Advantages of Applying a Steam Curing Cycle for the Production of Kaolinite-Based Geopolymers

In this study, a new approach, which involves the application of a steam curing cycle for the production of kaolinite-based geopolymers, is investigated. This approach aimed to accelerate geopolymeric reactions and eliminate the content of residual alkalis within the geopolymer mass and the formation of efflorescence at the surface of the specimens, thus increasing their mechanical strength. The experimental procedure involved initial curing followed by steam curing for different periods, up to 24 h. The mineralogy and the morphology of the produced specimens were determined using X-ray diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermogravimetric analysis was also used. The physical and mechanical properties of the final products were determined for dry and immersed in water specimens and involved compressive strength, bulk density, water absorption and shrinkage. Finally, the effect of steam curing on the presence of residual alkalis and the formation of water-soluble salts during geopolymerization was investigated.