Concrete is a strong and durable material; however, over time it can develop cracks or spalling that, if not addressed promptly, could have serious consequences. To address these issues correctly, it is essential to first identify their causes.
The formation of cracks can be due to:
- Poor pouring of the structure.
- Thermal variations.
- Concrete shrinkage processes.
- Freezing and thawing of the ground.
- Improper assembly.
- Corrosion of reinforcing steel.
- Exposure to salts and sulfates.
- Mechanical impacts.
Not all cracks pose an immediate structural risk. For example, horizontal cracks with a narrow opening can be considered benign. In harsh environments, their width should not exceed 0.2 to 0.3 mm, while outdoors exposed to frost, humidity, or UV rays, the recommended limit is up to 0.4 mm.
The choice of repair material depends on the width, orientation, and progression of the crack, as well as the condition of the concrete (whether it has cured or is still active). Common materials include epoxy resin, mortar-cement mixtures, liquid glass (silicate), polymer sealants, and self-expanding cords.
The 3 most widespread and effective methods
- Injection (directed injection)
It consists of drilling holes oriented towards the crack and injecting under pressure a special mixture—such as mortar-cement, epoxy resin or liquid glass—that penetrates and solidifies, guaranteeing adhesion and preventing the crack from spreading. - Spraycrete (pneumatic projection or spraycrete)
uses a special mixture of mortar or cement reinforced with polymers (such as resin, bitumen, or latex), sprayed at high pressure onto the damaged surface. This creates a new layer that fills and reinforces the affected area. - Sealing with polymer mixture
This method involves filling the crack with a mortar-cement mixture enhanced with polymers (to improve adhesion and flexibility), followed by the application of a sealant over the surface, which helps to waterproof and protect the repair.
Additional tips for a better result
- Pre-cleaning : Before applying any method, remove dust, loose particles, or material debris with a wire brush or compressed air. A clean surface ensures better adhesion.
- Humidity control : Outdoors, wait for dry weather before carrying out the repair. Excessive humidity can reduce the effectiveness of the applied products.
- Prepare the crack : In very fine cracks, it is advisable to open them a little with a tool (widen them in a “V” shape) to facilitate the penetration of the filling material.
- Post-repair protection : After repairing, protect the surface with a waterproof sealant or special concrete paint. This will extend the life of the repair.
- Regular maintenance : Inspect concrete structures periodically. Addressing small cracks promptly prevents them from becoming larger problems.
- Consult a professional : If the cracks are very wide, run through the entire structure, or continue to grow, it is best to consult an engineer or specialist to rule out structural risks.