Investigation of cementitious properties of different constituents in municipal solid waste incineration bottom ash as supplementary cementitious materials

Abstract

To investigate the municipal solid waste (MSW) incineration bottom ash (IBA) as a value-added building material, this study focuses on evaluating different IBA constituents (such as glass, ceramic, mineral, slag-I with low-ferrous sintered phase and slag-II with high ferrous sintered phase) to be used as supplementary cementitious materials (SCMs) and then comparing to commercial SCMs (ground-granulated blast-furnace slag-GGBS and fly ash-FA). The investigated IBA constituents were milled into powder and then used as SCMs to partially replace cement in mortars. Their influences on cement hydration were evaluated by an isothermal calorimeter and the pozzolanic activities were assessed through the modified Chapelle test. The strength development of the mortars was studied to quantify their contributions as SCMs when compared to that of GGBS and FA. The microstructure of the hydrated mortar with IBA constituents was further evaluated. The experimental results showed that, at an early age of the IBA blended cement hydration, the powdered IBA constituents contributed to an increase in heat release, which was higher than that of FA and lower than that of GGBS; and the formation of monosulphate was accelerated. After 90 days’ curing, the powdered glass and ceramic fractions derived from IBA contributed significantly to the mortar strength compared to other constituents, indicating their relatively high reactivity that was confirmed by their high consumption of portlandite in the modified Chapelle test. The samples prepared with glass and ceramic powders derived from IBA had a relatively higher efficiency strength index (ESIt,FA/GGBS) than other IBA constituents, indicating their higher potential to be used as SCM alternatives. Therefore, it is suggested that the ground ceramic and glass fractions separated from IBA can be used as SCM alternatives, which can achieve over 80% and over 93% ESI of that of FA and GGBS, respectively. Furthermore, the other fractions of IBA, namely the coarse IBA and IBA-minerals can only be used as fillers.