Mortars with alkali-activated municipal solid waste incinerator bottom ash and fine recycled aggregates

Milled municipal solid waste incinerator bottom ash was used as a precursor in the production of alkaliactivated mortars with recycled concrete aggregates as a sand substitute. Fly ash was used as control precursor and sodium hydroxide as an alkaline activator. Different thermal curing regimens were used: 24 h in ambient conditions; 24 h/70 degrees C; 48 h/70 degrees C; and 24 h/90 degrees C. Mechanical and durability-related performances were evaluated (i.e. flexural and compressive strength, modulus of elasticity, ultrasonic pulse velocity, carbonation, capillary water absorption, and shrinkage). The reaction between metallic aluminium from municipal solid waste incinerator bottom ash and OH- ions produced hydrogen gas, causing expansion, porosity increase and thus decline in performance. Low stability in high relative humidity settings due to leaching of highly soluble compounds was also observed. A further decline in performance was observed in mixes containing recycled aggregates. Alkali activated municipal solid waste incinerator bottom ash presented fast carbonation but also a considerable strength enhancement. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study found that using municipal solid waste incinerator bottom ash and recycled concrete aggregates in the production of alkali-activated mortars can lead to issues such as hydrogen gas generation, expansion, and performance decline. Low stability in high relative humidity settings due to leaching of highly soluble compounds and further performance decline in mixes containing recycled aggregates were also observed. Alkali activated municipal solid waste incinerator bottom ash showed fast carbonation but also considerable strength enhancement.