Shear thickening of cementitious suspensions: effect of high solid volume fraction and hydration

During pumping of concrete, the lubrication layer (LL) formed at the interface of the concrete and the pipe plays a crucial role in facilitating the process. Shear thickening in this layer affects the concrete pumping significantly. However, very few studies are available in understanding the onset and intensity of shear thickening behavior of the lubrication layer. In this study, the effect of solid volume fraction (SVF), superplasticizer (SP) dosage, supplementary cementitious materials (SCMs) and hydration on the shear thickening (Continuous and discontinuous) behavior of cementitious suspensions are investigated. Results show that an increase in SVF, reduces the shear thickening intensity in case of cement (OPC) systems whereas the intensity is amplified for systems with fly ash (FA) and ground granulated blast furnace slag (GGBS). An increment in the SP dosage results in an early onset and increases the shear thickening intensity, regardless of the binder used. GGBS based systems show the highest shear thickening intensity, followed by OPC and FA based systems. Based on the results, it is evident that the optimization of SP dosage for OPC based systems needs to be carried out based on the structural build-up, while for FA or GGBS based systems, the SP optimization needs to be carried out based on shear thickening behavior with respect to hydration.