Microprestress–solidification theory of concrete creep: Reformulation and improvement

Concrete creep is strongly affected by the evolution of pore humidity and temperature, which depend on environmental conditions and on the geometry of the concrete member. One advanced model accounting for such phenomena is the extended version of the B3 model referred to as the microprestress–solidification theory. It postulates a differential equation governing microprestress relaxation and generation of additional microprestress caused by changes of temperature and humidity. Here, this equation is rewritten in terms of viscosity, which leads to a reduction of the number of parameters and their easier identification. Based on numerical simulations it is shown that the evolution of mechanical strain measured in creep tests at constant and monotonically increasing temperature can be captured properly by the original microprestress–solidification theory, but certain deficiencies are detected for repeated temperature cycles. An improved version is proposed, identification of new parameters is discussed and good agreement with experimental data is demonstrated.