Effects of mineral admixtures and additional gypsum on the expansion performance of sulphoaluminate expansive agent at simulation of mass concrete environment

• Mineral admixtures and sulphoaluminate expansive agent were used simultaneously.
• Simulated mass concrete curing condition was used.
• The expansion effects were influenced by mineral admixtures.
• Both strength and expansion effects of GGBS samples were enhanced by adding gypsum.

Shrinkage cracks are easily occurred in mass concrete. To compensate the shrinkage, the sulphoaluminate expansive agent is usually used. Besides, high volume mineral admixtures are usually used to decrease the hydration thermal and delay the appearing of temperature peak of mass concrete. However, the expansion effect and compressive strength were probably affected by the mineral admixtures and expansive agent interactively. In this study, the effects of GGBS and FA on the expansion performance at the simulated mass concrete temperature were investigated, and moderate additional gypsum was used to eliminate these negative effects. Besides, XRD, TG-DTG and SEM were used to analyze the hydration process, hydration products and the morphology of products. The results show that the expansion effect and compressive strength were decreased by the addition of GGBS and FA at simulated curing condition. Both expansion effect and compressive strength of samples blended with GGBS were increased by gypsum, because of the gypsum promoted the generation of AFt and stimulated the hydration of GGBS. But for samples blended with FA, the gypsum promoted the generation of AFt but seriously prolonged the setting time of samples, resulted in the consuming of expansion energy in the plastic deformation.