Service life estimation of cracked and healed concrete in marine environment

In the aggressive seawater environment, the durability of concrete is strongly influenced by the presence of chlorides and sulfates. Marine structures mostly have an important social function with a high economic impact, which makes durability a key issue. In addition, early-age cracks are a common problem, specifically for massive structural components. Repair of cracks is expensive and often impossible due to inaccessibility. Self-healing concrete is a promising solution to make marine structures more durable. In this study, capsules containing Polyurethane (PU) prepolymers were embedded in the concrete to release their contents when cracks appear. In cracked mortar, the chloride diffusion coefficients in the zone immediately around the crack significantly increased compared to uncracked mortar. The crack width dependency could be introduced into the service life model using a crack effect function. For crack widths in the range of 100 mu m to 300 mu m a service life decrease of around 80% was calculated. Autonomous crack healing had a beneficial influence on the resistance against chloride diffusion. However, for about one third of the cracks the healing mechanism failed, probably due to shifting of the tubes, tubes not rupturing properly, too high capillary forces in the tubes, etc. Nevertheless, on average, the service life of autonomously healed structures by means of encapsulated polyurethane increased with around 100% compared to cracked, unhealed structures. Moreover, in the most beneficial situation of proper healing, a service life increase of 150-550% was obtained, reaching values similar as for sound structures.

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