Application of an Improved Empirical Model for Rheology Prediction of Cement Pastes Modified with Filler from Manufactured Sand

There is a need for simple but precise prediction models for proportioning concrete with manufactured sand, for use in ready-mix concrete production. For the last two decades, the particle-matrix model has been used in Norway for proportioning and prediction of concrete flow based on the properties and proportions of two concrete phases: coarse particles and filler modified cement paste (matrix). This paper presents experimental testing of 117 cement pastes of which 107 contain filler, i.e. particles < 125 microns, from manufactured sand. Based on compositions and properties of ingoing materials in these mixes, an empirical equation is developed that predicts the rheological properties plastic viscosity, yield stress, flow resistance ratio and mini slump flow. Optimization by regression analysis provides a practical microproportioning equation that readily can be used as input in concrete proportioning with the particle-matrix model. The equation provides a coefficient of determination R² = 0.98 for plastic viscosity, R² = 0.95 for mini slump flow, R² = 0.91 for flow resistance ratio and R² = 0.80 for yield stress.