Effect of Compressive Creep on Fracture Properties of Concrete: Strengthening versus Weakening

Abstract For nuclear power plant containment, concrete is subjected to sustained compressive stresses due to prestressing, and the time-dependent creep deformation of concrete can alter its mechanical and fracture properties. To assess the cracking resistance of concrete in under extreme loads, this study investigated the effect of compressive creep on the fracture performances of concrete. Firstly, compressive creep tests were conducted on prism specimens under three stress levels, i.e., 40%, 60%, and 80% of the axial compressive strengths, and three durations, i.e., 30, 90, and 180 days. Then three-point bending fracture tests and basic mechanical property tests were conducted in succession to measure the basic mechanical properties and fracture parameters of concrete after undergoing the compressive creep. Finally, the tension-softening constitutive laws of the concrete were derived and then simplified as the bilinear laws. The results indicate that the compressive creep has both strengthening and weakening effects on the basic mechanical properties and fracture parameters of concrete. After undergoing compressive creep, the tensile strength, compressive strength, initial fracture toughness and fracture energy exhibited increasing tendencies, and there was a peak strengthening effect under 60% of the axial compressive strength. However, the unstable fracture toughness had an obvious decreasing tendency induced by the obvious decreasing tendency of the critical crack length. In addition, a practical model is proposed to predict the tension-softening constitutive laws after undergoing compressive creep via the tensile strength, fracture energy, and compressive strength of concrete.