Rheo-morphological investigation of Reynolds dilatancy and its effect on pumpability of self-consolidating concrete

Abstract

Reynolds dilatancy is one of the main mechanisms responsible for the lubrication layer (LL) formation during pumping of self-consolidating concrete (SCC). In this study, the effect of morphological characteristics of coarse aggregate on Reynolds dilatancy of 30 different SCC mixtures was investigated. The Reynolds dilatancy measurements were carried out using a coaxial-cylinders tribometer. New methodology to evaluate the morphology of coarse aggregate using 3D image analysis was also proposed. The Reynolds dilatancy values of the investigated SCC mixture were well correlated to both the morphological characteristics of coarse aggregate (>1.25 mm) and visco-elastoplastic properties of the suspending fine mortar (<1.25 mm). The established correlations revealed that higher 3D surface area and roughness, as well as lower mean diameter and elongation of coarse aggregate can lead to higher Reynolds dilatancy.Moreover, the thickness, composition and rheological properties of the LL, as well as the rheological properties of the investigated SCC mixtures were successfully evaluated using the Reynolds dilatancy and morphological measurements. The pumpability of the investigated SCC mixtures were then predicted using the estimated rheological properties of the investigated mixtures and their corresponding LL. The results showed that higher Reynold dilatancy and lower rheological properties of SCC can decrease the pressure loss and facilitate the pumping process. Moreover, the pumpability of SCC was found to be more controlled by the volume of cement paste, concentration, and packing density of coarse aggregate.