Characterization of Geopolymer Masonry Mortars Incorporating Recycled Fine Aggregates

This study evaluates the characteristics of geopolymer masonry mortars (GMMs) made with slag–fly ash binder and up to 100% recycled fine aggregates (RFAs). For each RFA replacement rate, two types of GMMs, namely N and S types based on ASTM C91, were proportioned and tested for mechanical, physical, and durability properties. Results revealed that using geopolymeric binder enhanced the flow, water retention, compressive strength, sorptivity, and abrasion resistance of GMMs compared to cementitious counterparts but reduced the initial setting time by up to 75%. Subsequent RFA additions negatively affected the flow, setting time, density, water absorption, porosity, and bulk resistivity but enhanced the water retention, sorptivity, and abrasion resistance of GMM. It also reduced the compressive, pull-off, and flexural strengths by 36, 44, and 27%, respectively. Furthermore, S-type mortars exhibited improved bulk resistivity, sorptivity, and abrasion resistance compared to N-type counterparts. A multifunctional performance index deduced that the GMM mixes incorporating 100% RFAs were superior to geopolymeric or cementitious masonry mortars made with natural fine aggregates (NFAs). Such findings emphasize the sustainability of GMMs made with RFAs in masonry construction, eliminating the need for water curing while maintaining comparable or even superior properties compared to cement-based mortars made with NFAs.