Corrosion is one of the biggest structural threats in reinforced concrete structures, causing the reinforcement to weaken over time and the life of the structure to be seriously shortened. In particular, penetration of moisture into structures can cause steel reinforcement to oxidize and lose its durability.
This process jeopardises the safety of the structure by reducing the strength of the load-bearing systems. One of the most effective methods to ensure the longevity of structures and to minimise corrosion-related damage is waterproofing. Waterproofing, performed with the right materials and application techniques, provides strong protection against moisture damage, extending the life of the structure.
In this article, after answering the question of “What is corrosion?”, we will discuss the critical role of waterproofing in combating corrosion and consider the most effective protection methods.
What is Corrosion in Reinforced Concrete? What are the Factors Affecting Corrosion Development?
The problem of corrosion in reinforced concrete is one which is frequently encountered and affects structures throughout their lifetime. Corrosion is a natural process where metal surfaces oxidise, losing their structural integrity and in some cases the metal, in this case steel, expands. This expansion can cause the bond of the concrete to the reinforcement to be lost, exposing the steel and accelerating the corrosion and weakening the structure.
The main causes of corrosion:
Moisture: Humidity in the air accelerates oxidation reactions and triggers corrosion.
Chemical Substances: Acidic substances, such as sulphates which are commonly found in cements, can cause corrosion by directly affecting metal surfaces.
Electric Current: Electro-chemical reactions can increase corrosion on conductive metal surfaces.
High Temperature: Hot environments may increase the risk of corrosion, causing materials to deteriorate more rapidly.
Therefore, protecting steel reinforcement within concrete, from moisture, salts (or sulphates) and gases through cracks in the concrete is critical.
How Do Corrosion Effects Occur in Reinforced Concretea
The biggest factor that threatens the life and durability of structures is water. Much of the building stock in the UK contains reinforced concrete
Moisture penetrating into a structure can cause corrosion of the reinforcement, causing the load-carrying capacity to decrease significantly and fall below the required design values, thus posing a risk to the safety of the structure and reducing service life.
Corrosion is usually caused by water or moisture vapour entering the structure and reaching the steel reinforcing, through cracks or imperfections in the surface of the concrete.
Water reaching the reinforcement expands the steel and breaks down the concrete over time. Corrosion produces enough pressure to crack the concrete shell due to this volume increase. The volume of corroding steel can increase by as much as 2 to 4 times.
Corrosion shortens the life of building materials, reduces their performance and can lead to costly repairs.
How to Prevent Corrosion Damage in Structures? (Corrosion Protection Methods)
In order for structures to maintain their durability for many years, during the construction phase ground surveys should be conducted to understand the sites’ unique water table profile and appropriate waterproofing strategies should be considered. When designing a structure correct drainage planning should be implemented to keep the building safe from the effects of water and moisture. Waterproofing should be applied to foundations and to any external walls which are below the ground level, thereby protecting any below ground reinforced concrete structure from the effects corrosion caused by water ingress.
In particular, basements should be ventilated to ensure the extraction of humid and dirty air. Cracks and holes should not be allowed to form on building facades, cladding, or within rain gutters.
Specialist construction chemicals should be used within concrete mixes that are to be poured below ground level. These additives create a waterproof concrete surface as they react with the water and free lime in the cement mix to form crystals within the capillary voids and pores of the concrete, which in turn prevents ingress of water, moisture vapour and sulphates. Since these chemicals are reactive, they continue to react with moisture molecules throughout the life of the concrete thus protecting the steel reinforcement from corrosion caused by these elements. Whilst these chemicals create a waterproof structure, they still allow the structure to breath, preventing damp smells.
It should be noted that all concrete and reinforcement is designed in accordance with the appropriate building standards, and the correct concrete cover over any steel reinforcing is in accordance with all technical requirements and current legislation.
In existing buildings some structural roof elements may cause corrosion to begin and spread. For example, rainwater gutters, gullies, downpipes, etc. should be inspected and repaired if necessary.
Ventilation of airless spaces, especially basements, should always be ensured.
Reinforcement Corrosion Repair
Once corrosion of the reinforcement has reached a certain point, there is often no effective repair method. However, repairs can be carried out in structures where levels of damage are not too extreme, reinstating original design strengths and preventing damage from spreading.
First of all, renovation begins with cleaning damaged areas and steel reinforcement to remove any corrosion layers. Corrosion should be cleaned away with compressed air, so that in any areas where corrosion is observed, metal reinforcements are completely cleaned of rust before any repair work can be carried out. Steel surfaces should be primed with an appropriate primer to prevent any future corrosion and then covered with a suitable (cement or epoxy based) corrosion control mortar. Once these have cured appropriate waterproofing should be applied to prevent any future moisture ingress.
How to Choose the Right Waterproofing Materials to Increase Corrosion Resistance?
Waterproofing materials play a vital role in creating long-lasting structures. These materials are resistant to environmental factors for many years and significantly reduce the risk of corrosion when used properly in construction projects.
Waterproofing products and applications vary widely in their properties.
Structural Waterproofing:
As we have seen, waterproof concrete can be created by introducing additives to the mix. This method commonly known as ‘structural waterproofing’
Structural waterproofing involves the use of powdered or liquid construction chemicals added to concrete during installation. These additives improve concrete quality, make handling easier, and provide impermeability by reducing the ingress and effects of water.
Surface waterproofing:
As we have seen, waterproof concrete can be created by introducing additives to the mix. This method commonly known as ‘structural waterproofing’
But this is not the only way to create an impermeable layer between moisture in the environment and the steel reinforcement within. There are many surface applied waterproofing materials available which can be applied to the concrete after it is installed. These ‘surface applied’ waterproofing systems can be applied on their own or in addition to structural waterproofing.
Surface applied waterproofing systems often offer additional benefits over structural waterproofing such as flexible crack bridging, decorative finishes or chemical resistance.
Therefore, waterproofing materials should be selected according to the structure use, water pressure in the environment, local ground conditions, any movement expected in the structure, possible loads on the product and details in the structure.
Preventing corrosion of steel within reinforced concrete using structural waterproofing and surface applied waterproofing should be considered to ensure a safe and long life of buildings.
Waterproofing is vital for protecting and extending the life of structures. FİXA protects the value of structures and provides a safe living space with structural and surface waterproofing materials for co rrosion-resistant structures. These products reduce the risk of corrosion by protecting structures from the harmful effects of water and extend the life of the structure.
For detailed information and offers about FİXA Waterproofing Products, you can reach us at +44 (0) 2081760680 and info@fixaco.uk e-mail address.
FAQ
1- What is corrosion and why is it important in the construction sector?
Corrosion is the deterioration or wear of metal, concrete or other building materials due to environmental factors. In the construction sector, corrosion threatens structural integrity, increases costs and endangers safety. Therefore, preventing and managing corrosion is of great importance.
2- What are the most common types of corrosion in construction?
The most common types of corrosion in the construction sector include rust (in iron and steel), carbonation and chloride effect in concrete, and also galvanic corrosion. Each type occurs in different ways depending on the type of material and the environmental conditions.
3- What methods can be used to prevent corrosion?
There are various methods to prevent corrosion. These include protective coatings such as paint and galvanization, the use of passivating agents, cathodic protection systems, and the preference for corrosion-resistant alternatives in material selection.
4- What measures can be taken to prevent corrosion in concrete?
The measures that can be applied to prevent corrosion in concrete include correct mixture design, appropriate water/cement ratio, a good curing process, the use of water-proofing additives, and a sufficiently thick protective concrete coating.
5- What methods are used to detect corrosion?
A variety of methods can be used to detect corrosion. These methods include techniques such as visual inspection, ultrasonic thickness measurement, electrical resistance measurement, as well as laboratory tests. The combination of these methods helps to more accurately assess the current state of corrosion.
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