Reinforced concrete corrosion - A silent killer

Concrete structures are typically designed for a lifespan of 50–125 years. To keep these structures in service, a significant amount of infrastructure budget is reactively put towards repairs, rather than investment in new construction. The largest contributing factor for the high cost of repairs and for infrastructure not meeting its service life expectancy is corrosion of reinforcement found in concrete.

Water movement through the concrete allows waterborne chlorides to penetrate reinforcing steel and causes corrosion, resulting in expansive pressure and cracking. Once cracking has started, water movement increases and the rate of deterioration increases leading to a drastically shortened lifespan.

The problem is that concrete on its own is not waterproof. Concrete is filled with interconnected capillary pores that allow the concrete to ‘breathe’, but also allow water to pass through.

Due to concrete’s high pH level, it is typically good at protecting reinforcement. The steel reinforcing bars are passivated by an iron oxide film that protects the steel. However, the passive layer can break down over time due to atmospheric carbon dioxide, which through carbonation, lowers the pH of the concrete until the passive layer becomes unstable. The passive layer can also be rapidly broken down by aggressive chemicals such as chloride brought in by water. Once the passive layer is compromised, reinforced steel will begin to corrode if there is moisture and oxygen present at the surface of the steel. Mitigating water ingress through the concrete over its lifespan is critical to the overall integrity, durability and sustainability of new construction.

Prevention is always better than a cure – and in waterproofing, this is no different.

The most effective way to waterproof your concrete is during the building stage. Waterproofing admixtures are products added to the concrete during mixing to make the concrete water-resistant by blocking the passage of water through capillary pores and cracks.

The most unique and effective long-term feature of Kryton crystalline technology is the ability to ‘self-seal’. When moisture enters the concrete, new crystals form and grow, blocking and filling any cracks that form due to drying shrinkage, seismic activity, etc. Crystalline technology may help to reduce the long-term maintenance and repair costs and extend the life of a concrete structure.