It is absolutely essential that the root causes of damages are identified.
Most defects will initially become evident at locations where there is low cover and/or poor quality concrete. The reasons for damage, however, usually require greater investigation. It is important to carry out technically correct repairs, not just to treat th symptoms, but also to treat the latent damage to prevent continued deterioration.
Successful Repair Requirements
To ensure long-term protection, the
remedial treatment must satisfy the following basic
criteria:
- Any corroding reinforcement should be cleaned and then protected, preferably in an impervious alkaline environment.
- A strong bond should be created between the repair materials and the original concrete.
- Where necessary, repair materials should have a similar thermal expansion coefficient to the original concrete.
- Water vapor diffusion resistance should be similar to that of the original concrete.
- The system should offer active corrosion inhibition.
- The treatment should offer a high resistance to future carbon dioxide and chloride ion ingress.
- Materials should be physically compatible with any structural requirements. Particularly important is that they do not have excessively high compressive strength or higher modulus (and therefore increased rigidity) making them prone to failure. The ideal materials will have similar compressive strengths with lower modulus of elasticity to give minimum stress to the parent concrete.
- All materials should be supplied by a manufacturer with a proven quality management systems such as ISO 9000.
Depending on the nature of the structure, its function and exposure the following points may also be of importance.
- The structure should be aesthetically pleasing.
- Profiles and uniformity of concrete elements should be restored.
- Improvement of the environment by the strategic use of color can be considered.
Contractor Evaluation and Selection
In addition to the materials selection and assessment, a thorough evaluation of prospective contractors must be undertaken. This should include checking references of similar works and assessment of technical competence, management structure, any other relevant experience, and of course, financial standing and ability to fund the project throughout its duration.
