CONCRETE PATHOLOGIES

Today we would like to remind you of the most common pathologies of concrete structures.

The #concrete is a structural element that has its natural deterioration due to the passage of time and can be affected by external agents, as well as construction or design defects. The most common causes of the appearance of pathological processes in reinforced concrete structures are:

• • Excessive loads and inadequate construction designs

• • Structural movements by entries

• • Insufficient reinforcement coating

• • Excessive proportion of water or cement in the mixing process

• • High heat of hydration in cement

• • Environmental attacks: heat, cold, humidity, freeze-thaw...

• • Chemical attacks: reaction with environmental agents

The following are the main pathological processes that can be encountered:

Cracks

Although most cracks do not compromise the resistance of the structural elements, they can favor the appearance of other secondary pathological processes such as reinforcement corrosion or carbonation. The repair of these cracks not only responds to aesthetic reasons, but also to functional and durability issues.

These are some of the techniques for repairing cracks depending on their origin, although in order to carry them out we must make sure that they are inactive.

- Injection with epoxy resins or mortar grouts.

- Sealed

- Sewn with metal staples.

- Stitched with carbon fiber bands

I attach an image of the sealing and injection of some cracks that we made in the Fraga Tunnel.

Clogging and gravel nests:

Cokers and gravel nests are generally due to a lack of fluidity of the concrete in relation to the amount of passive steel or poor vibration of the concrete. They can also be caused by too rapid evaporation of the mixing water or by a leak in the formwork. The repair of these lesions responds to functional and durability issues, in order to avoid the appearance of other secondary pathological processes.

The most common treatment for the repair of cracks and gravel nests is the application of patching mortars, either aesthetic or structural, after preparation of the substrate and application of a bonding bridge when deemed appropriate.

Carbonation

It is one of the main problems of reinforced concrete. It is of chemical origin and is produced when the CO2 in the environment reacts with the calcium hydroxide in the mixture to form calcium carbonate, producing a drop in pH (acid) that favors the corrosion of the reinforcement. Corrosion increases the volume of the reinforcement, causing fractures, spalling and loss of cohesion in the concrete. The more ways of penetration of humidity and oxygen there are in the concrete (porosity, coking, gravel nests, fissures, cracks...), the faster and more intense the oxidation of the metal will be.

The most common treatments when corrosion has not been initiated are:

- Corrosion inhibitors

- Anti-carbonation paints

- Water repellent treatments

Treatments when corrosion has been initiated will depend on the degree of involvement:

- Localized sanitation

- Reinforcement of the structure

- And in the worst case, demolition.

I attach an image of the concrete repair work we are carrying out at the Seva Wastewater Treatment Plant.

Other pathologies of chemical origin.

Aluminosis. Pathology of chemical origin that involves an increase in porosity which implies a decrease in the mechanical strength of the concrete and a loss of adhesion with the reinforcement. Cement with aluminosis is also much more prone to carbonation. Depending on the state of the structure, we would proceed from the repair of fissures and cracks and the preventive treatment against carbonation to the treatment of the reinforcement and the reinforcement and repair of the structure.

Sulfate ion attack in the form of complex salts, highly expansive, which promotes cracking and deterioration of the concrete.

Arid-alkali reaction, another expansive reaction that favors cracking and deterioration of the concrete.

As we have seen, there are various types of injuries and pathological processes that affect concrete structures, for which there is no single solution, so it is essential to study an individualized treatment for each case.

At RVF we work with specialized engineering companies and we have great experience in structural repair works in projects of different types and complexity.

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