Hydration properties of portland cement plus calcium aluminate cement at 0∼20°C

Abstract

The hydration of Portland cement plus calcium aluminate cement (PAC) was investigated at 0°C, 5°C, 10°C and 20°C for its setting times and compressive strength using X-ray diffraction(XRD), thermal analysis(DTA-TG) and environmental scanning electron microscopy(ESEM). It was found that the 3-day compressive strength of PAC mortars decrease with decreasing temperature, but the 28-day compressive strength of PAC mortars cured at the lower temperature surpasses that of the PAC mortars cured at 20°C. Notably, the compressive strength increase with increasing temperature below 10°C, and reach the maximum when the content of CAC is 6%. In general, the optimal construction temperature of PAC is 10°C. In addition, the PAC paste is covered with film-like hydrates on the surface and the content of calcium hydroxide decreases significantly after 3 days of hydration, which informs that the hydration of Portland cement is delayed by calcium aluminate cement.