Sustainability Effects of Including Concrete Cracking and Healing in Service Life Prediction for Marine Environments

Abstract

With today's focus on sustainable design, it is necessary to adequately predict and prolong service life of concrete in marine environments. By introducing self-healing properties, service life extension can be achieved. However, in prediction models, the required concrete mix specific input is usually not available. Moreover, little attention goes to the unavoidable presence of cracks. Finally, autonomous crack healing has almost never been taken into account. In this paper, the relevant model input was estimated from experimental chloride profiles. It enabled an adequate prediction of the chloride-induced steel depassivation period for cracked and uncracked 15% fly ash concrete (8-104 years, respectively). Comparison with self-healing by means of encapsulated polyurethane indicated a 48-76% self-healing efficiency. It could extend the corrosion initiation period to 36-68 years. Being much less subject to timedependent repair, PU based self-healing concrete has a 77-88% lower environmental impact than traditional (cracked) concrete.

Quantification of the Service Life Extension and Environmental Benefit of Chloride Exposed Self-Healing Concrete

“…The hardened polyurethane inside the cracks clearly forms a partial barrier against immediate ingress of chlorides through the cracks. In order to make clear conclusions about the performance of the self-healing mechanism, a self-healing efficiency at every depth i below the exposed surface (SHE i ) was defined according to Van den Heede et al [ 53 ] (Equation (5)): with , the chloride content of the cracked specimen at depth i (m%/binder); , the chloride content of the healed specimen at depth i (m%/binder); and , the chloride content of the uncracked specimen at depth i (m%/binder). All chloride contents were based on the values of the fitted curves.…”

“…In this case study, this event is seen as the end of service life. In [ 53 ] it has been experimentally verified in accordance with the method prescribed by RILEM TC 235 CTC—time-dependent monitoring of the corrosion potential of embedded reinforcing steel until onset of active corrosion—that this critical chloride concentration should be at least equal to 1.22 ± 0.02 m%/binder for the studied concrete composition under submerged exposure conditions. The same preliminary value has been adopted in this paper.…”

“…For the accelerated chloride diffusion tests, cylindrical concrete specimens with a height of 50 mm and a diameter of 100 mm were made using plastic molds cut from a PVC tube with an inner diameter of 100 mm. Cracks were introduced into the specimens in an artificial way by introducing thin brass plates with a thickness of 300 µm into the fresh concrete upon casting [ 53 ]. The plates had a width of 60 mm and were positioned in the center of the cylindrical molds up to a depth of 25 mm.…”