Chloride-induced corrosion of reinforcing steel bars has a big impact on the performance of reinforced concrete (RC) structures subjected to saline environments, and it is essential to understand how chloride ions ingress in concrete. In this study, first, an experiment of chloride ingress in specimens under one-dimensional and two-dimensional diffusion was conducted in a climate chamber, and profiles of chloride concentration along the depth were obtained. Then, a mesoscopic model that considers environmental factors, i.e., temperature, relative humidity, and time of exposure, was developed to investigate chloride diffusivity in concrete. Concrete is treated as a three-phase composite: cement paste, aggregates, and interfacial transition zones (ITZs). It is assumed that chloride diffusivity can take place only in the cement paste and ITZ, whereas the aggregate is considered impermeable. Influence of ITZ thickness, i.e., 0, 50, and 80 μm, on chloride diffusivity in concrete is examined. Chloride concentrations, which are simulated with the mesoscopic model with consideration of environmental factors, are compared with previous test data. Finally, time to corrosion initiation of RC structures is predicted based on the developed mesoscopic model considering the distribution of aggregates, and the influence of environmental factors on the chloride concentration of the corrosion initiation point is investigated. It is found that ITZs have a significant effect on chloride diffusivity in concrete. However, different thicknesses of the ITZ, i.e., 50 and 80 μm, have a small impact on the chloride diffusivity in concrete; hence, an ITZ thickness 80 μm is recommended for efficiency. The simulation results with consideration of the environmental factors are in good agreement with the test data, and the corrosion initiation point on the surface of the steel embedded in concrete varies because of the distribution of aggregates. Corrosion initiation time decreases with increases in the water-to-cement (w/c) ratios but increases with increases in the thickness of cover, temperature, and humidity. An increase in either temperature or relative humidity can lead to a significant increase in the chloride concentration of the corrosion initiation point on the steel.

This paper mainly presents experimental results on the mechanical behavior of corroded reinforced concrete (RC) beams strengthened with steel plates considering the influence of the corrosion rate, thickness of the steel plate, and concrete cover on the strain of concrete and steel plate, ultimate bearing capacity, and deflection. Eighteen RC rectangular beam specimens were tested under monotonic loading in the experimental program, in which nine corroded RC beam specimens were strengthened using different schemes. Three RC noncorroded beams were strengthened with a steel plate as strengthened control beams. Six RC beam specimens were unstrengthened control beams, including three noncorroded beams and three corroded beams. After loading tests, the effect of corrosion on the mechanical behavior of tensile steel reinforcement was researched. Variance analysis was carried out to quantifiably examine the effects of the thickness of concrete cover and steel plate on the indicators of the mechanical behavior of strengthened corroded beams and verify the correctness of test results. It is concluded from the statistical results of corrosion effects that the ultimate bearing capacity of the corroded beams is best associated with maximum pit depth at the failure position rather than average corrosion penetration of the rebar. The distribution of the pit location along the steel reinforcement approximately obeys a Gaussian distribution. The test results confirm that strengthening with steel plates improves the strength and ductility of corroded beams. The failure mode of the strengthened corroded beams is diagonal tension failure because of the corrosion of steel reinforcement and the critical diagonal cracking. The ultimate load of strengthened corroded beams increases from 5 to 18 kN as the thickness of steel plate increases 1 mm. The variance analysis and experimental results both showed that the thickness of the steel plate has a significant influence on the ultimate load and ultimate deflection of strengthened corroded beams, whereas concrete cover has less influence on the structural behaviors of strengthened corroded beams.

The scale of fluctuation ( θ) of the material and geometrical parameters is the basis of studying the spatial variability of reinforced concrete structures. In this article, a new estimation method for the scale of fluctuation based on Bayesian information criterion is proposed. And based on the analysis of experimental data recorded on the three 36-year-old beams of the Jianggong Bridge and 246 corroded steel bars, the scale of fluctuation ( θ) of concrete compressive strength ( f _c ) and steel pitting factor ( R) are estimated. The theoretical bending moment of three test beams are calculated considering the influence of the spatial distributions of f _c , R, and other relative variables. The reasonableness and superiority of the Bayesian information criterion model than the auto-correlation function method and the semivariogram function model are verified by comparing the theoretical results with the measured bending moment of the three beams mentioned above.

The existence of axial and lateral compressive stress affect the diffusion of chloride ions in concrete will lead to the performance degradation of concrete structure. This paper experimentally studied the chloride diffusivity properties of uniaxial and biaxial sustained compressive stress under one-dimensional chloride solution erosion. The influence of different sustained compressive stress states on chloride ion diffusivity is evaluated by testing chloride concentration in concrete. The experiment results show that the existence of sustained compressive stress does not always inhibit the diffusion of chloride ions in concrete, and the numerical value of sustained compressive stress level can affect the diffusion law of chloride ions in concrete. It is found that the chloride concentration decreases most when the lateral compressive stress level is close to 0.15 times the compressive strength of concrete. In addition, the sustained compressive stress has a significant effect on chloride ion diffusion of concrete with high water/cement ratio. Then, the chloride diffusion coefficient model under uniaxial and biaxial sustained compressive stress is established based on the apparent chloride diffusion coefficient. Finally, the results demonstrate that the chloride diffusion coefficient model is reasonable and feasible by comparing the experimental data in the opening literature with the calculated values from the developed model.