Impact of temperature on C-S-H properties: Chemical composition, density, porosity, and specific surface area

A comprehensive investigation of the impact of temperature on C-S-H properties over 5-90℃ was conducted using six model cement systems prepared with different C 3 S/C 2 S ratios. A fast DTG deconvolution method and a novel algorithm based on water–vapor adsorption were proposed to guarantee the accuracy and accessibility of the derived C-S-H properties. Test results indicate that the Ca/Si ratio of C-S-H generated by hydration of silicate cement with different C 3 S/C 2 S ratios increases with increasing C 3 S content. The Ca/Si ratio (1.73–1.93) and the chemically bound water content (H 2 O/Si ratio of 1.56–1.89) of C-S-H remain relatively stable within 30-70℃. The total water (H 2 O/Si ratio of 2.57–4.10), gel water (H 2 O/Si ratio of 1.01–1.96), and intrinsic porosity (0.18–0.29) of saturated C-S-H are found to decrease with rising temperature, exhibiting a density range of 2.11–2.38 g/cm 3 , with maxima at 5 °C and 90 °C and minima at 30℃ and 70℃. The density of C-S-H solid phase is determined to be 2.59 ± 0.12 g/cm 3 . The water–vapor adsorption results indicate that dried C-S-H possesses a specific surface area ranging from 91 to 502 m 2 /g. The obtained C-S-H parameters at varying temperatures provide essential inputs for analyzing the engineering properties of a wide range of cement systems.