Characterization and application of municipal solid waste incineration (MSWI) bottom ash and waste granite powder in alkali activated slag

In this paper, the feasibility of using two solid wastes in alkali activated slag composites as construction and building materials is evaluated. One waste is the municipal solid waste incineration (MSWI) bottom ash, and the other one is fine granite powder from aggregate manufacturing. These two solid wastes are thoroughly characterized, and their effects on reaction process, gel composition, microstructure are investigated by isothermal calorimeter, TG/DSC, FTIR and SEM. Leaching properties and CO2 footprint of some typical mixes are evaluated. The results indicate that both bottom ash and granite addition can be regarded as non-reactive phases. Micro scale analyses show no evident chemical involvement of both wastes on the gel structure of the reaction products. Bottom ash addition reduces the compressive strength, and granite powder presents a lower influence; 28 d strengths of around 20-70 MPa can be achieved depending on the replacement levels. Most of the mixtures pass the Dutch regulation for heavy metal leaching, while the excessive chlorides and sulfates contents can be easily treated by methods such as washing. The carbon emission is significantly reduced due to the negative impact of the waste solids, and this value can be further lower if bottom ash with larger sizes is used to replace coarse aggregates. Therefore, these two solid wastes present promising application potential based on the identified performances and sustainability.