Post-fire residual mechanical and microstructural properties of waste basalt and glass powder-based geopolymer mortars

Abstract

The wastes that arise during the production process of the products required by the industry create environmental problems. In recent years, the activation of such wastes with alkaline activators has provided environmentally friendly and sustainable solutions. Different mixture designs have been realized for the production of geopolymer composites with basalt and glass powder waste. This study deals with the changes in the mechanical properties and microstructure of geopolymer mortars containing basalt powder (BP) and glass powder (GP) with the post-fire air curing effect. Geopolymer mixtures were prepared by using basalt powder and glass powder at 0 %, 25 %, 50 %, 75 %, and 100 % proportions. After casting and vibrating, the mortars were cured at 90 °C for 24 h. Flexural and compressive strength tests have been conducted on the specimens at the age of 1, 28, and 90 days. Additionally, the tests were applied to the heated specimens (400 °C, 600 °C, and 800 °C) after 1, 28, and 90 days from the heating process, separately. The effect of high temperature on mechanical, physical, and microstructural properties is examined comparatively. In addition, SEM/EDX analyses were performed on selected samples. As a result, the post-fire behavior of geopolymers is changeable with the precursor type. The compressive strength of the mortars containing %75 basalt and %25 glass powder had the best post-fire performance of all the mortars. The compressive strength of these mortars significantly increased from 1 day to 90 days after being subjection to high temperatures up to 800 °C.