Vitrified and nonvitrified municipal solid wastes as ordinary Portland cement (OPC) and sand substitution in mortars

This work aims to evaluate the potential suitability of nonvitrified and vitrified bottom ashes to serve as substitute materials for both OPC and sand in mortars on an industrial scale. Three bottom ashes were selected as OPC substitutes: one was vitrified inside the incinerator plant (W1-C), one was carbonated under ambient conditions for 3 months (W2-C), and part of the carbonated bottom ash was further washed with Ca(OH)2 (W2-W-C). Composition and phases of the bottom ash sources were assessed by XRF and XRD, respectively. Thereafter, mortars were prepared by replacing 10, 20 or 30 wt% of OPC with these bottom ashes. It was shown that even though Ca(OH)₂ washing step (W2-W-C) led to an increment of the compressive strength in final mortars compared to the use of W2-C, it failed to reach the mechanical performance of OPC. On the contrary, the use of vitrified bottom ashes (W1-C) could lead to obtaining compressive strength comparable to that of standard mortar if added up to 10 wt%. Regarding the sand substitution, vitrified bottom ashes could reach suitable compressive strength when replacing 20 wt% of standard sand. The alkali aggregate reaction test confirmed the neutrality of substitution material added up to 50 wt%.