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

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.