New insights into the surface coverage dependences of rheological properties of cement paste: Measurement and scaling analysis

Abstract

Recent findings indicate that the effect of superplasticizers on decreasing the yield stress of cementitious suspensions is attributed to the modification of percolation threshold in addition to interparticle force. These dual effects complicate the assessment of yield stress dependence on the superplasticizer type and dosage, as yield stress can no longer be expressed as a separable function of interparticle forces and the number of interacting particles. To address this challenge, our study proposed scaling laws that directly linked yield stress to the surface coverage of superplasticizer by incorporating the percolation threshold into the interparticle force function. The scaling relation between surface coverage and viscosity was moreover established. At low surface coverages, the combined contributions of interparticle force and percolation threshold to the yield stress were characterized using the square of polymer devoid contact frequency. Furthermore, the viscosity varied linearly with the square root of this frequency, scaling with the quarter power of yield stress. In the high surface coverage regime, the yield stress was linearly dependent on the polymer devoid contact frequency given the limited variation of interparticle force. The proposed scaling laws can account well for the rheological property dependences on superplasticizer adsorption over a wide range of cement suspensions, holding significant values for controlling the yield stress and viscosity of cement-based materials in industrial practice.