CALORIMETRIC STUDIES OF SPECIAL CEMENTS

The kinetics and even the mechanism of cement reaction with water can be successfully investigated by use of microcalorimetry. In this study this method was applied to follow the hydration of the new family of portland cements containing C(12)A(7) and C(11)A(7) . CaF2 addition a s well as special cement with C(3)A replacement by calcium sulphoalumi nate. It has been found that C(11)A(7) . CaF2 acted as hydration retar der. The heat evolution curves for C(12)A(7) containing samples withou t CaF2 are very similar to those for the reference portland cement sam ples. XRD and SEM studies confirm the results described above, relatin g to the retardation of alite hydration. The process is positively mod ified by the addition of anhydrite. In the presence of calcium sulphoa luminate (4CaO . 3Al(2)O(3) . SO3) the hydration at early stage occurs with the rapid formation of large amount of the ettringite phase. The calcium fluoride acts as a set retarder. The full compatibility of ca lorimetry with SEM and XRD results should be underlined.