Effect of ultrafine slag on hydration heat and rheology properties of Portland cement paste

The effects of ultrafine slag on the hydration heat, fluidity, rheological properties and setting time of Portland cement paste were investigated. The exothermic rate and total hydration heat of composite binder containing ultrafine slag are much higher than that of composite paste containing ordinary slag. The addition of ultrafine slag significantly reduces the fluidity of composite paste. The fluidity loss rate of paste containing ultrafine slag is evidently high compared to the paste containing the same amount of ordinary slag. The addition of ultrafine slag have an adverse effect on the rheological behavior of paste. The yield stress and plastic viscosity of paste containing ultrafine slag increase significantly with increasing the ultrafine slag content and rest time. The addition of ultrafine slag reduces the setting time of composite paste, while adding ordinary slag prolongs the setting time. Reducing water/binder ratio significantly shortens the setting time of paste containing ultrafine slag. [Display omitted] •Adding UFS obviously promotes the early hydration of composite binder.•The hydration heat of composite paste containing UFS increases significantly.•Composite binder with UFS has poor fluidity and large fluidity loss rate.•The addition of UFS negatively affects rheological property of composite paste.•The addition of UFS can reduce the setting time of the composite paste.