An experimental and numerical investigation of coarse aggregate settlement in fresh concrete under vibration

Fresh concrete needs vibration to compact, fill the mould and reach a dense state. During the compaction process, coarse aggregates (CAs) tend to settle, affecting the homogeneity and eventually the long-term durability of hardened concrete. In this study, a 3-D, multi-phase numerical model for fresh concrete is developed for better understanding the CA settlement under vibration. The settlement rate of the CA in vibrated concrete is considered based on the Stokes law, and the calibrated rheological parameter of mixtures is determined by the segmented sieving method. The model prediction shows that the vibration time has the greatest effect on CA settlement, followed by the particle size of CAs, whereas the density of CAs and the plastic viscosity of mixtures contribute a little compared with the aforementioned factors. Through experimental tests, the validity of prediction results is well verified. The proposed model provides a new method to understand and estimate the settlement behaviour of CAs.