The corrosion of reinforcing steel in concrete is a global problem that causes economic, aesthetic, and utilization issues. The corrosion of steel reinforcements in concrete accelerates in harsh environments, especially in coastal, tropical, or desert areas where the high salt levels and the extreme temperature tends to accelerate the corrosion rate. While the most exposed elements deteriorate first, in the case of concrete, much of the actual corroded reinforcement is not visible. It may take anywhere between 5 to 15 years of active corrosion before cracks initiate in the concrete.
Corrosive atmospheric elements like deicing salts and calcium chloride set-accelerators, fast-track construction practices, increased construction in aggressive environments, lower cover depths and poor construction practice, including inadequate supervision and changing cement composition resulting in finer grinding and lower cement contents, are some of the deciding factors of increasing corrosion in reinforced concrete structures.
One of the most significant advantages of planning for corrosion control and mitigation is that the service life of an asset is extended, leading to reduced maintenance time and costs. Subsequently, We cannot overlook that reduced maintenance requirements are bound to increase the asset’s overall utilization value and improve its environmental sustainability. In harsh environments, buildings will have stronger corrosion resistance and therefore possess better concrete durability. Increased durability will mean fewer repairs, greater structural integrity, and longer service life, leading to a more sustainable structure.
The method for concrete repair entirely depends on the amount of damage to the concrete reinforcement. If the corroded steel has already lost its substantial sectional area due to corrosion, replacing that steel with the rebar/lap method is necessary. If the rusted reinforced steel has only minor corrosion, it has not started to degrade yet and can be removed by applying rust remover with mechanical brushes. Another technique by which corroded structural elements are rehabilitated to regain their original load carrying capacity is by repairing corroded or deteriorated steel reinforcement and prestressing strands.
Traditionally, the cracked and degraded concrete is removed up to a depth of 20 to 30 mm underneath the reinforcing steel bars to fully expose the corroded area and move the degraded concrete away from the unaffected steel. Once the damaged metal is removed, the steel is treated for corrosion or may need to be replaced entirely. Lastly, concrete repair mortars are applied to the surface. Modifying the repair mortars with a polymer helps improve adhesion and resist the ingress of corrosive contaminants. Coatings are commonly used with patch repairs to further reduce advancing carbonation and chlorides.
Corrosion affects all concrete buildings and structures worldwide, with an estimated annual cost of billions of dollars to national economies. Therefore, owners of high-value assets must understand the cost implications of ignoring the effects of corrosion on concrete buildings and structures. However, suppose corrosion protection of reinforced concrete structures is considered in the design phase, and the right decisions are made before construction. In that case, we can ensure that buildings are built to resist corrosion from the beginning – making concrete repair solutions a history.