Zhe Yu, Xiangping Xian
Municipal solid waste incineration bottom ash (MSWIBA) has potential as a supplementary cementitious material (SCM) but is limited by poor compatibility with cement systems. This study investigates Ca(OH) 2 pretreatment to improve the suitability of MSWIBA for cement blending, using comprehensive analysis to characterize pretreatment effects and subsequent impacts on cement hydration and composite performance. Results show that Ca(OH) 2 reduces reactive Al and Zn (removal rate >80 % at 80 °C), enhancing MSWIBA stability. Higher temperatures promote reactions between Ca(OH) 2 and silica-rich phases, forming calcium silicate hydrate (C-S-H) gel precursors on particle surfaces. These precursors accelerate early hydration, strengthen the MSWIBA-cement interface, and mitigate preferential Ca(OH) 2 crystallization. At the optimal condition (80 °C, MSWIBA-to-Ca(OH) 2 mass ratio 20:1), the 28-day compressive strength of blended cement paste increases by 25 %, and porosity decreases from 39.8 % to 35.8 % compared to the untreated control. A supplementary case study using concrete washing wastewater (as an alternative Ca(OH) 2 source) achieves comparable performance enhancement. This work demonstrates that controlled Ca(OH) 2 pretreatment transforms MSWIBA into a high-value SCM, resolving performance and stability issues, and highlights the feasibility of upcycling waste with waste to improve economic and environmental sustainability. • The effect of Ca(OH) 2 (CH) on MSWIBA was explored under different temperatures. • CH had a positive effect on MSWIBA under different temperatures. • The CH induced the formation of C-S-H of MSWIBA particles at higher temperatures. • The paste with CH-pretreated MSWIBA showed a higher strength with lower porosity. • Replacing pure CH with CH-containing waste resulted in a comparable enhancement.