Resistance of cracked concrete healed by means of polyurethane against chloride penetration

A lot of damage is reported for constructions in marine environments. Marine environments are very aggressive, because of the high chloride concentration in sea water. Chlorides affect durability by initiating corrosion of the reinforcement steel. When cracks appear in the concrete structures, chlorides will penetrate faster and will initiate corrosion. A possible solution is self-healing concrete. Self-healing concrete has the ability to recover without external intervention. From the literature concerning self-healing concrete, it is clear that research focuses on the general concept, the mechanical properties and water permeability. Based on the water permeability it is concluded whether harmful substances will penetrate. Specific data on degradation of self-healing concrete in aggressive environments are not available. Nevertheless, these data are important to ensure a good estimation of the service life extension. In this research, the effect of the healed cracks on the resistance against chlorides was investigated for two concrete types, namely ordinary Portland cement concrete and blast-furnace slag concrete with 50 % cement replacement. Non-steady state migration tests, based on NT Build 492, were performed with uncracked, cracked and healed concrete. In our previous research, autonomous crack healing was obtained by encapsulating polyurethane healing agents. To release the healing agents, realistic cracks were formed by means of a controlled splitting test. In the current work, as a first step, cracks (notches) were manually healed with a two-component healing agent based on polyurethane. These cracks (notches) were formed by means of steel plates with a width of 0.1 and 0.3 mm. The migration tests were performed at constant setup parameters, namely 30 V and 8h. The chloride penetration front was visualized by means of the colorimetric method. By comparing the penetration depths, it seemed that concrete with a healed crack of 0.1 mm can fully regain its resistance against chloride penetration.