Rheological behaviour of fresh cement pastes formulated from a Self Compacting Concrete (SCC)

Self Compacting Concrete (SCC) has a high flowability and can be placed without vibration. It is defined as a concrete that exhibits a high deformability and a good resistance to segregation. This kind of concrete is of great interest and has gained wide use especially in the case of difficult casting conditions such as heavily reinforced sections. From a rheological point of view, the use of a Viscosity Enhancing Admixture (VEA) along with an adequate superplasticizer content enables to ensure high deformability and stability. However, little is known about the interactions between superplasticizer and viscosity agent. Hence, we propose to study several cement pastes formulated from the original paste of a typical SCC mix. Depending on their rheological behaviour, these pastes will be used later to study the stability of coarse aggregates. The major aim of this paper is to show that empirical tests such as spread and flow time are suitable to characterise the rheological behaviour of cement pastes instead of more complex ones. Rheological properties, i.e. viscosity and shear yield stress, are well correlated with empirical test results in the range of flowable mixes. Moreover, the experimental program leads to emphasize the effects of the mixing procedure on the rhelogical properties of cement pastes. Finally, test results enable to underline the interactions between superplasticizer and Viscosity Enhancing Admixture used in designing Self Compacting Concrete.