Manufacture of hybrid cements with fly ash and bottom ash from a municipal solid waste incinerator

Abstract

Concerns about the large volume of fly ash and bottom ash generated by the incineration of municipal solid waste (MSW) have induced the scientific community to seek ways to reduce their environmental impact. One of the proposals that has been researched most intensely is their valorisation as supplementary cementitious materials and aggregates in Portland cement-based pastes, mortars and concretes. The present paper proposes an alternative use for this waste: as a raw material in alkali-activated hybrid cements. A hybrid cement developed for that purpose by blending 60wt% clinker and 40wt% incinerator bottom ash and fly ash exhibited good 28-day mechanical strength (upward of 32.5MPa). The leaching of potentially toxic metals present in the hybrid cement as a result of the inclusion of MSW fly ash and bottom ash was tested with different leaching procedures. The findings and the results of the analysis of the leaching parameters measured (Li, Fij…) showed that the hybrid cement proposed can effectively immobilise the potentially hazardous metals present in MSW fly ash and bottom ash.