Optimization of proportions and solidification mechanism of all-solid waste cementitious materials based on circulating fluidized bed fly ash, calcium carbide slag, and red mud

Abstract

In order to reduce carbon emissions and consume a large amount of low-quality solid waste, CFBFA-RM-CS has been developed by utilising the synergistic effect of circulating fluidised bed fly ash (CFBFA), red mud (RM) and calcium carbide slag (CS).The solidification mechanism of the ternary paste was studied from both macroscopic mechanical properties and microscopic experiments including XRD, FTIR, TG-DTG, SEM-EDS tests. The results showed that the main hydration products of CFBFA-CS-RM pastes were AFt and C/N-A-S-H, and the generation of hemialuminate and monoaluminate depended on the contents of RM and CS. The highest strength of the pastes was achieved when the hydration produced just the amount of AFt and the gel products that did not cause cracking.Ca(OH)2 is the main reactant that triggers pozzolanic reaction in CFBFA and solidification of RM. The 3d strengths of both CFBFA and CFBFA-CS pastes were less than 0.4 MPa, and cracking problems occurred，which were solved by the addition of RM, and the early strength of the pastes was significantly improved.