Alkali-treated incineration bottom ash as supplementary cementitious materials

Municipal solid waste incineration bottom ash (IBA) contains metallic aluminum which generates gas when in contact with cement paste. To increase the utilization potential of IBA, alkali treatment for removal of metallic aluminum is proposed. This paper investigated the effects of alkalinity, reaction temperature, and alkali type on the properties of alkali-treated IBA and the resulting IBA blended cement mortars. Results showed that alkali treatment effectively removes the metallic aluminum in IBA and minimizes aeration in IBA blended cement mortars. Furthermore, alkali treatment enhances pozzolanic properties of IBA and the resulting alkali-treated IBA possessed pozzolanic reactivity similar to coal fly ash. The strength activity indices (SAI) of the resulting alkali-treated IBA blended cement mortars were above 75% of the control at the age of 28 days and beyond. In particular, the mix incorporating IBA treated with NaOH (pH = 14) at 25 °C has a strength comparable to that of control at the age of 90 days. The proposed method provides an effective, efficient, and fast means for the removal of metallic aluminum in IBA and the alkali-treated IBA can potentially be used as supplementary cementitious materials for concrete production.