Thermal analysis of blended cements

Hydration of blended cements from mixtures of Portland cement (PC), calcium aluminate cement (CAC) and calcium sulfate (C S) has been analyzed by thermal analysis in order to study the mechanism reactions at early ages. Several systems were studied, PC and PC/CAC ratios of 85/15 and 75/25, both with 0, 3 and 5 % of C S. The samples were cured during 6 h at 20 � C and 98 % of relative humidity ambient; after that, a serial of samples were maintained at the same ambient but another serial were cured under distilled water during 7 days more. Joint to the thermal analysis, the supporting characterization techniques used were X-ray diffraction and infrared spec- troscopy. The results have shown that these systems form an extra amount of ettringite when the amount of C Si s higher. The presence of AFm depends on the initial amount of CAC and C S. The presence of higher amount of calcium aluminate provides the formation of AFm phases that is delayed when grows the C S presence.