Correlation of viscosimetry and practical tests of fresh cement paste consistency

Abstract

The paper presents numerical modeling of fresh cement pastes correlated with viscosimetry measurements. Laboratory mini slump-flow tests are performed with three pastes of different fluidity. The mixtures are varying in water to cement ratio and amount of admixtures used. Static and dynamic viscosity examination using a rotational rheometer is performed in order to obtain material parameters of the Herschel-Bulkley model. Three material models are derived from different cycles of rheometer flow curves and fitted for every paste. The numerical simulation is performed with the computational fluid dynamics (CFD) package in ANSYS Fluent. The 2D axisymmetrical Volume of Fluid (VOF) with two variants of the model is prepared. The first variant is considering an instantaneous demoulding, which leads to overestimation of the final slump spread. The second variant considered mold lifting as a part of the simulation. The final spread is decreased compared to the variant with instantaneous demoulding. However, no model yields a satisfying agreement with experimental data. More complex models able to capture thixotropic behavior would be more appropriate for the tested cases.