Effect of MgO content of synthetic slag on the formation of Mg-Al LDHs and sulfate resistance of slag-fly ash-clinker binder

The effect of MgO content of synthetic slag on the formation of layered double hydroxides (LDHs) and sulfate resistance of slag-fly ash blended cement was studied. Hydration products of alkali-activated synthetic slag were LDHs and C-S-H. The content of LDHs increased with MgO content of slag due to the introducing of Mg, and C-S-H content did not change much with addition of different slags. Sulfate resistance of slag-fly ash-clinker mortar and paste under wetting-drying cycles increased with MgO content of synthetic slag, due to the favored formation of LDHs by high MgO content, denser microstructure and less porosity. There is no correlation between MgO content of slag and mass change and porosity of specimens during wetting-drying cycles in sulfate solution.