Carbonation Process of Reinforced Concrete Beams under the Combined Effects of Fatigue Damage and Environmental Factors

The carbonation process of reinforced concrete (RC) beams considering the combined effect of fatigue load and environmental factors was investigated experimentally in an environmental simulation chamber based on meteorological environmental data. Fourteen beams were constructed and tested, and a carbonation numerical model (CNM) considering medium transport and fatigue damage characteristics was proposed to simulate the carbonation process of RC beams. Based on the experimental results, CNM is extended to reveal the effects of ambient temperature, relative humidity, carbon dioxide concentration, and fatigue damage on the carbonation process of RC beams. The results showed that the change in the pore structure of concrete can directly and accurately characterize the effect of fatigue damage on the transport characteristics of concrete. The porosity of concrete substantially increased with increasing levels of fatigue damage. Although fatigue damage did not have a significant effect on the most probable pore radius of the concrete, the total pore volume of the most probable pore notably increased. The results showed that both the carbonation depth and fatigue damage exhibit a three-stage development law. The depth and rate of carbonation are related to concrete pores and macroscopic cracks. In the carbonation analysis of fatigue-damaged RC beams, the changes in both the pore structure and fatigue cracks caused by repeated fatigue loading on carbonation should be considered.