Correlation between the automated slump test and the rheological properties of portland cement mortars

Abstract

The aim of this work is to present a rheological assessment of mortars based on the automated slump test methodology. Was employed this equipment in order to monitor the transient and permanent regime of the slump test and its spread, correlating such parameters to rheological properties. Based on dimensionless slump/spread, yield stress and viscosity, were defined empirical models for obtaining rheological parameters, which provided correlations with an elevated coefficient of determination (R2 > 0.85). Through the analysis of the slump behavior of mortars, was able to define a correlation between the viscosity and the flow maximum slump velocity (R2 = 0.90), showing that the viscosity could be measured based on the slump velocity. Furthermore, with basis on a physical description of the slump test related to the Reynolds number, were defined three distinct stages in the slump process: the viscous (constituted by high viscosities), the intermediary (coexistence of viscous and inertial effects), and the inertial (characterized by low viscosities and a higher sensibility towards the lifting of the mold). Lastly, the dynamic similarity of the analyzed material (vertical and radial axes, Rez/Rer∼1) indicates that the shear rate can be measured based on the vertical direction of the flow (slump).