Composition of C-S-H in the Hydration Products of Fly Ash-Cement System

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Title: Composition of C-S-H in the Hydration Products of Fly Ash-Cement System

Author(s): P. Termkhajornkit and T. Nawa

Publication: Special Publication

Volume: 242

Issue:

Appears on pages(s): 361-374

Keywords: bonding water; C-S-H gel; fly ash; rietveld analysis; selective dissolution

Date: 4/1/2007

Abstract:
This paper describes the effect of fly ash on composition of C-S-H gel. The CaO/SiO2 ratio and chemical bonding water of C-S-H gel were estimated by the combination of the Rietveld analysis by XRD, the selective dissolution analysis and loss of ignition measurement. The results indicated that the CaO/SiO2 ratio of hydrate gel in fly ash-portland cement paste decreased as the hydration of fly ash proceeds, while the CaO/SiO2 ratio of C-S-H gel in portland cement paste did not vary with the progress of hydration. At the same amount of produced C-S-H gel, bonding water in C-S-H gel of paste prepared with 50% fly ash was higher than those of pastes prepared with of fly ash 25% and 0%. The corresponded results can be seen from decreasing of density of C-S-H gel when replacement ratio of fly ash increases. The bonding water in C-S-H gel decreases as its CaO/SiO2 ratio increases. The effect of chemical bonding water in C-S-H gel can be applied to modify the gel/space-strength model.