FATIGUE BEHAVIOR OF NANO-MODIFIED RECYCLED AGGREGATE CONCRETE UNDER UNIAXIAL COMPRESSION

Recycled aggregate concrete (RAC) is modified by nano-silica to study the fatigue behavior due to uniaxial compressive repeated loading. Considering the recycled aggregate replacement rate as the main parameter, the fatigue life, fatigue equation, fatigue deformation law and residual stress of RAC are recorded and analyzed. Microscopically, the influence of nano-silica on multiple interface transition zones of RAC is discussed based on nanoindentation. The results show that the fatigue life of each group well obeys the two-parameter Weibull probability distribution. Under 50% guarantee rate and 0.75 stress level, the fatigue life of RAC with 100% recycled coarse aggregates is 25.8% lower than that of ordinary concrete. The incorporation of nano-silica improves the fatigue life of RAC significantly. Compared with other test group through the strain evolution curve and the residual stress model, the residual strength attenuation nonlinearity is obvious for RAC incorporating nano-silica. Nano-silica improves the indentation modulus of the multiple interface transition zones, which is the reason for the improvement of the fatigue behavior of RAC.