Time-dependent reliability analysis on carbonation behavior of recycled aggregate concrete based on gamma process

- The gamma distribution can be used to describe the RAC carbonation depth.
- The RAC carbonation behavior was evaluated based on the reliability analysis.
- The gamma process was applied to calculate the time-dependent reliability.

The time-dependent reliability of carbonation behavior is investigated in recycled aggregate concrete (RAC). The gamma distribution of carbonation depth is tested with the data collected from previous investigations. The results show that the gamma distribution can be used to describe the carbonation depth. Thus, the gamma process is adopted to analyze the reliability of carbonation behavior with the maximum likelihood estimation (MLE) to determine the parameters of gamma process. With this methodology, four case studies are executed to investigate the influences of replacement ratio of recycled coarse aggregate (RCA), crushing procedure of RCA, water-to-cement ratio (w/c) and concrete cover depth on the reliability of carbonation behavior by calculating the probability density function (PDF) and failure probability. The results show that all these factors have an obvious influence on the reliability of RAC carbonation behavior. Finally, this paper concludes that the time-dependent reliability analysis by using gamma process is necessary because of its guidance in the optimization of mix design and determination of concrete cover depth which can further satisfy the durability design of RAC structures.