Preparation and characteristics of modified red mud-municipal solid waste incineration bottom ash binder

Abstract In this paper, red mud (RM) and municipal solid waste incineration bottom ash (MSWIBA) were thermal modified to improve the pozzolanic activity. A binder was prepared with modified RM and MSWIBA by activation of calcium hydroxide (CH). The hydration and mechanical behavior of the prepared binder was systematically studied. The results indicated that the calcium-rich RM (CRM) had a higher pozzolanic activity after modification than the iron-rich RM. The hydrates formed in the modified RM-MSWIBA-CH system at ambient temperature were essentially Ca–Al hydrotalcite and C-A-S-H gel. The hydration reaction in the pastes mainly concentrated in the early stages, whereas the high amount of CH was not conducive to this process. Moreover, the RM-MSWIBA-CH system could be easily carbonized in the atmosphere. The maximum compressive strength of paste was 5.18 MPa with a fluidity of 85.5 mm when the proportion of CRM to MSWIBA was 3:2 (with 20% CH), and the sample with proportion of CRM to MSWIBA was 2:3 (with 10% CH) had the highest fluidity (97.5 mm) with a compressive strength of 2.42 MPa. The developed binder with low CRM content holds great potential for applications as a controlled low-strength material (CLSM). The overall findings from this study provide new insights in low carbon and green recycling of RM and MSWIBA with wide application potential in construction industry.