Experimental study and modelling of concrete carbonation under the coupling effect of freeze-thaw cycles and sustained loads

In cold areas, freeze-thaw (F-T) cycles and sustained loads are usually the two main factors affecting the carbonation resistance of concrete, which has been paid more and more attention. In this paper, the effects of F-T cycles and sustained loads on concrete carbonation were studied. An alternating experiment of carbonation and F-T cycles combined with stress was carried out and the carbonation degree was measured by the carbonation depth. Test results show that F-T cycles and sustained loads both have obvious influence on concrete carbonation. F-T cycles and tensile stress could weaken the carbonation resistance of concrete, and the coupling of them has a promotion effect on carbonation. However, since the influence of compressive stress on carbonation is opposite to that of F-T cycles, the coupling effect of the two factors on carbonation depends on which factor plays the leading role. Furthermore, a theoretical carbonation model was established according to the carbonation mechanism and modified to consider the coupling effect of F-T cycles and sustained loads on carbonation. The modified model was proved to have a high accuracy and can be used to predict the carbonation depth of concrete simultaneously subjected to F-T cycles and sustained loads.