The Use of Parallel-Plate Rotational Rheometry to Determine the Superplasticizer to be Used in Cement Pastes Admixtures

Abstract

The usual test to obtain the better superplasticizer (SP) to be used and also their content in the admixture is the Marsh cone test, but it demands a lot of material to perform it. On other hand, the use of the parallel-plate rotational rheometry allows achieving those answers using very few materials and in a fast way. In this research, three different pastes were tested to see which one had the longer workability period, performing oscillatory time sweep test. This test allows observing the behavior of the elastic component (G′) in the time, fact that some authors correlated with the setting time. After choosing the SP that obtained the best behavior over time, flow tests in pastes with different amounts of additive were performed to obtain the saturation point. With the viscosity results, it was possible to analyze when the SP no longer influences this parameter. It was observed that very few materials were used in these tests, an important factor when working with expensive or rare materials. Determining the superplasticizer that did not indicate delay in casting time and their saturation point, could guarantee that the additive did not affect the compatibility between materials in the admixture.