A study of chloride pretreatment methods for enhancing strength of mortar by recycling Municipal Solid Waste Incineration (MSWI) bottom ash

This study explores four different ways (tap water, deionized water, sodium chloride, and seawater) as the pretreatment methods of municipal solid waste incineration (MSWI) bottom ash used in mortar. After incorporation of the bottom ash as partial replacement of fine aggregate, the mixtures were evaluated for compressive strength, heat of hydration, chloride content and shrinkage performance. The results reveal that all pretreated samples have comparable compressive strength at early age (day-7) and higher compressive strength at later age (day-120). Meanwhile, the pretreatment in tap water and deionized water can slightly reduce the chloride content, whereas the other two pretreatment methods induce extra chloride ions into the mixtures. The correlation between the chloride content and the peak temperature indicates the acceleration effect of chloride ions during hydration. In addition, all the specimens with pretreated MSWI aggregates have higher shrinkage regardless of pretreatment methods.