Fracture Energy of High-Strength Concrete

Abstract

The effects of water-cementitious materials ratio, age, and aggregate type on the compressive strength, flexural strength, and fracture energy of concretes with compressive strengths ranging from 20 to 99 MPa (2900 to 14,400 psi) are studied. Concrete mixtures contain either basalt or crushed limestone aggregate with maximum sizes of 12 or 19 mm (1/2 or 3/4 in.). Mixtures are tested at ages ranging from 5 to 180 days and have water-cementitious (w/cm) ratios ranging from 0.24 to 0.50. High-strength concrete containing the higher-strength, basalt coarse aggregate attains higher compressive and flexural strengths than high-strength concrete containing limestone. The compressive and flexural strengths of medium and normal strength concretes (fc¢ up to approximately 60 MPa [9000 psi]) are affected little by aggregate type. Concrete containing basalt yields significantly higher fracture energy than concrete containing limestone, with fracture energy governed principally by aggregate properties, independent of compressive strength, w/cm ratio, and age. Overall, 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 approximately constant. The result is increasingly brittle behavior as compressive strength increases.