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• CatBoost regression model for prediction of surface chloride level. • The regression model has MAE and RMSE scores of 0.11 and 0.16 respectively. • Increase in chloride ingress with the increase in temperature and humidity. • Exposure zone has a significant effect on chloride ingress. • Temperature and humidity of RCP 2.6 and RCP 8.5 considered for analysis. This paper presents the effect of climate change on the long-term reliability of concrete structures due to chloride ingress. The impact has been demonstrated for three regions across the globe for the best and worst-case climate change scenarios. The methodology adopted here can be divided into three main steps. The first one is the development of a machine learning regression model using CatBoost for estimation of surface chloride levels, which is a function of temperature, concrete material properties, exposure conditions, and chloride levels in the seawater. The CatBoost model fitted over the experimental data has a mean absolute error (MAE) and root mean square error (RMSE) value of 0.11 and 0.16, respectively, and a high R2 value of 0.82. The second step is solving the coupled non-linear partial differential equation for temperature, humidity, and chloride ingress in concrete with time. A parametric study considering the effect of external parameters (temperature, humidity, exposure condition, and chloride levels in water) reveals the complexity and the dependencies of the chloride ingress process on external parameters. The final step involves the reliability analysis to estimate the time for chlorides to reach threshold levels at the rebar level using the numerical model. The input for the numerical model is temperature and humidity condition for different representative concentration pathways (RCP) scenarios, the material properties of concrete, and the exposure conditions. The reliability analysis shows that, for the concrete structure located in Dubai, UAE, and Cascais, Portugal, the mean time to corrosion initiation decreases due to climate change and it increases for the structure located in Tasmania, Australia. Further, the structures that are built in the future may have lower service life compared to the structures that were built in the past. Based on the study it concluded that it is necessary to consider the impact of climate change on service life to design resilient structures. [ABSTRACT FROM AUTHOR]

Abstract: Natural weather changes due to diurnal and seasonal temperature and relative humidity cycles affect micro-environment of concrete; temperature and moisture content in the concrete fluctuate correspondingly with variations in the weather. At the same time, for concrete structures, the temperature and relative humidity in both the atmosphere and the concrete show obvious differences due to thermal conduction and pore structure densification of the concrete. Therefore, the temperature and moisture content in the concrete, which are defined as the micro-environmental indexes in the concrete in this paper, are main factors directly influencing concrete carbonation, chloride diffusion and the corrosion rate of steel bars. This paper mainly discusses the climate load based on natural weather and the effects of the climate load. The climate load includes the temperature, relative humidity, wind speed, sun shine and rain in a natural climate environment. The effects of the climate load are the responses of the micro-environment in the concrete under action of the climate load. Firstly, the experiments on responses of temperature and relative humidity in concrete were carried out in an artificial constant climate environment; at the same time, the behaviors about thermal conduction and moisture diffusion of the concrete were measured and modeled. Thereafter, a method for predicting the responses in concrete under a natural climate environment condition was built. In present studies, the temperature and the relative humidity responses in concrete under a natural climate environment condition show obvious hysteresis characteristics. The research findings illustrate that the predictions of the rate of the concrete carbonation, the chloride diffusion and the corrosion of bar in concrete should be depended on the micro-environment and the predictions based on the natural climate environment are not appropriate. [Copyright &y& Elsevier]

Abstract: Temperature and moisture content are the main factors that influence concrete carbonization, chloride diffusion, and corrosion rate of reinforced bars placed in concrete. Climate variations can induce the variation of the micro-environment of concrete. Therefore, temperature and relative humidity in the natural climate environment serve as the climate load, and the variations in the micro-environment corresponding to the climate variations are the effect of the climate load. Based on these, the present paper attempts to build climate temperature and relative humidity action spectrums as a climate load model. The climate action spectrums of temperature and relative humidity are built based on meteorological data of the temperature and the relative humidity variations. The effects of sunshine and rain are included in the construction of the action spectrum. Series of tests are conducted under artificially controlled climate environment (ACCE) and natural climate environment (NCE) conditions to support the construction of the spectrum. [Copyright &y& Elsevier]