Concrete Repair

What Does Concrete Repair Mean?

Concrete repair is the process of fixing a hardened concrete surface that, over time, has lost the ability to hold the binding concrete materials together due to damage or environmental exposure. Concrete repair is appropriate for cracks, physical impacts, chipped out surfaces or surface scaling.

Planning a project's reinforced concrete structure is crucial to the overall health of the structure being developed. Concrete structures, when exposed to elements like salt water, CO₂ and chloride, could be penetrated all the way through the concrete to the steel reinforcement, which results in corrosion.

Corrosion that is not properly monitored and managed has the ability to deplete the durability of the structure and eventually weaken it, which in many cases has serious safety risks. Corrosion rate tends to increase the longer the structure stands; so it's important to test and maintain them routinely.

Corrosion in reinforced steel and concrete is a worldwide problem that causes quite the wide range of issues—including economic, esthetic and usage issues. In cases where corrosion effects are considered in the design phase and the right decisions are made before and during construction, structures can be built to resist corrosion for a longer period of time.

Corrosionpedia Explains Concrete Repair

Corrosion in reinforced steel occurs in concrete structures. Steel corrosion produces rust, which will expand if unmanaged. This expansion, in turn, causes a build up in internal pressure until the concrete fails. This is called spalling. Spalling is the leading cause of concrete disfiguration and means special attention should be paid to preventing corrosion in reinforced steel—especially when it's a matter of safety.

Although corrosion is a serious issue in reinforcing steel, it can be reduced with the use of proper and rapid identification of faulting placements. Concrete mixtures designed for exposure to harsh and unfavorable environments will reduce the opportunities for corrosion. Rapid test methods also help by quickly approximating how corrosion-resistant the concrete in question is.

There are various ways to repair a concrete surface, all of which require some specific procedural steps, such as:

• Cleaning the concrete surface to ensure no loose material—such as chipped out concrete flakes, granules, oil, grease or dirt—exists. (A chisel or a sledgehammer can be used if required.)
• Using a bristle brush and broom to clean and scrub the area to be repaired.
• Flushing the area with water to ensure no loose material is left behind.
• Using one of the various cement repair solutions available—such as a vinyl-patching compound that can be mixed with water or any sort of bonding agent. A bonding agent is usually preferred.
• Troweling the mixture into the cracks and broken areas and tapping properly to remove air gaps. Then, level the surface and make it smooth.
• Allowing the surface to dry

Corrosion occurs when materials that are harmful to steel—such as CO₂ and chloride from de-icing salt—penetrate concrete and reach the structure’s steel reinforcement. Due to electrochemical reaction, electrons migrate from the anodic zone to the cathodic zone, releasing ferrous ions at the anode and hydroxide ions at the cathode. This would lead to a potential difference between the anodic and cathodic areas on the surface of the steel reinforcement. This creates rust as a by-product. Since rust occupies a larger volume than steel, it results in internal pressure—which causes the surrounding concrete to crack and become damaged. These cracks find their way to the surface of the concrete, which causes even more CO₂ and chloride to penetrate the concrete. When this happens, the entire corrosion process speeds up.

Corrosion is never just about repairing the current issue; it's also about diagnosing its cause—such as leakage, inadequate cover, poor concrete grade or an aggressive environment.

Impressed Current Cathodic Protection

Cathodic protection (CP) is the main alternative to patch repair.

Impressed current cathodic protection (ICCP), in particular, involves a small permanent current passing through the concrete with the goal of halting steel corrosion. ICCP can vastly reduce the need to remove and repair concrete, as it limits repairs to only the spalled and delaminated concrete. And, once ICCP has been installed, it can control corrosion long-term—eliminating future deterioration even in concrete severely contaminated with chloride or carbonation.

However, selecting the right anode system is vital when designing a durable and efficient ICCP system. If the wrong anode system is selected, the ICCP system may perform poorly and won't last as long.