Abstract
The presence of cracks is unavoidable in reinforced concrete structures and also a gateway for chloride into concrete, leading to corrosion of steel reinforcing bars. So, crack control, crack width limitation and chloride threshold levels are well-established concepts in durability of reinforced concrete structures. This paper reports on accelerated chloride-induced corrosion in cracked reinforced strain-hardening cement-based composites and reinforced mortar beams, both in loaded and unloaded states. Corrosion rates are monitored and loss of mass and yield force, as well as corrosion pitting depth in steel bars are reported. The chloride content at different depths in specimens is also determined through XRF, and through chemical testing of acid and water soluble chloride content by titration. Finally, different relationships are drawn between crack properties, mass loss, yield force, corroded depth and chloride levels at the steel surface for different cover depths. It is found that the crack spacing and free chloride at the steel surface level are best correlated to the corrosion damage in the specimens.
Highlights
Cracks in concrete act as pathways for quick ingress of chloride and water
Average and maximum crack widths and crack spacing in the R/strain-hardening cementbased composites (SHCC) are smaller for larger cover depth of the steel bar
From the particular type of SHCC used in this research, it appears that a 25 mm cover depth is the threshold cover depth for limiting the crack width in R/SHCC
Summary
Cracks in concrete act as pathways for quick ingress of chloride and water. There is evidence that a threshold crack width of about 0.05 mm exists for water permeability. For cracks wider than this threshold, water permeability increases by orders of magnitude (Wang et al 1997). In reinforced concrete structures (RCS) chloride ions act as a catalyst in the localised breakdown of the passive film on the steel surface. The passive film initially forms on steel as a result of the alkaline nature of the pore solution in concrete. A minimum concentration of chlorides on the steel, known as the chloride threshold level, is required to de-passivate the reinforcement and allow corrosion to occur (Angst et al 2009; Pacheco and Copyright Ó The Author(s) 2017.
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