Concrete is undoubtedly the element with the greatest presence in our infrastructures and in general in the world of construction, and although it is resistant and durable as a base, it is not immune to the passing of the years and even less when it comes to reinforced concrete. We offer best in industry products and services for Civil Works Contractors.
it is necessary to contemplate effective repair measures and, above all, protection, and prevention. Which capable of lengthening the useful life of these infrastructures.
Concrete has weaknesses, the most important being its tendency to crack and its affectation due to exposure to environmental conditions as reinforcement corrosion.
Resistance To Compression
Concrete is an element with remarkable resistance to compression. Which makes it the basis of construction in the modern era. On the contrary, its tensile strength limit. When the reinforcements oxidize, the iron oxides increase up to 4 times in volume compared to the original reinforcement.
Causing traction in the concrete of the coating that results in the appearance of cracks and breaks. In addition, when iron oxidizes it dissolves and therefore the reinforced concrete elements lose their structural capacity.
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Elements For Corrosion
For corrosion to occur, the following elements must be present: iron, oxygen, water, and optionally chlorides. Once these elements are present in the reinforced concrete, the iron reacts with water and oxygen, giving rise to the formation of iron oxides. Normally the first layer of oxide that forms is dense and adheres so well that it even performs a protective function on the reinforcement, but when this layer is broken due to carbonation processes and/or the presence of chlorides, corrosion of the the armors.
What Phenomena Favor Reinforcement Corrosion?
The main phenomena that favor reinforcement corrosion are carbonation and the presence of chlorides.
Corrosion Due To Carbonation
Carbonation is the phenomenon that occurs when the calcium hydroxide that is present in concrete reacts with atmospheric carbon dioxide in a gas state, giving rise to the formation of solid calcium carbonate and water. These carbonates that form in the concrete cause a drop in pH.
Corrosion Due To Alkaline Ph
New concrete has an alkaline pH above 9 which protects the reinforcement, passivating it and preventing corrosion in the presence of water and oxygen. When the pH of the concrete drops below 9. Its protective capacity loose and the reinforcements leave them unprotected.
Carbonation Process
It is at that moment when favor the corrosion process. Carbonation is a phenomenon that affects all concretes and that advances from the outside in like a front. The carbonates formed seal the concrete. So that the advance of the face tends to stop over time. In industrial environments, with a greater presence of CO2, concrete has an easier time carbonating.
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Pitting Corrosion
On the other hand, chlorides are electrolytes that catalyze the corrosion reaction and act as accelerators or promoters of it. Active corrosion begins when the ratio between the Cl – ion and the OH – ion is between 2.5 and 6, at concentrations of approximately 300 pm. Corrosion favored by the presence of chlorides also called pitting corrosion.
As distribute the chloride heterogeneously. With areas of higher concentration. Corrosion acts excessively at specific points. Giving rise to the pitting phenomenon where the reinforcements even section.
How To Protect Reinforced Concrete Against Corrosion?
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The standard for Repair and Protection of concrete structures contemplates the different methods of protection of concrete structures. From the application of water repellents, to impregnations or protection membranes. Within these solutions we could place the use of waterproofing agents, corrosion inhibitors, anti-carbonation paints, waterproof membranes and chemical re-alkalizers.
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Water Repellents Reduce Carbonation
Water repellents and inhibitors are transparent liquid products that penetrate and migrate through the concrete surface without forming a layer (they do not alter the surface). Water repellents act by reducing surface tension and therefore the entry of water and chlorides.
In the case of the product, to the waterproofing effect we must add the capacity to increase the resistivity of the concrete (its capacity to protect the reinforcement) and to inhibit the corrosion of the reinforcement, reducing the corrosion rate of the reinforcement in more than 90%.
Effectiveness Of Protection Systems
The application of protection systems in the form of membranes or especially recommend coatings. Due to their versatility and effectiveness in cases where does not contaminate the concrete structure with chlorides.
Silane-Based Corrosion Inhibitors Against Carbonation
Where other techniques such as the use of silane-based corrosion inhibitors are more effective and even complementary. The protection offered by these membranes, applied on the concrete surface, against carbonation is related to the quality of the material used and the dry application thickness.
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