Impact of different types of plasticizing admixtures on the rheological properties and hydration of blended cements

Abstract

Portland cement manufacturing significantly contributes to CO2 emissions into the atmosphere. In order to reduce CO2 emissions, limestone and slag mineral admixtures are most prospective both technologically and economically in cement production. For such cements, it is important to select a certain type and amount of plasticizer and evaluate what plasticizers influence the heat released during hydration. In order to achieve the objectives of research, viscosity, conductivity, and DSC analyses of cement pastes with A and B plasticizers were performed. This study analyzes the effect of polycarboxylate ester (A) and modified lignosulfonate (B) plasticizers amount on rheological properties and hydration processes of the limestone and slag cement pastes. The use of A additive in contrast to B additive has a long-term effect on viscosity of both cement pastes and is less sensitive to mineral composition. Optimal A additive amount in case of limestone cement is 1.25 % and in case of slag cement is 0.3 %. In limestone cement additive A reduces total heat value by 6 % and additive B by 15 % after 48 h of hydration. In slag cement additive A increases total heat value by 4 % and additive B by 2 % after 48 h of hydration. Exothermal profiles show that in limestone cement additive A extends the EXO maximum time by 25 % and additive B by 40 % in samples after 24 h of hydration. In slag cement additive A extends the EXO maximum time by 37 % and additive B by 25 % in samples after the same time of hydration.