Recycling of high-volume waste glass powder in alkali-activated materials: An efflorescence mitigation strategy

The increasing environmental burden at landfills due to the disposal of waste glass (WG) has motivated the scientific community to find alternative routes for its utilization. One of these promising routes is to use WG as a precursor in alkali-activated materials (AAMs). However, conventional AAMs (in particular alkali-activated slags) set rapidly and suffer severe efflorescence that restricts their field applications. This study investigates the setting behavior, compressive strength, and efflorescence characteristics of alkali-activated binder prepared principally with ground granulated blast furnace slag (GGBS), and large volumes of waste glass powder (WGP) were used as replacements of GGBS systematically to improve the properties of resulting binders. A range of properties was analyzed, including setting time, compressive strength, efflorescence characteristics, and microstructure of the alkali-activated GGBS/WGP (AASG) samples. The experimental results revealed that incorporating WGP to replace GGBS in AASG pastes reduced the compressive strengths and prolonged the setting time because of the low reactivity of WGP. Although using WGP as a replacement for GGBS decreased the strength, the incorporation of 75% WGP in AASG reduced the severity of efflorescence effectively. This reduction can be related to the lower Na/Si, Ca/Si, and the higher Si/Al in C-(N)-A-S-H type gel phases.