Effect of interparticle action on shear thickening behavior of cementitious composites: modeling and experimental validation

Shear thickening is a behavior of a material that displays an increase in viscosity with increasing shear rate. Research has indicated that in self-consolidating concrete (SCC), shear thickening is primarily caused by the formation of “particle clusters” due to collisions of particles in the low yield stress of the fluid material matrix of SCC at a high flow rate. Based on this theory, a previously developed particle–fluid model was modified and applied to predict the relationship between the shear stress and shear strain rate of cementitious composites that exhibit shear thickening behavior. The rheology test results indicated no apparent shear thickening behavior was observed for SCC paste mixtures while distinct shear thickening behavior was observed when the introduced fine aggregate volume fraction increased up to 40%. The modified model showed a power function between the shear stress and shear rate that could well capture the shear thickening behavior of mortar mixtures with various aggregate volume fractions and that agreed well with the results of the experimental study. The modified model also demonstrated that aggregate particles could generate local transient particle clusters during interactions due to the particles’ varying velocities, yielding shear thickening.