Rheological evaluation at varied temperatures of cementitious pastes containing different types of polycarboxylate superplasticizers admixtures

ABSTRACT

The study of the rheological parameters of the cementitious pastes can provide important information on the performance of fresh concretes in which they will be applied. In this context, this paper aims to study the effects of temperature on the rheological parameters of cementitious pastes added with superplasticizers. It is approached the analysis of the effect of type of cement in pastes rheological behavior, as well as the study of the action of superplasticizers based on polycarboxylate considering its function and its contents in the mixture. The pastes were evaluated by the mini-slump test and the parameters of yield stress, plastic viscosity and thixotropy were estimated by the rotational rheometry test and application of Bingham and Herschel-Bulkley fluid models. The results indicated that the increase in temperature led to a reduction of the yield stresses, plastic viscosities and thixotropy of pastes. A similar effect occurred after increasing the admixture content up to the saturation content. For formulations with the binder of highest content of pozzolan, the yield stress and plastic viscosities were higher by up to 80 and 70%, respectively. The rheological data indicate that admixtures of different functions (spreading, maintenance and multifunctional), although having the same base, influence in a different way the rheological parameters and plasticity of cementitious pastes.

Keywords
Rheology; Cements; Superplasticizers; Temperature effects