Effect of Freeze-thaw Damage and Pore Structure on Capillary Water Absorption of Gangue-based Concrete

Driven by capillary adsorption, moisture and aggressive media can easily intrude into unsaturated concrete and shorten the service life of concrete structures. In the present study, gangue-based concrete (GBC) was produced by replacing cement (substitution rate 0%, 10%, 20% and 30%) with mechanical-microwave activated coal gangue powder (ACGP) to explore the effect of freeze-thaw damage on the water absorption performance of GBC. ACGP improved the frost resistance of GBC, but the frost resistance declined at 30% mixing. The water absorption performance of GBC was promoted by freeze-thaw damage. Besides, the water absorption performance of GBC decreased first and then enhanced with the growth of ACGP content, especially the weakest at 20% content. The correlation analysis between the macroscopic characteristics of freeze-thaw damage and water absorption performance suggested that the coefficient of capillary absorption was highly linearly correlated with the damage layer thickness (R-2 > 0.9). The pore structure of GBC was optimized by the increase of small pores as well as the decrease of large pores after ACGP mixing. Furthermore, the coefficient of capillary absorption showed an apparent positive correlation with the transitional pores.