MECHANICAL CHARACTERISTICS AND MODULUS OF ELASTICITY OF HIGH-PERFORMANCE CONCRETES MADE WITH VARIOUS TYPES OF COARSE AGGREGATE

In this study, the effects of coarse aggregate on the mechanical and e lastic properties of high performance concrete are examined. Four type s of rock were selected and coarse aggregates were prepared from each. Eight high performance concretes were made with water/cement ratios o f 0.27 and 0.22. In addition to characterizing some physical and mecha nical properties of the rocks and concretes, the mechanical and elasti c properties were investigated of four normal strength concretes made using the same four coarse aggregates with a water/cement ratio of 0.5 0. Test results showed that the compressive strength and modulus of el asticity of high performance concrete can vary by as much as 24% and 5 0%, respectively, depending on the type of coarse aggregate in use. Th is study, however, raises some questions concerning the validity, in s ome cases, of equations recommended in national codes and of some prop osed mathematical models and empirical relationships used to determine the modulus of elasticity of concrete. The study proves that the stre ngth of the cement paste, which depends on the water/cement ratio, con trols the width of the hysteresis loops in the stress-strain curves, w hereas the coarse aggregate controls the shape of these curves.