Properties evolution of high-early-strength cement paste and interfacial transition zone during steam curing process

Abstract

At present, concrete prefabricated elements commonly used in railway engineering in China were produced by steam curing. Steam curing is a complex hygro-thermal coupling process that has a significant impact on the hydration process and microstructure formation of cement-based materials. This paper investigated the macroscopic mechanical properties, hydration process, pore structure, microstructure formation and micromechanical properties of cement-based materials during steam curing process. It is discovered that the evolution of cement-based materials under steam curing is a dynamic process that can be divided into three stages. The fastest evolution stage of the performance is the rising stage and the first 2 h of treatment stage. At this time, the microstructure of the pastes is rapidly formed, and the mechanical properties are significantly improved. Porosity and interfacial transition zone widths also rapidly decrease. The reaction activity of cementitious material is one of the critical factors affecting the properties evolution of steam-cured paste. In addition, an evolution model of the pore structure was established based on the change in the hydration degree during steam curing, which is proved to be well consistent with the measured results.