HIGH-PERFORMANCE CONCRETE - INFLUENCE OF COARSE AGGREGATES ON MECHANICAL-PROPERTIES

Test results are reported from an experimental study in,which the effe ct of four coarse aggregate types, locally available in central Texas, on the mechanical properties of low water-cement ratio mires, namely compressive strength, elastic,modulus, and flexural strength was inves tigated. Crushed river gravel, trap rock, dolomitic limestone, and cal citic limestone were used in high-performance concrete (HPC) productio n in varying amounts: 36, 40, and 44 percent by concrete volume. A con stant water-cement ratio of 0.28,vas employed for all mixes. The miner alogical characteristics of coarse aggregate, as rt ell as the aggrega te shape, surface texture, and hardness, appear to be responsible for the differences in the performance of HPCs. It was observed that HPCs ,with different coarse aggregates appear to lack a single equation tha t estimates the elastic modulus or flexural strength with sufficient a ccuracy as in the case of normal strength concretes. This could be att ributed to the increased role of coarse aggregate in concrete mires wi th low water-cement ratios, as a result of improved cement paste and t ransition zone.