High Performance Concrete 1994

Durability of portland cement concrete is defined by its ability to resist weathering action, chemical attack, abrasion, or any other process of deterioration. This report discusses causes of concrete deterioration, and gives recommendations on how to prevent such damage. Chapters are included on freezing and thawing, aggressive chemical exposure, abrasion, reactive aggregates, corrosion of embedded materials, repair methods, and the use of coatings to enhance durability.

3579
ACI Committee 213
"GUIDE FOR STRUCTURAL LIGHTWEIGHT AGGREGATE CONCRETE"
ACI Manual of Concrete Practice, 1994, Part 1, 27 pp.

The guide summarizes the present state of technology. It presents and interprets the data of lightweight aggregate concretes from many laboratory studies, accumulated experience resulting from successful use, and the performance of structural lightweight aggregate concrete in service. The guide is intended for all sections of ACI readership. It includes a definition of lightweight aggregate concrete for structural purposes and it discusses in condensed fashion the production methods for and inherent current practices for proportioning, mixing, transporting, and placing; properties of hardened concretes; and the design of structural concrete with special reference to ACI 318.

3580
ACI Committee 226
"USE OF FLY ASH IN CONCRETE"
ACI Manual of Concrete Practice, 1994, Part 1, 29 pp.

Fly ash from coal burning power plants is used in concrete primarily because of its pozzolanic and cementitious properties. These properties contribute to strength gain and improved durability when used with portland cement. Other principal reasons for using fly ash include economy and beneficial modification of certain properties of fresh and hardened portland cement concrete. This state-of-the-art report gives an overview of the properties of fly ash and its proper use in production of portland cement concrete. The report contains information and recommendations concerning the selection and use of Class C and Class F fly ashes generally conforming to the requirements of ASTM C 618. Topics covered include the effect of fly ash on properties of concrete, a discussion of quality assurance of fly ash, guidance regarding the handling and use of fly ash in concrete, and the use of fly ash in specific applications. Referenced documents give more information on each topic.

3581
Aitcin, P-C. and Lessard M.
"CANADIAN EXPERIENCE WITH AIR-ENTRAINED, HIGH-PERFORMANCE CONCRETE"
Concrete International, Oct 1994, Vol. 16, No. 10, pp 35-38.

This paper describes the successful Canadian experience in producing air-entrained high-performance concrete for the construction of the Highway 50 Bridge and the Bortneuf Bridge in the province of Quebec. The experience showed that if the materials were selected and proportioned correctly there were no particular problems in delivering air-entrained high-performance concretes having a design strength of 70 MPa (10,000 psi) and an average air void spacing factor below 200 m (0.008 in).

3582
Aitcin, P-C, Miao, B., Cook, W. D., and Mitchell, D.
"EFFECTS OF SIZE AND CURING ON CYLINDER COMPRESSIVE STRENGTH OF NORMAL AND HIGH-STRENGTH CONCRETES"
ACI Materials Journal, Jul-Aug 1994, Vol. 91, No. 4, pp 349-354.

The influence of cylinder size and curing on measured compressive strength was investigated for different strength concretes. The batches of ready-mixed concrete with target compressive strengths of 35, 90, and 120 MPa (5,000, 13,000, and 17,500 psi) were used. The curing conditions included air-cured, sealed, and water-cured for the 100-, 150-, and 200-mm (4-, 6-, and 8-in.) diameter cylinders. The beneficial effects of preventing moisture loss and water-curing are directly observed in the test results. The increased apparent strengths with decreasing cylinder size are also presented. Relationships for compressive gain are given for normal strength, high-strength, and very high-strength concretes studied, and for different curing conditions and different cylinder sizes.

3583
"APPLICATION OF HIGH PERFORMANCE CONCRETE"
Report of the CEB-FIP Working Group on High Strength/High Performance Concrete; Comite Euro-International du Beton (CEB), Lausanne, Switzerland, CEB Bulletin d'Information, Nov 1994, No. 222, 66 pp.

This report is a follow-up study of the State of the Art on High Strength Concrete report issued by CEB/FIP in 1990. Case studies of the use of high strength/high performance concrete in railway bridges, tunnels, floating oil platforms, high rise buildings, nuclear power plant, as well as pavements are herein reported. In addition, a list of worldwide projects using high strength/high performance concrete, the rules and regulations affecting the use of high strength concrete in different countries, and the current research projects are given.

3584
Asai, Y., Itoh, Y., Kante, S., Sakai, M., and Saeki, H.
"STUDY ON THE CHARACTERISTICS OF HIGH-STRENGTH LIGHTWEIGHT CONCRETE FOR ICY WATERS"
Proceedings of the 4th International Offshore and Polar Engineering Conference, April 10-15, 1994, Osaka, Japan; International Society of Offshore and Polar Engineers (ISOPE), Golden, CO, 1994, Vol. 4, pp 363-368.

The authors have developed a new lightweight coarse aggregate whose surface is covered by a high molecular paraffin to prevent water absorption into the aggregate under high pumping pressure. The coated aggregate makes it possible to produce lightweight concrete with high durability against freeze/thaw cycles, abrasion and fire. In order to verify the efficiency of the coated aggregate and the durability of the concrete using the aggregate, various tests on the coated aggregate and concrete have been carried out. This paper reports on the main results obtained from various tests.

3585
Aziz7 inamini, A., Kuska, S. S. B., Brungardt, P., and Hatfield, E.
"SEISMIC BEHAVIOR OF SQUARE HIGH-STRENGTH CONCRETE COLUMNS"
ACI Structural Journal, May-Jun 1994, Vol. 91, No. 3, pp 336-345.

Results of a study investigating flexural capacity and ductility of square high-strength concrete columns are presented. As part of the investigation, nine 2/3-scale test columns were subjected to constant axial load and cyclic lateral loads. It is concluded that high-strength concrete columns subjected to axial load levels below 20 percent of their axial load capacity and designed based on the seismic provisions of ACI 318-89 have sufficient ductility. However, the ACI 318-89 code provision overestimates flexural capacity of high-strength concrete columns subjected to both axial load and bending moment, even columns with confining steel, as required by seismic provisions of the code. Modifications to be incorporated into ACI 318 to calculate conservatively the flexural capacity of high-strength concrete columns are suggested.

3586
Baalbaki, M. and Aitcin, P-C.
"CEMENT/SUPERPLASTICIZER/AIR-ENTRAINING AGENT COMPATIBILITY"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp. 47-62. (ACI SP-148)

As concrete slump is increasingly restored at the jobsite using superplasticizer instead of retempering with water, it is essential that slump increase does not alter the total air content and the air-void system if the concrete is to be frost resistant. Since mixed results have been reported when superplasticizer is added to air-entrained concrete at jobsite, a research program was undertaken to study the compatibility between three air-entraining agents, four water reducers, and one polynaphthalene sulfonate superplasticizer currently used in Eastern Canada. Experimental results conducted on twelve different combinations of admixtures with a Type 10 (ASTM Type I) portland cement show that the addition of superplasticizer nearly always increased the air content without changing the bubble spacing. The only case in which air bubble spacing was significantly altered was when the air content of the concrete was lower than 4.5 percent 70 minutes after batching. In this case, the total air content decreased after the introduction of the superplasticizer, while the spacing factor increased significantly. A second Type 10 cement was used to duplicate these results. No significant difference was found between the results of the two sets of experiments.

3587
Bartlett, F. M. and MacGregor, J. G.
"EFFECT OF MOISTURE CONDITION ON CONCRETE CORE STRENGTHS"
ACI Materials Journal, May-Jun 1994, Vol. 91, No. 3, pp 227-236.

In accordance with the provisions of ASTM C 42-90 and ACI 318-89, it is current practice to either dry concrete core specimens in air for 7 days or soak them in lime-saturated water for at least 40 hr before they are tested. In this paper, the effect of moisture condition on the strengths of mature cores obtained from well-cured elements is investigated by reviewing available literature and performing regression analyses of data from tests of 727 core specimens. It is shown that the compressive strength of a concrete specimen is influenced both by moisture content changes that are uniform throughout the specimen volume and moisture content gradients between the surface of the specimen and interior. The air-drying and soaking periods specified in ASTM C 42-90 and ACI 318-89 are too short to cause a uniform change of moisture content throughout the volume of the core. The effect of these treatments is to create a moisture gradient that artificially biases the test result. The strength of air-dried cores is on average 14 percent larger than the strength of soaked cores. The strength of cores with a negligible moisture gradient is on average 9 percent larger than the strength of soaked cores. These general average values are constant for concretes with strengths ranging from 2,200 to 13,400 psi. However, the strength ratios for any particular mix may differ appreciably from these general average values.

3588
Bartlett, F. M. and MacGregor, J. G.
"EFFECT OF CORE LENGTH-TO-DIAMETER RATIO ON CONCRETE CORE STRENGTHS"
ACI Materials Journal, Jul-Aug 1994, Vol. 91, No. 4, pp 339-348.

Data are analyzed to determine the effect of the specimen length-to-diameter ratio (l/d) on the magnitude and precision of the compressive strength of concrete cores. The data represent strength tests of 758 core specimens, all 4 in. in diameter, obtained from 10 different elements cast from ordinary portland cement concretes with strengths between 2,000 and 14,000 psi. Strength correction factors are determined for converting the strength of a core with an l/d ratio between 1 and 2 to the strength of an equivalent standard specimen with an l/d of 2. The data indicate that both the core moisture condition and the core strength significantly affect the strength correction factors. The proposed strength correction factors differ only slightly from those currently recommended in ASTM C 42-90. The single-operator coefficient of variation is found to be independent of the core length-to-diameter ratio. Typical values are 4 percent if the effect of spatial variation of the in situ strength is accounted for, or 5 percent otherwise.

3589
Bartlett, F. M. and MacGregor, J. G.
"EFFECT OF CORE DIAMETER ON CONCRETE CORE STRENGTHS"
ACI Materials Journal, Sept-Oct 1994, Vol. 91, No. 5, pp 460-470.

Data are analyzed from studies by others concerning the effect of specimen diameter on the magnitude and precision of the compressive strength of concrete cores. The data indicate that the effect of damage to the cut surface of the core counteracts and overwhelms any effect that might be inferred by the weakest link theory or attributed to systematic bias caused by testing procedures. Based on the analyses, the predicted average strength of a 2-in. diameter core is 94 percent of the predicted average strength of a 4-in. diameter core and 92 percent of that of a 6-in. diameter core. These overall average values do not reflect the considerable scatter of the data and therefore should be used with caution. The large variability commonly attibuted to small-diameter specimens is often caused by the large variability of the in situ concrete strength within the element being cored. The data also indicate that the effect of the core length-to-diameter ratio on the compressive strength is more significant for 2-in. diameter cores than for 4-in. diameter cores.

3590
Bartlett, F. M. and MacGregor, J. G.
"CORES FROM HIGH-PERFORMANCE CONCRETE BEAMS"
ACI Materials Journal, Nov-Dec 1994, Vol. 91, No. 6, pp 567-576.

An experimental investigation involving 287 concrete core specimens obtained from large beams cast from 45 to 90 MPa (6,500 to 13,000 psi) ordinary portland cement concretes is described. The data indicate the effect of variations of core size and test moisture condition on the measured compressive strength of cores from elements made of high-performance concrete. The relationship between the flexural capacity of the beams and the strength of the cores obtained from the beams is investigated. The data indicate that the least-biased estimate of the in situ concrete compressive strength is found by increasing the strength of sealed cores by 6 percent to account for damage sustained during drilling of the core. However, a reasonable estimate of the in situ concrete compressive strength may be obtained by correcting the strengths from tests of air-dried or soaked cores to account for both core damage and moisture condition factors.

3591
Bilodeau, A., Sivasundaram, V., Painter, K. E., and Malhotra, V. M.
"DURABILITY OF CONCRETE INCORPORATING HIGH VOLUMES OF FLY ASH FROM SOURCES IN THE U.S."
ACI Materials Journal, Jan-Feb 1994, Vol. 91, No. 1, pp 3-12.

This paper presents the results of investigations to determine the various durability aspects of high-volume fly ash concrete using eight fly ashes and two portland cements from U.S. sources. Briefly, in high-volume fly ash concrete, the water and cement content are kept low at about 115 and 155 kg/m3 of concrete, respectively, and the proportion of fly ash in the total cementitious materials content ranges from 55 to 60 percent. The durability aspects investigated included resistance to the repeated cycles of freezing and thawing (ASTM C 666 Procedure A), the deicing salt-scaling resistance (ASTM C 672), the resistance to the chloride-ion penetration (AASHTO T 277-83) and the determination of water permeability coefficient. Based upon the test results, it is concluded that regardless of the type of fly ash and the cements used, the air-entrained high-volume fly ash concrete exhibited excellent durability characteristics in the tests investigated. The only exception was the deicing salt-scaling test in which the performance of the concretes investigated was less than satisfactory.

3592
Bilodeau, A. and Malhotra, V. M.
"HIGH-PERFORMANCE CONCRETE INCORPORATING LARGE VOLUME OF ASTM CLASS F FLY ASH"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 177-193. (ACI SP-149)

This paper describes the development of a new type of high-performance concrete incorporating large volume of ASTM Class F fly ash. The concrete incorporates about 56 per cent fly ash by weight of cement, and has a water-to-cementitious materials ratio of about 0.32. The portland cement and fly ash contents are of the order of 155 and 215 kg/m3 of concrete, respectively. The flow slumps are achieved by the use of large dosages of superplasticizers. Because of the low cement content, the temperature rise in this concrete is low, and this concrete is ideally suited for concrete structures where excessive temperature rise is a concern. Also, the high-volume fly ash concrete has all the attributes of a high-performance concrete. It has excellent mechanical properties, and demonstrates superior resistance to freezing and thawing cycling, chloride-ion penetration, sulphate attack, carbonation and marine environment. Also, it has low permeability, and shows excellent performance in reducing potential expansion due to alkali-aggregate reaction.

3593
Bisillon, A., Rivest, M., and Malhotra, V. M.
"PERFORMANCE OF HIGH-VOLUME FLY ASH CONCRETE IN LARGE EXPERIMENTAL MONOLITHS"
ACI Materials Journal, Mar-Apr 1994, Vol. 91, No. 2, pp 178-187.

The paper presents comparative data on high-volume fly ash concrete made with ASTM Type I cement, and control concrete for mass concrete applictions made with ASTM Type I and a modified version of ASTM Type II cements. The concrete was supplied by a ready-mix concrete producer for casting five large rectangular monoliths, each measuring 2.5 x 4.0 x 5.0 m. The maximum and effective temperature rises were measured, and in situ strength was determined by testing drilled cores. Also, the mechanical properties and durability of the concrete for the monoliths were determined. The adequate strength development and low temperature rise characteristics of high-volume fly ash concrete, combined with the ability to place the concrete in one 5-m continuous lift, make this type of material a possible alternative to conventional concrete used for mass concreting applications. The high-volume fly ash concrete had excellent resistance to freezing and thawing cycling when tested in accordance with ASTM C 666, and no difficulty was experienced in entraining air in the system.

3594
Caldarone, M. A., Gruber, K. A., and Burg, R. G.
"HIGH-REACTIVITY METAKAOLIN: A NEW GENERATION OF MINERAL ADMIXTURE"
Concrete International, Nov 1994, Vol. 16, No. 11, pp 37-40.

High-Reactivity Metakaolin (HRM) is a reactive aluminosilicate pozzolan formed by calcining purified kaolinite at a specific temperature range. Chemically, HRM combines with calcium hydroxide to form calcium silicate and calcium aluminate hydrates. HRM has shown proise as a product capable of expanding the applications of high-performance concrete. This paper describes a study carried out to compare the relative performance of concretes produced with HRM and silica fume at various addition rates. Comparisons included plastic properties, strength development, chloride ion permeability, drying shrinkage, scaling resistance, air void systems, and freeze-thaw durability. The results of the study indicated that HRM in powder form is a quality-enhancing mineral admixture that exhibits premium level engineering properties that are comparable to, and in some cases better than, silica fume slurry.

3595
Carino, N. J., Guthrie, W. F., Lagergren, E. S., and Mullings, G. M.
"EFFECTS OF TESTING VARIABLES ON THE STRENGTH OF HIGH-STRENGTH (90 MPa) CONCRETE CYLINDERS"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 589-632. (ACI SP-149)

A full factorial experimental design was used to investigate the effects of the variables on cylinder strength: end preparation (sulfur capping vs. grinding), cylinder size (100 vs. 150 mm diameter), type of testing machine (1.33-MN capacity vs. a 4.45-MN capacity), and nominal stress rate (0.14 vs. 0.34 MPa/s). Two levels of strength were used (45 and 90 MPa), and three replicates were tested for each run. Specific gravities were measured to check on the consistency of cylinder fabrication. Statistical analyses indicated that all the factors had significant effects on the measured compressive strength. On average, the 100 mm cylinders resulted in about 1.3% greater strength, the faster stress rate produced about 2.6% greater strength, the ground cylinders were 2.1% stronger, and the 1.33-MN testing machine resulted in about 2.3% greater strength. There were significant interactions among the factors, so that the effects were greater than the average values for particular factor settings. For example, the effect of end preparation depended on the strength level. For the 45-MPa concrete, there was no strength difference due to the method of end preparation, but for the 90-MPa concrete, grinding resulted in as much as 6% greater strength in certain cases. Analysis of dispersion indicated that the 100-mm cylinders had higher within-tests variability, but the differences were not statistically significant. Recommendations for modifications to testing standards are provided.

3596
Chen, B. and Nawy, E. G.
"STRUCTURAL BEHAVIOR EVALUATION OF HIGH-STRENGTH CONCRETE BEAMS REINFORCED WITH PRESTRESSED PRISMS USING FIBER OPTIC SENSORS"
ACI Structural Journal, Nov-Dec 1994, Vol. 91, No. 6, pp 708-718.

Thirteen high-strength concrete, simply supported composite beams with a span of 9 ft (2743 mm) were tested to failure, and their general structural bending properties were evaluated and reported. Precast prestressed concrete prisms were used as main tension reinforcement in all the test specimens. High-strength concrete with compressive strength fc' in the range of 12,000 to 14,000 psi (84.4 to 98.5 MPa) was used for both prisms and situ-cast main beams. Test results showed that the presence of precast prestressed prisms as tension reinforcement significantly increases the cracking capacity and improves flexural stiffness of the test beams, with consequent reduction in deflection and crack width at service load. A novel fiber optic sensor, Bragg grating, was used to develop smart structures by instrumenting all the test beams for direct and quantitative measurement of load-induced strains in the concrete and reinforcement. Typical results, such as average steel strains and crack widths obtained from fiber optic Bragg grating sensors, are evaluated.

3597
Chung, W. and Ahmad, S. H.
"MODEL FOR SHEAR CRITICAL HIGH-STRENGTH CONCRETE BEAMS"
ACI Structural Journal, Jan-Feb 1994, Vol. 91, No. 1, pp 31-41.

In this paper the development of a nonlinear finite element model that employs a biaxial stress-strain constitutive relationship of concrete based on equivalent uniaxial approach is summarized. The main feature of the model is its ability to predict the post-peak load-deflection response of shear critical reinforcement concrete members failing under diagonal tension. This post-peak behavior is a relative measure of shear ductility. The predictions of the model are compared with the available experimental data, and the comparisons are judged good. A parametric study was conducted to quantify the effects of variables influencing the failure of shear critical reinforced concrete beams.

3598
"CONCRETE BRIDGES IN AGGRESSIVE ENVIRONMENTS: PHILIP D. CADY INTERNATIONAL SYMPOSIUM"
held November 9-10, 1993, Minneapolis, MN; Ed. by Richard E. Weyers; American Concrete Institute, Detroit, MI, 1994, viii, 296 pp. (ACI SP-151)

The symposium volume includes fifteen papers on concrete bridges in aggressive environments. The papers address the performance, protection, assessment, and the repair and rehabilitation of concrete bridges. The performance papers include the corrosion protection afforded by concrete bridge deck overlays, corrosion in prestressed concrete bridges, and the use of calcium nitrite in field structures. Protection papers address the performance of silane sealers, coatings, and waterproofers. Condition assessment technologies include measuring the corrosion rate of steel in concrete and the diffusion of chloride ions in bridge decks with overlays. Experiences in the repair and rehabilitation of concrete bridges by practitioners are also presented.

3599
"CONCRETE 2000 - ECONOMIC AND DURABLE CONCRETE CONSTRUCTION THROUGH EXCELLENCE"
Proceedings of the International Conference, held Sep 7-9, 1993 at the University of Dundee, Scotland, UK; Ed. by Ravindra K. Dhir and M. Roderick Jones; E & FN Spon, London, 1994, 2 Vols.

This book forms the proceedings of the international conference in Dundee in September 1993 reviewing the key developments in concrete construction technology and practice during the next decade and beyond. Contents: Preface; New trends in specification and design; Efficient concrete production and new materials; Construction techniques; Infrastructure; Research, development and education; New applications-the future; Index.

3600
"CONCRETE TECHNOLOGY: PAST, PRESENT, AND FUTURE"
Proceedings of V. Mohan Malhotra Symposium, held Mar 21-23, 1994 at the ACI Annual Convention in San Francisco, CA; Ed. by P. Kumar Mehta; American Concrete Institute, Detroit, MI, 1994, ix, 683 pp. (ACI SP-144)`

Eighteen review papers and twelve research papers are included in the proceedings. The first four papers contain an overview of the concrete technology today and the forces that are shaping tomorrow's world. Three state-of-the-art papers and seven research papers address some of the critical issues in durability. There are two comprehensive papers on trends in construction technology: one concerning off-shore and marine structures, and the other on roller compacted concrete for dams. Eight papers highlight the concrete materials and products for the future, including new cements, superplasticizers, mineral admixtures, reinforcing fibers and polymers. Among the remaining six papers, one deals with the history and trends in the methods of proportioning concrete mixtures, and five discuss testing methods and quality assurance.

3601
Cusson, D. and Paultre, P.
"HIGH-STRENGTH CONCRETE COLUMNS CONFINED BY RECTANGULAR TIES"
Journal of Structural Engineering, Mar 1994, Vol. 120, No. 3, pp 783-804.

An experimental study of the behavior of large-scale high-strength concrete columns confined by rectangular ties under concentric loading is described. The investigation studied the effects of key variables such as the concrete compressive strength, the tie yield strength, the tie configuration, the transverse reinforcement ratio, the tie spacing, the longitudinal reinforcement ratio, and the spalling of the concrete cover. It was found that the behavior of high-strength concrete columns is characterized by the sudden separation of the concrete cover, leading to a loss of axial capacity before the lateral confinement becomes effective.

3602
de Almeida, I. R.
"ABRASION RESISTANCE OF HIGH STRENGTH CONCRETE WITH CHEMICAL AND MINERAL ADMIXTURES"
Durability of Concrete, Proceedings of the Third International Conference, held May 22-28, 1994, Nice, France; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 1099-1113. (ACI SP-145)

Abrasion resistance of ten concrete mixtures with compressive strength ranging from 60 to 110 MPa at 28 days old and with W/C ranging from 0.24 to 0.42 was evaluated. Mixtures studied contained silica fume, fly ash or natural pozzolan, with or without the addition of a superplasticizer, which was used to reduce the mixing water, concrete workability remaining constant. Tests were carried out following a Portuguese Standard, similar to the Brazilian standard and the German Standard DIN 52108, using the Dorry apparatus. Porosity and compressive strength of concretes were also determined. The main conclusions are as follows: (a) Cement replacement by mineral admixtures always reduced the abrasion resistance at rates between 10 to 25%; worse results were obtained with condensed silica fume concretes; (b) Addition of superplasticizer increased the abrasion resistance about 25%; (c) Abrasion resistance varied inversely with W/C, cement paste volume and porosity of concretes; (d) General correlation was poor between abrasion resistance and compressive strength, pointing to a strong influence of the type of cementing material, mainly in the case of silica fume; (e) There was evidence that bad performance of condensed silica fume concrete can be ascribed to self-desiccation; (f) Even the worst results obtained in this series of tests were equivalent to abrasion resistance at least six times higher than that of ordinary concrete with 20 MPa compressive strength.

3603
Delagrave, A., Marchand, J., Pigeon, M., Ranc, R., and Marzin, J.
"FREEZE-THAW DURABILITY OF ROLLER-COMPACTED CONCRETE MADE WITH ROLAC BINDER"
Materials and Structures/Materiaux et Constructions, Jan-Feb 1994, Vol. 27, No. 165, pp 26-32.

This paper presents the main results of a research project concerning the freezing and thawing durability of roller-compacted concrete made with Rolac binder. This project was carried out in order to understand the influence of the cement, water and air content of roller-compacted concrete on frost resistance. Eighteen laboratory mixtures of roller-compacted concrete were submitted to cycles of freezing in air and thawing in water (ASTM C 666 Procedure B). The air and void characteristics of all mixtures was determined using the Modified Point Count method of ASTM Standard C 457, the spherical air bubbles being separated from the irregularly-shaped compaction air voids. The results indicate that it is possible to entrain air in these dry concretes (approximately 1.5 to 2% of spherical air bubbles) and that such an air content is sufficient to protect concrete from frost deterioration. All mixtures made without an air-entraining agent were destroyed in less than 50 cycles, and all mixtures made with an air-entraining agent withstood 300 cycles without any significant deterioration.

3604
Detwiler, R. J., Fapohunda, C. A., and Natale, J.
"USE OF SUPPLEMENTARY CEMENTING MATERIALS TO INCREASE THE RESISTANCE TO CHLORIDE ION PENETRATION OF CONCRETES CURED AT ELEVATED TEMPERATURES"
ACI Materials Journal, Jan-Feb 1994, Vol. 91, No. 1, pp 63-66.

It has long been known that elevated curing temperatures, while accelerating the early strength gain of concrete, reduce the ultimate strength. Recent research has shown that elevated curing temperatures can also reduce the resistance to chloride diffusion of plain portland cement concretes. This paper describes an investigation of the chloride penetration of 0.40 and 0.50 water-cement ratio (w/c) concretes containing either 5 percent silica fume or 30 percent blast furnace slag (substitution by mass) cured at elevated temperatures. Plain portland cement concretes were used as controls. The concretes were cured at constant temperatures of 23, 50, or 70 C (73, 122, or 158 F) to a degree of hydration of approximately 70 percent. Supplemental tests were performed on concretes cured overnight using a steam-curing regime. Both the silica fume and slag concretes performed better than the controls in these tests.

3605
Dhir, R. K., Jones, M. R., Byars, E. A., and Shaaban, I. G.
"PREDICTING CONCRETE DURABILITY FROM ITS ABSORPTION"
Durability of Concrete, Proceedings of the Third International Conference, held May 22-28, 1994, Nice, France; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 1177-1194. (ACI SP-145)

This paper discusses the current approach for specifying the durability of concrete in structures. The shortcomings of the use of bulk parameters such as strength, water/binder ratio and binder content to specify durability are discussed. Studies carried out over the last ten years at Dundee University, using simple permeation tests, which are sensitive to curing, cement type and grade of concrete, have shown close association between permeation properties and the durability of concrete. The Dundee-modified Initial Surface Absorption Test (ISAT) was used to measure concrete durability. A wide range of concrete mixes made with ordinary portland cement and blends with pulverized-fuel ash (PFA) and ground-granulated blastfurnace slag were designed. The duration of moist curing was varied from 0 to 28 days, and the maximum aggregate size from 5 to 40mm. All mixes were tested for absorptivity and aspects of durability including freeze/thaw resistance, carbonation, chloride ingress and mechanical wear. The results show that the absorptivity of concrete, measured with the ISAT, could be used as an accurate specification for concrete durability, irrespective of curing, grade or mix constituents. A tentative surface absorptivity classification for durability was proposed.

3606
Domone, P. L. J. and Soutsos, M. N.
"AN APPROACH TO THE PROPORTIONING OF HIGH-STRENGTH CONCRETE MIXES"
Concrete International, Oct 1994, Vol. 16, No. 10, pp 26-31.

This paper presents a study in which the proportioning of high-strength concrete mixes is based on a volumetric approach. The initial concept is that the aggregate should occupy as large a relative volume of the concrete as possible with voids being filled with the water-cementitious material paste. The ratio of w/(c m) is chosen according to the required strength. The concept is not new, and was termed the "maximum density theory" in the 1920's. The result is a minimum cement paste content, which is attractive in high-strength concrete since increasing cement content does not necessarily increase the strength.

3607
"DURABILITY OF CONCRETE"
Proceedings of the Third International Conference, held May 22-28, 1994, Nice, France; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, xii, 1224 pp. (ACI SP-145)

The papers included herein deal with the deicer salt scaling of concrete, freezing and thawing phenomenon, performance of concrete in marine environments, corrosion of steel to chloride-ion attack, alkali-aggregate reactivity, coatings for concretes, carbonation, high-volume fly ash concrete and papers in the general area of durability of concrete. In addition to the papers which have been published in this volume, more than 40 other papers were presented at the conference. A number of these were published as "supplementary papers."

3608
Fang, I-K., Wang, C-S., and Hong, K-L.
"CYCLIC BEHAVIOR OF HIGH STRENGTH CONCRETE SHORT BEAMS WITH LOWER AMOUNT OF FLEXURAL REINFORCEMENT"
ACI Structural Journal, Jan-Feb 1994, Vol. 91, No. 1, pp 10-18.

Experimental investigation of the cyclic behavior of high-strength concrete (HSC) short beams with lower flexural reinforcement ratio is reported. Fifteen cantilever beam specimens were subjected to monotonic loading and various types of cyclic loadings. The main variables included shear span-to-depth ratio, compressive strength of concrete, and loading histories. The compressive strength of concrete varied from 32 MPa to 70 MPa. Test results indicated that the displacement ductility factor of HSC is about 5 to 6. The trend of degradation in strength and stiffness, as well as the energy dissipation capacity of beam specimens, became more pronounced as the shear stress level in the plastic hinge region increased.

3609
Farny, J. A. and Panarese, W. C.
"HIGH-STRENGTH CONCRETE"
Portland Cement Association, Skokie, IL, Engineering Bulletin, No. EB114.01T, 1994, 48 pp.

This publication describes the history, development, properties, and various projects that have used high-strength concrete. It includes information on the types, dosages, and uses of chemical and mineral admixtures; detailed discussions of compressive strength, ultimate strength, and in-place strength - including drilled cores; strength comparisons between cylinders of various dimensions; modulus of elasticity and durability; and methods of developing optimal mixture proportions with available materials. Current and future applications of HSC are discussed.

3610
Feldman, R. F., Chan, G. W., Brousseau, R. J., and Tumidajski, P. J.
"INVESTIGATION OF THE RAPID CHLORIDE PERMEABILITY TEST"
ACI Materials Journal, May-Jun 1994, Vol. 91, No. 3, pp 246-255.

High-quality impermeable concrete as cover of reinforcing steel is one of the best methods of preventing chlorides from initiating corrosion. AASHTO T 277 and ASTM C 1202-91 Rapid Chloride Permeability Test were developed because of a need to rapidly measure permeability of concrete to chloride ions. Some criticisms have been made, mainly concerning the fact that conditions under which measurements are made may cause changes to the specimens. This work was designed to observe how changes in the testing procedure affect results. Factors such as temperature, AC impedance, initial DC current, charge passed, and chloride ion profiles were monitored during polarization of four different concretes. It was found that simple measurement of initial current or resistivity gave the same ranking as conventional tests for the four concretes and can replace the rapid chloride test with a considerable time saving.

3611
Forster, S. W.
"HIGH-PERFORMANCE CONCRETE -- STRETCHING THE PARADIGM"
Concrete International, Oct 1994, Vol. 16, No. 10, pp 33-34.

The factors that affect the performance of concrete were discussed in this paper. High-performance concrete was defined by the author as "a concrete made with appropriate materials combined according to a selected mix design and properly mixed, transported, placed, consolidated, and cured so that the resulting concrete will give excellent performance in the structure in which it will be placed, in the environment to which it will be exposed, and with the loads to which it will be subjected for its design life." In essence high-performance concrete may be another term for "quality concrete structures that performs well throughout their design life."

3612
Gautefall, O., Hammer, T. A., Havdahl, J., and Vennesland, O.
"EXPERIENCE FROM NINE YEARS OF EXPOSURE OF CONCRETE IN THE TIDAL/SPLASH ZONE"
Nordic Concrete Research, 1994, Publication No. 15, pp 21-33.

Ten concrete blocks (1.5x1.5x0.5 m) have been exposed in the tidal/splash zone in the Trondheim fjord since 1983. Concrete parameters were concrete strength grade (C35 and C65 according to Norwegian standard) and content of microsilica (0, 10 and 20 % as cement replacement). After nine years of exposure an evaluation of the corrosion condition of the reinforcement was made based on visual inspection, surface potentials and chloride profile.

3613
Gjorv, O. E., Tan, K., and Zhang, M-H.
"DIFFUSIVITY OF CHLORIDES FROM SEAWATER INTO HIGH-STRENGTH LIGHTWEIGHT CONCRETE"
ACI Materials Journal, Sept-Oct 1994, Vol. 91, No. 5, pp 447-452.

As part of a more comprehensive research program on high-strength lightweight concrete (50 to 100 MPa), test results on the diffusivity of chlorides from natural seawater are presented. The chloride diffusivity of the various concrete mixes was very low, with effective diffusion coefficients typically varying from 2.7 to 5.6 x 10-9 cm2/sec. Of the various material parameters included in the test program, it was the presence of silica fume that had the most dominating effect on the diffusivity. Nine percent replacement of the cement by silica fume reduced the chloride diffusivity by a factor of about 5, while an increasing content of the total amount of cementitious materials from 440 to 660 kg/m3 decreased the diffusivity by a factor of about 2. Five different types of lightweigtht aggregate with increasing particle densities from 1.07 to 1.44 g/cm3 were used. The difference of the concretes with the least dense aggregate was about two times higher than those obtained with the most dense aggregate. Type of fine aggregate and maximum aggregate size had only a minor effect on the chloride diffusivity. The impact of the obtained chloride diffusivity on service life is also discussed.

3614
Goltermann P., Larsen, H., and Ingholt, N. U.
"STRENGTH AND STIFFNESS RELATIONS IN LIGHTWEIGHT AGGREGATE CONCRETE WITH OPEN STRUCTURE"
Nordic Concrete Research, 1994, Publication No. 15, pp 35-45.

The formulas for estimating bending tensile strength and modulus of elasticity in lightweight aggregate concrete with an open structure (LAC) are presented and documented in this paper. The extensive test material covers LAC with dry density ( ) in the range of 500-1,800 kg/m3 and compressive strength (fc') in the range of 2-30 MPa. A representative documentation for the LAC-types used in roof or floor components and in wall components is presented and an alternative to the currently obligatory testing is given.

3615
Hansen, M. R., Leming, M. L., Zia, P., and Ahmad, S. H.
"DEVELOPMENT AND PRODUCTION OF HIGH-PERFORMANCE CONCRETE"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 347-362. (ACI SP-149)

The Strategic Highway Research Program (SHRP) awarded a contract to North Carolina State University (NCSU) to investigate the use of High Performance Concrete (HPC) in highway pavements and bridge structures. This paper summarizes the development of the mixture proportions for three classes of HPC; namely, Very Early Strength (VES), High Early Strength (HES), and Very High Strength (VHS) concrete. Included in the paper are the strength and serviceability requirements for the mixtures. Recommendations are made for adapting the HPC mixtures for local materials.

3616
"HIGH-PERFORMANCE CONCRETE"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, viii, 844 pp. (ACI SP-149)

This volume contains 45 papers of those presented at the ACI International Conference covering topics such as the use of admixtures, engineering properties, testing and production, various structural behavior and applications of high performance concrete.

3617
"HIGH PERFORMANCE CONCRETES AND APPLICATIONS"
Ed. by S. P. Shah and S. H. Ahmad; Edward Arnold, London, 1994, xii, 403 pp.

This reference book contains eleven chapters individually contributed by experts from USA, Canada, France, Norway, Spain and Japan so as to give the book a broad perspective of the prevailing state-of-the-art in different parts of the world. It covers the selection of materials and proportions; the short term mechanical properties; creep, shrinkage and temperature effects; bond and fatigue characteristics; durability and its implication for the performance of concrete; fracture mechanics; behavior of structural members; ductility of structural members; structural design considerations and applications; high strength lightweight aggregate concrete; and applications in Japan and South East Asia.

3618
Hindy, E. E., Miao, B., Chaallal, O., and Aitcin, P-C.
"DRYING SHRINKAGE OF READY-MIXED HIGH-PERFORMANCE CONCRETE"
ACI Materials Journal, May-Jun 1994, Vol. 91, No. 3, pp 300-305.

The paper reports on drying shrinkage undergone by ready-mixed high-performance concrete (HPC). Shrinkage measurements were carried out on concrete specimens as well as on instrumented reference columns. Two different HPC were tested. The first one had a compressive strength of 98 MPa (14,200 psi) at 91 days and the second had a compressive strength of 80 MPa (11,600 psi). The first contained silica fume but the second did not. The effects of the following factors were investigated: curing time, curing conditions, silica fume content, and water-cementitious materials ratio. It was found that the longer the curing time the lower the drying shrinkage, and that the lower the water-cementitious materials ratio the lower the drying shrinkage. Drying shrinkage of small specimens was compared to that of actual large-sized columns made with the two types of HPC. Shrinkage measured by a conventional laboratory test was found to overestimate shrinkage of HPC in a real structure. The validity of using an ACI 209 expression derived for ordinary concrete to predict drying shrinkage of HPC was also investigated. It was found that this expression can be used for high-performance concrete only if new parameter values are considered.

3619
Husbands, T. B., Malone, P. G., and Wakeley, L. D.
"PERFORMANCE OF CONCRETES PROPORTIONED WITH PYRAMENT BLENDED CEMENT"
Technical Report; Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, MS, Apr 1994, 103 pp. (CPAR-SL-94-2)

Pyrament Blended Cement (PBC) is known in the construction industry for its ability to gain strength rapidly and achieve very high early strength. The Waterways Experiment Station (WES) conducted a laboratory evaluation of concrete made with PBC to determine if these concretes perform better than concretes made with ordinary portland cement (OPC) in tests of various aspects of concrete durability. For this study, six concretes based on PBC-XT were proportioned with three cement contents and two aggregate types. The objective was to determine if the cement, advertised as giving high early strength and marketed initially as a rapid-construction material, is durable enough to justify its use for long-term performance in addition to shorter construction time. Concretes prepared from PBC-XT cement were subjected to analyses of its resistance to damage during cycles of freezing and thawing, expansion in a high-sulfate environment, damage from underwater abrasion, penetration of dissolved chlorides, scaling from deicing chemicals, and expansion from chemical interaction between alkalies in the cement and silica in aggregate. In all categories, the PBC-XT cement concretes achieved or exceeded expected performance based on the manufacturer's product literature. In all but the last category, PBC-XT concretes performed better than is generally expected of high-quality OPC concretes. As an example of superior performance, PBC-XT concretes made with seven sacks of cement per cubic yard and limestone aggregate were tested to 500 cycles of freezing and thawing according to ASTM C 666, through which they retained 90 percent of their initial dynamic modulus. Also, samples tested for sulfate expansion gave values consistently below the ASTM C 595 limit of 0.1 percent after 180 days. In tests of rapid chloride permeability (AASHTO T 277), PBC-XT concrete samples tested as early as 7 days after casting achieved "low" permeability ratings ( 1,000 coulombs). Values for year-old specimens averaged a remarkable 100 coulombs. Other aspects of performance investigated included: effects of various temperatures and water-cement ratios on workability, time of setting, and rate of strength gain; bonding to existing concrete; dry shrinkage; creep under sustain load; and effects of different storage conditions.

3620
Iravani, S. and MacGregor, J. G.
"HIGH PERFORMANCE CONCRETE UNDER HIGH SUSTAINED COMPRESSIVE STRESSES"
Department of Civil Engineering, University of Alberta, Edmonton, Alberta, Canada, Jun 1994, Structural Engineering Report No. 200, 314 pp.

The main purpose of the study was to investigate high performance concrete under high sustained compressive stresses. High performance concretes with 56 day compressive strengths of 65 MPa to 75 MPa (without silica fume), 95 MPa to 105 MPa (with and without silica fume), and 120 MPa (with silica fume) were studied. Stress intensities ranged from 70 to 95 percent of the short term ultimate strength. The effects of moment gradient and silica fume were also studied. A supplementary test program was carried out on the same series of high performance concrete to study the mechanical properties of high performance concrete. The long term sustained compressive strength of high performance concrete is between 70% to 75%, 75% to 80%, 85% to 90%, and 85% to 90% of the short term ultimate strength for 65 MPa to 75 MPa, 95 MPa to 105 MPa (without silica fume), 95 MPa to 105 MPa (with silica fume), and 120 MPa concretes, respectively. The long term sustained compressive strength of high performance concrete under small eccentric loads is approximately 5% higher than under the concentric loads. A modification of the ACI 318M equation for the modulus of elasticity of normal weight high performance concrete was recommended.

3621
Kagaya, M., Tokuda, H., Kawakami, M., and Kaneko, T.
"WORKABILITY CHARACTERISTICS OF HIGH-STRENGTH CONCRETE INCORPORATING AN AIR-ENTRAINING, HIGH-RANGE WATER-REDUCING ADMIXTURE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp. 121-130. (ACI SP-148)

High strength concrete with air-entraining high range water-reducing admixture (AHW), 0.35 water-to-cement ratio, 148 kg/m3 unit water content and about 60 MPa compressive strength was produced, and the admixture content and sand percentage were varied. The consistency property was measured by the slump test, and the compaction property and segregation resistance was determined by the flow time through an inverted slump cone. An appropriate mixture which balanced these properties relative to the admixture content and the sand percentage was determined from the test. The appropriate mixture can be consolidated by using shorter vibrating time and a lower frequency than in the case of ordinary concrete.

3622
Kinoshita, M., Suzuki, T., Yonezawa, T., and Mitsui, K.
"PROPERTIES OF AN ACRYLIC GRAFT COPOLYMER-BASED NEW SUPERPLASTICIZER FOR ULTRA HIGH-STRENGTH CONCRETE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, vii, pp. 281-299. (ACI SP-148)

In order to place ultra high strength concrete with a compressive strength exceeding 100 MPa on site, a technology is required to impart high fluidity to the concrete, with a water-to-cementitious material ratio in an extremely low range of 0.25 or less. For this purpose, the authors synthesized a new superplasticizer comprising water-soluble acrylic graft copolymer, which has an excellent cement dispersing capability. This paper reports the investigation of the surface chemical properties of this new superplasticizer and the properties of the cement paste and mortar containing it. It was confirmed that the new superplasticizer imparts a higher fluidity to cement paste and mortar with an extremely low range water-to-cementitious material ratio than conventional superplasticizers. It was also found that the surface tension of the solution of the new superplasticizer is similar to that of conventional polycarboxylate superplasticizers, whereas the adsorption by cement and zeta potential of the new superplasticizer are between those of the -naphthalene superplasticizers and the polycarboxylate superplasticizers. The high fluidity of the cement paste and mortar containing the new superplasticizer with a very low range water-to-cementitious material ratio may be particularly attibutable to the above-mentioned properties with respect to surface tension as well as the molecular weight and chemical structure of the graft copolymer.

3623
Lange, D. A.
"LONG-TERM STRENGTH DEVELOPMENT OF PAVEMENT CONCRETES"
Journal of Materials in Civil Engineering, Feb 1994, Vol. 6, No. 1, pp 78-87.

This paper discusses the development of pavement concrete compressive strength, flexural strength, and splitting tensile strength as a function of time. Significant gain of strength beyond the 28-day strength was found in compressive, flexural and tensile strength. This is true for high- and normal-strength concretes, concretes with and without fly ash, and concretes cured in air and moist conditions. Although modern concretes have higher early compressive strength gains than concretes produced in 1940-56, both modern and 1940-56 concretes exhibit similar long-term trends in strength development when normalized to their 28-day strengths.

3624
Leshchinsky, A. and Pattison, J.
"HIGH-PERFORMANCE CONCRETE FOR AUSTRALIAN FREEWAYS"
Concrete International, Oct 1994, Vol. 16, No. 10, pp 45-48.

The continuously reinforced concrete pavement of the Lapstone Extension to the M4 Motorway in the foothills of the mountains west of Sydney, Australia, was constructed by placing a 150 mm (6 in) thick, 5 MPa (725 psi), lean-mix sub-base overlaid with a 200 mm (8 in) thick, 32 MPa (4600 psi), reinforced concrete base. In November and December of 1992, 10,000 m3 (13,000 yd3) of concrete was placed. This article describes the quality assurance program set up by the concrete producer for supply of the 32 MPa (4600 psi) base concrete. The program ensured that the concrete not be just high strength, but that it be high-performance in terms of uniformity.

3625
Lessard, M., Dallaire, E., Blouin, D., and Aitcin, P-C.
"HIGH-PERFORMANCE CONCRETE SPEEDS RECONSTRUCTION FOR MCDONALD'S"
Concrete International, Sept 1994, Vol. 16, No. 9, pp 47-50.

High-performance concrete was used for a routine concrete sidewalk at the entrance of a McDonald's restaurant to accelerate the traffic reopening in 24 hours and to minimize the loss of customers and revenue. Composition and properties of the fresh concretes as well as hardened concretes are described in the paper. Compressive strength of 20 MPa (3000 psi) aimed at 24 hours for air-entrained concrete was achieved. The same concrete achieved a compressive strength of 69 MPa (10,000 psi) in 28 days. Economic comparisons indicated that the use of high-performance concrete increased the cost for the sidewalk by 16% over the cost of a 30 MPa (4400 psi) normal concrete sidewalk.

3626
Li, Y., Langan, B. W., and Ward, M. A.
"FREEZING AND THAWING: COMPARISON BETWEEN NON-AIR-ENTRAINED AND AIR-ENTRAINED HIGH-STRENGTH CONCRETE"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 545-560. (ACI SP-149)

The freezing and thawing (F/T) durability of non air-entrained cement pastes and mortars was evaluated by measuring the decrease in compressive strength. At the water-cementitious (w/c) ratio of 0.24, both the paste and mortar showed excellent F/T resistance at 0, 5 and 10% silica fume levels. When the w/c was higher than 0.24, the paste and mortar durability was significantly reduced. The F/T durability of the non air-entrained concrete was determined according to ASTM C 666, Procedure A. At the w/c of 0.24, the non air-entrained concretes were F/T durable regardless of the silica fume and total cementitious content but the durability was reduced for concretes with a w/c greater than 0.24. The salt scaling of non air-entrained concrete at different w/c was tested according to ASTM 672. No scaling was found in the concrete at the w/c of 0.24 and 0.27. The results from the paste, mortar and concrete showed that w/c was the most important factor in evaluating F/T resistance of these concretes.

3627
Limsuwan, E.
"CURRENT DEVELOPMENT AND UTILIZATION OF HPC IN THAILAND"
Preliminary Publication, International Workshop on High Performance Concrete, held Nov 21-22, 1994, Bangkok, Thailand; American Concrete Institute, Detroit, MI, 1994, pp 4-1 to 4-21.

This paper describes the development of material acquisition, mix proportions, concrete properties, structural behaviors and industrial utilization of high performance concrete in Thailand. Since strength of local aggregates is very good with minimum defect of internal cracks, mix design can be easily adjusted by superplasticizer and pozzolanic materials. Concrete properties in various aspects of structural application have been tested to satisfy the performance in workability, strength, serviceability and durability.

3628
Mak, S. L., Attard, M. M., Ho, D. W. S., and Darvall, P. Le P.
"CROSS-SECTIONAL STRENGTH GRADIENTS IN HIGH STRENGTH CONCRETE COLUMNS"
Cement and Concrete Research, 1994, Vol. 24, No. 1, pp 139-149.

A series of columns of two cross-sectional dimensions were cast in the laboratory for concrete mixes with 28-day compressive strengths ranging from 40 to 115 MPa. Compressive strength results of vertically drilled cores showed the presence of significant cross-sectional strength gradients. Three-dimensional core strength distributions were constructed from which effective cross-sectional strengths of unreinforced in-situ concrete were calculated.

3629
Mak, S. L. and Lu, A. "ENGINEERING PROPERTIES OF HIGH-PERFORMANCE CONCRETES CONTAINING BLAST FURNACE SLAG UNDER "IN SITU" MOISTURE AND TEMPERATURE CONDITIONS"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 159-175. (ACI SP-149)

A high performance concrete may possess satisfactory performance in many aspects other than compressive strength. In the context of in-situ strength development, the performance of concrete at an early age is important. The temperature development, resistance to thermal cracking, early age engineering properties and in-situ strength development may all play a significant role in ensuring satisfactory long-term performance. This paper describes the engineering properties of some very high strength and high performance concretes containing blast furnace slag with compressive strength in excess of 80 MPa under simulated "in-situ" conditions of restricted moist curing and high hydration temperatures. The influence of blast furnace slag content and the implications of the in-situ development of engineering properties on performance are discussed.

3630
Marzouk, H. and Jiang, D.
"EFFECTS OF FREEZING AND THAWING ON THE TENSION PROPERTIES OF HIGH-STRENGTH CONCRETE"
ACI Materials Journal, Nov-Dec 1994, Vol. 91, No. 6, pp 577-586.

Freeze-thaw cycles pose a serious problem for concrete structures in cold environments. This investigation deals with the exposure of high-strength concrete to rapid freezing and thawing in a controlled environment. Experimental tests consisted of measuring the relative dynamic modulus of elasticity, modulus of rupture, direct tensile strength, and change in mass of air-entrained concrete specimens. The tests were conducted on 20 x 75 x 300-mm and 75 x 75 x 350-mm prisms for both high-strength concrete (70 MPa) and normal strength concrete (40 MPa) at intervals of every 100 cycles up to 700 cycles. Test results revealed that high-strength concrete was still durable after 700 cycles of freezing and thawing in accordance with ASTM C 666. After 700 cycles, standard 75 x 75 x 350-mm prisms of high-strength concrete showed a reduction in mass of less than 1 percent, reduction in compressive strength between 10 to 15 percent, and reduction in modulus of rupture up to 15 percent. For the thin concrete 20 x 75 x 300-mm specimens used for the direct tension tests, the direct tensile strength was reduced between 15 to 25 percent. The post-cracking behavior of high-strength concrete after 700 cycles of freezing and thawing was evaluated in terms of the stress-strain curve and fracture energy. Specimens of normal strength concrete were used as reference specimens. The normal strength concrete prisms had deteriorated severely after 250 to 300 cycles. For the thin concrete specimens, the average value of the relative dynamic modulus of elasticity based on resonant frequencies at 300, 600, and 700 cycles was 72, 54, and 39 percent, respectively, compared with the corresponding values of 82, 69, and 66 percent, respectively, for high-strength concrete.

3631
Mitsui, K., Yonezawa, T., Kinoshita, M., and Shimono, T.
"APPLICATION OF A NEW SUPERPLASTICIZER FOR ULTRA HIGH-STRENGTH CONCRETE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra, American Concrete Institute, Detroit, MI, 1994, pp. 27-45. (ACI SP-148)

The key to casting high-strength concrete with compressive strength of more than 100 MPa into complicated reinforced structures is to give the concrete high fluidity as well as to improve strength. The authors developed an acrylic copolymer-based new superplasticizer that can improve fluidity of concrete with water to binder ratio of around 0.20. This paper gives the results of a series of studies conducted to determine the properties of fresh and hardened high-strength concrete using the newly developed superplasticizers. The new superplasticizer needed much less dosage than conventional superplasticizers to attain a certain slump (250 mm) for a water to binder ratio of around 0.20 and it significantly reduced the viscosity of concrete. Sufficient workability was kept for 2 hours without much delay in setting time while conventional superplasticizers showed large slump loss and excessive delay in setting time. The results of strength development, drying shrinkage and freezing and thawing resistance did not show any harmful effect. Field studies were conducted on application of the high-strength concrete to a prestressed concrete bridge with design strength of 100 MPa using the new superplasticizer. Workability and strength development of concrete were tested and resulted in sufficient quality.

3632
Molina, L. and Alvarsson, Y.
"ROBOT REVIBRATOR IMPROVES HSC QUALITY"
Concrete International, May 1994, Vol. 16, No. 5, pp 35-37.

Research on the surface treatments of high strength concrete pavements has developed a robot revibrator called Rollit Robot Method (RRM) which travels on the fresh surface layer achieving a higher flatness, and securing a high density of the outer skin of construction. Densification occurs as a result of mechanical consolidation and increased hydration. The robot may be any size from a small remote-control operated machine to a large, drivable vehicle that covers the full width of a road or bridge deck. The details of the motor vibrator mounted on the robot and a prototype used successfully in Sweden are described. Future study at actual construction sites to verify the RRM are planned in Scandinavia.

3633
Nagi, M., Janssen, D. J., and Whiting, D.
"DURABILITY OF CONCRETE FOR EARLY OPENING OF REPAIRED HIGHWAYS --FIELD EVALUATION"
Durability of Concrete, Proceedings of the Third International Conference, held May 22-28, 1994, Nice, France; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 811-833. (ACI SP-145)

Under the Strategic Highway Research Program (SHRP) contract C-206
"Optimization of Highway Concrete Technology"
constructibility and performance of concrete for early opening of highway repairs were evaluated. A variety of concrete mixes using different types of rapid strength cements and admixtures were used for full-depth repair (slab replacement) of concrete pavements and for bridge deck overlays in the states of Ohio, Kentucky, and Georgia. Eight mixtures having different strength-gain capacity allowing for a variety of traffic opening times ranging from 2 to 24 hours were evaluated for pavement applications. Latex modified concrete with Type III cement and silica fume mixes were used for bridge deck overlays. Durability evaluation of these mixtures included freeze-thaw resistance, characterization of air void system and deicer scaling tests, and measurement of chloride permeability. Test results showed that overlay mixes have excellent freeze-thaw resistance. Latex modified concrete mixes showed moderate scaling using the deicer scaling test. Chloride permeability of cores taken from silica fume overlays was lower than that from latex modified concrete overlays. Poor freeze-thaw performance of many of the pavement repair mixes indicates that many questions still remain regarding durability of concretes designed for early opening applications. Proper air content and adequate air void systems are necessary, but not sufficient, conditions for obtaining the desired freeze-thaw performance in freeze-thaw testing. The use of calcium chloride should be avoided as it contributes to reduced freeze-thaw resistance.

3634
Naik, T. R., Singh, S. S., and Hossain, M. M.
"ABRASION RESISTANCE OF CONCRETE AS INFLUENCED BY INCLUSION OF FLY ASH"
Cement and Concrete Research, 1994, Vol. 24, No. 2, pp 303-312.

This research was conducted to evaluate abrasion resistance of high-volume fly ash concrete. A reference plain portland cement concrete was proportioned to obtain 28-day strength of 41 MPa. Concrete mixtures were also proportioned to have two levels of cement replacements (50 and 70%) with an ASTM Class C fly ash. Abrasion tests were carried out using the rotating cutter method as per ASTM C-944. In this work all the concrete specimens made either with or without fly ash passed the abrasion resistance requirements per ASTM C-779, Procedure B. An accelerated test method was also developed to evaluate abrasion resistance of concrete. This method used the rotary cutter device having dressing wheels equipped with smaller size washers. A measured amount of standard Ottawa sand was added to the surface being abraded at one minute intervals. The accelerated test results exhibited lower abrasion resistance for high-volume fly ash concrete systems relative to no-fly ash concrete.

3635
Nasser, K. W. and Ghosh, S.
"DURABILITY PROPERTIES OF HIGH STRENGTH CONCRETE CONTAINING SILICA FUME AND LIGNITE FLY ASH"
Durability of Concrete, Proceedings of the Third International Conference, held May 22-28, 1994, Nice, France; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp 191-214. (ACI SP-145)

A comprehensive study was undertaken to determine the effect of sulfates and freezing and thawing on the durability of high strength concrete containing silica fume and lignite fly ash. The concrete mixtures contained normal CSA Type 10 (ASTM Type 1) portland cement, 10% silica fume and different amounts of fly ash that varied between 0 and 80% of the weight of binder in the mixture. The aggregates to binder ratio by weight was maintained at 5 and the weight of the superplasticizer was varied between 1.5 and 2.2% of the binder while the water to binder ratio was maintained at 0.27. Results of the freezing and thawing tests, as well as those of the sulfate tests (using Na2SO4), were encouraging. Concrete with either 20 or 35% fly ash replacement along with 10% silica fume gave satisfactory resistance to frost action, while concrete with up to 50% fly ash and 10% silica fume suppressed the sulfate attack considerably. Strength of concrete at 28 days with up to 60% fly ash and 10% silica fume was equal or more than the strength of control concrete of 100% Type 10 cement (ASTM Type 1). A study of matrix morphology and microstructure bonding using scanning electron microscope (SEM) showed that fly ash + silica fume concrete had denser paste microstructure (compared to the control) and this played an important role in enhancing compressive strengths and resistance to frost and sulfates. However, increasing fly ash contents beyond 50% weakened the matrix bonding due to the presence of too many unreacted fly ash particles which adversely affected the compressive strengths and resistance to frost and sulfates.

3636
Okamura, H. and Ozawa, K.
"SELF-COMPACTABLE HIGH PERFORMANCE CONCRETE IN JAPAN"
Preliminary Publication, International Workshop on High Performance Concrete, held Nov 21-22, 1994, Bangkok, Thailand; American Concrete Institute, Detroit, MI, 1994, pp 2-1 to 2-16.

Self-compactable high performance concrete requiring no consolidation on site has been recently developed in Japan to improve the reliability of concrete and concrete structures. This concrete can be recognized as a material innovation for new generation of concrete structures. Outlines of the concrete and the applications are described.

3637
Ozyildirim, C.
"A FIELD INVESTIGATION OF CONCRETE PATCHES CONTAINING PYRAMENT BLENDED CEMENT"
Virginia Transportation Research Council, Charlottesville, VA, Jun 1994, 16 pp. (FHWA/VA-94-R26)

During roadway repairs, state highway officials try to minimize lane closure times. This reduces inconvenience to travelers, reduces traffic control needs, and helps minimize work zone accidents. For rapid repairs, materials that provide high early strength are needed. Pyrament blended cement (PBC) is marketed to produce concretes having a high early strength and long-term durability in varying climatic conditions. Concretes containing PBC were placed in full-depth patches in August 1989 and March 1990 under different temperature conditions. Type III cement concretes were used as controls in patches placed during August only, since specifications did not permit their use when the ambient temperature was below 13oC (55oF). Tests of the concretes and the field performance of the patches indicated that PBC concrete has high early and 28-day strengths, even in cold weather, and that the temperature and strength development is faster than in the control concretes. PBC concretes have the low permeability needed for durability and provide satisfactory resistance to freezing and thawing without the addition of an admixture during mixing.

3638
Ozyildirim, C.
"LABORATORY INVESTIGATION OF LOW-PERMEABILITY CONCRETES CONTAINING SLAG AND SILICA FUME"
ACI Materials Journal, Mar-Apr 1994, Vol. 91, No. 2, pp 197-202.

Chloride-induced corrosion causes significant deterioration in transportation structures where uncoated reinforcing steel is used. Concretes with a very low permeability are used to prevent the intrusion of chlorides into concrete to the level of the reinforcing steel. This study evaluates the strength and permeability of various combinations of silica fume and slag in concrete. It was determined that when silica fume is added in small amounts (3 to 5 percent) to concretes with up to 47 percent slag at a water-cement ratio of 0.40 and 0.45, economical concretes with very low permeability and adequate strength can be produced.

3639
Ozyildirim, C. and Halstead, W. J.
"IMPROVED CONCRETE QUALITY WITH COMBINATIONS OF FLY ASH AND SILICA FUME"
ACI Materials Journal, Nov-Dec 1994, Vol. 91, No. 6, pp 587-594.

Portland cement concretes and concretes with various combinations of cement (Types II and III), fly ash (Class F), and silica fume were tested to establish parameters for strength and chloride permeability. The effects of different curing temperatures and different durations of moist-curing were also determined. In general, the laboratory tests showed that in the temperature range of 23 to 38 C (73 to 100 F), concretes at a water-cement ratio of 0.40 to 0.45 with satisfactory 28-day strengths and good resistance to chloride-ion penetration at 28 days can be obtained with either type of cement and various combinations of fly ash and silica fume. Similar specimens cured at 6 C (43 F) generally did not develop an adequate early strength, and the chloride permeability was high. Combinations of the pozzolans with Type III cement yielded a higher strength and lower chloride permeability than did similar combinations with Type II cement.

3640
Papworth, F. and Ratcliff, R.
"HIGH-PERFORMANCE CONCRETE -- THE CONCRETE FUTURE"
Concrete International, Oct 1994, Vol. 16, No. 10, pp 39-44.

In this paper the authors discuss four areas of development in concrete construction that provide for high-performance concrete. They include cathodic protection for control of steel corrosion, admixtures for high strength and high durability concrete, steel fibers to provide toughness for concrete in floors and industrial linings, and controlled permeability formwork (CPF) for durable concrete.

3641
Pasko, T. J., Jr. and Frohnsdorff, G. J.
"THE UNITED STATES GOVERNMENT'S ROLE IN HIGH-PERFORMANCE MATERIALS FOR INFRASTRUCTURE"
Proceedings of ACI International Conference, held November 15-18, 1994, Singapore; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp. 1-20. (ACI SP-149)

Sixteen agencies of the United States Federal Government have developed an interagency proposal for promoting the use of high performance concrete and other materials for use in the Nation's infrastructure. They are working jointly with the Civil Engineering Research Foundation (CERF) to enlist private sector support for sponsoring a research and development program aimed at getting the materials into use. CERF is drawing upon the technical community, such as that in ACI, to define the various research needs and studies which will lead to materials acceptance. Materials other than concrete are addressed in other parts of the total program. Workshops were held in the spring and fall of 1993 to develop schedules and priorities. A tentative cost for the concrete program is approximately $200 million over 10 years, which includes some technology transfer and which would be expected to be matched by some private sector funding.

3642
PCI Committee on Durability
"ALKALI-AGGREGATE REACTIVITY -- A SUMMARY"
PCI Journal, Nov-Dec 1994, Vol. 39, No. 6, pp 26-35.

This PCI Committee report presents information on the alkali-aggregate reactivity phenomenon that can adversely affect the durability of precast/prestressed concrete products. Although other types of alkali-aggregate reactions can occur, only the alkali-silica reaction is considered in this report. After describing the chemical reactions, methods for detecting the condition of the concrete surface are given together with measures to prevent the problem from occurring. Lastly, current research and two case studies are presented.

3643
PCI Committee on Durability
"GUIDE TO USING SILICA FUME IN PRECAST/ PRESTRESSED CONCRETE PRODUCTS"
PCI Journal, Sept-Oct 1994, Vol. 39, N0. 5, pp 36-45.

This PCI Committee report provides guidelines to the industry for producing high performance precast/prestressed concrete products containing silica fume. The mechanism, physical characteristics, benefits, and production aspects of concrete made with silica fume are described. Recommendations are given for measuring, mixing, handling, transporting, placing, finishing, and curing concrete with silica fume additives.

3644
Pfeifer, D. W., McDonald, D. B., and Krauss, P. D.
"THE RAPID CHLORIDE PERMEABILITY TEST AND ITS CORRELATION TO THE 90-DAY CHLORIDE PONDING TEST"
PCI Journal, Jan-Feb 1994, Vol. 39, No. 1, pp 38-47.

This paper reviews documents referenced by ASTM C1202
"Electrical Indication of Concrete's Ability to Resist Chloride Ion Penetration" and explores the correlation of ASTM C1202 to AASHTO T259
"Resistance of Concrete to Chloride Ion Penetration". The procedure outlined in ASTM C1202 is based on the AASHTO Test Method T277
"Rapid Determination of the Chloride Permeability of Concrete"
initially developed in 1981. Chloride penetration in both ASTM C1202 and AASHTO T277 is expressed as charge passed, or coulombs. The scope of ASTM C1202 states that this method is applicable to concretes in which a correlation has been established between the coulomb value and the amount of chloride ingress. This correlation testing is rarely performed by specifiers or researchers. Thus, selection or rejection of concrete based solely on ASTM C1202 can result in improper decisions and the rejection of concrete known to be durable. Based on the review of the documents referenced in ASTM C1202, it is concluded that reliable and proper correlations do not exist between the rapid test procedure results and 90-day ponding test results. The ASTM C1202 or AASHTO T277 test procedures should not be used in specifications without proper correlation to long-term tests. It is recommended that the table relating chloride penetration to coulomb values in these test procedures be removed since it is inaccurate and can be misleading.

3644a
Ralls, M. L. and Carrasquillo, R.
"TEXAS HIGH-STRENGTH CONCRETE BRIDGE PROJECT"
Public Roads, Spring 1994, Vol. 57, No. 4, pp. 1-7.

This paper describes the design and construction details for Louetta Road Overpass, two adjacent bridges on State Highway 249 in Houston, Texas. These structures showcase the use of high-strength concrete and are the first bridges in the United States to fully use high-strength concrete in all aspects of design and construction. They are also the first in the United States to use 15.24 mm (0.6 in.) diameter strands in a pretensioned concrete application and on a 50 mm (1.97 in.) grid spacing. The structures used pretensioned concrete U-beams with concrete strength in the range of 69 to 89.6 MPa (10 to 13 ksi) at 56 days. The U-beams were specially designed as an economical, aesthetic alternative to the standard I-beams. The U-beams supporting pretensioned concrete panels as stay-in-place forms were made composite with cast-in-place reinforced concrete deck to provide finished roadways. For purposes of comparison, the southbound mainlanes used 55.16 MPa (8 ksi) concrete while the northbound mainlanes used the Texas standard 27.6 MPa (4 ksi) concrete.

3645
Razvi, S. R. and Saatcioglu, M.
"STRENGTH AND DEFORMABILITY OF CONFINED HIGH-STRENGTH CONCRETE COLUMNS"
ACI Structural Journal, Nov-Dec 1994, Vol. 91, No. 6, pp 678-687.

Strength and deformability of confined high-strength concrete columns were investigated based on available experimental data. Up to 250 columns, tested either under monotonically increasing concentric loading or reversed lateral loading, were evaluated in terms of load, ductility, and drift capacities. The results indicate that the confinement requirements for high-strength concrete columns are significantly more stringent than those for normal strength concrete columns. However, it is possible to obtain ductile behavior in high-strength concrete columns through proper confinement. Although the requirements for volumetric ratio of confinement reinforcement are high for high-strength concrete columns, the use of high-strength confinement steel reduces the need to impose unrealistically high volumetric ratios to attain deformabilities usually expected of normal strength concrete columns. The results further indicate that the product of the volumetric ratio and strength of confinement steel, normalized with respect to concrete strength, can be used as a design parameter. Unconfined strength of concrete in column core was found to vary between 85 and 100 percent of the strength determined by a standard cylinder test. However, cover in high-strength concrete columns may buckle prematurely under high compressive stresses when it is separated from the core by closely spaced reinforcement. This may result in strength reduction if the confinement of the core is not sufficient to compensate for instability of the cover.

3646
Russell, B. W.
"IMPACT OF HIGH STRENGTH CONCRETE ON THE DESIGN AND CONSTRUCTION OF PRETENSIONED GIRDER BRIDGES"
PCI Journal, Jul-Aug 1994, Vol. 39, No. 4, pp 76-89.

The use of high strength concrete in the fabrication and construction of pretensioned concrete girder bridges can result in lighter bridge designs, with corresponding economic advantages, by allowing longer span lengths and increased girder spacings for standard shapes. A parametric study was performed comparing the required girder spacings and/or the allowable span limits for four commonly used cross-sectional shapes: the Texas Type C, the AASHTO Type IV, the AASHTO Type IV Modified, and the newly developed Texas Type U54B. The results clearly show that the use of high strength concrete can lengthen the allowable bridge span for concrete girders made from standard cross-sectional shapes or can decrease the number of girders required for a given design case. Furthermore, the results demonstrate that the flexural efficiencies of the different cross sections are similar if the depth of the cross sections is the same. Perhaps most significantly, this investigation illustrates that, through the use of high strength concrete, longer spans can be achieved using shallower cross sections in place of deeper cross sections.

3647
Schemmel, J. J., Arora, V., and Williams, J.
"SPLIT ADDITION OF A HRWRA AND ITS EFFECT ON HIGH-PERFORMANCE CONCRETE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp. 301-316. (ACI SP-148)

High-performance concretes (HPC's) typically have low w/c's in order to achieve the desired levels of strength and durability. As a result, HPC's have a tendency to be stiff and to lose their workability rather quickly. Often high-range water-reducing admixtures (HRWRA) are used to improve the workability of HPC. Care must be exercised when using any admixture, or combination of admixtures, to insure that there are no detrimental side effects which might shorten the life of the concrete. Research has shown that although retempering concrete with a HRWRA will generally improve the workability and maintain the strength of low w/c concretes, it may also reduce the resistance to freezing and thawing. Thus, an experimental study was undertaken to evaluate the use of naphthalene based HRWRA in the production of a high-early strength (HES) HPC. In a laboratory investigation, dosing the HRWRA was split to mimic both batch plant and jobsite addition. The results indicated that significantly higher slumps were found when the proportion of HRWRA added after 20 minutes of mixing was greater than that initially added. The air content of the fresh concrete was relatively unaffected by the split addition. Compressive strength appeared to be influenced more by the air content than by the dosage sequence of HRWRA. Resistance to freezing and thawing was good when an equal or greater proportion of the HRWRA was added at the batch plant.

3648
Sennour, M. L., Wheat, H. G., and Carrasquillo, R. L.
"THE ROLE OF CONCRETE MIX DESIGN IN THE CORROSION OF STEEL IN REINFORCED CONCRETE"
in Concrete Bridges in Aggressive Environments: Philip D. Cady International Symposium held November 9-10, 1993, Minneapolis, MN; Ed. by Richard E. Weyers; American Concrete Institute, Detroit, MI, 1994, pp 147-161. (ACI SP-151)

This paper deals with the contribution of concrete to the corrosion of rebars in reinforced concrete. Twenty six mix designs that represent concretes that could be used today were selected for study. Variables included cement content, water content, amount and type of fly ash, the addition of superplasticizers, and air entrainment. Strength and macrocell current were measured as a function of chloride exposure. The results of one year of cyclical exposure to 3.5% NaCl solution revealed that concrete influences the corrosion process greatly. Furthermore, modification of concrete can become another method of corrosion protection through a better understanding of the relationship between the corrosion process and concrete mix design.

3649
Sheikh, S. A., Shah, D. V., and Khoury, S. S.
"CONFINEMENT OF HIGH-STRENGTH CONCRETE COLUMNS"
ACI Structural Journal, Jan-Feb 1994, Vol. 91, No. 1, pp 100-111.

The paper presents results from 4 high strength concrete specimens, 3 nonprismatic and 1 prismatic, tested under constant axial load and cyclic lateral loads simulating earthquake forces, and comparison is made with similar specimens of normal strength concrete. Concrete strength varied between 4500 and 8500 psi. Relevant provisions of the ACI Building Code are evaluated in light of the test data. Increase in the lateral steel contents resulted in an almost proportional increase in ductility and energy-absorption capacity of confined high strength concrete, just as in the case of normal strength concrete. The required amount of confining steel appears to be proportional to the strength of concrete for a certain column performance if the axial load is measured in terms of Po rather than as a fraction of f'c Ag. Comments are made on the useable compressive strain.

3650
"SPECIAL CONCRETES - WORKABILITY AND MIXING"
Proceedings of the International RILEM Workshop, held March 2-3, 1993 at the University of Paisley, Scotland; Ed. by Peter J. M. Bartos; 1st ed., E & FN Spon, London, 1994, xiii, 264 pp. (RILEM proceedings, Vol. 24)

This book contains contributions on theoretical and practical aspects of the use of special concretes, with a particular focus on their behaviour in the fresh state. The mixes of special concretes differ significantly from that of ordinary concrete. These are used where high performance is needed or for special applications, such as high strength concrete, underwater concrete, flowing concrete, sprayed concrete. Mixes containing fibres, silica fume, polymers, special aggregates and cements, also demand a different approach to normal practice, such as the use of modified mixing equipment.

3651
St. John, D. A., McLeod, L. C., and Milestone, N. B.
"THE DURABILITY OF DSP MORTARS EXPOSED TO CONDITIONS OF WETTING AND DRYING"
Preliminary Publication, International Workshop on High Performance Concrete, held Nov 21-22, 1994, Bangkok, Thailand; American Concrete Institute, Detroit, MI, 1994, pp 3-1 to 3-11.

DSP mortar bars used to measure volume changes as a result of exposure to wetting and drying have expanded and failed. Petrographical investigation showed that the failures have occurred due to alkali-aggregate reaction of undispersed agglomerates of silica fume. Investigation of the particle size ranges and dispersability of a range of silica fumes showed that they were all agglomerated to varying degrees and that the dispersability is dependent on source and age of the silica fume. It is concluded that unless silica fume can be adequately dispersed in DSP materials there will be a potential for alkali-aggregate reaction to occur where the exposure conditions involve wetting and drying.

3652
Stephan, D. E.
"TECHNOLOGY TRANSFER: AN INDUSTRY POINT OF VIEW"
Preliminary Publication, International Workshop on High Performance Concrete, held Nov 21-22, 1994, Bangkok, Thailand; American Concrete Institute, Detroit, MI, 1994, pp 1-1 to 1-8.

Technology transfer within the construction industry is difficult due to (1) organization of the industry, (2) lack of construction industry participation in research, and (3) societal impediments. These barriers are discussed in relation to transferring innovation to practice. Differing activities that can mitigate the barriers are discussed and recommendations are offered to enhance the transfer of technology from research results to application in the construction industry.

3653
"SUPERPLASTICIZERS AND OTHER CHEMICAL ADMIXTURES IN CONCRETE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra, American Concrete Institute, Detroit, MI, 1994, vii, 455 pp. (ACI SP-148)

This symposium volume contains 25 refereed papers presented at the conference covering various applications of superplasticizers, set accelerators, latex modifiers and chemicals for controlling alkali-aggregate reactions. Mixture proportion, strength, durability, shrinkage and cracking of flowing concrete are discussed by a number of authors.

3654
Swamy, R. N., Sakai, M., and Nakamura, N.
"ROLE OF SUPERPLASTICIZERS AND SLAG FOR PRODUCING HIGH PERFORMANCE CONCRETE"
Proceedings of the Fourth CANMET/ACI International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, Oct 1994, Montreal, Canada; Ed. by V. M. Malhotra; American Concrete Institute, Detroit, MI, 1994, pp. 1-26. (ACI SP-148)

This paper presents a detailed investigation into the role and effectiveness of ground granulated blast-furnace slag and a high range water reducer (HRWR) on the quality of concrete in terms of bleeding, setting times, heat evolution, strength development and pore structure. The tests were carried out in two parts. (a) A slag of normal fineness was used, and both the replacement level and water-binder ratio were varied. It was found that both the slag and the HRWR acted as set retarders in terms of setting times and heat evolution. The water-binder ratio was the predominant factor affecting the rate of bleeding. The presence of slag, on the other hand, caused low early strength and slow strength development but had significant beneficial influence on the total pore volume and pore size distribution. (b) The fineness of slag was varied from 453 to 1160 m2/kg and the replacement level was kept constant at 50%. It was then possible to obtain compressive strength in excess of 30 MPa at 3 days and 100 MPa at 28 days with very substantial reductions in total porosity and water permeability. The bleeding rate was also reduced and the setting times also improved. The overall conclusion of this study is that a judicious combination of HRWR and slag fineness can lead to a very effective synergic interaction to produce concretes of high strength, high modulus and very low porosity.

3655
Tachibana, D., Kumagai, H., Yamazaki, N., and Suzuki, T.
"HIGH-STRENGTH CONCRETE (fc' = 600 kgf/cm2) FOR BUILDING CONSTRUCTION"
ACI Materials Journal, Jul-Aug 1994, Vol. 91, No. 4, pp 390-400.

In this study, tests were performed on mix proportions and material properties to investigate high-strength cast-in-place concrete with a specified strength of fc' = 58.8 MPa (600 kgf/cm2) for use in building construction. The results indicate that concrete meeting the desired strength and durability, with satisfactory workability, can be obtained if: (1) the water -cement ratio is set to 0.285; (2) a slump of 23 cm is achieved by adding a slump-controlling-type high-range water-reducing agent; and (3) sound quality control is provided, using a water content control system. This type of high-strength concrete has actually been used in construction, and quality control testing confirms excellent results.

3656
Takeuchi, H., Higuchi, M., and Nanni, A.
"APPLICATION OF "FLOWABLE" CONCRETE IN A TUNNEL LINING"
Concrete International, Apr 1994, Vol. 16, No. 4, pp 26-29.

This article describes how highly durable, homogeneous, and labor saving concrete structures can be constructed with flowable concrete. Flowable concrete is high performance concrete that has enhanced ease of placement and high resistance to segregation. The project in which it was used consisted of the construction of a tunnel in Yokohama City, Japan, at a depth of 20 m to protect a residential area from flooding. Concrete mixture constituents and proportions are described. Transportation of the mixture and the quality control, as well as the construction are also described. It was found that the flowable concrete is a very effective construction material, especially for structures with congested reinforcement.

3657
Thomsen, IV, J. H. and Wallace, J. W.
"LATERAL LOAD BEHAVIOR OF REINFORCED CONCRETE COLUMNS CONSTRUCTED USING HIGH-STRENGTH MATERIALS"
ACI Structural Journal, Sept-Oct 1994, Vol. 91, No. 5, pp 605-615.

The paper summarizes results of an experimental and analytical study of reinforced concrete columns constructed with high-strength materials and subjected to simulated seismic loadings. The primary objective of the study was to investigate the suitability of using high-strength concrete columns in regions of moderate-to-high seismic risk. The experimental program consisted of testing 12, approximately quarter-scale, rectilinearly confined, high-strength reinforced concrete columns with concrete compressive strengths of approximately 12 ksi. The primary variables of the testing program were: the spacing, configuration, and yield strength of the transverse reinforcement; and the level of axial stress acting on the column. Experimental and analytical results indicate substantial column deformation capacity with no decrease in flexural strength up to a lateral drift level of 2 percent, and that the use of high-yield-strength transverse reinforcement without a well-defined yield plateau provides more effective confinement than Grade 60 reinforcement. An analytical model for stress-strain of high-strength concrete is evaluated, and code provisions for buckling of longitudinal reinforcement are investigated.

3658
Whiting, D. and Nagi, M.
"STRENGTH AND DURABILITY OF RAPID HIGHWAY REPAIR CONCRETES"
Concrete International, Sept 1994, Vol. 16, No. 9, pp 36-41.

This article describes an investigation of the strength and durability of field concretes used for rapid full-depth highway pavement repairs. Two test sites were chosen, one on I-20 west of Augusta, Georgia, and the other on State Route 2 near Vermilion, Ohio. Three different concrete mixes were used at the first site, and eight at the second site. Three categories of opening times were considered: 2 to 4 hours, 4 to 6 hours, and 12 to 24 hours. Fresh concrete properties, compressive and splitting tensile strengths development, freeze-thaw durability, and air-void systems of different concrete mixes were compared. The study showed that strengths over 4000 psi (28 MPa) at one day can be obtained with the concrete repair mixes evaluated. Relatively high long term compressive strengths can be achieved using a variety of the rapid pavement repair materials and in most cases strengths in excess of 6,000 psi (41 MPa) at 90 days are easily achievable. Where proper air contents, air-void system parameters, and w/(c m) were achieved, performance of rapid repair mixes within severe freeze-thaw conditions was good.

3659
Whiting, D., Nagi, M., and Okamoto, P.
"EARLY STRENGTH GAIN OF RAPID HIGHWAY REPAIR CONCRETE"
Concrete International, Aug 1994, Vol. 16, No. 8, pp 28-35.

This paper presents the results of field studies of nine separate concrete mixes used for full-depth highway pavement repairs with early opening for traffic (2 to 24 hours). Tests were conducted at two sites, one on I-20 west of Augusta, Georgia, and the other on State Route 2 near Vermilion, Ohio. Field test techniques included determination of water content using microwave oven drying, temperature matched curing, maturity monitoring, and ultrasonic pulse velocity measurement. Using these techniques, the strength development with time and the predicted strength compared with the core strength were obtained.

3660
Winslow, D. N., Cohen, M. D., Bentz, D. P., Snyder, K. A., and Garboczi, E. J.
"PERCOLATION AND PORE STRUCTURE IN MORTARS AND CONCRETE"
Cement and Concrete Research, 1994, Vol. 24, No. 1, pp 25-37.

The cement paste in concrete and mortar has shown to have a pore size distribution different from that of plain paste hydrated without aggregate. For mortar and concrete, additional porosity occurs in pore sizes larger than the plain paste's threshold diameter as measured by mercury intrusion. Based on the assumption that these larger pores are essentially present only in the interfacial zones surrounding each aggregate, an experimental program was designed in which the volume fraction of sand in a mortar was varied in a systematic fashion and the resultant pore system probed using mercury intrusion porosimetry. The intrusion characteristics were observed to change drastically at a critical sand content. Similar results are observed for a series of mortar specimens in which the cement paste contains 10% silica fume. To better interpret the experimental results, a hard core/soft shell computer model has been developed to examine the percolation characteristics of these interfacial zone pores. Using the model, interfacial zone percolation in concretes is also examined. Finally, the implications of interfacial zone percolation for transport properties and durability of mortar and concrete are discussed.

3661
Xie, Y., Ahmad, S. H., Yu, T., Hino, S., and Chung, W.
"SHEAR DUCTILITY OF REINFORCED CONCRETE BEAMS OF NORMAL AND HIGH-STRENGTH CONCRETE"
ACI Structural Journal, Mar-Apr 1994, Vol. 91, No. 2, pp 140-149.

A total of 15 shear critical reinforced concrete beams without and with shear reinforcement (web) were tested in a stiff testing facility, and complete load-midspan deflection curves, including the post-peak portion, were obtained. The experimental variables were the concrete compressive strength, shear span-to-depth ratio (a/d), and the amount of shear reinforcement. For the range of variables tested, the results indicate that shear reinforcement (web) improves the shear ductility index of reinforced concrete beams of normal as well as high-strength concrete. High strength reinforced concrete beams with a/d of 3 show a plastic post-peak response when shear reinforcement provided is about twice the minimum recommended by the ACI Building Code. These and other findings are presented.