Quantitative analysis of ettringite formed in the hydration products of high-alite cements

This paper reports on the characterisation and quantitative analysis of ettringite in the hydration products of several high-alite cements. The study has three main parts: (a) the investigation of the microscopic morphology of ettringite; (b) an X-ray diffraction characterisation; and (c) a quantitative analysis of the ettringite in the hardened cement pastes. The results show that the ettringite could be selectively extracted by an ethylene glycol/methanol solvent with a volume ratio of 1:3, which thereby proved to be an effective method for the quantitative analysis of ettringite. Combined with the results of the X-ray diffraction analysis, the formation and transformation mechanisms of ettringite could be characterised and described in more detail. During the 90-d aging period, the reaction degree of the coal gangue was higher than that of fly ash and had a greater impact on the formation and transformation of ettringite. The amount of ettringite formed from the hydration of coal gangue cement was higher than that from neat Portland cement, whereas the amount of ettringite formed from the hydration of fly ash cement was lower than that from neat Portland cement.