Effect of temperature on the hydration of the main clinker phases in Portland cements: Part II, blended cements

The hydration of three blended cements, i.e., Portland cement blended with GGBFS, PFA, and volcanic ash, based on two neat cements investigated previously, has been followed at five temperatures ranging from 10 degrees C to 60 degrees C. The cements were cured under water and tested at various time intervals over a period of one year. The hydration products were characterised by means of quantitative X-ray diffraction and thermogravimetry. As with the neat cements, a temperature inversion in the degree of hydration was observed, leading to a reduction in the degree of hydration at 60 degrees C compared with that at 10 degrees C, but the presence of the replacement materials changed the hydration patterns of the individual cement phases. There was a clear acceleration of the hydration of alite, C(3)A, and the ferrite phase, although PFA did not accelerate alite hydration to the same extent as the other replacement materials. The rate of hydration of belite was retarded by PFA at higher temperatures, but accelerated by the presence of slag or volcanic ash. The depletion of CH by PFA and volcanic ash was shifted to earlier times and lower maximum values of CH content at higher temperatures. (C) 1998 Elsevier Science Ltd.