Influence of elevated curing temperature on the properties of cement paste and concrete at the same hydration degree

Three different curing temperatures (20 °C, 40 °C, and 60 °C) were set, so that the nonevaporable water (w_n) contents of plain cement pastes cured at these three temperatures were measured to determine the hydration degree of cement. Tests were carried out to compare the pore structure and strength of cement paste, as well as the strength and permeability of concrete under different temperature curing conditions when their cements were cured to the same hydration degree. The experimental results show that either at a relatively low hydration degree (w_n=15%) or high hydration degree (w_n=16.5%), elevated curing temperature has little influence on the hydration products of cement paste, while it has a negative influence on the pore structure and compressive strength of cement paste. However, this negative effect is weaker at high hydration degree. The large capillary pore (>100 nm) volumes of cement pastes remain almost the same at high hydration degree, regardless of curing temperatures. As for the concrete, elevated curing temperature also has negative influence on its compressive strength development, at both low hydration degree and high hydration degree. And this negative effect is stronger than that on cement paste’s compressive strength at the same hydration degree. On the whole, elevated curing temperature has little influence on the resistance of concrete to chloride ion penetration.