Hydration evolution of calcium sulfoaluminate cement modified with styrene-butadiene copolymer: Effect of various temperatures and relative humidity

Abstract

The behavior of styrene-butadiene copolymer (SB) modified calcium sulfoaluminate (CSA) cement hydrated under different temperatures and relative humidity conditions was studied. X-ray diffraction (XRD) and thermogravimetry (TG) were used to investigate cement hydration development in different temperatures (5 °C, 20 °C, and 40 °C) and relative humidity (low, middle, and high) conditions at different ages (28 days, 1 year and 2 years), as well as the micro-morphology of hydration products was analyzed by scanning electron microscope (SEM). Meanwhile, a control group test was set up in a natural environment. The results showed that the hydration products were susceptible to environmental temperature and humidity. With the temperature rising, the hydration degree of CSA cement was promoted, and the content of AH3, monosulfate, and hemicarbonate increased, but the ettringite content decreased. With environmental humidity rising, the hydration degree and content of the main hydration products (ettringite and AH3) increased, while the content of hemicarbonate increased among 30% RH ∼ 60% RH and then decreased among 60% RH ∼ 90% RH. The presence of SB restrained the formation of CAH10, monosulfate, and strätlingite, but increased the content of ettringite and AH3. A hydration model under different environmental conditions was proposed.