Synthesis of alkali-activated materials blended with fly ash: Optimization of curing conditions and precursor dosage

Abstract

Metakaolin, calcined clay, and sodium and potassium silicates are frequently utilized materials in the alkali activation process to produce alkali-activated materials. This study investigates various approaches to enhance the reactivity of low-quality natural clay to manufacture alkali-activated bricks with improved strength. Two types of clay were employed: natural and calcined clays. The results demonstrate that the optimal compressive strength was achieved by combining non-calcined clay with chamotte, sand, and 25 % olive pomace fly ash (OPFA). This selection provides environmental and energy benefits since it reduces the energy consumption and environmental effects associated with high-temperature clay calcination. The best conditions for increasing the compressive strength of the alkali-activated binder involve curing in a dry environment at 80 °C for 8 h. The mineralogical and microstructural characterization of the optimized material revealed a more or less dense structure with the possibility of the presence of hydrated calcium silicate gel, in addition to the hydrated sodium silicate gel due to the pozzolanic nature of the olive pomace ash used.