Calorimetry Analysis of High Strength Cement Pastes Containing Superabsorbent Polymer (SAP)

Abstract

With the application of isothermal calorimetry technique, the speed of the hydration reactions can be evaluated in a simplified and efficient way, over time, by the heat evolution curves. This technique can become a suitable tool to understand the process of absorption and desorption of the SAPs in the cement matrix, a fundamental parameter that determines the efficiency of the polymers as mitigating agents of autogenous shrinkage and their behavior during the fresh state. It is also possible to identify the water retention or early release during the fluid period of the pastes. This methodology also permits a better understanding of the participation of the water incorporated by the polymer, in the kinetics of hydration of the cement, over time. It was possible to observe that the presence of the SAP slightly alters the reaction kinetics of the cement as it reduces its rate of acceleration of the curve of the second calorimetric peak. The higher the SAP content, the lower the acceleration rate of the curves. The addition of the SAP generated a lightly delay of the second peak time of the pastes and a deceleration of the kinetics reaction of the cement, as compared to the reference mixture. This behavior seems to be related to the desorption kinetics of the polymers. It was also possible to conclude that the higher the SAP amount, the higher the total quantity of accumulated heat in the end of 3 days of test, that is, a higher volume of hydration reactions.