Study on Early Cracking Behavior and Temperature Stress Development of Confined Low Heat Cement Concrete

Temperature stress cracking in low-heat cement concrete is a critical issue in hydraulic engineering due to uneven restraints and complex curing conditions in massive structures. This study investigates the early-age thermomechanical behavior of low-heat cement concrete under varying restraint levels (0%, 50%, 75%, and 100%) and curing-cooling regimes by utilizing Temperature Stress Testing Machine. Results show that higher restraint amplifies compressive stress by restricting thermal expansion but reduces cracking stress via stress localization. Cracking temperature difference decreases with increasing restraint but increases with curing age due to microstructural densification and delayed stress relaxation. The ability of concrete to resist cracking is weakened by increased confinement. Under different curing modes, the characteristic parameters of temperature stress under various restraints are not significantly different. The variation in the equivalent thermal expansion coefficient and elastic modulus of concrete is primarily influenced by internal stresses, microstructural changes, and the degree of restraint during curing. Future research should integrate multiple external factors such as ambient temperature, relative humidity, and wind speed, and investigate their synergistic impact with restraints on interlayer properties of dam concrete to refine crack prediction and enhance durability in mass low heat cement concrete.