Performance of eco-friendly fly ash-based geopolymer mortars with stone-cutting waste

Abstract

In this study, the physical and mechanical properties of the geopolymers formed by substituting red (RSW) and yellow (YSW) stone-cutting wastes into geopolymer mortars based on class F fly ash at 10–40 wt% rates were investigated. Sodium hydroxide (NaOH) solution was used as an activator in the production of the mortars. Produced samples were thermally cured at 90 °C for 24 h. Workability, unit weight, flexural strength, compressive strength, water absorption, porosity, and elevated temperature resistance tests (400, 600, and 800 °C) were applied to the produced geopolymer mortars. In addition, the chemical analysis (XRF), crystal phase analysis (XRD) of wastes/selected mortars, and microstructural analysis (SEM) of before and after elevated temparature resistance tests were carried out to investigate the effect of stone-cutting wastes on geopolymer mortars. SW up to 40% enhances mechanical strength up to 26–30.7 MPa from 16.4 MPa due to its high Si/Al ratios and Ca content and needle-like crystals formed by stone-cutting waste. The crystalline phases are determined to be mullite, quartz, anorthite, and zeolite derived from stone-cutting waste in the selected mortars. As a result, it was seen that the use of stone-cutting wastes up to 40% improved the physical, mechanical, and microstructural properties of fly ash-based geopolymer mortars.