Effect of Two Thermal Activation Methods on Shale Residue Based Geopolymer

Abstract In this study, microwave heating (MH) was applied for thermal activation of shale residue (SR) to prepare geopolymers and the results were compared with those obtained by conventional heating (CH). The compressive strength of the geopolymers by MH was mostly higher than those by CH, and the optimal activation conditions for MH and CH was 600 ℃ and 700 ℃ with 15 min, corresponding to the strength of 19.78 and 16.19 MPa, respectively. This may be caused by the reason that MH activated SR effectively and led to a higher proportion of fine particles, low crystallinity of quartz, which also can be proved by the leaching concentration of Si and Al in alkaline solution. Thus, the better activated SR can produce the geopolymers with higher compressive strength. These results demonstrate that MH can be used as a more efficient method for the thermal activation of solid waste to prepare geopolymers.