Although the ingress of chloride into concrete is normally controlled by absorption and diffusion mechanisms, external loads can affect this process by modifying the microstructure of concrete. To predict the chloride ingress into real structures under service conditions, the effects of external loads on the chloride transport should be considered. In this paper, the effects of compressive and flexural loads on chloride transport were studied. The experimental results indicated that the chloride concentration and apparent chloride diffusion coefficient Dapp decreased with the increase of the compressive stress, up to 55% of the compressive strength, and they increased with the increase of the flexural stress. On the basis of these results, a model for predicting the chloride diffusion process under different loading conditions is established by accounting for various parameters, such as stress level, water-cement ratio, curing time, temperature, concrete age, humidity, and chloride diffusion coefficient. ...

This paper studies the chloride diffusivity of concrete subjected to long-term exposure in a simulated marine environment with sustained compressive loading for up to 224 days. A series of concrete prisms were loaded under five different compressive stress levels (0, 0.2, 0.3, 0.5, and 0.7fc) and were subjected to different numbers (4, 8, 12, and 16) of wet/dry seawater exposure cycles. At the end of each exposure period, the concrete specimens were analyzed to determine their chloride penetration profile, the apparent chloride diffusion coefficient Da of the concrete, and the surface chloride content Cs. It was found that the Da and Cs values are both time and stress dependent and that these two dependencies have complex interactions. The value of Da decreases with time due to the hydration of the cement matrix, whereas the value of Cs increases over time. The effects of compressive stress on the values of Da and Cs strongly depend upon the applied stress level, which has a threshold value at app...

The effect of saturation coupled with loading rate on the tensile strength and the compressive mechanical properties of concrete, namely static and dynamic strengths, Young's modulus and critical strain, were studied by splitting and uniaxial compression tests respectively. The experimental results indicate that the static tensile and compressive strengths of saturated concrete are lower than those of concrete in dry state, but the dynamic strengths of saturated concrete is higher than those of concrete in dry state. The difference increases when the loading rate increases. Based on physics and cracking rules of concrete, physical explanations on the effect of saturation and loading rate on the concrete strength were given with the consideration of the harmful and favorable effects of free water in the cracks. In addition, proving experiments were also carried out to investigate that whether the state of water in the cracks affects the surface energy of solid, and the results showed that surface energy was valid to explain the variation of tensile strength of concrete.

The research reported herein studied the permeability of concrete containing recycled-concrete aggregate (RA), superfine phosphorous slag (PHS), and ground granulated blast-furnace slag (GGBS) with and without stress. Test results showed that the chloride diffusion coefficient of RA concrete (RAC) without external loads decreased with time, and the permeability of RAC is much lower than that of the reference concrete due to the on-going hydration and the pozzolanic reaction provided by the PHS and GGBS additives in the RAC mixture. The permeability of chloride under flexural load is much more sensitive than that under compressive load due to the differences in porosity and cracking pattern. At low compressive stress levels, the permeability of chloride decreased by the closing of pores and microcracks within RAC specimens. However, in a relatively short time the chloride diffusion coefficient and the chloride content increased rapidly with the increase of compressive stress when it exceeded a threshold stress level of approximate 35% of the ultimate compressive strength. Under flexural stress, the chloride transport capability increased with the increase of stress level and time. At high compressive and flexural stress levels, creep had a significant effect on the permeability of chloride in the RAC specimens due to the damage from the nucleation and propagation of microcracks over time. It is apparent that mortar cracking has more of a significant effect on the chloride transport in concrete than cracking in the interfacial transition zone (ITZ).