Influence of steam curing on hydration and microstructure of cement paste containing high-volume lithium slag

Abstract

The application of supplementary cementitious materials (SCMs) of concrete reduces the carbon emissions due to the reduced cement. But the early properties of mortar or concrete with high-volume SCMs are degraded, which hinders the expanded applications of concrete. However, early properties of mortar or concrete containing high-volume SCMs concrete can be effectively improved by steam curing. The influence of different steam curing systems on the microstructure and strengths of cement paste with high-volume of lithium slag (LS) are studied. The results manifest the early-compressive strengths, the content of chemically bound water and the hydration degree of the specimens are improved due to the different curing systems. The early-compressive strengths of specimens under steam curing-II is better than that under steam curing-I, but the compressive strengths at later ages is not as good as the steam curing-I, which is because of the maximum steam curing temperature. The scanning electron microscope (SEM) images show that cement paste with LS have a denser microstructure under the action of steam curing. This is not only due to the filling effect of LS, but also because LS is further activated under high temperature conditions, which promotes generation of hydration products and fills the internal pores. The data of mercury intrusion porosimetry also proves the above phenomenon.