Influence of prewetted lightweight aggregates on the behavior and cracking potential of internally cured concrete at an early age

High-performance concrete (HPC) is widely used in practice. The water-to-cement ratio of HPC is low, and self-desiccation and high temperature rise occur. Internal curing (IC) with prewetted lightweight aggregates (LWAs) is applied to enhance the early-age behavior of concrete structures in terms of temperature, shrinkage, creep deformation, and stress, thus resulting in low cracking potential. Although tests on the effect of prewetted LWAs on the cracking potential of concrete under semi-adiabatic or isothermal conditions have been conducted, studies on the influence of the amount of prewetted LWAs on the cracking potential of internally cured concrete under adiabatic conditions remain lacking. In this study, the cracking potential of internally cured concrete with prewetted LWAs was experimentally investigated with a temperature stress testing machine. The effect of prewetted LWAs in reducing the cracking potential in HPC was investigated with different amounts of LWAs (0%, 10%, 30%, and 50%) in four pairs of large prismatic HPC specimens tested simultaneously under free and fully restrained shrinkage. Test results showed that (1) both temperature rise and drop of concrete occurred as prewetted LWAs increased; (2) the autogenous shrinkage and cracking stress of concrete decreased with the increase in the amount of prewetted LWAs; (3) the tensile stress rate of concrete with prewetted LWAs decreased; (4) the ratio of cracking stress to the tensile strength of concrete increased with the increase in the amount of prewetted LWAs; (5) the cracking age of concrete with the LWAs increased; (6) the specific tensile creep of concrete with prewetted LWAs decreased; and (7) the cracking potential of concrete with prewetted LWAs was reduced, as obtained from the integrated criterion. Internally cured concrete with prewetted clay LWAs is more robust for construction at early ages.