Mechanical properties and microstructure evolution of recycled sand concrete under high-frequency flexural fatigue load

Abstract

In this paper, recycled sand (RS) was used in ballastless track concrete and the fatigue performance of recycled sand concrete (RSC) was studied. DIC and X-CT method were employed to investigate the fatigue strain and the microstructure evolution of RSC. The results indicate that the fatigue life of RSC follows the Weibull distribution. When the replacement ratio of RS in concrete is 50 wt.% (RSC40-50), the damage accumulation rate based on the fatigue strain is reduced by 12.7% and 7.0% compared to RS-free concrete (RSC40-0) and 100 wt.% recycled sand concrete (RSC40-100), respectively. The porosity of RSC exhibits a linear increase with loading cycles. Before fatigue loading, the porosity of RSC40-0, RSC40-50 and RSC40-100 was 0.91%, 1.08% and 3.01%, while it increased to 5.89%, 4.66% and 5.28% before the final failure. The increase in pore volume and the decrease in aspect ratio results in the formation of elongated pores and microcracks, ultimately leading to the fatigue failure.