Recovery potential of municipal solid waste incineration bottom ash graded by particle size in an alkali-activated cementitious material system: Curing properties and environmental leaching risk

Currently, municipal solid waste incineration bottom ash (MSWI BA) is considered for use in alkali-activated cementitious materials (AACMs). However, a comparison of relevant studies revealed large differences in the reaction kinetics performance of MSWI BA. This finding presented difficulties in assessing the use of the MSWI BA in AACM. Compositional differences among particle sizes and design bias caused by the content of reactive components are two of the scientific shortcomings. In this work, MSWI BAs were categorized as S1 (0-2 mm), S2 (2-4 mm), S3 (4-8 mm), and S4 (8-16 mm). The reactivities of S1 to S4 were characterized. The mixing proportions of the AACMs were also designed on the basis of the reactivity components. The results showed that more glassy phases and synthetic ceramics in S4, as well as a lower Ca/Si ratio (1.08) in the final product, increased the strength. The maximum value of the 28 d compressive strength was 36.4 MPa. Among the final AACM products, most of the compressive strengths of AS1 and AS2 developed early, with strength increases of 3.1 % and 15.1 %, respectively, over the 7-28 d process. In addition, the Ca/Si ratios of C-S-H in AS1 and AS4 deviated slightly from the design values of 7.3 % and 4.6 %, respectively. The final product exhibited optimized pore distribution and densification, highlighting the physical encapsulation effect on toxic elements. Moreover, the leaching values of heavy metal elements are within the permissible range of Chinese standards.