Effect of cracking on water and chloride permeability of concrete

The goal of this research was to study the relationship between cracking an d concrete permeability and to support accounting for permeability and crac king resistance to other factors besides strength, as criteria to be consid ered in mix design to achieve a durable concrete. The effect of material co mposition [normal-strength concrete (NSC) and high-strength concrete (HSC) with two different mix designs] and crack width (ranging from 50 to 400 mu m) on water and chloride permeability were examined. Cracks of designed wid ths were induced in the concrete specimens using a feedback-controlled spli tting tensile test. Chloride permeability of the cracked samples was evalua ted using a rapid chloride permeability test and the water permeability of cracked concrete was then evaluated by a low-pressure water permeability te st. Uncracked HSC was less water permeable than NSC, as expected, but crack ing changed the material behavior in terms of permeability. Both NSC and HS C were affected by cracking, and the water permeability of cracked samples increased with increasing crack width. Among the tested materials, only HSC with a very low water-to-cement ratio chloride permeability was sensitive with respect to cracking. Results indicate that the water permeability is s ignificantly more sensitive than the chloride permeability with respect to the crack widths used in this study.