Weathered bottom ash from municipal solid waste incineration: Alkaline activation for sustainable binders

Alkali-activated binders (AABs) stand out as promising candidates to replace ordinary Portland cement (OPC) since waste can be used as raw material for their manufacture. This study addresses the environmental feasibility of using weathered bottom ash (WBA) and metakaolin (MK) as alkali-activated binder precursors (AA-WBA/MK). Different proportions of WBA and MK were mixed (100/0, 75/25, 50/50, 25/75, and 0/100 wt%) with a mixture of waterglass (WG) and NaOH 8 M as an alkaline activator solution. The effect of increasing MK content was assessed from a chemical, physical, mechanical, and environmental perspective. The results revealed the formation of secondary reaction products of C-(A)-S-H, (C,N)-A-S-H, and N-A-S-H gels. The compressive strength of AA-WBA/MK binders decreased (from 61.6 MPa to 12.6 MPa) as the MK content increased. The monolithic tank test validated the use of AA-WBA/MK binders for construction purposes, although with some restrictions due to their content in As, Sb, and V. Finally, the encapsulation efficiency and mechanical performance of AA-WBA/MK binders was enhanced as the curing period increased.