Concerns have been raised that design methods and safety factors cannot be extrapolated for concretes of this strength, principally because of the reduced ductility of the higher-strength concrete. There are also concerns about the consistency of the strength of the material in place. This article addresses some of these concerns and approaches that have been or could be followed.

3567
Xu, Z., Deng, Y., Wu, X., Tang, M., and Beaudoin, J. J.
"INFLUENCE OF VARIOUS HYDRAULIC BINDERS ON PERFORMANCE OF VERY LOW POROSITY CEMENTITIOUS SYSTEMS"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 462-470.

The influence of various hydraulic binders on the mechanical properties of very low porosity cement-based materials was investigated. Alkali-activated slag cement and aluminate cement systems were compared with the ordinary portland cement system. The results demonstrate that the alkali-slag system has the highest compressive strength and aluminate cement intermediate values. Development of structure and properties confirms that very low porosity cement pastes hydrate continuously during 90 days of cure. Regression analysis of the porosity-strength relation described by Schiller's equation indicates that the constants at "zero strength" are much less than those for normal porosity systems. These relations indicate that alkali-slag cement and aluminate cement systems have potentially higher performance characteristics than portland cement due to their different products. The role of hydration products, e.g. crystalline Ca(OH)2, on mechanical properties is discussed.

3568
Xu, Z., Tang, M., and Beaudoin, J. J.
"AN IDEAL STRUCTURAL MODEL FOR VERY LOW POROSITY CEMENTITIOUS SYSTEMS"
Cement and Concrete Research, Mar 1993, Vol. 23, No. 2, pp 377-386.

An ideal structural model for very low porosity cementitious materials is proposed. The model is based on energy, structural stability and durability criteria. It is suggested that the ideal structure consists of surface reactive fine fillers and cementitious products combined to form a chemically stable mature network with good interfacial bond. A new method involving treatment of aggregate surfaces was investigated for use in forming ideal structures. Effects of matrix and filler characteristics on interfacial bond are discussed. A method of replacing a large quantity of unhydrated cement in very low porosity cementitious systems was investigated. The experimental results demonstrate that interfacial bond is an important factor affecting mechanical properties; replacing unhydrated cement by inert fine aggregates results in a considerable decrease of strength. Surface treatment of aggregates was effective in maintaining the compressive strength of mortar at the same level as pure cement pastes. Surface hydraulic aggregates were effective in producing the ideal structure for very low porosity cementitious materials. It appears that a key factor in approaching ideal structure is changing inert aggregate surfaces into chemically reactive ones.

3569
Xu, Z., Tang, M., and Beaudoin, J. J.
"RELATIONSHIPS BETWEEN COMPOSITION, STRUCTURE AND MECHANICAL PROPERTIES OF VERY LOW POROSITY CEMENTITIOUS SYSTEMS"
Cement and Concrete Research, Jan 1993, Vol. 23, No. 1, pp 187-195.

Relationships between composition, structure and mechanical properties of very low-porosity cementitious materials were investigated. It was found that the principal factor determining the development of structure and strength is initial porosity which depends on the compacting pressure. The maximum degree of hydration was much higher than the limit described by Powers. A non-linear relationship between porosity and degree of hydration was found. The density of hydration products at an early age was found to be much lower than at later times. The hydration process appeared to proceed as if pore space was present in the structure of cement paste. It was proposed that the presence of a large quantity of clinker in the mature structure may be a harmful factor on the stability and durability of very low-porosity cementitious materials, because the chemical energy stored in clinker would be released through hydration in confined space. The development of structure and properties has shown that porosity was reduced sharply and compressive strength increased considerably during the early stage of hydration. The relation between compressive strength and porosity can be described by Schiller's equation using parameters obtained from helium and mercury porosity. It was suggested that the helium porosity-compressive strength relation is suitable to describe the behavior of very low-porosity cementitious materials.

3570
Yurugi, M., Mizobuchi, T., and Terauchi, T.
"UTILIZATION OF BLAST-FURNACE SLAG AND SILICA FUME FOR CONTROLLING TEMPERATURE RISE IN HIGH STRENGTH CONCRETE"
Proceedings of the 4th International Conference on the Use of Fly Ash, Silica Fume, Slag, and Natural Pozzolans in Concrete, held May 3-8, 1992, Istanbul, Turkey; Sponsored by CANMET in Association with the American Concrete Institute and Others; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1993, Vol. 2, pp 1433-1450. (ACI SP-132)

This study was conducted to determine whether the merits of slag and silica fume addition can be combined to develop a low heat high strength concrete, in which the heat generation could be controlled by blending the cementitious constituents keeping the compressive strength about 80 MPa at 91 days. It was found that from an overall view, a blend of cement:slag:silica fume in a proportion of 2:7:1, using a slag with 600 sq cm/g yields the best results. In Phase II, it was verified that the temperature rise could be brought down by as much as 30 deg C without adversely affecting the strength at 91 days (about 80MPa) though the early age strength was slightly lower.

3571
Zia, P., Ahmad, S. H., Leming, M. L., Schemmel, J. J., and Elliott, R. P.
"MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 3: VERY EARLY STRENGTH CONCRETE"
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xi, 116 pp. (SHRP-C-363)

This report details the laboratory investigation of the mechanical behavior and field trials of high performance concrete for highway applications. High performance concrete (HPC) is defined as concrete with much higher early strength and greatly enhanced durability against freezing and thawing in comparison with conventional concrete. Very early strength concrete is one of the three categories of HPC investigated in this program. The objective was to obtain information on the mechanical behavior of VES concrete. The laboratory investigation consisted of tests for both the fresh or plastic concrete and the hardened concrete. Tests for the plastic concrete included slump, air content, unit weight, and concrete temperature. The results of these tests are presented in volume 2 of this report series, Production of High Performance Concrete. The laboratory tests for the hardened concrete included compression tests for strength and modulus of elasticity; tension tests for tensile strength, flexural strength, and tensile strain capacity; freezing-thawing tests for durability factor; shrinkage tests; rapid chloride permeability tests; tests for AC impedance; and tests for concrete-to-concrete bond. The results of the laboratory work indicated that VES concretes with enhanced frost resistance can be successfully produced in the laboratory and utilized in the field for highway applications.

3572
Zia, P., Ahmad, S. H., Leming, M. L., Schemmel, J. J., and Elliott, R. P.
"MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 4: HIGH EARLY STRENGTH CONCRETE"
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xi, 179 pp. (SHRP-C-364)

This report documents the laboratory investigations of the mechanical behavior and field trials of high performance concrete for highway applications. High performance concrete is defined as concrete with much higher early strength and greatly enhanced durability against freezing and thawing in comparison with conventional concrete. High early strength (HES) concrete is one of the three categories of HPC investigated in this program. The objective was to obtain information on the mechanical behavior of HES concrete and to demonstrate its use under field conditions. The laboratory investigation consisted of tests for both the fresh or plastic concrete and the hardened concrete. The plastic concrete tests included slump, air content, etc.; the results of these tests are presented in volume 2 of this report series, Production of High Performance Concrete. The hardened concrete tests included compression tests for strength and modulus of elasticity, tension tests for tensile strength and flexural modulus, freezing-thawing tests for durability factor, shrinkage tests, rapid chloride permeability tests, tests for AC impedance, tests for concrete-to-concrete bond, and tests for bond between concrete and steel reinforcement. The field experiments were conducted in five states that represented a wide variety of environmental and exposure conditions: New York, North Carolina, Arkansas, Illinois, and Nebraska. The results of the laboratory work and field experiments indicated that HES concretes with enhanced frost resistance can be successfully produced in the laboratory and used in the field for highway applications.

3573
Zia, P., Ahmad, S. H., Leming, M. L., Schemmel, J. J., and Elliott, R. P.
"MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 5: VERY HIGH STRENGTH CONCRETE"
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xi, 101 pp. (SHRP-C-365)

This report documents the laboratory investigations of the mechanical behavior of high performance concrete for highway applications. High performance concrete is defined as concrete with much higher early strength and greatly enhanced durability against freezing and thawing in comparison with conventional concrete. Very high strength (VHS) concrete is one of the three categories of high performance concrete investigated in this program. The objective was to obtain information on the mechanical behavior of VHS concrete. The laboratory investigation consisted of tests for both the fresh or plastic concrete and hardened concrete. The plastic concrete tests included slump, air content,etc.; the results of these tests are presented in volume 2 of this report series, Production of High Performance Concrete. The hardened concrete tests included compression tests for strength and modulus of elasticity, tension tests for tensile strength and flexural modulus, freezing-thawing tests for durability factor, shrinkage tests, creep tests, rapid chloride permeability tests, tests for AC impedance, and test for bond between concrete and steel reinforcement.

3574
Zia, P. and Caner, A.
"CRACKING IN LARGE-SIZED LONG-SPAN PRESTRESSED CONCRETE AASHTO GIRDERS"
Final Report, Research Project 23241-93-3, Center for Transportation Engineering Studies, North Carolina State University, Raleigh, NC, 1993, xi, 87 pp. (FHWA/NC/94-003)

An investigation was conducted to study a cracking problem associated with the production of large-sized long span prestressed concrete AASHTO girders. During the production of these girders in the prestressing plant, vertical cracks often develop near the mid-third of the span after the girders were cured overnight on the casting bed and before the prestressing strands were detensioned. The cracks would extend across the top flange of the girder transversely and penetrate vertically down through the girder web, reaching toward the bottom flange. The objective of the investigation was to identify the cause(s) of the problem, and to develop and recommend its remedies. It was found that the most probable cause of the cracking problem was due to restrained thermal contraction of the entire casting system (i.e., the girders with the linking tendons) during the cooling period after the overnight steam or heat curing. The potential for cracking the girder may be minimized by increasing the total length of the exposed tendons outside the girders, or by reducing the cooling period and thus minimizing the temperature reduction as much as possible. The cracks caused by the restrained thermal contraction are closed immediately as soon as the prestressing tendons are detensioned. Given an adequate supply of moisture, the cracks will heal and the concrete will virtually regain its full strength.

3575
Zia, P. and Hansen, M. R.
"DURABILITY OF HIGH PERFORMANCE CONCRETE"
Proceedings: Pacific Rim TransTech Conference, July 25-28, 1993, Seattle, WA; Ed. by Chris T. Hendrickson and Kumares C. Sinha; ASCE, New York, 1993, Vol. 2, Intermodal ties management systems, propulsion technology, Strategic Highway Research Program, pp. 398-404.

This is a summary of a study of the freeze-thaw (F/T) durability and the resistance to chloride penetration of high performance concrete (HPC) developed for highway applications. The tests covered here include the following: freeze-thaw test; rapid chloride permeability test (RPCT); and the impedance test. It was found that the F/T resistance of the HPC exceeded the enhanced F/T durability requirement by a considerable margin. This can be achieved if the concrete has a minimum of 5% well entrained air and the coarse aggregate used in the concrete is F/T resistant. Despite its high F/T resistance, HPC may indicate quite high coulomb values in the RCPT because of the additional ions introduced into the concrete by the various admixtures. These and other findings are presented and discussed.

3576
Zia, P., Leming, M. L., Ahmad, S. H., Schemmel, J. J., Elliott, R. P., and Naaman, A. E.
"MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 1: SUMMARY REPORT"
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xi, 98 pp. (SHRP-C-361)

This report presents a summary of each phase of a 4-year research program sponsored by the Strategic Highway Research Program under contract C-205. For each phase of the research, the objective, scope, results, and conclusions are summarized. The report covers the literature search and review, the development of mixture proportions of three categories of high performance concrete, the laboratory studies and field trials of the concretes, and the laboratory studies of high early strength fiber reinforced concrete. An assessment is made of how the research met its objectives and what the limitations of the research are. Finally, the report points out the need to remove certain limitations in some of the current specifications that prevent the use of high performance concrete and concludes with a list of future research needs. To provide guidance to engineers, concrete producers, and contractors, two technical guides on the production and use of high performance concrete, as well as two proposed specifications for test methods, are included in the appendixes.

3577
Zia, P., Leming, M. L., Ahmad, S. H., Schemmel, J. J., and Elliott, R. P.
"MECHANICAL BEHAVIOR OF HIGH PERFORMANCE CONCRETES, VOLUME 2: PRODUCTION OF HIGH PERFORMANCE CONCRETE"
Strategic Highway Research Program, National Research Council, Washington, D. C., 1993, xi, 92 pp. (SHRP-C-362)

This report details the laboratory developmental work on producing high performance concrete for highway applications. High performance concrete is defined as concrete with much higher early strength and greatly enhanced durability against freezing and thawing in comparison with conventional concrete. The objective was to explore the feasibility of developing appropriate mixture proportions for three different categories of high performance concrete with only locally available, conventional constituent materials and normal production and curing procedures. The constituent materials are described in detail in terms of their physical, chemical, and mineral properties. The method of proportioning and the selection of materials are discussed, and the mixing and curing procedures are summarized. A total of 360 trial batches were mixed from which 21 different mixture proportions were selected for in-depth study and evaluation of the mechanical behavior of the concrete. The mixture proportions and the plastic and strength properties of each trial batch are summarized in two appendixes. The results of the laboratory work and field trials indicated that concrete with high performance requirements can be successfully produced, and several precautionary steps are suggested for quality assurance in the production of such concrete.