Assessing the effect of fly ash with a high SO3 content in hybrid alkaline fly ash pastes (HAFAPs)

Abstract Hybrid alkaline fly ash pastes (HAFAPs) are a new generation of alkaline-activated binders that use low amounts of Portland cement and high amounts of fly ash (FA). New sulfur emissions requirements in power plants are generating quantities of FAs with high SO3 (>5%) content, which are discarded into landfills. This paper investigates the effects of high-SO3 FA on the mechanical properties, durability, and characterizing chemical behavior of HAFAPs. The main results indicate that depending on the exposure condition, high SO3 content leads to the generation of efflorescence, affecting the mechanical performance and durability of HAFAPs.