Time-dependent reliability analysis of recycled aggregate concrete beams

Abstract

This paper investigates the time-dependent reliability of recycled aggregate concrete (RAC) beams made with 50% incorporation of recycled coarse aggregates. A basic method based on the series system model is adopted to calculate the reliability index, and the case studies show that the reliability index decreases with the service time: the reliability indices decrease from the values of 3.27 and 3.70 to 3.02 and 3.55 for RAC beams and normal aggregate concrete (NAC) beams during the service period of 50 years (target reliability index is 3.2 according to Chinese code) in the first case study, also indicating that the reliability index of RAC beams is lower than that of the NAC beams. Then, influencing factors such as the compressive strength , reinforcement ratio, thickness of concrete cover, carbonation rate and corrosion rate are analyzed based on a parametric study . All these factors affect the time to surface cracking and the time to reach the limit crack width of concrete cover. Finally, this investigation concludes that the methods, such as increasing the compressive strength or appropriately increasing the strength of concrete and reinforcement ratio at the same time, are feasible methods for meeting the requirements of the time-dependent reliability of concrete beams. • The reliability index of RAC beams is lower than that of NAC beams. • Factors influencing the reliability index of concrete beams are analyzed based on a parametric study. • Feasible methods for improving the time-dependent reliability of concrete beams are proposed.