Investigating the Properties of GGBFS Hazelnut Ash–Based Cement-Free Mortars Produced at Ambient Temperature under Different Curing Conditions

Abstract

One of the main problems that reduces the prevalence of alkali-activated binders is the heat-curing process that is required to produce them. In addition, the chemical alkaline solutions used can be corrosive, caustic, and expensive. With this innovative study, the production of alkali-activated mortar made entirely from waste materials without the use of thermal curing or a chemical solution was carried out. In this study, the physical and mechanical effects of alkali-activated mortars produced by using ground granulated blast-furnace slag (GGBFS) and hazelnut shell bottom ash (HA) were investigated. Instead of GGBFS, 10%, 20%, 30%, 40%, 50%, and 60% HA was substituted in the samples produced. In addition, the samples produced at ambient temperature were subjected to four different curing conditions. Unit weight, porosity, water absorption, ultrasonic pulse velocity, and compressive strength tests were applied to the mortar samples on Days 3, 7, and 28. Moreover, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray fluorescence analysis (XRF), and X-ray diffraction analysis (XRD) were used to examine the changes in the microstructures of the mortars. As a result of the study, it was determined that the use of HA up to 50% improved the compressive strength and other physical properties. The mortars containing 50% HA obtained 14.45 MPa when kept under ambient conditions and 19.54 MPa when kept under ambient conditions for 3 days and in water for 25 days. Also, water-cured samples showed better performance in other tests.