Impact of C₃A Polymorphism, Lignosulfonate Admixture, Limestone, and Calcium Sulfate Sources in the Hydration Kinetics and Rheology of Cement Pastes

The effect of C(3)A polymorphism, the calcium sulfate source, and the addition of limestone on the hydration kinetics and rheology of cement pastes and their interaction with a lignosulfonate-based admixture were analyzed. Two clinkers produced in industrial cement rotary kilns using the same raw materials and process were produced; their crystallinity was changed by using different fuel sources for research purposes. The cements containing mostly orthorhombic C(3)A (ORT) had a more extended induction period than cements with mostly cubic C(3)A (CUB). The phosphogypsum increased apparent viscosity and yield stress, as well as delaying the hydration of both clinkers (with a higher retardation effect on ORT clinker hydration). The limestone increased the apparent viscosity and the yield stress of the samples, besides accelerating the hydration due to the dilution and filler effects. The lignosulfonate admixture delayed the hydration of all cements tested. In ORT cements, the admixture was more efficient in reducing apparent viscosity and yield stress.