Chloride transport in cracked RC beams under dry-wet cycles

摘要

The coupled effect of transverse cracking and cyclic drying-wetting conditions on chloride penetration in concrete is explored in this paper. The transport mechanisms of chloride in cracked concrete subjected to drying-wetting cycles are described and simplified. An experimental investigation was conducted for sustained cracked concrete beams and the results are reported here. It is found that the depth interval of the convection region in cracked concrete varies from approximately 10 to 20 mm, which is slightly greater than that found in sound concrete. Also, it increases with the increase in crack width and decreases with the increase in fly ash content. At the cracked sections, the speed of chloride penetration is increased by the presence of cracks. It is shown that the modified diffusion model is still practicable for describing the chloride distribution in transversely cracked concrete when the crack width is within a range close to 0.30 mm. Finally, a regressive relationship between equivalent chloride diffusion coefficient, D-Cl(eq) , and crack width, w(cr), is proposed with a quadratic function of crack effect.