Micro-macro characterizations of mortar containing construction waste fines as replacement of cement and sand: A comparative study

This work shows a comparison on the micro-macro characterizations of sustainable mortar containing construction waste fines (0-0.15 mm) as cement and sand replacement, and the construction waste fines included waste concrete fines (WCF) and waste brick fines (WBF). The results showed that WCF/WBF had certain pozzolanic activity, good nucleation and micro-aggregate filling effects. Reusing WCF as cement replacement increased the porous structure of the paste, but incorporating moderate WBF as cement replacement refined pore structure; besides, substituting WCF/WBF for partial sand refined the pore structure of paste. Mixing appropriate WCF/WBF as cement replacement reduced the drying shrinkage of mortar, but the drying shrinkage continuously increased with the addition of WCF/WBF as sand replacement. When reusing construction waste fines as cement replacement, incorporating WCF reduced the strength and permeability resistance of blended mortar, but the strength and permeability resistance were first improved and then declined with the increase of WBF content; specifically, substituting WCF and WBF for 30% cement resulted in 23.2% and 14.0% reduction in the compressive strength. When reusing construction waste fines as sand replacement, mixing WCF and WBF both improved the strength and permeability resistance, and substituting WCF and WBF for 30% sand resulted in 35.0% and 48.6% rise in compressive strength. Particularly, WBF blended mortar had superior properties to WCF blended mortar, and substituting WCF/WBF for both 10% cement and 10% sand can prepare sustainable mortar owning similar or superior properties to plain mortar.