Influence of waste aggregate type on the mechanical strength and durability of slag–rice husk ash-based geopolymer composites

This study explores the utilization of construction and demolition waste (CDW), ceramic waste (CW), and marble waste (MW) as partial sand replacements in geopolymer mortars produced with granulated blast furnace slag (GBFS) and rice husk ash (RHA). Mortars were prepared with 75% GBFS and 25% RHA, activated using sodium silicate and 12M sodium hydroxide, and cured at ambient conditions for 28days. Waste aggregates were substituted at 10%, 20%, and 30%, while mix ratios were kept constant. Hardened properties, drying shrinkage, and high temperature performance (300 and 600C) were evaluated, alongside microstructural analyses (X-ray diffraction, scan ning electron microscopy, thermogravimetric analysis/derivative thermogravimetric). Results showed MW10 achieved the highest compressive strength with an increase of 27%, while CW20 exhibited the best flexural strength with an increase of 8%. CW and MW reduced drying shrinkage, whereas CDW increased it and caused significant strength loss at elevated temperatures. Combining waste aggregates with industrial by-products boosts sustainability and performance.