Abstract
For the evaluation of strength development with or without elevated temperature due to heat of hydration, specific surface area of hardened cement paste, which affects the strength of hardened cement paste, is focused. The hardened cement paste（hcp）of water to cement ratio of 55％ and 40％ with 20℃ constant temperature and maximum 60℃ temperature as mass concrete temperature history is prepared. The amount of C-S-H and CaO/SiO2 molar ratio of C-S-H are identified by XRD/Rietveld analysis and phase composition model, and at the same time, specific surface area is measured by moisture sorption isotherm and BET theory. Additionally, specific surface area of hardened cement paste is compared to that of synthesized C-S-H. As a result, 1）when the hcp is subjected to elevated temperature history in early ages, the development of specific surface area of hardened cement paste increase rapidly in early age but het a peak, 2）CaO/SiO2 molar ratio decreases rapidly in early age but increases gradually in a long term, 3）specific surface area of C-S-H in hardened cement paste for CaO/SiO2 molar ratio is higher than synthesized C-S-H, and 4）specific surface area of hardened cement paste with/without elevated temperature history can be evaluated by the amount of C-S-H in hardened cement paste with a single curve.
