Predicting carbonation service life of reinforced concrete beams reflecting distribution of carbonation zones

Thoroughly understanding the influence of the distribution of carbonation zones, including the complete carbonation zones and the semi-carbonation zones with different pH ranges in load-free zone, tensile zone and compressive zone, respectively, on the carbonation service life of reinforced concrete beams under load effects remains important and should be further explored. In this study, the distribution of carbonation zones in a reinforced concrete beam under four-point bending is first investigated using theoretical analysis, and the carbonation zone widths in different zones under two stress levels are then calculated through numerical analysis, respectively. After comparing the predicted results with and without reflecting the distribution of carbonation zones, a calculating methodology for the carbonation service life of the reinforced concrete beam is put forward. The numerical and theoretical results show that the service life results considering the distribution of carbonation zones are lower than those without considering. It is also uncovered that using the width sum of the complete carbonation zone and the semi-carbonation zone with the pH value from 9.0 to 11.5 in tensile zone is the most conservative method to calculate the carbonation service life of reinforced concrete beams under load effects, whereas the service life values determined by the predicted results from the compressive zones and load-free zones with and without considering the semi-carbonation zone with the pH value from 9.0 to 11.5 are overstated.