Study on the drying shrinkage of alkali-activated coal gangue-slag mortar and its mechanisms

This study mainly explores the impacts of slag content, modulus of alkali activator and alkali-activator solid content on the setting time, strength and drying shrinkage of alkali-activated coal gangue-slag (AACGS) mortar. In addition, the drying shrinkage mechanisms are analyzed in-depth by using MIP and SEM-EDS. The test results show that AACGS mortar exhibits greater drying shrinkage than cement mortar. It is found that higher slag content and sodium silicate modulus will cause greater drying shrinkage. The unreacted coal gangue plays the role of filling and skeleton and inhibits the drying shrinkage of AACGS specimens. However, the collapse and recombination of the gel produced by the polymerization reaction lead to the decrease of the specimens volume, the refinement of the internal pore structure, and the increase of the capillary tensile stress. The drying shrinkage is characterized by incomplete elasticity.