Influence of retarder admixtures on the hydration, rheology, and compressive strength of white Portland cements under different temperatures
Rayara Costa, Thiago da Silva Gusmão Cardoso, Maxwell Degen, Laura Silvestro, Erich D. Rodríguez, Ana Paula Kirchheim
Abstract
White cement is characterized by higher tricalcium aluminate (C3A) contents than conventional Portland cement; thus, it can present a reduced setting time, especially under hot weather conditions, limiting the material's application period. An approach to delay these materials' setting time is using retarder admixtures (RA). Nevertheless, there is a knowledge gap regarding the effect of RA on the rheological properties of white cement. This study aimed to evaluate the effect of two types of RA on the mini-slump, rheological parameters, hydration kinetics, and compressive strength of two white cements. Furthermore, the effect of temperatures of 25 and 40 ⁰C on the performance of the admixtures was also assessed. Both RA showed a dispersing effect, reducing cement pastes' dynamic yield stress and plastic viscosity. Moreover, the admixtures extended the induction period of cement hydration by up to 15.4 h without significantly affecting the 72-h cumulative heat at a temperature of 25 ⁰C. At 40 ⁰C, both RA exhibited a lower dispersing and retarding effect. Although RA delayed the initial hydration reactions of the WC, it enhanced the mechanical performance of the mortars after three days of hydration.