Abstract
To enhance the carbonation resistance of reclaimed concrete, several key factors affecting its performance were investigated. An orthogonal array L (16)(4³ × 2⁶) was employed to design the carbonation tests for steel fiber (SF) reinforced concrete. The study included varying SF volume ratios, along with considerations of different concrete ages (T) and water-cement ratios (W/R). The effect of SF volume ratio, regenerated crude aggregate (RCA) replacement rate, W/R, and T on the carbonation resistance of recycled concrete was analyzed. The test results indicated a trend of increasing carbonation depth over time. However, a lower W/R ratio resulted in a reduced carbonation depth. Notably, a 50 % RCA replacement rate led to a shallower carbonation depth compared to other replacement rates. After 28 d, recycled concrete containing 1 % SF exhibited a carbonation depth that was 6.9 %, 1.5 %, 1.5 %, and 9.3 % lower than concrete with 0 %, 0.5 %, 1.5 %, and 2 % SF, respectively. Therefore, the incorporation of 1 % SF was found to be the most effective in improving carbonation resistance. Orthogonal polynomial regression analysis was employed to develop a regression equation relating carbonation depth to SF volume ratio, RCA replacement rate, W/R, and T. The regression coefficients were calculated and tested, leading to the identification of the optimal regression equation and its corresponding confidence interval.