Carbonation resistance and freeze thaw cycle performance of composite limestone powder tailings mixed sand concrete

An experimental investigation was conducted to investigate the carbonation resistance and freeze thaw cycle performance of composite limestone powder–tailings mixed sand concrete (CLP-TMS concrete) and to reveal the influences of tailings mixed sand (TMS) and supplementary cementing materials (SCMs) with limestone powder (LP) on the carbonation depth, dynamic modulus of elasticity, and mass loss of concrete. Nine types of concrete mixtures were designed for the experiments, with LP contents of 5%, 10%, 15% and 20% in the manufactured sand. The results indicated that TMS can significantly increase the carbonation resistance and slightly increase the freeze resistance of concrete. SCMs reduced the carbonation resistance and exacerbated freeze thaw damage. Among the SCMs, when the LP content reached 10%, the carbonation resistance effect was greatest before 14 days, and the freeze resistance first peaked and then decreased as the content increased. With respect to the degradation mechanism of CLP-TMS concrete, increasing the amount of LP can inhibit the early conversion of AFt to AFm, hence increasing the AFt content and reducing the generation of Ca(OH)₂. On the basis of the single-factor model correction parameters, a coupled model of carbonation and freeze thaw cycles was established. • Degradation of the freeze-thaw resistance of composite limestone powder concretes under freeze–thaw environment was explored. • As the water cement ratio decreases, the compressive strength of composite limestone powder concrete increases, and the freeze-thaw resistance significantly decreases. • After adding industrial solid waste materials such as limestone powder and fly ash slag, the quality loss of concrete changes little, but the relative dynamic modulus is relatively low and large. • Based on the single-factor model correction parameters, a coupled model of carbonation and freeze thaw cycles is established.