STRUCTURAL EVALUATION OF HIGH Ca/Si RATIO C-S-H BY THE ISOSTERIC HEAT OF WATER ADSORPTION CALCULATED FROM LOW-PRESSURE WATER VAPOR ADSORPTION ISOTHERMS

Abstract

This paper reports on the structural evaluation of C-S-H with a high Ca/Si molar ratio by the isosteric heat of water adsorption calculated from low-pressure water vapor adsorption isotherms. As a result, a sharp increase in the adsorbed volume at P/P₀＝2×10^－4 is more pronounced in 1.1nm Tobermorite that has high regularity of （002） reflection and decreases with decreasing crystallinity. The results indicate that the adsorption near P/P₀＝2×10^－4 is occurring for the interlayer space. Also, the rate of increase in the isosteric heat of adsorption and the maximum heat value of adsorption decreased with the decrease in the number of adsorption （silica） sites in the C-S-H interlayer.