Experimental determination of chloride penetration in concrete with real cracks

Abstract

It is well known that the presence of cracks in reinforced concrete structures in aggressive environments accelerates rebar corrosion. The influence of real cracks in concrete structures on the penetration of chlorides and the resulting service life is being investigated in this study. Investigations were carried on at the Magnel Laboratory for Concrete Research of Ghent University, Belgium within a bilateral agreement with University Politehnica Timisoara, Romania. Non-steady state migration tests were realized according to NT BUILD 492, using an electrical field and real cracks in order to determine the chloride profile. Samples with different crack patterns, obtained by drilling from a reinforced concrete slab exposed to a simulated accidental failure of the central support and subsequent vertical loading until collapse, were used in the study in order to provide a more realistic image of the geometry of the cracks. The crack widths were measured using an optical microscope. The chloride penetration depth was measured with a colorimetric method on each specimen and the non-steady state diffusion coefficients were determined. For evaluating the parameters which have the most influence on chloride migration on the samples used in this experiment, a two-level factorial experiment was designed and carried out in the early stage. Afterwards, using a higher number of samples, the influence of the existence of cracks and also the influence of crack widths on chloride penetration was studied by means of other statistical procedures: comparison of two means, one-way ANOVA. The results obtained provide a better understanding of the diffusion process when dealing with concrete structures with real crack.