Rheology of high-performance cement pastes: effect of calcined kaolin

Abstract

The search for a quality of concrete is a major concern in Algeria especially after the 2003 earthquake (East- Algeria). So it's necessary to improve the properties of concrete using fine particles such as mineral additions as a solution. These are currently used in the concrete to develop its performance and reduce consumption of clinker. This reduction will contribute to economic and easy way to solve problems related to the environment. In this work, an experimental rheological investigation was conducted to evaluate the performances of Algerian metakaolin MK on cement pastes. The latter is obtained from calcined natural kaolin found in large amounts in eastern Algeria (Tamazert- Milia). Several rheological tests were carried out by using the stress controlled rheometer AR2000, on the fresh cement pastes incorporating 0%, 5%, 10%, 15% and 20% of MK. The effects of metakaolin on the rheological behaviour of pastes were discussed. The parameters such as shear stress, viscosity, compliance, loss and storage shear modulus were evaluated by means of rheological techniques of both flow test, oscillatory and creep dynamic tests. The study in dynamic mode allow to give information on the evolution of the paste structure related to practically interesting problems such as workability. The results obtained have shown that the metakaolin improves the flowability and exhibits viscous rheological behaviour of cement pastes compared to the elastic behaviour of control paste (0%MK). Moreover, the creep test has shown that MK exhibits a viscoelastic liquid behaviour of cement pastes compared to a viscoelastic solid behaviour of control paste. In addition, it seems that the replacement rate of 10% of MK is an optimum for better rheological behavior of cement pastes. The rheological tests give promising results that encourage the use of metakaolin as component for a high performance concrete designated for industry.