Assessment of cracks in reinforced concrete by means of electrical resistance and image analysis

• Reinforced concrete specimens were subject to cracking.
• Influence of cracks on concrete electrical resistance was examined.
• Crack geometry and volume of cracks were assessed by image analysis.
• Relative increase in electrical resistance and crack volume were dependent on the crack opening displacement (COD).

The durability of cracked reinforced concrete is a serious concern in the construction industry. Cracks represent fast routes for chloride penetration, which can result in reinforcement corrosion. Bending or tapered cracks have the characteristic of being wider at the surface and becoming narrower towards the reinforcement. In reinforced concrete, secondary cracks can be found at the concrete steel interface. Their influence on concrete durability remains uncertain. Electrical resistance and resistivity have been commonly related to transport properties of concrete. This paper studies bending cracks in reinforced concrete specimens by measuring the electrical resistance across the crack. Cut sections of the specimens were subsequently impregnated and photographed. Image analysis tools were employed for determining the crack dimensions. It was found that the relative increase in electrical resistance and the crack volume were related to the crack opening displacement (COD) at the concrete surface.