论文部分内容阅读
The aim of this study is to understand the expansion mechanisms of ettringite forming in systems based on calcium aluminate cement (CAC) or calcium sulfoaluminate cement (CSA) in presence of added gypsum.Ettringite systems are used in special mortars for their high early age performance: rapid hardening, rapid drying and shrinkage compensation.However a non-optimized formulation can lead to long term expansion up to material degradation.The dimensional stability of blends with different additions of gypsum has been studied.The long term expansion under water increases with the gypsum content.There is a slight and progressive increase of the expansion until a certain threshold of calcium sulfate concentration.Above this threshold the expansion increases rapidly.Compositions below (low expansion systems) and above (high expansion systems) the calcium sulfate threshold have been selected for both systems in order to compare the hydration kinetics, the microstructure and the dimensional stability.