How does corrosion happen in concrete?
Corrosion in reinforced concrete is one of the main concerns when talking about reinforced concrete structures. Typically, the reinforcements embedded into the concrete are protected by the high pH environment of the Portland cement around the reinforcements, which prevents corrosion from occurring (typically with pH levels around 12.5 or higher). However, when chlorides and other contaminants begin infiltrating the concrete through cracks and gel pores, it alters the state of the pH (pH of 10 or less), lowering it to levels where corrosion can occur on the reinforcements.
What causes corrosion in concrete?
There are many reasons why corrosion occurs in concrete, carbonation, electrolysis, alkali-aggregate reactions, excess moisture penetration, chemical contamination, and the actual makeup of the surrounding Portland cement. Below we look at some of these types of corrosion in detail.
Water Leakage into Concrete: If the concrete has a high permeability, then excess water in the environment from leaky pipes, nature, or high moisture environments can lead to water seepage into the concrete, which acts as an electrolyte within the concrete and accelerates corrosion.
Carbonation: Over time, the free hydroxide within the concrete reacts with atmospheric carbon dioxide and forms calcium carbonate, which results in shrinkage cracks. These shrinkage cracks make the concrete more suspectable to penetrating moisture. This moisture and exposure change the alkalinity of the concrete, bringing it to a level that allows for corrosion of the steel reinforcements.
Impurities in Mixing: When the water used to mix the concrete contains impurities, it can affect the result. As per the IS:456, if the total organic compounds are more than 3000 mg/l, sulphates are more than 500 mg/l, or chlorides are more than 1000 mg/l, then it leads to steel corrosion in concrete. ult of the concrete.
Exposure to Seawater: When concrete is exposed to seawater, the effects are determinantal if the permeability of the concrete is especially high. Seawater contains extra elevated levels of chlorides, which accelerates corrosion within the concrete.
Alkali-Aggregate Reaction: Alkalis like sodium oxide (Na2O) and potassium oxide (K2O) are present in the cement which react with silicious constituents of aggregate and cause the cracking in concrete. Hence, lowering of alkalinity promotes the corrosion of steel in the presence of moisture.
What happens when the reinforced steel in concrete corrodes?
When the reinforced steel corrodes, the rust that accumulates around the steel creates outward pressure on the concrete surrounding the reinforcement. Because the rust is a new material forming within the concrete, it takes up more space than the original rebar. From this pressure caused by the new material, the concrete begins to crack and degrade.
How to prevent corrosion in concrete?
The best way to prevent corrosion in concrete is by a corrosion inhibiting admixture. Corrosion inhibiting admixtures either extend the natural corrosion inhibiting properties of the Portland cement or they reduce the corrosion rate of the embedded metal and there are some admixtures that provide both benefits.
What are the ways to protect concrete from corrosion?
There are several ways to protect concrete from corrosion. Corrosion inhibiting admixtures, talked about above, are one of the best ways to preventatively stop corrosion from occurring in your concrete. Another fantastic way to protect concrete from corrosion is using SurCoShield. SurCoShield solutions are proven to penetrate concrete surfaces to restore and enhance cement phase properties for durability and hardness, as well as abrasion and impact resistance.
The chemical resistance of concrete is improved through neutralizing reactive cement components and rendering them chemically inert. SurCoShield renders concrete surfaces impermeable to chemical solutions, providing protection for incidental chemical spillage. Surtreat’s concrete surface repair solutions are chemically reactive and a permanent solution existing entirely within the concrete microstructure cannot be peeled or scratched off. Water-repellent components are added to SurCoShield solutions depending on project requirements.
SurCoShield is a surface protective agent and corrosion inhibitor that penetrates the concrete surface. All the benefits of this application are internal to substrates and encompass the protection of architectural components such as brick, block, mortar, and stone.
How to repair corrosion in concrete?
SurCoRepair is a group of concrete repair products used to restore the properties of deteriorating concrete structures without extensive remove and replace efforts. Our products also protect new surfaces. SurCoRepair can be used to restore and protect structures’ brick, stone, and block components.
SurCoRepair chemical solutions target the causes of the deterioration as opposed to just addressing the symptoms such as spalls and delamination. The resulting improvements to the properties of treated substrates allow the longevity of structures to be increased. Concrete repair solutions penetrate fully to harden surfaces, restore bonds, reduce water permeability, and increase chemical resistivity of treated substrates.