Experimental Studies on Chloride Penetration and Steel Corrosion in Cracked Concrete Beams under Drying-Wetting Cycles

摘要

In order to investigate the effect of transverse cracks on chloride penetration and steel corrosion in concrete beams, two series of cracked specimens, Series A, with sustained flexural cracks, and Series B, with precracks, were designed and tested under a cyclic drying-wetting condition of NaCl solution. Profiles of free chloride concentration were obtained from the cracked beams in Series A after 30 and 60 weeks; the corroded rebars were removed from the precracked beams in Series B after nearly 4 years. Experimental and analytical results showed that the depth of the surface convection zone in the cracked concrete varied from 10 to 20 mm, which was greater than that in the sound concrete, and increased with increasing crack width. Around the steel bar located in the inner concrete, beyond the convection zone, chloride content was mainly influenced by concrete type when crack width was less than 0.2 mm, and then by crack width. For precracked concrete, pitting corrosion in the steel was obviously seen where cracks were located, and the scope of localized corrosion expanded when crack width increased. The effect of transverse cracks on steel corrosion depends on the coupled actions of cover depth and crack parameters. For the same specimens, a great difference in the effect of crack width (~0.2 mm) on steel corrosion was observed when crack spacing decreased from 250 to 150 mm, especially for the steel bar with a lower cover depth of 20 mm.