Concrete or steel, corrosion doesn’t discriminate: Why we should rethink durability

Corrosion silently eats away at both concrete and steel, compromising the structure and safety. As architecture intersects with science, understanding corrosion behaviour and prevention is crucial for building long-lasting, future-ready structures.

Both concrete and steel corrode under adverse external conditions. While steel corrosion is evident in the form of rust, with which everyone is acquainted, concrete corrosion is still under a stage of ignorance, and even skilled engineers tend to overlook the issue.

Both these types of corrosion have their respective conducive conditions under which they corrode.  Identifying the magnitude of deterioration in structural parameters under corrosion is the first step towards mitigating it. Concrete corrosion broadly would mean depolarisation of the concrete matrix. Its homogeneity is reversed, and the concrete turns heterogeneous under the corrosion phenomenon.

Surveying the corrosion potential of corroded concrete involves conducting the following tests: an ultrasonic pulse velocity test, a carbonation test, and a water permeability test. For corroded steel structures, the following tests are conducted to assess the damage potential: ultrasonic thickness measurement, magnetic particle test, dye penetration test, and microstructure analysis.

Every test has its significance, and the results of these tests, as well as other physical tests, must be comprehensively evaluated to determine the root cause of potential corrosion and its probable magnitude.

The protection methodology for corroded concrete and steel structures, as is universally accepted,  involves protecting them from the source of corrosion. Accordingly, a protective treatment that is compatible with resisting the corrosive attack of each respective chemical and corrosive condition that aggravates the corrosion process is to be designed with the help of materials science and executed according to its standard application process.

Currently, some induced methods are also gaining momentum, where the corrosion potential, in terms of equivalent current, is controlled by breaking the corrosion circuit. Although this concept has some limitations, it is found to be useful under specific situations. As mentioned earlier, the material selected for protecting concrete or steel structures needs to be compatible with the chemical and corrosive conditions to resist. Some chemicals become aggressively corrosive under high pressure, temperature, and humidity; hence, the selected protective treatment is required to perform under all these corrosion accelerators.

Preventive measures to be taken during the design of concrete and steel structures to reduce the incidence of corrosion include avoiding continuous exposure to corrosive conditions, designing wastewater outlets to function without choking and implementing effective waterproofing treatments.

This is the era of AI, which is gradually supplanting human intelligence. Regular inspection of the structure, especially from a forensic inspection angle, LiDAR and drone-type surveys, and in-built instruments at strategic locations are a few of the many means through which corrosion can be detected early. A Residual Life Assessment study with technological support is an emerging trend in this direction. Creating a structure is a massive task. Let us put in a holistic effort to ensure that it doesn’t corrode!

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