High Performance Concrete 1989

This paper evaluates the durability performance of concretes made with Type V, Type I and blended OPC (ordinary portland cement) - blast furnace slag cement using Dhahran limestone and Ras Al Khaima gabbro coarse aggregates, exposed to the splash zone marine environment of the Arabian Gulf. The study entailed making eleven mixes with water to cementitious materials in the ratio of 0.40 and cement factors of 400, 300 and 250 kg/m3. The test specimens have been positioned on a specially erected concrete platform 1.2 m above the MSL which forms part of a national weathering exposure station located on the north side of the border station at the King Fahad Causeway. The results reported after two years of exposure show that significantly more scaling occurs in concrete made with Dhahran limestone compared with concrete made with Ras Al-Khaima gabbro. The scaling in blended OPC-blast furnace slag concretes is higher than in Type V/I cement concrete. At a depth of 0.625 inches, chloride concentrations were found to be 3 to 5 times higher in Type V/I cement concretes than in blended OPC-blast furnace slag concrete. Cement content has a pronounced effect on the scaling of concrete made with Dhahran limestone aggregates, and on chloride penetration in Type V/I cement concretes. Blended OPC blast furnace slags showed increased scaling for higher cement contents.

3002
Al-tayyib, A. H. and Al-mana, A. I.,
"INFLUENCES OF THE ARABIAN GULF ENVIRONMENT ON CONCRETE DURABILITY"
IABSE Report, 1989, Vol. 57/1, pp 169-174.

In an experimental study, the temperature at various depths of concrete slabs exposed in the field environment of the Arabian Gulf countries has been measured. The effect of the temperature of concrete, which has been found different from that of the ambient air temperature, on its durability has been explained. The surface layer of a deteriorated concrete structure has been chemically analyzed to emphasize the role of air suspended particulate matter in concrete durability.

3003
Anderson, G. M. and Sweeney, P. J.,
"CONCRETE DETERIORATION AND ENVIRONMENTAL EXPOSURE TRIALS IN DUBAI, UAE"
Proceedings of [the] 3rd International Conference on Deterioration and Repair of Reinforced Concrete in the Arabian Gulf, held Oct 21-24, 1989, Bahrain; Bahrain Society of Engineers, Manama, Bahrain, 1989, Vol. 1, pp 337-351.

This article examines the relationship between concrete deterioration and exposure conditions in the typical Middle East coastal province of Dubai. The basic geomorphology and geochemistry of Dubai is described first, with special reference to chloride and sulfate concentrations. Analysis of concrete samples and a survey of the extent of cracking and deterioration of concrete structures from which the samples were taken was also undertaken. The relationship between chloride and sulfate concentrations, age, cracking, deterioration and exposure condition (location) was examined by statistical means. The results showed significant linear correlations between all of these parameters in each of the environments concerned except in elevated structures, where the only relationship found was between cracking and chloride content. Further research carried out as part of the ACT (Advanced Concrete Technology) project is also described and compared with the earlier research results. In this project, mass concrete specimens either of normal or air entrained concretes made of 7 different mix categories were placed at various test sites, and the relative performance over 8 months was monitored and compared. The following tests were undertaken: sulfate and chloride ingress, depth of carbonation, salt weathering, resistance to chloride ion penetration, and compressive strength development. The effects of location, mix design and concrete type (normal or air entrained) upon concrete durability are analyzed and discussed.

3004
Asselanis, J. G., Aitcin, P-C., and Mehta, P. K.,
"EFFECT OF CURING CONDITIONS ON THE COMPRESSIVE STRENGTH AND ELASTIC MODULUS OF VERY HIGH-STRENGTH CONCRETE"
Cement, Concrete, and Aggregates, Summer 1989, Vol. 11, No. 1, pp 80-83.

High-strength concrete mixtures contain relatively high cement content, a superplasticizing mixture, and very low water content (for instance, corresponding to about 0.3 water/cement ratio). Such mixtures can achieve a discontinuous pore structure and low permeability within a few days of cement hydration. The purpose of the laboratory study reported here was to evaluate the influence of curing conditions on the properties of high-strength concrete. Compressive strength, elastic modulus, and strength-strain behavior were among the properties investigated.

3005
Baluch, M. H., Al-Nour, L. A. R., Azad, A. K., Al-Mandil, M. Y., Sharif, A. M., and Pearson-Kirk, D.,
"CONCRETE DEGRADATION DUE TO THERMAL INCOMPATIBILITY OF ITS COMPONENTS"
Journal of Materials in Civil Engineering, Aug 1989, Vol. 1, No. 3, pp 105-118.

The paper reports an experimental study on the influence of several variables on thermal incompatibility of concrete constituents (TICC)-related damage to concrete by monitoring: (1) fracture toughness; (2) modulus of rupture; and (3) permeability of concrete. In addition, the coefficient of thermal expansion was determined for one source of aggregate. It was found that the effect of TICC-related damage on a key durability parameter, permeability, has been established both from testing of samples in a laboratory environment as well as in an outdoor exposure site. Other salient features of the study are also noted.

3006
Banthia, N. and Sicard, V.,
"EFFECTS OF CURING TEMPERATURE ON THE COMPLETE STRESS-STRAIN PLOTS FOR HIGH STRENGTH CONCRETE"
Fracture of Concrete and Rock: Recent Developments: Papers Presented at the International Conference, Sep 20-22, 1989, University of Wales, College of Cardiff, School of Engineering; Ed. by S. P. Shah, S. E. Swartz, and B. Barr; Elsevier Applied Science, London, 1989, pp 587-595.

Complete stress-strain plots were obtained for high strength concrete containing silica fume by testing 53.4 mm x 106.8 mm cylinders in parallel with two or more instrumented steel tubes. Three curing temperatures of 2, 22, and 38 deg C were investigated. Tests were conducted at the ages of 1, 3, 7 and 28 days. Several conclusions were drawn. (1) It is possible to obtain the complete stress-strain plot by the technique chosen. (2) Low temperature curing results in lower strengths at early ages; however, the differences diminish at later ages. (3) Concrete brittleness increases with age. Finally, an attempt has been made to quantify the post peak behaviour by Ductility Indices.

3007
Barton, R. B.,
"WATER-CEMENT RATIO IS PASSE"
Concrete International: Design & Construction, Nov 1989, Vol. 11, No. 11, pp 75-78.

This article points out the misuse of current ACI water-cement ratio tables. Maximum water-cement ratio specifications are often counter-productive in promoting shrinkage cracks and shrinkage stresses, curling, high cement factors and high heat concrete, general cracking, job problems over slump versus water-cement ratio, concrete complaints, and low bids by suppliers. Each of these areas is discussed. Comments are made on effective mass placement, durability, permeability, high strength concrete, and effective water cement ratio. Slump and mix specifications are also discussed.

3008
Bentur, A. and Goldman, A.,
"CURING EFFECTS, STRENGTH AND PHYSICAL PROPERTIES OF HIGH STRENGTH SILICA FUME CONCRETES"
Journal of Materials in Civil Engineering, Feb 1989, Vol. 1, No. 1, pp 46-58.

Work is described which characterizes high strength silica fume concretes from the points of view of heat generation, shrinkage and sensitivity to curing, and compares their performance with that of concretes made of portland cement only, having either the same cement content or the same water to cementitious materials ratio. It was found that the presence of silica fume resulted in a marked increase in strength, especially at 28 days, but also at 1 day. This, however, was not accompanied by excessive heat liberation. Calorimetric measurements suggest an accelerating effect of the SF on the reaction of the portland cement. These and other observations are noted and discussed.

3009
Berke, N. S. and Rosenberg, A.,
"TECHNICAL REVIEW OF CALCIUM NITRITE CORROSION INHIBITOR IN CONCRETE"
Transportation Research Record, 1989, No. 1211, pp 18-27.

Calcium nitrite has been used as a corrosion inhibitor against chloride attack and as a set accelerator in concrete for more than 20 years. Considerable data are available concerning its effects on corrosion inhibition, setting times, freeze-thaw resistance, strength, and other properties. Although much of the data have been published in the open literature, a full-scale review is not available. This paper reviews past and present research on the properties of calcium nitrite in concrete. While the bulk of the data has been generated by W.R. Grace & Co., considerable information is available from outside sources, including the U.S. Federal Highway Administration (FHWA), departments of transportation, universities, and independent test laboratories. It is shown that calcium nitrite is an effective corrosion inhibitor for steel in concrete, based upon extensive corrosion testing in laboratory and field concrete specimens. The effects of mix design and concrete cover on corrosion resistance with calcium nitrite are also discussed. Furthermore, in most cases, calcium nitrite improves the compressive strength of the concrete mix and, with proper air entrainment, is freeze-thaw durable. In conclusion, the data generated in the last 20 years show that calcium nitrite is a proven corrosion-inhibiting admixture to be used to protect concrete structures in a chloride environment.

3010
Blades, J. T. and Perl, G. C.,
"DURABILITY PROVISIONS FOR PRESTRESSED CONCRETE"
IABSE Report, 1989, Vol. 57/2, pp 517-523.

The consequences of durability-related damage to structures comprising prestressed concrete are potentially greater than for those comprising reinforced concrete. This paper discusses the differences between durability behaviour of prestressed and reinforced concrete. Recommendations of codes and code provisions for durability of prestressed concrete are given. Results of a survey investigating the durability provisions of European, Australian and American concrete codes of practice are presented. The codes which are compared are: a) the Australian AS1480 (1982), AS1481 (1978), and AS3600 (1988); b) the American AC1318M (1983); c) the British CP110 (1980) and BS8110 (1985); d) the European CEB-FIP MC78 (1978) and FIP (1984); and e) the Danish DS411 (1984). The water/cement ratio, cement content and compressive strength at 28 days are compared.

3011
Bunte, D. and Rostasy, F. S.,
"TEST METHODS FOR ON-SITE ASSESSMENT OF DURABILITY"
IABSE Report, 1989, Vol. 57/1, pp 335-340.

This paper discusses the potentialities and limitations of several on-site methods for assessing the tightness of concrete cover, and thus predicting concrete durability. On-site methods have the advantage of being non-destructive; their principal aim is to obtain information on the influence of curing or the combined influence of curing and water/cement ratio on the permeability of concrete to carbon dioxide and water vapour. The methods presented here are: (1) the air permeability test method of Schoenlin & Hilsdorf and that of Figg, and (2) the initial surface water absorption (ISA) test. They meet certain standards with respect to: strength, selectivity, repeatability, simplicity, and cost. Permeability tests are used for assessing concrete quality and curing. Absorption tests serve the same purposes, and can also be used to predict durability. The ISA test measures the absorption of water on-site, and is standardized in British Standard BS 1881, Part 5. It uses a cap which is sealed onto the concrete surface and then filled with water with a small pressure head.

3012
Burnett, I.,
"HIGH-STRENGTH CONCRETE IN MELBOURNE, AUSTRALIA"
Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 17-25.

In late 1987 three major projects were begun that required placement of concrete by pump, and specified strengths of 60 and 65 MPa at 28 days. These projects involved more than 170,000 m3 of concrete, of which approximately 20,000 m3 was high-strength. The three current projects - Melbourne Central, Bourke Place, and 530 Collins Street - all required concrete for the slabs, columns, and core walls to be pumped. This included the concrete with specified 28-day strengths of 60 and 65 MPa. On the Bourke Place project another significant factor was involved: the core wall was to be slipformed from 60 MPa concrete. Each of the projects is discussed in the article.

3013
Cabrera, J. G., Cusens, A. R., and Lynsdale, C. J.,
"POROSITY AND PERMEABILITY AS INDICATORS OF CONCRETE PERFORMANCE"
IABSE Report, 1989, Vol. 57/1, pp 249-254.

This paper is based on the results of an extensive laboratory study, and proposes empirical statistical models which correlate oxygen permeability with several characteristics of concrete. The models were applied to predict adequate levels of performance for concrete in bridge structures. The authors also propose the use of the models to set criteria for designing durable concrete mixes. The mix design used in this investigation was based on the criterion of minimum porosity, which involves selecting the components of concrete to achieve maximal packing. The relevant parts of British Standard BS 1881 were used for some of the measurements, and the concrete samples were cured in a fog room kept at 20 degrees C and 100% relative humidity. The authors conclude that: (1) the parameters affecting the oxygen permeability of concrete are: (a) air content; (b) water/cement ratio; (c) porosity; (d) age; (2) oxygen permeability is related to the porosity/strength ratio, and this relationship is influenced by the presence of pfa (pulverised fly ash) in the concrete; (3) oxygen permeability, porosity, and strength influence concrete's performance in a specific environment, and at least two of these three parameters are needed to predict concrete performance; and (4) a suitable one-day target value for oxygen permeability for design is 10 (super-16) square m.

3014
Chatterji, S., Thaulow, N., and Jensen, A. D.,
"STUDIES OF ALKALI-SILICA REACTION. PART 5. VERIFICATION OF A NEWLY PROPOSED REACTION MECHANISM"
Cement and Concrete Research, Mar 1989, Vol. 19, No. 2, pp 177-183.

To explain the roles of CaOH2 and alkali chlorides in alkali-silica reaction, it has been proposed that during the chemical reaction alkali and hydroxyl ions enter the reactive silica grains leaving behind calcium and chloride ions in the liquid phase. This postulated reaction has been verified by estimating calcium ions and hydroxide ions in the liquid phase of the system reactive silica-CaOH2-alkali chloride water. The results of this investigation indicate that other things being constant the rate of alkali-silica reaction is determined by the size of the hydrated alkali ion; the larger the size the lower is the rate of reaction. It seems that the reactivity of an aggregate may be evaluated in a cement-free system. The results suggest that the alkali-silica reactivity of an aggregate could be evaluated simply by measuring hydroxide ion concentration in the system: reactive sand-CaOH2-saturated alkali chloride solution and comparing it with that of the system: quartz sand-CaOH2-saturated alkali chloride solution.

3015
Chengju, G.,
"MATURITY OF CONCRETE: METHOD FOR PREDICTING EARLY-STAGE STRENGTH"
ACI Materials Journal, Jul-Aug 1989, Vol. 86, No. 4, pp 341-353.

Various expressions of maturity of concrete are studied with particular regard to the influence of temperature. A parabolic maturity function is proposed that is materially identical to one based on the Aarrhenius equation of reaction rate. The applicability of various maturity functions as well as strength-maturity equations are reviewed by analyzing a series of published data. It is concluded that the maturity concept may serve as an effective means of predicting the early-stage strength of in situ concrete in spite of its inherent limitations. The principle and performance of a commercial maturity meter, which is based on the evaporation of liquid, are examined.

3016
Cohen, M. D. and Olek, J.,
"SILICA FUME IN PCC: THE EFFECTS OF FORM ON ENGINEERING PERFORMANCE"
Concrete International: Design & Construction, Nov 1989, Vol. 11, No. 11, pp 43-47.

Silica fume is commercially available in 3 forms: water-slurry, dry compacted powder, and dry densified powder. Results to clarify uncertainties on the effects of the form of silica fume on 28- and 56-day compressive strengths, resistance to freezing and thawing cycles, and resistance to chloride permeability of high-quality air-entrained concrete are presented and discussed. The effects of the form of silica fume on the fresh properties (slump and percent air content) of concrete are also presented and discussed. Based on the results obtained, the authors do not advocate the use of any specific form of silica fume as there were significant differences observed in the engineering properties of concretes containing either of the 3 forms of silica fume.

3017
Collins, R. J.,
"ALKALI AGGREGATE REACTIVITY IN DENSE CONCRETES CONTAINING SYNTHETIC OR POROUS NATURAL AGGREGATE"
Cement and Concrete Research, Mar 1989, Vol. 19, No. 2, pp 278-288.

Studies have been conducted to investigate the relative importance of pore solution dilution, accommodation of gel pressures and potential reactivity of porous aggregate in the suppression of alkali aggregate expansion in concretes containing a critical proportion of thames valley sand. The results also indicate that the alkalinity of the pore solution may be a more direct measure of susceptibility to reaction than the Na2O equivalent content of the concrete. Slow reactivity in some sintered aggregates has been monitored for up to 10 years and the relatively low expansions are discussed in terms of fluxing impurities in the glassy phases.

3018
Collins, T. M.,
"PROPORTIONING HIGH-STRENGTH CONCRETE TO CONTROL CREEP AND SHRINKAGE"
ACI Materials Journal, Nov-Dec 1989, Vol. 86, No. 6, pp 576-580.

Results of an experimental creep and shrinkage program on high-strength concrete are presented. Variations in paste content and maximum aggregate size also are investigated. Five test mixes were prepared based on historical data. These mixes varied in paste content, aggregate size, and the use of high-range water-reducing admixtures. The creep test conditions varied only in intensity of load. The results of the test program showed that creep and shrinkage deformations are somewhat less for concrete mixtures with lower paste contents and larger aggregate size.

3019
Cook, J. E.,
"10,000 PSI CONCRETE"
Concrete International,: Design & Construction, Oct. 1989, Vol. 11, No. 10, pp. 67-75.

This article describes the investigation of local materials in a search for concrete that would meet a specified design strength of 10,000 psi for InterFirst Plaza, a proposed Dallas Main Center Project. The structural system used in the 72-story building significantly advances the technology of tall building construction. At 921 feet (280.7 m), the building is Dallas' tallest and among the tallest in the world. The ratio of height to structural width of 7.24:1 makes it the most slender of the 12 tallest buildings. The World Trade Center Towers in New York City, in comparison, have height to width ratios of 6.49:1.

3020
Cunningham, J. C., Dury, B. L., and Gregory, T.,
"ADSORPTION CHARACTERISTICS OF SULPHONATED MELAMINE FORMALDEHYDE CONDENSATES BY HIGH PERFORMANCE SIZE EXCLUSION CHROMATOGRAPHY"
Cement and Concrete Research, Nov 1989, Vol. 19, No. 6, pp 919-928.

This article describes an investigation into the adsorption characteristics of super plasticisers sulphonated naphthalene formaldehyde condensates (snfc) on cement particles. The cement used was cmf specification ordinary portland cement. High performance size exclusion chromatography has been used to measure the average molecular weight and molecular weight distribution of sulphonated melamine formaldehyde condensate admixtures. The method was then used to study the adsorption of these molecules on to the surfaces of cement particles. It was found that the molecules in the higher molecular weight fractions preferentially adsorbed on to the cement particles.

3021
Dahl, H. and Brincker, R.,
"FRACTURE ENERGY OF HIGH-STRENGTH CONCRETE IN COMPRESSION"
Fracture of Concrete and Rock: Recent Developments, Papers Presented at the International Conference, Sep 20-22, 1989, University of Wales, College of Cardiff, School of Engineering,; Ed. by S. P. Shah, S. E. Swartz, and B. Barr; Elsevier Applied Science, London, 1989, pp 523-536.

Compression tests are usually carried out in load control. This implies the termination of the test at the peak point of the load-displacement curve, while the fracture under these conditions becomes unstable at the descending branch of the load displacement relation. However, the descending branch is essential for understanding the fracture mechanisms of concrete in compression. In this paper a series of tests is reported, carried out for the purpose of studying the fracture mechanical properties of concrete in compression. Including the measurement and study of the descending branch, a new experimental method has been used to investigate the influence of boundary conditions, loading rate, size effects and the influence of the strength on the fracture energy of high-strength concrete over the range 70 MPa to 150 MPa expressed in nominal values.

3022
de Larrard, F.,
"ULTRAFINE PARTICLES FOR THE MAKING OF VERY HIGH STRENGTH CONCRETES"
Cement and Concrete Research, Mar 1989, Vol. 19, No. 2, pp 161-172.

The manufacture of very high strength concrete (28-day compressive strength higher than 80 mpa) often involves the addition of ultrafine particles together with large proportions of organic admixtures. This article compares the effectiveness of different fillers and their mixture. Silica fumes are found to be the most effective addition, and they are looked into more particularly in terms of their effect on the properties of mortars according to their proportion (optimum proportion) and quality (chemical composition).

3023
de Larrard, F. and Puch, C.,
"FORMULATION OF HIGH-PERFORMANCE CONCRETES: THE SLURRY METHOD"
Bulletin de Liaison des Laboratoires des Ponts et Chaussees, May-Jun 1989, No. 161, pp 75-83.

The authors describe a specific method for the composition of high-performance concretes (HPC). First, an empirical formula for strength prediction is presented, together with a theoretical model of the viscosity of a granular mix in suspension. With these two instruments, an experimental method is devised for the formulation of a concrete possessing given properties. It is assumed in this approach that the optimum concrete has a low content of binding paste and a high proportion of super-plasticizer. The primary advantage of the method is that it is economical in terms of manpower and materials, because most of the manipulations are performed on slurries. Furthermore, the resulting concrete, besides meeting conventional requirements with respect to strength and workability, possesses satisfactory secondary characteristics. In French.

3024
Detwiler, R. J., Dagleish, B. J., and Williamson, R. B.,
"ASSESSING THE DURABILITY OF CONCRETE IN FREEZING AND THAWING"
ACI Materials Journal, Jan-Feb 1989, Vol. 86, No. 1, pp 29-35.

Concretes subjected to cycles of freezing and thawing can deteriorate rapidly unless they are designed properly for these conditions. Standard tests are used to determine the suitability of a particular concrete for service under cycles of freezing and thawing. However, in these tests, failure takes place by a different mechanism than would occur in service. It may be possible to obtain a better prediction of the actual performance of the concrete in service by including an examination of the microstructure of the air-void system as part of the test procedure. Scanning electron micrographs of two concretes exposed to the same environmental conditions illustrate this point.

3025
Detwiler, R. J. and Mehta, P. K.,
"CHEMICAL AND PHYSICAL EFFECTS OF SILICA FUME ON THE MECHANICAL BEHAVIOR OF CONCRETE"
ACI Materials Journal, Nov-Dec 1989, Vol. 86, No. 6, pp 609-614.

Appropriate use of silica fume improves both the mechanical characteristics and durability of concrete. In this work, carbon black, which is physically similar to silica fume but is not pozzolanic, is used to evaluate the relative significance of physical and pozzolanic effects. Results show that at an early age, the influence of silica fume on the compressive strength of concrete may be attributed mainly to physical effects. By the age of 28 days, both physical and chemical effects become significant. However, even at the age of 7 days, there is a difference in the resistance to subcritical crack growth in the cement paste-aggregate transition zone between silica fume and carbon black mixes.

3026
Durekovic, A., Calogovic, V., and Popovic, K.,
"FROST RESISTANCE OF OPC-CSF MORTARS INVESTIGATED BY MEANS OF REPEATED CYCLE- AND ONE CYCLE-FREEZING TEST"
Cement and Concrete Research, Mar 1989, Vol. 19, No. 2, pp 267-277.

Mortars of ordinary portland cement containing 0, 5 and 10 per cent of condensed silica fume (csf), and with water/binder ratio of 0.6 and 0.44, each non-aerated and aerated, were subjected to frost resistance investigation at 50 days age. This was done by repeated cycle freezing test (up to 150 cycles) and by one cycle freezing test method. The air void spacing factor was determined as well. The results obtained by both methods confirmed that silica fume presence improves the mortars' frost resistance but the results also indicated the necessity of air entrainment if high freeze-thaw resistance of csf-containing mortars is requested or if such composites are supposed to be exposed to severe freezing conditions. Useful data ("b-point" of freezing, rw-value), as a feed-back information of the composites' pore structure, are obtained after evaluation of the one cycle freezing curves.

3027
Ezeldin, A., Balaguru, P. N., and Shah, S. P.,
"HIGH STRENGTH CONCRETE: PROPORTIONING, BEHAVIOR AND APPLICATIONS"
Structural Materials, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by James F. Orofino; ASCE, New York, 1989, pp 21-30.

Generally, concrete with a cylinder compressive strength higher than 6000 psi (41.4 MPa) is designated as high strength concrete. High strengths are achieved using stronger coarse aggregates, relatively higher cement contents and lower water/cement ratios. In most, if not all recent applications, high range water reducing admixtures have been used to improve the workability at low water/cement ratios. The other two common admixtures used in high strength concrete are condensed silica fume and fly ash. With these admixtures strengths up to 20,000 psi (138 MPa) have been obtained. This paper provides an overview of making and using high strength concrete for various structural applications.

3028
Figg, J.,
"CONCRETE SURFACE PERMEABILITY. MEASUREMENT AND MEANING"
Chemistry and Industry (London), Nov 6, 1989, No. 21, pp 714-719.

For concrete, low permeability is the key to good durability. However, permeability for concrete is ill defined. The tests described are low-pressure measurements related to exposure conditions for conventional structures, not high-pressure methods relevant to, say, North Sea oil rigs. In addition, the theoretical basis of permeability studies and results of recent work in the field are discussed.

3029
Fiorato, A. E.,
"PCA RESEARCH ON HIGH-STRENGTH CONCRETE," Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 44-50.

This is a review of Portland Cement Association- sponsored research on high-strength, normal-weight concrete. The study was an effort to address the need for technological information about high-strength concrete applications for prestressed members, buildings, and bridges, and in situations where durability rather than strength is the primary concern. High-strength concrete for prestressed members is considered, as well as high-strength concrete for buildings. Materials development, structural design, time-dependent deformations, and fire endurance are covered. High-strength concrete for permeability and freeze-thaw resistance are also covered. Areas for future research are noted.

3030
Fwa, T. F.,
"EFFECTS OF CYCLIC WETTING-DRYING WEATHERING ON WEAR RESISTANCE OF CONCRETE PAVEMENT"
Transportation Research Record, 1989, No. 1234, pp 87-93.

This paper describes the development of a laboratory test procedure to assess the weathering effects of a wet tropical climate on wear resistance of concrete pavements. An accelerated weathering model was fabricated to provide cyclic wetting and drying treatment in a laboratory simulation of the weathering effects of Singapore's climate. The effects of weathering on wear resistance were evaluated by means of a rotating drum test conducted on plain cement mortar specimens with and without weathering treatment. The study showed that cyclic wetting and drying weathering significantly reduced the wear resistance of cement mortar test specimens. Although no correlation relationship is available at this stage between test data of the proposed procedure and field performance of in-service pavements, results obtained in this study suggest that the test procedure could find useful application in evaluating the relative surface wear resistance and durability of various concrete pavement materials.

3031
Giraldi, A.,
"HIGH-STRENGTH CONCRETE IN WASHINGTON, D.C.," Concrete International: Design & Construction, Mar 1989, Vol. 11, No. 3, pp 52-55.

The article traces the evolution of high-strength concrete in the Washington, D.C. area as experienced by a ready-mixed concrete producer. The proportioning process and the use of local materials are reviewed. As strength requirements increased, the experience gained from each preceding mix was used in formulating the higher strength mixes. Improved field and laboratory testing techniques for high-strength concrete are recommended.

3032
Glassgold, I. L.,
"SHOTCRETE DURABILITY: AN EVALUATION"
Concrete International: Design & Construction, Aug. 1989, Vol. 11, No. 8, pp. 78-85.

This paper reviews the shotcrete literature of the last 80 years and addresses the issue of the durability of dry-mix shotcrete. The controversy over the lack of air entrainment and the freeze-thaw durability of dry-mix shotcrete are discussed, as are application equipment, high-versus low-velocity shotcrete, and shotcrete materials. It is noted that shotcrete that is installed using the best of materials and practice can provide suitable and acceptable durability, and that certain non-air-entrained concretes, including shotcrete, can be freeze-thaw durable materials. It is believed that the quality of in-place shotcrete, including durability, is directly proportional to the exit velocity from the nozzle. Test results indicate that nominal addition of silica fume to standard portland cement mixes has beneficial effects on the durability properties of dry-mix shotcrete.

3033
Goldman, A. and Bentur, A.,
"BOND EFFECTS IN HIGH-STRENGTH SILICA-FUME CONCRETES"
ACI Materials Journal, Sep-Oct 1989, Vol. 86, No. 5, pp 440-447.

The strengthening effects in high-strength silica-fume concretes were evaluated in terms of water-reducing effect associated with the reduction in water requirement in the silica fume system and in terms of an inherent effect that reflects the increase in strength of the silica-fume concrete over a similar water/cement ratio concrete without silica fume. The inherent effect was found to be as important as the water-reducing effect, and it is suggested that its origin is in the improved aggregate-matrix bond. This enhanced bonding is associated with the formation of a dense microstructure in the transition zone of the silica-fume concrete.

3034
Gran, J. K., Florence, A. L., and Colton, J. D.,
"DYNAMIC TRIAXIAL TESTS OF HIGH-STRENGTH CONCRETE"
Journal of Engineering Mechanics, 1989, Vol. 115, No. 5, pp 891-904.

The results are presented of triaxial compression experiments performed at strain rates between 0.5/s and 10/s. The data was obtained by using an explosively driven traxial loading device called the 4-kbar loader, which will load 150-mm diameter specimens in dynamic triaxial compression at stresses up to 400 MPa with rise times as short as 0.5ms. The measurements of stress and strain provide not only failure data but also the complete nonlinear relation between the stress and strain tensors up to failure. The data are self-consistent and show only moderate scatter. Details of the experimental techniques are described, and the experimental results are discussed. Additional unconfined compression experiments at strain rates between 0.5/s and 5/s could be performed to more accurately define the rate dependence in this range.

3035
Grube, H. and Rechenberg, W.,
"DURABILITY OF CONCRETE STRUCTURES IN ACIDIC WATER"
Cement and Concrete Research, Sep 1989, Vol. 19, No. 5, pp 783-792.

When planning and erecting concrete structures, one of the factors to be considered is the attack on the concrete by chemical substances. The degree of a solvent attack is generally expressed in terms of concentration (mg/l and ph value) of attacking acid. An evaluation of the literature and the authors' own experiments have shown that the conditions of transport of the attacking and the dissolved substances often have a much greater influence on the loss of mass than the concentration of the attacking substances. This phenomenon is due to a protective layer of silicon oxide gel. As a result of experiments in connection with a diffusion model the loss of mass to be expected under practical conditions can be estimated in advance, in terms of quantity, as a function of the type and concentration of the attacking acid solution, the composition of the concrete and the state of the protective layer.

3036
Hilsdorf, H. K.,
"DURABILITY OF CONCRETE - A MEASURABLE QUANTITY?"
IABSE Report, 1989, Vol. 57/1, pp 111-123.

This paper considers the durability of concrete and presents a test method for its evaluation. Durability depends mainly on the resistance of concrete to the ingress of aggressive substances. Although there are several different mechanisms for the transport of these substances, the author investigates whether a single parameter, the air permeability of concrete, is suitable for the general characterisation of concrete durability. The absorption of water by concrete may occur in one of the following ways: (1) permeation of water under an external pressure; (2) capillary suction of water; (3) diffusion of water vapour. In the Schoenlin concrete air-permeability test method, the concrete sample is cast directly into a rubber ring, cured for a suitable period, and then stored in a constant environment up to the time of testing at age 56 days. Test results are presented on: (1) the effect of water-cement ratio and curing duration; (2) air permeability and concrete micro-structure; (3) permeability and carbonation; (4) permeability and capillary suction; (5) permeability and other concrete durability properties. The author concludes that Schoenlin's test procedure can be used to determine rapidly and reliably the characteristic air permeability coefficient of a standard concrete specimen that has been cured and preconditioned in a standardized way.

3037
Howard, N. L. and Leatham, D. M.,
"PRODUCTION AND DELIVERY OF HIGH-STRENGTH CONCRETE"
Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 26-30.

High-strength concrete is becoming increasingly popular in the greater Seattle area. Testing labs and consultants in the area claim that because of the high quality of aggregates available, concrete with a strength of 20,000 psi should not be difficult to produce. Results of many laboratory tests have proven this to be true, but much of this research has gone on without fully considering the ready-mixed concrete suppliers. They are very important to the team effort that is necessary to produce high-strength concrete, and therefore must be involved in all aspects of the job, including the planning.

3038
Irassar, F. and Batic, O.,
"EFFECTS OF LOW CALCIUM FLY ASH ON SULFATE RESISTANCE OF OPC CEMENT"
Cement and Concrete Research, Mar 1989, Vol. 19, No. 2, pp 194-202.

Low calcium fly ash is a good pozzolan to improve sulfate resistance of ordinary portland cement (opc). Beneficial effects produced by this pozzolan on opc are studied in the present paper. Results of sulfate resistance evaluated by Koch & Steinegger method are presented for four opc + fly ash cements. The changes in the mineralogical composition of mortar are analyzed by x-ray diffraction, scanning electron microscopy, and energy dispersive analysis of x-ray (edax). Fly ash addition delays ettringite formation-cracking phenomenon and decreases the acid attack.

3039
John, R. and Shah, S. P.,
"FRACTURE MECHANICS ANALYSIS OF HIGH-STRENGTH CONCRETE"
Journal of Materials in Civil Engineering, Nov 1989, Vol. 1, No. 4, pp 185-198.

It has been shown that the 2-parameter fracture model has been successfully used to study the tensile and flexural fracture of high-strength concrete. This model is based on the observation that to evaluate a size-independent fracture parameter or parameters for concrete, one must include pre-critical stable crack growth. The size-independent fracture parameters, critical stress intensity factor at the tip of an effective crack, and critical crack tip opening displacement have been determined to depend on the static uniaxial compressive strength of concrete. Empirical relations were derived for concretes having compressive strength up to 110 MPa (16,000 psi). The ACI equation for determining Young's modulus was found to be adequate for high strength concrete. These and other conclusions drawn from the study are discussed.

Johnson, D. C.,
"DURABILITY OF SILICA FUME CONCRETES FOR HIGH-STRENGTH PRECAST PRESTRESSED CONCRETE BRIDGE GIRDERS IN ALBERTA"
Proceedings of the 1989 Annual Conference of the Roads and Transportation Association of Canada, pp B55-B75.

Durability tests used in this study include the following: 20-hour and 28-day compressive strength, 28-day flexural strength, resistance to freezing and thawing, scaling in the presence of deicing salt, and chloride permeability. The determination of air void parameters and their relationship to the durability of laboratory test specimens and the performance of selected in-service bridge elements is an integral part of the work. The results illustrate the difficulties in relating air void parameters to performance both in the field and in the laboratory. In the field, scaling does not correlate well with air content, spacing factor and specific surface (ASTM C457) in both the Alberta study and a larger similar study in the U.S. In the laboratory, the entrainment of air void systems in superplasticized silica fume concretes that comply with currently accepted criteria is shown to present no real difficulty with the particular admixtures employed. However, the results of durability tests show that scaling in particular may occur even when the air void system meets these criteria, that accelerated curing may increase scaling and chloride permeability, and that silica fume enhances resistance to scaling as well as impermeability to chloride.

3041
Johnson, M. K. and Ramirez, J. A.,
"MINIMUM SHEAR REINFORCEMENT IN BEAMS WITH HIGHER STRENGTH CONCRETE"
ACI Structural Journal, July-Aug 1989, Vol. 86, No. 4, pp 376-382.

The adequacy of the minimum shear reinforcement provision in higher strength reinforced concrete beams was investigated. Eight rectangular beams with concrete compressive strengths in the range of 5000 to 10,500 psi and with web reinforcement indexes in the range of 0 to 100 psi designed to fail in shear were tested. Truss models were used to illustrate the ultimate shear behavior of such members. From an evaluation of the results of this experimental investigation and previous studies, it was concluded that the overall reserve shear strength after diagonal tension cracking diminished with the increase in fc' for beams with the current minimum amount of shear reinforcement.

3042
Jumppanen, U.,
"EFFECT OF STRENGTH ON FIRE BEHAVIOUR OF CONCRETE"
Nordic Concrete Research, 1989, Publication No 8, pp 116-127.

The use of high strength concretes enhances the economy of structures, but this involves also a knowledge of their high temperature behaviour because the structures may be subjected to high temperatures (e.g. fire) and they must be correspondingly designed. High temperature behaviour of different high and ultra high strength concretes has been investigated. Studies comprised mechanical properties and the chemical and physical background of their alteration due to heating. The high strength concretes showed a stronger loss of strength and a higher risk of spalling than normal strength concretes.

3043
Kashi, M. G. and Weyers, R. E.,
"FREEZING AND THAWING DURABILITY OF HIGH STRENGTH SILICA FUME CONCRETE"
Structural Materials, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by James F. Orofino; ASCE, New York, 1989, pp 138-148.

Specimens from 27 batches of concrete with a water to cementitious (cement plus silica fume) ratio of 0.25 to 0.32, with and without entrained air, were tested for freeze-thaw durability in accordance with ASTM C666, procedure A (freezing and thawing in water). In addition, another set of similar specimens were moist cured for 28 days instead of 14 days and tested in accordance with ASTM C666, procedure A to determine the effect of curing time on the freeze-thaw durability of high strength concrete. Results show that non-air entrained high strength concrete with water-cementitious ratio of less than 0.30, regardless of the length of curing time, is frost resistant. Non-air entrained concrete with water-cement ratio of 0.32 is durable if silica fume is not used.

3044
Kawakami, H., Yagi, J-I., and Waki, K.,
"A STUDY OF THE RAPID ESTIMATION OF 28-DAY COMPRESSIVE STRENGTH OF CONCRETE"
Transactions of the Japan Concrete Institute, 1989, Vol. 11, pp 69-76.

This paper reports a study regarding the rapid estimation of the 28-day compressive strength of concrete by 30 minutes curing of the wet-screened mortar in boiling water. It was demonstrated that the method, simple and rapid, is a possible way for rapid estimation of the 28-day compressive strength of concrete before the concrete is placed.

3045
Khaloo, A. R. and Ahmad, S. H.,
"BEHAVIOR OF HIGH-STRENGTH CONCRETE UNDER TORSIONAL TRIAXIAL COMPRESSION"
ACI Materials Journal, Nov-Dec 1989, Vol. 86, No. 6, pp 550-558.

Sixty-four solid cylinders [ 3 x 9 in. (76.2 x 228.6 mm)] using high-strength concrete were tested under uniaxial compression, shear, cylindrical triaxial compression with low lateral stresses, and torsional cylindrical triaxial compression loadings to determine strength and behavior of concrete under these loading paths. For cylindrical triaxial compression, the concrete-filled steel tube specimens were tested under strain control condition, and complete axial stress-axial strain and axial stress-lateral strain curves were obtained. Comparison between the results of this study under cylindrical triaxial compression with low lateral stresses for high-strength and those of other studies for normal-strength concrete reveals that normal strength concrete exhibits a relatively flatter postpeak behavior.

3046
Kollek, J. J.,
"DETERMINATION OF THE PERMEABILITY OF CONCRETE TO OXYGEN BY THE CEMBUREAU METHOD - A RECOMMENDATION"
Materials and Structures, May 1989, Vol. 22, No. 129, pp 225-230.

A committee was set up in 1981 by the Cembureau Working Party on the Quality of Concrete with the following aims and objectives: (1) to develop a suitable method for the measurement of the permeability of concrete to gas or water and to determine the effects of mix proportions and curing, and (2) to establish the feasibility of obtaining concordant results in a number of participating laboratories. Eight European laboratories have participated in the study and carried out a number of cooperative programs in the course of six years. This recommendation of the method, inclusive of apparatus and procedure, is based on the findings of the committee. The work has given rise to a number of reports, some of which have been published with the approval of this committee. A limited bibliography of recent papers which the committee has considered and discussed is appended to the recommendation.

3047
Kozeliski, F. A.,
"EXTENDED MIX TIME CONCRETE"
Concrete International: Design & Construction, Nov. 1989, Vol. 11, No. 11, pp. 22-26.

Traditionally, specifications often allow 1 and 1 1/2 hour maximum mixing times before concrete is delivered to the job site. However, traffic and equipment problems can make maximum mixing times as great a concern on large metropolitan projects as it is for delivery of quality concrete to remote areas. The author suggests that concrete mixtures can now be designed for delivery to projects within three to four hours after the cement and water are mixed if retarders are used and if the concrete temperature is no higher than 90o F (32o C) when placed into forms. Research on admixture has shown that the initial and final set of concrete can be extended two to six hours from initial set of cement with different dosages of retarders at different temperatures. High-range water reducers can increase the slump at the project site, if required, without changing the water-cement ratios. Therefore the time limit can be increased by making use of the admixture and concrete technology of today.

3048
Kuennen, T.,
"FAST CURE FOR AILING COUNTY BRIDGE DECK"
Roads and Bridges, Jun 1989, Vol. 27, No. 6, p 77.

The fast setting of a bridge deck replacement on a chilly April day in Indiana is described. A new deck was placed on an overcast, blustery day using a new proprietary blended hydraulic cement, Pyrament. The primary considerations in its use were quick turnaround of the bridge deck, and long-term durability. Details of the construction are briefly noted. The concrete was batched just as conventional concrete. The plastic concrete was pumped and distributed over rebar ahead of a deck finisher. Other details of the construction are noted. Anticipated resistance of the cured Pyrament concrete to chloride ion penetration permitted use of reinforcing steel without epoxy coating.

3049
Kunishima, M. and Okamura, H.,
"DURABILITY DESIGN FOR CONCRETE BRIDGE STRUCTURES"
Structural Design, Analysis and Testing, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by A. H-S. Ang; ASCE, New York, 1989, pp 1029-1038.

The concept of durability design for concrete structures including bridge structures is proposed on the basis of comprehensive evaluation of materials, design details and construction works under a certain environmental condition. The fundamental design philosophy has been developed by the authors and was principally accepted by the Subcommittee on durability design for concrete structures in the Japan Society of Civil Engineers (JSCE). In the Subcommittee, where H. Okamura is chairman and M. Kunishima is a member, the new concept on durability index has been introduced. The methodology to calculate the index quantitatively has been discussed and the proposed recommendation for durability design of concrete structures shall be published in 1989 by the committee on concrete in JSCE. This paper describes the framework for the new durability design of concrete structures and several case studies for its applications to practical concrete bridge structures.

3050
Langley, W. S., Carette, G. G., and Malhotra, V. M.,
"STRUCTURAL CONCRETE INCORPORATING HIGH VOLUMES OF ASTM CLASS F FLY ASH"
ACI Materials Journal, Sep-Oct 1989, Vol. 86, No. 5, pp 507-514.

Results of investigations dealing with concrete incorporating high volumes of ASTM Class F fly ash are given. Concrete mixtures containing 56 percent of fly ash by weight of total cementitious materials were evaluated in the laboratory at several water-to- cementitious materials ratios. The concretes investigated were air entrained and had cement contents of 100, 150, and 180 kg/m3 of concrete and water contents ranging from 100 to 120 kg/m3. In spite of the relatively low cement factors used, the concretes investigated had excellent mechanical and elastic properties, and performed satisfactorily in freeze-thaw tests done in accordance with ASTM C 666, Procedure A.

3051
Laplante, P. and Aitcin, P-C.,
"UTILIZATION OF HIGH-STRENGTH CONCRETE IN CANADA"
Canadian Journal of Civil Engineering, Oct 1989, Vol. 16, No. 5, pp 661-668.

In the late sixties, several concrete producers in the Chicago area developed very high strength concrete. The compressive strength of this new type of concrete was increased gradually, and it is now possible to buy 100 MPa ready-mixed concrete in several places in North America. Of significant technological importance, very high strength concrete is becoming popular all over North America due to its profitability. In Canada, very high strength concrete is beginning to be used in the Toronto and Montreal area. This paper summarizes the principal results obtained on two specific projects: the construction of an experimental column in Montreal in 1984, and the construction of Nova Scotia Plaza in Toronto in 1986. In French.

3052
Lee, G. C., Shih, T. S., and Chang, K. C.,
"BASIC MECHANICAL PROPERTIES OF NORMAL AND HIGH STRENGTH CONCRETE AT LOW TEMPERATURE"
Proceedings of the Eighth International Conference on Offshore Mechanics and Arctic Engineering, Mar 19-23, 1989, The Hague, Neth.; ASME, New York, 1989, Vol. 3, pp 591-594.

The basic mechanical properties of concrete under low temperature are important for cold regions engineering. The results of a series of laboratory studies on selected mechanical properties of normal and high-strength concrete in the temperature range of plus 20 degree C to minus 70 degree C (plus 68 degree F to minus 94 degree F) are presented. Test results show that concrete compressive, local bond, and splitting tensile strength, Young's modulus, and Poisson's ratio increase as the temperature decreases, and the rate of increase for high-strength concrete at different corresponding low temperature is generally lower than that for normal strength concrete.

3053
Luther, M. D.,
"MICROSILICA (SILICA FUME) CONCRETE DURABILITY IN SEVERE ENVIRONMENTS"
Structural Materials, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by James F. Orofino; ASCE, New York, 1989, pp 95-105.

Microsilica (silica fume) concrete has provided increased durability in a variety of aggressive environments. Technical information is presented for microsilica concretes exposed to fire, abrasion, frost, marine, and various chemical environments including chlorides, sulfates, and acids. Also, the resistance of microsilica concrete to the actions of burglars (jackhammering, coring, torching, etc.) is discussed. Examples of structures that have used microsilica concretes to improve durability in severe environments are presented. The performance of the microsilica concretes used in these structures has, to date, generally confirmed the favorable results predicted by many laboratory investigations.

3054
Mak, S. L., Darvall, P. Le P., and Attard, M. M.,
"A REVIEW OF THE USE OF SILICA FUME IN VERY HIGH STRENGTH CONCRETES"
Department of Civil Engineering, Monash University, Clayton, Victoria, Australia, Civil Engineering Research Report, No. 7/1989, 73 pp.

Silica fume has for some years been used in the Scandinavian countries to improve the quality of concrete but is relatively unknown to the Australian concrete industry. Silica fume has for some time been used in various applications to improve the overall quality of concrete both in the fresh and the hardened state. It has been used extensively to improve the durability of concrete. It is an extremely efficient repair material given its thixotropic properties and its use in roller compacted concrete has been successful. The use of silica fume in abrasion resistant concrete is an economically attractive one and its applications in offshore structures have also been successful. In recent years, silica fume has been used in the production of high strength concretes. At the present state of the art, field placeable concretes with compressive strengths in excess of 100 MPa have been produced successfully only when silica fume was used as a partial replacement for portland cement. This is a survey of some of the most recent developments, both in research and in actual applications, on the production, behavior and properties of concretes containing silica fume. The ways in which silica fume may affect the properties of the fresh and hardened concrete are examined.

3055
Malhotra, V. M.,
"MECHANICAL PROPERTIES AND FREEZING AND THAWING DURABILITY OF CONCRETE INCORPORATING A GROUND GRANULATED BLAST-FURNACE SLAG"
Canadian Journal of Civil Engineering, Apr 1989, Vol. 16, No. 2, pp 140-156.

A series of fifteen 0.06 m3 concrete mixtures were made with water-to-(cement plus slag) ratios (W/(C plus S)) ranging from 0.70 to 0.45. The percentage of slag used as a partial replacement for normal portland cement ranged from 0 to 100% by weight. All mixtures were air entrained. A number of test cylinders and prisms were cast for determining the mechanical properties and freezing and thawing resistance of concrete. The test results indicate that the ground granulated blast-furnace slag can be used with advantage as a partial to placement for portland cement in concrete at 50% or lower replacement levels, especially at W/(C plus S) of the order of 0.55 or lower. The compressive strength of the concrete incorporating slag is comparable with that of the concrete made with normal portland cement. The flexural strength of the slag concrete is comparable with or greater than the corresponding strength of the control concrete. Durability of air-entrained slag concrete exposed to repeated cycles of freezing and thawing is satisfactory.

3056
Malhotra, V. M.,
"SUPERPLASTICIZERS: A GLOBAL REVIEW WITH EMPHASIS ON DURABILITY AND INNOVATIVE CONCRETES"
Proceedings of the Third CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1989, Ottawa, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1989, pp. 1-17. (ACI SP-119)

This review paper traces the development of superplasticizers in Japan and Germany, describes briefly their mode of action, and discusses the properties of superplasticized fresh and hardened concrete. Data are presented on the use of superplasticizers in Australia, Canada, Japan, Singapore, U.K., U.S.A. and Western Europe. The performance of superplasticized concrete under freezing and thawing conditions both in the laboratory and in the field is discussed, and the use of superplasticizers in the development of innovative concretes is described. The ASTM and Canadian specifications dealing with superplasticizers are discussed. A list of pertinent references is included.

3057
Malhotra, V. M., and Painter, K. E.,
"EARLY-AGE STRENGTH PROPERTIES, AND FREEZING AND THAWING RESISTANCE OF CONCRETE INCORPORATING HIGH VOLUMES OF ASTM CLASS F FLY ASH"
International Journal of Cement Composites and Lightweight Concrete, Feb 1989, Vol. 11, No. 1, pp 37-46.

This paper reports results of an investigation to determine the early-age strength and the freezing and thawing resistance of concrete incorporating high volumes of ASTM class F fly ash. Three series of concrete mixtures were made. In series 1, the cement content was kept constant at 145 5 kg/m3, and the fly ash amount was varied from 110 to 197 kg/m3. The water-to-cementitious material ratio ranged from 0.32 to 0.42, and the entrained-air content of the mixture was 9.5 1.0%. The mixtures of series 2 were similar to those of series 1 except that the air content was reduced to a conventional amount, i.e., 5.5 1.0%. In series 3 mixtures, the fly ash content varied from 183 to 275 kg/m3; the resulting water-to-cementitious materials ratio ranged from 0.28 to 0.35, with the entrained-air content at 4.0 0.5%. The strength properties of the concrete were determined at ages up to 91 days, and the freezing and thawing tests were performed in accordance with ASTM C 666 procedure A. The results of this investigation show that the compressive strength of concrete incorporating high volumes of ASTM class F fly ash increases with decreasing water-to-cementitious materials ratio, i.e., with the increasing amounts of fly ash. The optimum amount of fly ash appears to be about 200 kg/m3 of concrete. The concretes investigated had adequate early-age strength, and the freezing and thawing resistance of the concretes was satisfactory except that the test prisms suffered moderate to considerable surface scaling.

3058
Malier, Y., Pliskin, L., Millan, A., Hagolle, D., Hoguet, P., Cadoret, G., Leboulicaut, J-P., Regnier, J-M., de Larrard, F., Schaller, I., Bonnet, G., Sudret, J-P., and Brazillier, D.,
"HIGH-PERFORMANCE BRIDGE: THE EXPERIMENTAL STRUCTURE OF JOIGNY (YONNE REGION OF FRANCE)"
Travaux, Apr 1989, No. 642, pp 57-65.

The experimental bridge of Joigny was launched under the aegis of France's national project for 'New Avenues for Concrete'. What is involved is the construction of a bridge using concrete with a characteristic 28-days strength of 60 MPa. The mix design of this concrete has no silica fume and was produced by the traditional network of ready-mix plants. Using rigorous quality control measures, this project was completed successfully. Experimentation is still under way, but it is already certain that the durability of this type of concrete has been considerably improved. New possibilities for the design of bridges are thus offered, benefiting from these gains in strength and durability. In French.

3059
McCurrich, L. H.,
"ADMIXTURES. TRENDS IN THEIR USE, LONG TERM DURABILITY AND PROPOSED EURO-STANDARD"
Concrete (London), Aug 1989, Vol. 23, No. 7, pp 25-28.

Today it is estimated that over 50% of concrete produced contains a chemical admixture, and there is now general recognition that a chemical admixture provides a cost effective method of improving the quality and durability of concrete. This article illustrates some of trends and describes some of the laboratory research work which has been done to verify the long term performance of admixtures in concrete. The use and performance of chemical admixtures is now widely covered by International Standards and the article concludes by reviewing the progress currently being made in drafting a Euro-Standard for admixtures.

3060
Mitsui, K., Kasami, H., Yoshioka, Y., and Kinoshita, M.,
"PROPERTIES OF HIGH-STRENGTH CONCRETE WITH SILICA FUME USING HIGH-RANGE WATER REDUCER OF SLUMP RETAINING TYPE"
in Proceedings of the Third CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1989, Ottawa, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1989, pp. 79-97. (ACI SP-119)

This paper presents the results of laboratory investigations to determine the effect of a slump-retaining type high-range water reducer. Various effects such as temperature, mix proportions and admixture dosages on rheological and mechanical properties of concrete before and after hardening of concrete were examined. Slump, air content and flow were tested after mixing. Setting time and bleeding were also measured. The hardened concrete was tested for strength, modulus of elasticity, shrinkage and durability. The results indicated that it was possible to produce workable high strength concrete and retain its workability by the admixture better than conventional superplasticizers. Higher temperature at mixing resulted in the retention of higher workability. Too much dosage of the admixture delayed the setting time, while no other adverse effects were noticed on mechanical properties of hardened concrete.

3061
Montgomery, F. R., Long, A. E., and Basheer, P. A. M.,
"ASSESSING SURFACE PROPERTIES OF CONCRETE BY IN-SITU MEASUREMENTS," IABSE Report, 1989, Vol. 57/2, pp 871-876.

This paper describes three test methods, developed at the University of Belfast, which are used to assess the surface strength, surface permeability, and abrasion resistance of on- site concrete. It describes the successful application of these methods in the laboratory, and gives details of on-site tests in Northern Ireland. The pull-off test using the LIMPET allows the determination of the compressive strength of a surface layer of concrete. This uses an epoxy resin adhesive to attach a circular steel probe to the specimen under test. Its accuracy was assessed during the construction of a multi-story car park. The CLAM permeability test enables the coefficient of permeability to be determined for the surface layer. This uses compact equipment that does not disturb the concrete. It was assessed in a multi-story car park. The TEREDO was developed for the on-site assessment of abrasion resistance. This uses three sets of spiked steel dressing wheels, mounted on a central spindle, to accelerate abrasion. Extensive experience of the tests shows that: (1) the LIMPET test is quick, accurate, and reasonably consistent; (2) the CLAM test is quick and reliable; (3) the TEREDO is portable, and can be used easily to measure the surface abrasion of concrete floors; and (4) by using the tests in combination, it should be possible to predict many of the problems related to durability of concrete structures before they become serious.

3062
Mor, A., Monteiro, P. J. M., and Hester, W. T.,
"OBSERVATIONS OF HEALING OF CRACKS IN HIGH-STRENGTH LIGHTWEIGHT CONCRETE"
Cement, Concrete, and Aggregates, Winter 1989, Vol. 11, No. 2, pp 121-125.

This paper describes the microscopic characterization of the cracking pattern which developed during fatigue tests on reinforced beams made with high-strength lightweight concrete. The results of observations from selected sections lightweight concrete beams which failed under fatigue loading are presented. Scanning electron microscopy was used to characterize the cracking pattern, particularly at the transition zone between aggregate and reinforcing steel. The healing process was also studied.

3063
Moukwa, M., Aitcin, P-C., Pigeon, M., and Hornain, H.,
"FREEZE-THAW TESTS OF CONCRETE IN SEAWATER"
ACI Materials Journal, Jul-Aug 1989, Vol. 86, No. 4, pp 360-366.

The paper discusses the freeze-thaw durability of air-entrained concrete (w/c=0.44, 4 % air) in seawater for marine construction. Two laboratory procedures were used. The first procedure approximates the field freeze-thaw conditions the concrete undergoes in the tidal zone. The second procedure was similar to the one recommended in ASTM C 666, Procedure A. The experiments were performed in fresh water and seawater. The results of the study suggest that, in the performance of concrete under arctic conditions, surface effects probably play an important role in the deteriorative mechanisms.

3064
Moukwa, M., Aitcin, P-C., and Regourd, M.,
"DURABILITY OF CONCRETE UNDER SIMULATED ARCTIC CONDITIONS"
Cement, Concrete, and Aggregates, Summer 1989, Vol. 11, No. 1, pp 45-51.

The durability of 0.44 W/C concrete under simulated arctic conditions was studied. The length change of concrete specimens was monitored throughout the test. Samples taken from the concrete specimens before and after the test were analyzed to determine the effects of simulated arctic conditions on the microstructure of the concrete. The results showed that the alternating conditions of immersion in seawater and exposure to cold air mostly affect the surface layer of the concrete and facilitate a deep migration of aggressive ions like magnesium and sulfate.

3065
Muguruma, H., Watanabe, F., and Komuro, T.,
"APPLICABILITY OF HIGH STRENGTH CONCRETE TO REINFORCED CONCRETE DUCTILE COLUMN"
Transactions of the Japan Concrete Institute, 1989, Vol. 11, pp 309-316.

To investigate the possibility of the ductility enhancement of high-strength concrete column, eight column specimens confined by lateral reinforcement were tested under reversed cyclic lateral loads with constant axial compressive load levels from 0.254 to 0.629. The concrete compressive strengths were 85.7 and 115.8 MPa. Test results indicated that the very large ductility could be achieved by using high yield strength lateral reinforcement even for such high-strength concrete columns. Modifications of previously proposed stress-strain models on confined concrete were also made for extensive applications to the calculation of moment-curvature relationships of confined high-strength concrete members.

3066
Naik, T. R., and Ramme, B. W.,
"HIGH-STRENGTH CONCRETE CONTAINING LARGE QUANTITIES OF FLY ASH"
ACI Materials Journal, Mar-Apr 1989, Vol. 86, No. 2, pp 111-116.

The paper presents research performed to identify and recommend mix designs for high fly ash content 3000 and 4000 psi (21 and 28 MPa) structural grade concrete utilizing Class C fly ash. The fly ash was produced at Wisconsin Electric Power Plant.

3067
Nmai, C. K. and Corbo, J. M.,
"SODIUM THIOCYANATE AND THE CORROSION POTENTIAL OF STEEL IN CONCRETE AND MORTAR," Concrete International: Design & Construction, Nov. 1989, Vol. 11, No. 11, pp. 59-67.

This paper presents a detailed review of studies using electrochemical and time-to-corrosion test procedures for ordinary reinforcing steel and stress-corrosion cracking tests for prestressing wire to investigate the corrosivity of sodium thiocyanate. The data clearly indicate that sodium thiocyanate-based admixtures either reduced or did not affect the corrosion rate of steel in concrete at the maximum dosage levels currently recommended. Brief summaries of some corrosion studies on three other inorganic salts are also presented.

3068
Owens, P. L.,
"WATER AND ITS ROLE ON CONCRETE"
Part 1 of 2, Concrete Interntional: Design & Construction, Nov. 1989, Vol. 11, No. 11, pp. 68-74.

Water plays such an important role in concrete that a better understanding of the various beneficial or destructive phenomena is needed, as well as what has to be done to produce more stable and durable concrete. The article discusses mix water quality, fresh water, non-fresh water, and water temperature. Cement freshness, organic matter, and admixtures are discussed, as well as coping with impure mix water. Mix water quantity is considered, as well as the effect of temperature on the viscosity of water, aggregate size, aggregate angularity and grading compatibility, aggregate absorption, aggregate/concrete density, workability, cement type, and cement content.

3069
Owens, P. L.,
"WATER AND ITS ROLE IN CONCRETE"
Part 2 of 2, Concrete International: Design & Construction, Dec. 1989, Vol. 11, No. 12, pp. 68-71.

Many of the current theories relating to the durability of concrete date from about 50 years ago, when principles of concrete manufacture were considerably different. The water content of concrete is seen as an important consideration in the future. Effectively reducing the volumes of pore water in the concrete to significantly below 10 percent will dramatically increase the durability without increasing costs. Durability proposals should encompass the important effect of the heat of hydration and temperature generated which have been shown to have a strong influence on the permeability and other characteristics of the finished concrete in which water plays a principal role. This article discusses hydration and pore water, and the influence of solutions of water on hardened concrete.

3070
Penttala, V. E.,
"EFFECTS OF MICROPOROSITY ON THE COMPRESSION STRENGTH AND FREEZING DURABILITY OF HIGH-STRENGTH CONCRETES"
Magazine of Concrete Research, 1989, Vol. 41, No. 148, pp 171-181.

High-strength concretes were produced using four different binder combinations. Curing and heat treatment tests were conducted and the results were used to validate a theory relating binder paste microporosity, concrete compression strength and freezing durability. The porosities of the test concretes were measured by mercury porosimetry and the microporosity of the hardened cement paste by nitrogen adsorption. Thin-section microscopy was also used. Compression and flexural strength values of the test concretes were obtained. The freezing durability of the test concretes was examined by a freeze-thaw test in water and by a salt freeze test, where freezing and thawing took place in a salt solution.

3071
"PERMEABILITY OF CONCRETE"
Concrete Construction, Oct 1989, Vol. 34, No. 10, pp 870, 872.

Concrete used in water-retaining structures, exposed to severe weather, or exposed to an aggressive environment must be virtually impermeable or watertight. Watertightness refers to the ability of concrete to hold back or retain water without visible leakage. Permeability refers to the amount of water migration through concrete when the water is under pressure, and also to the ability of concrete to resist penetration of any substance, be it liquid, gas, or chloride ion. The growing awareness of the role permeability plays in the long-term durability of concrete has led to the need for ways to quickly assess the permeability of concretes. The use of admixtures such as silica fume, latex emulsions, and high-range water reducers allows placement of highly impermeable concrete. The study confirmed that several rapid-test procedures are available for estimating permeability instead of more complex flow testing.

3072
Pierre, A., Lamarche, J. M., Mercier, R., and Foissy, A.,
"ADSORPTION OF A CEMENT PLASTICIZER IN CALCIUM CARBONATE"
Cement and Concrete Research, Sep 1989, Vol. 19, No. 5, pp 692-702.

Adsorption isotherms of naphthalene formaldehyde condensate in CaCO3 dispersions have been determined versus ph, ionic strength and calcium ion concentration. The higher the ph, the lowest the polymer adsorbates. Increase of the ionic strength enhances the adsorption. Macroscopic properties such as stability and rheology have been compared both to the polymer adsorption and to the induced surface charge. A compilation of the results shows how the calcium ions play a major role in the adsorption process. At high ionic strength (greater than 1m per l), the stability modifications are also related to polymer adsorption although electrostatic interactions should not be invoked.

3073
Pigeon, M.,
"THE FROST RESISTANCE OF CONCRETE"
Materials and Structures, Jan 1989, Vol. 22, No. 127, pp 3-14.

There are two distinct manifestations of frost damage in concrete: internal microcracking and surface scaling. Although scaling is much more frequent, its mechanisms are not as well known as those of internal microcracking. It is known, however, that the use of salt is an important cause of scaling. The theories that describe the mechanisms of frost deterioration in concrete concern mostly the internal microcracking. They are summarized in the first part of the paper. These theories all point out the importance of air bubbles and their spacing for concrete durability. Thus air entrainment and the air void spacing factor are very important. The critical air void spacing factor concept (i.e. the maximum air void spacing over which frost damage occurs under given conditions) developed at Laval University is discussed. Results of field tests are presented. The choice of aggregate is important since certain aggregates are frost-susceptible. In French.

3074
Randall, V. R., and Foot, K.,
"HIGH-STRENGTH CONCRETE FOR PACIFIC FIRST CENTER"
Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 14-16.

Strict testing and quality control insured successful placement of high-strength concrete in the construction of a building in Seattle, Washington. The design strength of the concrete was 14,000 psi, and the actual strength achieved was measured at 18,000 psi. The article describes various methods for testing and production to accommodate this very high-strength mix. The high-strength concrete mix used a 3/8-inch pea gravel aggregate and a coarse sand with a fineness modulus of 3.2. Admixtures consisted of a water reducer/retarder, superplasticizer, and condensed silica fume. The cementitious portion of the mix was made up of Type I cement having low water demand characteristics, together with one sack of fly ash per cubic yard. 4 x 8 inch test specimens were determined to yield the best results. Compressive test results are described. Modifications to conform to field conditions are also described. Quality control and problems in production and handling are described.

3075
Rasheeduzzafar, Al-Gahtani, A. S., and Al-Saadoun, S. S.,
"INFLUENCE OF CONSTRUCTION PRACTICES ON CONCRETE DURABILITY"
ACI Materials Journal, Nov-Dec 1989, Vol. 86, No. 6, pp 566-575.

Data have been developed on the effects of curing period length, type of curing water, aggregate washing, and the degree of consolidation on corrosion resistance characteristics of concrete. The effects of curing period and consolidation on the sulfate resistance of concrete have also been evaluated. Results show that concretes cured for 28 days performed 4.4 times better in terms of corrosion of reinforcement and showed 59 percent strength reduction and 40 percent weight loss improvements to sulfate resistance compared to concretes cured for 7 days. The beneficial effect of aggregate washing is, on average, about 15 to 20 percent for the aggregates tested in this study. Degree of consolidation has a significant effect on concrete durability.

3076
Rose, K., Hope, B. B., and Ip, A. K. C.,
"FACTORS AFFECTING STRENGTH AND DURABILITY OF CONCRETE MADE WITH VARIOUS CEMENTS," Transportation Research Record, 1989, No. 1234, pp 13-23. (see also Cement and Concrete Research, May 1989, Vol. 19, No. 3, pp 476-486.)

This investigation examined variables influencing the 28-day compressive strength and 50-cycle salt scaling loss of concretes made with 18 Type 10 cements. Statistical analysis was performed on test data consisting of chemical and physical properties of cements; properties of fresh concretes; compressive strength, salt scaling loss, and air void parameters of mature concretes. For a similar water-cement ratio and cement content, results from the correlation analysis indicated that the 28-day concrete strength and 50-cycle salt scaling loss were influenced significantly by the chemical and physical properties of the cement used in the mix. Compressive strength has a strong negative correlation with alkali content, indicating that cements with a high alkali content produced concretes with lower compressive strength. Fineness (percent of particles in the 4 to 20-micro m range) is related to low salt scaling loss. Equations predicting strength and salt scaling loss of concrete were developed by using multiple linear regression.

3077
Rosenburg, A. M. and Gaidis, J. M.,
"A NEW MINERAL ADMIXTURE FOR HIGH-STRENGTH CONCRETE"
Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 31-36.

A new silica fume admixture in liquid form has been developed that is easier to handle than conventional powder forms. With this product, consistently high strength can be obtained regardless of portland cement source. The strength increase does not appear to be related to reduced porosity. The permeability of concrete is reduced when this new admixture is used. The use of high-strength aggregate did not increase mortar strength. It was found that in concrete made with the new admixture, a water layer does not form around the aggregates, and the amounts of calcium hydroxide and ettringite are reduced, leading to a stronger interfacial paste. Silica fume does not densify concrete in the usual sense, but enhances the paste-aggregate bond, which is usually the weakest part of concrete.

3078
Russell, H. G., Gebler, S. H., and Whiting, D.,
"HIGH STRENGTH CONCRETE: WEIGHING THE BENEFITS"
Civil Engineering, Nov 1989, Vol. 59, No. 11, pp 59-61.

Advances in technology have made possible concrete with a compressive strength of 10,000 psi and also created concrete that is more durable and resists corrosion and abrasion better than conventional mixes. Together with this comes a responsibility for more careful attention to concrete design, specification, production and testing, and increased need for coordination and communication between the design and construction teams. High strength concretes, used commonly in high rise buildings, are now being used in bridges: East Huntington Bridge over the Ohio River and the Annicis Bridge near Vancouver. Concrete with a compressive strength of 9,000 psi has been used in several prestressed girder bridges in Washington State. Other recent uses include parking garages, bridge deck overlays, dam spillways, offshore structures, etc. Other mechanical properties which dictate the selection of high strength concrete are discussed: modulus of elasticity, tensile strength, and creep. Lower water-to-cementitious materials ratios, and more restricted, less continuous internal void spaces make high strength concrete less permeable and more resistant to corrosive agents such as chlorides.

3079
Russell, H. G. and Larson, S. C.,
"THIRTEEN YEARS OF DEFORMATIONS IN WATER TOWER PLACE"
ACI Structural Journal, Mar-Apr 1989, Vol. 86, No. 2, pp 182-191.

Water Tower Place, an 859 ft (262 m) high reinforced concrete building, was instrumented to measure the time-dependent vertical deformations of columns, walls, and caissons. Vertical shortening of individual members and their relative vertical displacements were measured at selected floor levels. Most measurements were taken during the first 5 years after construction started. Additional measurements were obtained after about 13 years. Laboratory tests were performed on concrete obtained in the field. The variation of compressive strength, modulus of elasticity, coefficient of thermal expansion, creep, and shrinkage with age of concrete were determined for each concrete strength. Measurements of creep and shrinkage on the high-strength concrete continued for over 13 years. Measured deformations were compared with calculated deformations, and satisfactory agreement was obtained. Deformations were calculated based on actual construction schedule, estimated loads during construction and occupancy, and measured material properties.

3080
Salandra, M. A. and Ahmad, S. H.,
"SHEAR CAPACITY OF REINFORCED LIGHTWEIGHT HIGH-STRENGTH CONCRETE BEAMS"
ACI Structural Journal, Nov-Dec 1989, Vol. 86, No. 6, pp 697-704.

Sixteen beams made of lightweight high-strength concrete were tested to determine their diagonal cracking and ultimate shear capacities. The variables in the test program were concrete strength, which varied between 7800 and 10,500 psi (53.8 and 72.5 MPa); shear span-to-depth ratio a/d equals 0.56, 1.56, 2.59, and 3.63; and web reinforcement. Eight of the test beams had no reinforcement and the other eight had web reinforcement along the entire length of the beam. Test results indicate that the ACI Building Code predictions of Eq. (11-3) and (11-6) for lightweight concretes are unconservative for beams with tensile steel ratios of 1.45 percent, a/d ratios greater than 3.63, and compressive strengths in excess of 10,000 psi (69 MPa).

3081
Shih, T. S., Lee, G. C., and Chang, K. C.,
"ON STATIC MODULUS OF ELASTICITY OF NORMAL-WEIGHT CONCRETE"
Journal of Structural Engineering, Oct 1989, Vol. 115, No. 10, pp 2579-2587.

This paper reports a study which examined the value of concrete modulus of elasticity based on laboratory test results. The observed Young's modulus was compared with the value given by ACI-318 (ACI Building Code 1983) and with those reported by others. The results suggest that Young's modulus of high-strength concrete has a somewhat higher value than that of normal-strength concrete. Details of the experimental study and results are discussed. It is noted that Pauw's equation for modulus of elasticity of concrete which is based on experimental normal-strength concrete needs to be reexamined. These and other observations are discussed.

3082
Shin, S-W. and Ghosh, S. K.,
"FLEXURAL STRENGTH OF ULTRA-HIGH STRENGTH CONCRETE MEMBERS"
in Structural Design, Analysis and Testing, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by A. H-S. Ang; ASCE, New York, 1989, pp 576-581.

Various proposals have been made for the prediction of strength of high strength concrete sections. One of the most important parts of any strength computation procedure is the assumption of a suitable compression concrete stress block. Another important aspect of a strength prediction procedure is the assignment of a value to the ultimate compression strain of concrete u and the value of Ec. These investigations were undertaken to address those concerns. A rectangular stress block of the ACI Code was also found to give acceptably conservative strength predictions over the entire range of concrete strength from 27.6 MPa (4ksi) to 103.5 MPa (15ksi). Some of the measured maximum extreme compression fiber strain do fall below 0.003 at high concrete strength. u equals 0.0025 would be a more conservative lower bound.

3083
Shin, S-W., Ghosh, S. K., and Moreno, J.,
"FLEXURAL DUCTILITY OF ULTRA-HIGH-STRENGTH CONCRETE MEMBERS"
ACI Structural Journal, Jul-Aug 1989, Vol. 86, No. 4, pp 394-400.

While reinforced concrete columns possess little flexural ductility under high axial loads, concern has been expressed that at any axial load such ductility may decrease further with the use of very high-strength concrete. An experimental investigation was undertaken in 1984 at the University of Illinois at Chicago to address that concern. Three sets of 12 specimens each were manufactured with concrete compressive strengths of 4, 12, and 15 ksi (27.6, 82.7, and 103.4 MPa). The test variables were concrete strength, amount of longitudinal reinforcement, and spacing of ties. Although the tests in this study were conducted on members without axial load, the concern about the flexural ductility of high-strength concrete columns appears to be unfounded on the basis of the test results.

3084
Siebel, E.,
"AIR-VOID CHARACTERISTICS AND FREEZING AND THAWING RESISTANCE OF SUPERPLASTICIZED AIR-ENTRAINED CONCRETE WITH HIGH WORKABILITY"
in Proceedings of the Third CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1989, Ottawa, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1989, pp. 297-319. (ACI SP-119)

Superplasticizers based on melamine and naphtalene sulphonates were used in the main program of study and lignosulfate based products in a subsidiary program. Some of these contained de-airing agents. The air-void distribution and the spacing factor were measured as well as the freezing and thawing resistance with de-icing chemicals. When superplasticizers were used in a high workability air-entrained concrete, the number of pores with a diameter up to 300 m decreased, while the content of pores larger than 500 m and the bubble spacing factor increased. Small pores coalesced and formed larger pores. Although the air content of the fresh concrete was sufficient, the superplasticized concrete sometimes had a spacing factor above 0.20 mm. For this reason, concrete with superplasticizers did not always have adequate freezing and thawing resistance. No effect due to the type of superplasticizer could be detected, while the de-airing agents of the superplasticizers had a considerable effect. Some additional tests with plasticizers and retarders show that these admixtures also alter the air-void distribution of air entrained concrete.

3085
Simons, B. P.,
"GETTING WHAT WAS ASKED FOR WITH HIGH-STRENGTH CONCRETE"
Concrete International: Design & Construction, Oct. 1989, Vol. 11, No. 10, pp. 64-66.

Reading and understanding a set of project specifications dealing with high-strength concrete is fairly simple. Unfortunately, providing a material that successfully complies with all of the requirements through the course of the project is far more difficult. Depending on the specifications and the applications of the material, there can be several different ways to develop the proper mix proportions. This article deals with the beginning aspects of the process of producing high-strength concrete including the initial work that must be done in the laboratory and the subsequent work that must be done in the field. It does not address any of the coordination efforts required by various members of the team, nor does it address the various quality control and quality assurance aspects of this material.

3086
Smadi, M. M. and Slate, F. O.,
"MICROCRACKING OF HIGH AND NORMAL STRENGTH CONCRETES UNDER SHORT- AND LONG-TERM LOADINGS"
ACI Materials Journal, Mar-Apr 1989, Vol. 86, No. 2, pp 117-127.

The effects of both monotonic and sustained uniaxial compressive stresses on the relationships among microcracking, strength, and deformation of high-strength concrete were studied using x-ray techniques and compared with those of low and medium strength concretes. The formation, propagation, and stability of microcracks and their contribution to the failure of concrete under both types of loadings are examined and discussed. The stress levels investigated ranged from 40 to 95% of ultimate for the three materials. High-strength concrete showed significantly smaller amounts of cracking at all stress levels than normal strength concretes. As a result, lesser inelastic deformations and higher creep-stress linearity limits were associated with the former rather than with the others.

3087
Smith, G. J. and Rad, F. N.,
"ECONOMIC ADVANTAGES OF HIGH-STRENGTH CONCRETES IN COLUMNS"
Concrete International: Design & Construction, Apr 1989, Vol. 11, No. 4, pp 37-43.

A study is reported which investigated the economic advantages of using high-strength concretes in columns in low-rise and medium-rise buildings. The study considered varying parameters relating to loading, geometry of the structure, and concrete strength, and costs. The cost advantages of the reduction in reinforcing steel and other costs items appear to outweigh significantly the additional costs of using high-strength concretes.

3088
Stark, D.,
"EFFECT OF LENGTH OF FREEZING PERIOD ON DURABILITY OF CONCRETE"
Research and Development Bulletin, No. RD096.01T, Portland Cement Association, Skokie, IL, 1989, 9 pp.

Concretes with different entrained air void systems were subjected to long and short cycles of freezing and thawing in 4% sodium chloride solution. Results indicated that the long freeze-thaw cycles were more severe than the short freeze-thaw cycles for the same number of cycles, even where air void spacing factors were no greater than 0.008 in. These findings agree with the ice accretion theory of frost damage in concrete.

3089
Stark, D.,
"INFLUENCE OF DESIGN AND MATERIALS ON CORROSION RESISTANCE OF STEEL IN CONCRETE"
Research and Development Bulletin, No. RD098.01T, Portland Cement Association, Skokie, IL, 1989, 40 pp.

The effects of w/c ratio, cover over steel, use of galvanized steel, fly ash replacements for cement, cracks extending from the surface to the reinforcing steel, and mixed steel in reinforcing mats on the corrosion resistance in concrete were investigated. Test cycles included ten days of drying at 73 F and 50% RH followed by four days ponding with 4% NaCl solution. Some tests were run to five and one half years. Tests also evaluated the effect on corrosion of calcium chloride admixture. Results confirmed advantages of low w/c ratio concrete and increased cover to improve corrosion resistance. Galvanized steel provided little or no additional corrosion protection. Cracks extending to the steel led to almost immediate active corrosion during ponding. The fly ash level that provided maximum resistance to corrosion depended on the w/c ratio. Mixed black and galvanized steel in a reinforcing mat resulted in essentially the same corrosion resistance as either steel used separately. Corrosion induced by CaCl admixture depended on both the amount present and relative humidity of the concrete. In general, the higher the chloride content, the lower the relative humidity required to arrest active corrosion.

3090
"SUPERPLASTICIZERS AND OTHER CHEMICAL ADMIXTURES IN CONCRETE"
Proceedings of the Third CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1989, Ottawa, Canada; Ed. by V. M. Malhotra, American Concrete Institute, Detroit, MI, 1989, vii, 665 pp. (ACI SP-119)

This proceedings volume contains 33 papers presented at the conference dealing with various issues relative to the applications of superplasticizers and chemical admixtures including rheological behavior of fresh concrete, cement paste and mortar; effects on concrete durability; properties of lightweight concrete; and several case studies.

3091
Suprenant, B., Zayed, A. M., and Anderson, M.,
"ADVANCED CHEMICAL TECHNIQUES FOR THE ANALYSIS OF HARDENED CONCRETE. PHASE 2. INVESTIGATION OF MATERIALS FOR PILES IN TAMPA BAY BRIDGES"
Final Report, Department of Civil Engineering and Mechanics, University of South Florida, Tampa, FL, 1989, 81 pp. (FL/DOT/RMC-0422-3023; PB92-102698)

The investigation addresses the effects of material properties on the durability of bridge piles in the Tampa Bay area. Four bridges were selected for this study, namely, New and Old Gandy and New and Old Skyway Bridges, because of the similarity in the water salinity. These bridges cover a time span of approximately 20 years. The tools used in this study included wet chemical analysis, microscopy, x-ray diffraction and fluorescence, mechanical and physical testing. It was found that concrete ingredients in the bridges are not different in quantity and quality. Significant differences in physical properties with the older bridges of better quality were attributed to construction practices, specifically, consolidation. It is recommended that future work should address porosity and permeability, in addition to the effects of crystallization of salts, on concrete durability.

3092
Swamy, R. N.,
"SUPERPLASTICIZERS AND CONCRETE DURABILITY"
in Proceedings of the Third CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1989, Ottawa, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1989, pp. 361-382. (ACI SP-119)

For too long water-reducing agents, plasticizers and superplasticizers have been looked upon as workability/pumping agents with possible savings in cement and increase in compressive strength. It is suggested that this concept of these admixtures is misleading and ill-informed. While good workability is recognized as an essential component of placing and compacting, the critical role of superplasticizers should be seen to reduce the porosity and sorptivity of concrete through water reduction. This paper presents test data on concrete and mortar mixes with blended cements and superplasticizers and having water-binder ratios of 0.35 to 0.40. The properties of these concretes are presented and discussed in terms of strength development, permeability, pore structure, carbonation and microstructure. It is shown that superplasticizers should be seen as agents of concrete durability rather than as agents of concrete workability.

3093
"TAILOR MADE CONCRETE FOR HARBOR TUNNEL"
Journal of the Institution of Engineers, Australia, May 19, 1989, Vol. 61, No. 9, p 51.

The widely differing environments of the various elements of the Sydney Harbor Tunnel have called for tailor made concrete mixes. The immersed marine tunnel units are being constructed in a huge casting basin at Port Kembla. Each unit is being constructed in 27 pours, with the base, walls and roof being poured separately in a controlled sequence. A mix that is structurally strong and durable enough to survive the tunnel's 100-year design life was required. It has to have low shrinkage properties to reduce the frequency and width of cracks in reinforced concrete sections and a low heat of hydration to minimize thermally induced cracking.

3094
Thomas, M. D. A.,
"AN INVESTIGATION OF CONVENTIONAL ORDINARY PORTLAND CEMENT AND PULVERISED FUEL ASH CONCRETES IN 10 YEAR-OLD CONCRETE BRIDGES"
Proceedings of the Institution of Civil Engineers, Part 1, Design and Construction, Dec 1989, No. 86, pp 1111-1128.

Results are presented from tests carried out on concrete cores taken from two similar 10-year-old, reinforced concrete bridges, one constructed using ordinary portland cement concrete the other using predominantly pulverized fuel ash concrete. Concrete properties measured included compressive and tensile strength, depth of carbonation, permeability to gases and water, chloride concentration profiles and ca(oh)2 content. In addition, petrographic thin sections were examined and microstructural observations were made using scanning electron microscopy. The results show that after 10 years both concretes were in satisfactory condition with very little carbonation in evidence and low levels of chloride ingress. Some indication of alkali-silica reaction was observed in the ordinary portland cement concrete but this had not led to any noticeable expansion or cracking. No evidence of any alkali-silica reaction was found in the pulverized fuel ash concrete. The pulverized fuel ash concrete exhibited increased strength (compressive and tensile) and reduced permeability compared with the ordinary portland cement concretes and these improvements are attributed to the long-term benefits of the pozzolanic reaction.

3095
Tikalsky, P. J. and Carrasquillo, R. L.,
"THE EFFECT OF FLY ASH ON THE SULFATE RESISTANCE OF CONCRETE"
Research Report (Interim); Center for Transportation Research, University of Texas, Austin, 1989, 338 pp. (CTR-3-5/9-87-481-5; FHWA/TX-90+481-5; PB90-267097)

The durability of concrete is determined by its ability to endure the physical and environmental surroundings without losing the functional properties and structural integrity of the original design. Concrete containing fly ash can be proportioned to meet the durability requirements of a wide range of applications, such as concrete for mass structures, pavements, structural members, and high strength applications. One area where the long term performance of concrete containing fly ash is not clearly understood is in sulfate environments. The sulfate attack mechanism in concrete containing fly ash has been related in recent years to the mineralogical and chemical composition of the cementitious and pozzolanic material. This study investigated the interrelationship between the physical, mineralogical and chemical characteristics of portland cement, fly ash, and their proportions, and the sulfate resistance of concrete containing fly ash. Eighteen fly ashes and five portland cements have been studied at four levels of volumetric replacement of fly ash for portland cement. Other variables studied were workability, air content, curing conditions, and permeability. The fly ashes were characterized by performing chemical, physical and mineralogical analyses. Over 700 specimens were submerged in a 10% sodium sulfate solution. The specimens were measured for expansion, mass change, and cracking. The study has revealed a strong correlation between the glassy composition of fly ash and the sulfate resistance of concrete.

3096
Tikalsky, P. J. and Carrasquillo, R. L.,
"SULFATE ATTACK ON CONCRETE CONTAINING FLY ASH"
in Structural Materials, Proceedings of the Sessions at the ASCE Structures Congress '89, May 1-5, 1989, San Francisco, CA; Ed. by James F. Orofino; ASCE, New York, 1989, pp 123-137.

The use of fly ash as a portland cement replacement in concrete may provide many technical and economic advantages. One such technical advantage is the improvement of the resistance of concrete to sulfate attack. However, this benefit is not realized with all types of fly ash. Some fly ashes have been shown to reduce the sulfate resistance of concrete and others may have no effect on the durability of concrete in sulfate environments. In order to clarify the effect of fly ash on concrete exposed to sulfates, a study is being conducted using 14 different fly ashes from bituminous, subbituminous and lignite sources. The fly ashes have been catalogued by chemical and crystalline phase composition.

3097
Vogler, R. H. and Grove, G. H.,
"FREEZE-THAW TESTING OF COARSE AGGREGATE IN CONCRETE: PROCEDURES USED BY MICHIGAN DEPARTMENT OF TRANSPORTATION AND OTHER AGENCIES"
Cement, Concrete, and Aggregates, Summer 1989, Vol. 11, No. 1, pp 57-66.

A survey of procedures used to evaluate the durability of coarse aggregate in concrete by freezing and thawing indicates that a number of state agencies use the procedures in place of, or in addition to, sulfate soundness and other tests. ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666) describes the procedures for freeze-thaw cycling and gives partial information on expressing test results, but ASTM has no standard procedure to guide the testing agency in important aspects such as aggregate grading, aggregate moisture treatment and pretreatment, and concrete mixture proportioning (including cement content, air content of concrete, or curing procedure). The ASTM method of expressing results of change in length does not permit comparison between different aggregates. This paper will assist ASTM Committee C9 on Concrete and Concrete Aggregates in preparing a practice for evaluation of coarse aggregate in concrete by freezing and thawing.

3098
Washa, G. W., Saemann, J. C., and Cramer, S. M.,
"FIFTY-YEAR PROPERTIES OF CONCRETE MADE IN 1937"
ACI Materials Journal, July-Aug 1989, Vol. 86, No. 4, pp 367-371.

Three long-time concrete test programs were started at the University of Wisconsin-Madison in 1910 (Series A), 1923 (Series B), and 1937 (Series C). Previous reports were published in the ACI Journal in 1931, 1943, 1961, and 1975. The 1937 program required 480 cylinders of 6 multiplied by 12 in. and 36 prisms of 4 multiplied by 6 multiplied by 24 in. Compressive strength, unit weight, and volume changes up to 50 years are given. In addition, transverse strength and static and dynamic moduli of elasticity at 50 years are given. Variables included cement type, mix proportions, consistency, and methods of placement. All specimens made in 1937 were cured outdoors after a 28-day moist-curing period. Generally, compressive strength at 50 years showed little change from the strength at 10 years.

3099
Zia, P., Schemmel, J. J., and Tallman, T. E.,
"STRUCTURAL APPLICATIONS OF HIGH STRENGTH CONCRETE"
Final Report, Center for Transportation Engineering Studies, Department of Civil Engineering, North Carolina State University, Raleigh, NC, Jun 1989, 330 pp. (FHWA/NC-89/006; PB91-198622)

Parametric studies were conducted to determine the structural efficiency and cost effectiveness of using high strength concrete for highway bridge construction. Included in this investigation were prestressed concrete hollow core slabs, prestressed concrete girders, and reinforced concrete piers. For the hollow core slabs, the concrete compressive strength varied from 5,000 psi to 14,000 psi. For the girders and piers, concrete strengths varying from 6,000 psi to 12,000 psi were considered. The current AASHTO design procedures for flexural and compression members were used for high strength concrete except that the modulus of elasticity and the rupture modulus of the concrete were computed according to the recommendations of ACI Committee 363. High strength concrete appeared to be economically feasible and practical, especially for the purposes of increasing the span range of the current hollow core slab bridges. A concrete strength of 8,000 psi was most advantageous. The standard AASHTO and PCI girder sections showed a 30% increase in their maximum spans when the concrete strength was increased from 6,000 to 12,000 psi. For the box beams, as much as 20% increase was obtained. In general, a concrete strength of 10,000 psi appeared to be most desirable for these girder and beam sections. The study of the pier sections indicated clearly the economic benefits of high strength concrete. The cost of carrying a specific level of axial load decreased with increasing concrete strength.