Composition, morphology and nanostructure of C-S-H in white Portland cement pastes hydrated at 55 °C |
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Authors: | A.V. Girã o,C.B. Porteneuve |
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Affiliation: | a School of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom b W.R. Grace and Company, 62 Whittemore Avenue, Cambridge, MA 02140, USA c Institute for Materials Research, University of Leeds, Leeds LS2 9JT, United Kingdom |
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Abstract: | The C-S-H present in water- and alkali-activated hardened pastes of white Portland cement hydrated at 55 °C has been characterized. The mean length of the aluminosilicate anions in the C-S-H was similar in both systems and increased with age. Inner product C-S-H generally had a fine scale, homogeneous morphology. Outer product C-S-H was generally fibrillar with water, and foil- or lath-like with alkali. There were some regions of C-S-H with coarse morphology. It was not possible to determine the chemical composition of C-S-H using the SEM; TEM-EDX was necessary. The C-S-H formed in the alkali-activated paste had a lower mean Ca/(Al + Si) ratio than that formed with water, which was offset by a larger quantity of calcium hydroxide. The potassium in the KOH-activated paste was present either within the C-S-H structure charge balancing the substitution of Al3+ for Si4+, or adsorbed on the C-S-H charge balancing sulfate ions. |
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Keywords: | Portland cement C-S-H Temperature TEM NMR |
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