Study on the hydration and hardening mechanism of the high-water rapid-setting material

High-water rapid-setting material is a type of cement-based material, which is high water contained, rapid hardening and has early strength. Hydrating and hardening mechanism of this material have been studied by XRD and SEM, the influence of different curing time, gypsum lime content and water-cement ratio on the hydrating and hardening process was explored. The hydration products were measured by XRD. The results show that ettringite is the main product of hydration and hardening. With the increase of curing age, the amount of ettringite increases gradually. The amount of limestone gypsum affects the amount of ettringite. The lower the water-cement ratio is, the more ettringite is formed. SEM analysis shows that hydration reaction will continue with age. The shape of ettringite turns from the acicular to the columnar. Gradually it becomes compact forming network structure. Hydrated calcium aluminate and aluminium hydroxide filled in the network structure which makes the material more compact. Increasing the amount of gypsum within a certain range will promote the formation of ettringite. The lower the water cement ratio is, the more compact the ettringite is and the stronger the material is. Finally, based on the hydration products and microstructure of the material, the hydration reaction equation was established and the growth process of strength was analyzed, and it provides the basis for the study of the durability of the material.