The evolution of early-age cracking of cement paste cured in low air pressure environment

In recent years, infrastructure constructions have rapidly developed in plateau areas. The research on the surface cracks of cement-based materials in low air pressure environment in plateau areas is critical in improving the long-term durability of concrete structures as well as the harmony between the building and environment. In this work, the evolution of early-age cracking in cement pastes cured in low air pressure environment was examined by drying measurement, thermogravimetric analysis (TG), nitrogen adsorption-desorption, and micromorphology. The cumulative moisture loss and evaporation rate, total crack area, degree of hydration, and microstructure analyses were evaluated to analyze the evolution mechanism of early-age cracking. The results indicate that the development of early-age cracking on cement paste surfaces is related to air pressure. The moisture evaporation of cement paste accelerates in low air pressure environment, making early-age cracking and pores more noticeably exposed to the cement paste surface. Further, the cement hydration decreases and the volume of micropores and mesopores of cement paste increases in low air pressure environment, forming a loose and porous microstructure and increasing the risk of early-age cracking on the cement paste surface.