Microwave curing of alkali-activated binder using hwangtoh without calcination

Microwaves were used to accelerate the curing of alkali activated hwangtoh paste (AAHP); the resulting compressive strength, porosity and composition were then compared against conventional heat-cured specimens. This found that a compressive strength of similar to 20 MPa can be developed within 4 h, versus 72 h with conventional heat. While the Si-29 NMR analysis showed the similar trends in the chemical shift with the curing time, the MIP results showed that the microwave-cured AAHP contained a greater cumulative pore volume and mean pore size than the conventional thermal-cured AAHP of the equal strength. The compressive strength of microwave-cued AAHP was attributed to the formation of a well-crystallized hydroxysodalite phase and an internal temperature gradient generated during curing. (C) 2015 Elsevier Ltd. All rights reserved.