Effect of Calcium Aluminate Cement on Hydration Properties and Microstructure of Portland Cement

Abstract:

Setting times, mechanical strength and drying shrinkage ratio of Portland cement and calcium aluminate cement(less than 25%) blended systems were investigated, which were also characterized by means of calorimetry, X ray diffraction and environmental scanning microscopy. Results show that with the increasing of calcium aluminate cement, setting times of blended systems is shortened; the compressive strength first increases slightly (reach the utmost with 6% of calcium aluminate cement) and then decreases significantly, and the drying shrinkage grows continuously. In addition, except that the ettringite formation content increases slightly, lower content of calcium aluminate cement do not have obvious impact on the hydration of Portland cement; while higher content will delay the hydration of Portland cement prominently, furthermore, the ettringite formed at early age also transfer to monosulphoaluminate and the unstable calcium aluminate hydrates transfer to stable garnets, which does great harm to the microstructure.

Key words:calcium aluminate cement; Portland cement; hydration; mechanism; property