Experiment and simulation study on coarse aggregates settlement in vibrated concrete based on transparent granular suspensions

Abstract

It is difficult to directly obtain the movement of coarse aggregates (CAs) since concrete is opacity. This paper mixes a transparent granular suspensions similar to fresh concrete for the vibration experiment, using white oil, silica powder, fused quartz sand and fused quartz stone. The vibration destroys the initial network structure of the granular suspensions causing the support force acting on CAs to decrease and CAs to rapidly accelerate sinking. Then, the granular suspensions gradually form a steady network structure making the support force increase as a logarithmic function and the sinking speed of CAs decrease. The variation law is combined with numerical simulation and concrete vibration experiments to obtain CAs settlement process in concrete with different vibration parameters. Under the same vibration frequency and different amplitudes, unit mass of concrete absorbs similar energy to reach the same distribution state of CAs and vibrated state, and this energy increases with the increase of vibration frequency. Therefore, the low-frequency and high-amplitude has higher construction efficiency than high-frequency and low-amplitude vibration. However, the high-frequency and low-amplitude vibration has larger range of optimal vibration time. The proposed method is helpful to better understand the settlement process of CAs and the energy can be used to evaluate the compactness and segregation state of vibrated concrete.