Effect of aggregate gradation and mortar rheology on static segregation of self-compacting concrete

Abstract

Due to the high flowability of self-compacting concrete (SCC), compared with ordinary concrete, it is more prone to have stability problems and segregation. In order to study the segregation of SCC, a random irregular aggregate generation algorithm is developed to simulate the actual aggregate gradation, and a fluid-particle coupling method based on immersed boundary method (IBM) is proposed to simulate the rheological behavior of SCC. To verify the accuracy of the simulation method, a validation experiment is carried out, by comparing the results of the experiment and the simulation, it can be found that the numerical simulation method is reasonable and feasible. The influences of aggregates and mortar on the SCC static segregation are systematically studied by comparing the simulation results of different aggregate gradation and mortar rheological properties. The stress generated by gravity and buoyancy of large aggregates can easily overcome the mortar yield stress and settle in the mortar when the large aggregate content is higher and the mortar yield stress is lower. Then SCC is more prone to segregation while mortar viscosity only affects the time required to achieve stability and does not affect the static segregation results. Therefore, by adjusting aggregate gradation and mortar rheology, SCC can reach a relatively stable state, which has a guiding significance for the practical preparation of SCC in preventing its segregation.