Effects of eco powders from solid waste on freeze-thaw resistance of mortar

Abstract

This study investigates the long-term properties of green mortar, including mechanical properties and freeze-thaw resistance. Within the green mortar mixtures, the recycled concrete powder (RCP) and spontaneous combustion gangue powder (SCGP) were designed alone or in combination as a substitute for different proportions of cement. The findings indicate that the pozzolanic activity of eco powders and the mixed eco powders (RCP: SCGP = 1:1, by mass ratio) can meet the criteria for pozzolanic activity. Benefitting from the prolonged pozzolanic reaction, the green mortar containing 30% eco powder (e.g., RCP, SCGP, or RCP + SCGP) can achieve acceptable mechanical behavior at 300 days. Experimental results reveal that SCGP has positive effects on the freeze-thaw resistance of green mortar, while RCP behaves oppositely. This phenomenon is attributed to the different contributions caused by different eco powders on the pore structure of green mortar. The better freeze-thaw resistance of RM-0R-30C can be attributed to a dense microstructure of green mortar by pozzolanic reaction induced by SCGP. The filling effect of RCP gradually weakens after the initial damage under frost attack, and the high water absorption of inert RCP particles leads to aggravated freeze-thaw damage as the number of freeze-thaw cycles increases.