Meso-scale modelling of the effect of coarse aggregate properties on the creep of concrete

The effects of coarse aggregate properties on concrete creep were explored in the paper by mesoscale modelling approach, in which concrete was divided into coarse aggregate and matrix. Firstly, the creep constitutive model parameters of matrix were determined based on macroscopic and indentation creep tests, and then the evolution of creep and the influences of aggregate properties were discussed based on 2D meso-scale simulation. The simulation results of macroscopic creep test showed that the creep was unevenly distributed in the concrete, and the creep of matrix in vertical direction (y direction) of aggregate was greater than that in horizontal direction (x direction). Through parametric studies, it was found that: (1) the shape and gradation of course aggregate had little effect on the macroscopic creep, but the creep distribution of the matrix was changed by the aggregate shape; (2) the higher the aggregate content, the smaller the creep of concrete; (3) the larger the elastic modulus, the smaller the creep, and the matrix creep in x direction of aggregate of decreased with the increase of elastic modulus ratio of aggregate to matrix. Based on the simulation results, stress redistribution and continuous retardation time spectrum were discussed. Stress redistribution at meso-scale mainly occurred in the matrix in the x direction of aggregate. Through the retardation time spectrum, the creep process including two short-term creeps and a long-term creep and their transition retardation time were determined. The aggregate content had no effect on the transition retardation time, while transition retardation time between two short-term creep was increased by the increase of elastic modulus of aggregate.