Investigation on the continuous dehydration process of calcium silicate hydrate with C/S 1.5 during heating in the air was carried out. Results showed that the heating at 200°C of C-S-H resulted in decreasing basal spacing from 1.2 nm to 1.0 nm, and the basal spacing disappeared as the temperature raised to 400°C. Small amount of the dehydrated calcium silicate hydrate, portlandite and calcite were detectable in the heated sample at 400°C. The phases in the samples heated at 500°C and 650°C are β-C2S, quartz, and calcite. At 800°C and 900°C, α′-C2S, β-C2S, and quartz are main phases in the heated sample.
