Self-healing of concrete cracks by the release of embedded water repellent agents and corrosion inhibitors to reduce the risk for reinforcement corrosion

From the worldwide steel production, approximately 50 per cent is required to replace corroded steel [1]. In the case of reinforced concrete structures, corrosion of the reinforcement steel causes crack formation and spalling which leads to serviceability problems. Especially when small cracks are already present in the cementitious matrix in combination with aggressive ions present within the environment, a high risk for corrosion exists. Therefore, regular inspection, maintenance and crack repair are insurmountable for concrete structures. However, costs related to repair works mount up as not only the direct costs of the repair but also the indirect costs resulting from traffic jams and possible loss in productivity need to be taken into account. Self-repair of concrete cracks will have a high economic benefit as the indirect costs as well as a part of the direct costs can be avoided. In addition, it is assumed that self-repair will lead to more durable concrete structures as the risk for reinforcement corrosion may be decreased. The possibility to implement self-healing properties in concrete has been investigated for several years now. One of the studied self-healing approaches relies on the use of encapsulated healing agents which are embedded in the matrix. When cracks appear, the capsules break and the healing agent is released in the crack, causing crack repair. In previous research [2, 3] it was shown that by using this approach, part of the mechanical properties and the water tightness of cracks was restored. In this study we investigate whether by encapsulation and embedment of a water repellent agent (WRA) and/or a corrosion inhibitor (CI), we can reduce the risk for reinforcement corrosion. A selection of WRA and/or CI were encapsulated and embedded inside reinforced concrete beams which were cracked to trigger the self-healing mechanism. By electrochemical measurements it was shown that the risk for reinforcement corrosion was reduced in comparison to untreated cracks when the cracked beams, containing encapsulated WRA and/or CI, were exposed to a chloride solution