Fracture Energy of High-Strength Concrete

This paper studies effects of water-cementitious (w/cm) materials ratio, age, and aggregate type on the compressive and flexural strength and fracture energy of concretes with compressive strengths ranging from 20-99 MPa. Concrete mixtures contain either basalt or crushed limestone aggregate with maximum sizes of 12 or 19 mm. Mixtures are tested at ages ranging from 5-180 days and have w/cm ratios ranging from 0.24-0.50. High-strength concrete containing the higher-strength, basalt coarse aggregate attains higher compressive and flexural strengths than that containing limestone. The compressive and flexural strengths of medium- and normal-strength concretes are affected little by type of aggregate. Concrete containing basalt yields much higher fracture energy than concrete containing limestone, with fracture energy governed principally by aggregate properties, independent of compressive strength, w/cm ratio, and age. As compressive strength increases, the energy stored in the material at the peak tensile load increases while the ability of the material to dissipate energy remains roughly constant. The result is increasingly brittle behavior as compressive strength increases.