Examination of Cement Pastes Hydrated Phases, and Synthetic Products by X-Ray Diffraction

Abstract
Pastes of three cements were examined by X-ray diffraction at five ages in seven laboratories. Six of the laboratories used X-ray diffractometers and one used a focusing camera of the Guinier type. Six laboratories examined hydrated phases and synthesized hydrates. Pastes of all three cements were mixed at water-cement ratios of 0.35 and 0.65 and were examined after hydration had been stopped at ages of 1, 7, 28, 90, and 365 days. Pastes of Type I cement at 0.35 water-cement ratio contained ettringite, tetracalcium aluminate monosulfate-12-hydrate, calcium hydroxide, calcium silicate hydrate gel, and residual cement constituents. Tetracalcium aluminate monosulfate-12-hydrate was detected at 7 days and increased thereafter at the expense of ettringite. Compositions of pastes of this cement at 0.65 water-cement ratio were similar to those of the pastes 0f 0.35 water-cement ratio; the sequences of hydrates appearing and increasing, and cement constituents diminishing and in some instances disappearing, were more conspicuous.

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