Drying shrinkage properties of one-part geopolymer prepared by mechanochemistry

The large drying shrinkage of geopolymer seriously hinders its industrial production and application. In this study, mechanochemical processing was introduced into the one-part geopolymer to alleviate its drying shrinkage. The effects of ball-to-powder ratios, ball milling duration and steam time on the mechanical properties and drying shrinkage of one-part geopolymer were investigated. The drying shrinkage mitigation mechanism was explained by testing hydration products, pore structure and infrared spectroscopy. The results indicated that by extending the ball milling time and increasing the ball-to-powder ratios, the macropore volume and total porosity were significantly reduced, and the mechanical strength of the one-part geopolymer was enhanced (28 days compressive strength was about 22.2% higher than that of the simple mixed group). However, as the pore size distribution of the mortars becomes finer, drying shrinkage and mass loss exhibited the opposite trend. In addition, steam curing significantly enhanced the early compressive strength of one-part geopolymer mortar and simultaneously reduced the drying shrinkage rate (the drying shrinkage rate at 56 days was approximately 79.5% lower than that of the specimens without steam curing).