Experimental study of chemical shrinkage or expansion of alkali-inspired cementitious materials

alkali-excited cementitious materials;  chemical shrinkage;  amorphous zeolites;  NH4+ ion exchange capacity

The chemical shrinkage or expansion of alkali-jerked cementitious material and water-cement system was experimentally studied, and the water-cement system was used as a contrast sample. The results showed that chemical shrinkage occurred in the water-cement system, alkali-excited slag and alkali-excited fly ash system at room temperature (20±1)°C, and the shrinkage value increased with the extension of reaction age. The chemical shrinkage of the water-cement system is greatest at the same age. The chemical shrinkage of alkali-excited slag systems is minimal; Chemical expansion occurred in alkali-inspired metakaolin system, and its expansion value increased with the extension of reaction age. The reaction product of alkali excitation metakaolin is amorphous zeolites (because of the NH4+ ion exchange properties of zeolite), in which the products with low polymerization degree contribute greatly to chemical expansion; The properties of the main reaction products of alkali-excited slag system and alkali-excited fly ash system are similar to those of cement products, but there is a small amount of amorphous zeolite, which partially counteracts chemical shrinkage.