Concrete Crack Repairs

Any concrete damage will manifest itself in two areas; cracks in the concrete, and possibly visible corrosion of the steel within.

It is essential to determine the underlying cause of the concrete crack to ensure that the correct repair is carried out.

This is fundamental to the success or failure of the repair, and a lack of adequate attention at this point can jeopardise the whole job.

Below you’ll find the main types of repairs we do for concrete cracks.

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These are the Trade and Industry Certifications attained by Sussex Rope Access

Concrete Crack Repairs – The options

Concrete Patch Repairs

If the problem has been diagnosed as being due to carbonation induced or chloride induced corrosion of the reinforcement, patch repairs may be used, although with the latter, there are precautions needed to ensure a successful repair.

We use patch repairs where the damage is evidentially cracking and spalling due to reinforcement corrosion only. If the problem has been diagnosed as due to ASR or any of the other mechanisms of failure, the repair may need to be specifically designed for that particular contract and structure, and it is impossible to generalise about the approach which might be taken.

Cathodic Protection

This is a recently developed process for dealing with corrosion of steel in concrete.

If we can make the cathodic reaction predominate along the steel, we will stop corrosion. In electrochemical techniques we apply an external anode to the concrete surface. This generates the electrons instead of the anodic reaction, and the steel has only the cathodic reaction occurring on its surface.

The systems re-establish a “passive” environment around the steel that will last many years.One requirement for all electrochemical treatment is good electrical continuity to ensure that current flows from the anode to all areas of steel. Electrical continuity must be checked and, if necessary, established in all applications of these techniques. The reverse side of that issue is that there must be no short circuits between the steel and the surface.

Chloride Removal

The chloride ion is a catalyst to corrosion. As it is negatively charged, we can use the electrochemical process to repel the chloride ion from the steel surface and move it towards an external anode. The most popular anode is the same coated titanium mesh used for Cathodic Protection. Instead of embedding it permanently in a cementitious overlay, a temporary anode system is used. This is placed inside a cassette shutter. Where the shape of the member is especially difficult, a sprayed papier mache system can be applied over the anode, soaked with the electrolyte.

Corrosion Inhibitors

Research has been carried out and it is evident that in some low risk situations, corrosion inhibitor materials can have a role in concrete repair. In our opinion, based upon current research, their effectiveness is limited to 1. Concrete suffering from carbonation with shallow cover, say up to 15mm. Their ability to work with deeper cover depends on their ability to penetrate adequately to the reinforcement. This varies from concrete to concrete and cannot be guaranteed. 2. Concrete containing up to 0.6% chloride as chloride ion, by mass of cement. Research has not supported their effectiveness at higher values. Notwithstanding this, repair contracts are being carried out using a combination of patch repairs, corrosion inhibitors and coatings. In some cases an insurance backed warranty is being offered, for typically 10 years. Given the combined effectiveness of inhibitors and coatings together, with existing damage dealt with by patch repair, then if the warranty is considered acceptable, we see no reason why the Client should not accept this approach, provided caution is exercised. We would not, however, consider this approach to be likely to be successful in high chloride situations.
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