Selection of materials for repair is the most important tasks. They help to ensure durable and trustworthy repair of the concrete structure. The materials for repair of the concrete should be of the non-shrink type. They should also be compatible with parent material. Besides being of compatible properties, materials for repair of the concrete structure shall also be easy to apply. It needs no attention after the repair has been applied.
Essential Parameters: Materials for Repair of Concrete Structure:
- Low shrinkage properties
- Requisite setting/hardening properties
- Good bond strength with existing substrate
- Compatible co-efficient of thermal expansion
- Compatible mechanical properties and strength to that of the substrate
- Should allow relative movement (I.e. sealing of cracks and dealing with expansion joints)
- Curing requirement
- Alkaline character
- Low air and water permeability
- Aesthetics to match with surrounding
- Non-hazardous and non-polluting
A wide range of materials for repair of concrete is available differing in cost and their performance. Here are the materials for repair of concrete.
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Cement is the most important materials for repair of the concrete structure. Cement which has revolutionised construction technology in last two centuries is a major construction material even for repairing of the concrete structures as cement remains the basic material for concrete.
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Our Gharpedia team have already shared a lot of articles which provides detailed information on cement, its types and its various properties as an important building material.
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Aggregates are important materials for repair of the concrete structure in the construction industry.
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Our Gharpedia team have already shared a lot of articles providing the detailed introduction of the aggregates as building materials.
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03. Wire Meshes:
Wire meshes play a major role to reduce, restrict or arrest the cracks in the building and it serves as good materials for repair of the concrete structure.
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The places of use and size of mesh are interdependent, and its judicious use will help you to reduce the most of the separation cracks.
Use 3 inch to 14 inch wide chicken wire mesh for masonry wall and RCC beam joints, masonry wall and RCC column joints, and over and along all electrical conduits laid under masonry walls duly plastered.
Use 4 inch to 7 inch wide wire mesh for brick or block reinforcement work as per IS:2212-1991.
7 inch wide wire mesh should be used at all wall corners before corner plastering.
Remember wire mesh will not be useful in arresting structural cracks particularly expanding in nature. It is more or less a facial treatment which can be just a cosmetic touch.
Admixtures are the important materials for repair of the concrete structure. The advancement in material chemistry and technology have revolutionised construction industry and more particularly repairing industry.
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It has helped in overcoming the limitations of routine materials and is capable of imparting much-needed strength and durability to the structures. There are various types of admixtures available each with different properties satisfying different needs. Our Gharpedia team have shared a lot of articles which include the detailed introduction of admixture as building materials.
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05. Bonding Agents:
Bonding agents are natural, compounded or synthetic materials used to join the individual member of the structure without employing mechanical fasteners. The main types of bonding agent used in construction are specified below:
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(a) Latex Emulsion Bonding Agent:
- They are further classified as Styrene Butadiene (SBR) latex, Polyvinyl Acetate (PVA) latex (Non Re-Emulsifiable and Re-Emulsifiable), Acrylic Latex, and Epoxy Latex (Produced from liquid epoxy resin mixed with the curing agent or wetting agent or emulsifying agent).
- They are mainly used to bond fresh concrete to old concrete. They are also used in waterproofing sandwich layers of joint, are water resistant and also can be used as the anti-carbonation coating over concrete. It can be applied over moist surface also.
(b) Epoxide Resin Bonding Agent:
They are used to bond fresh concrete to cured concrete and concrete to steel. This will give monolithic bond capable of transmitting high stresses. They contain resins which are 100 percent solid. Resin possesses excellent water and alkali resistance.
They are also used for cold joints of concrete and cement plaster/guniting, reinforcing existing concrete structure or elements and also in jacketing of columns.
06. Corrosion Protection of Reinforcement:
Corrosion is major diseases in modern buildings. Most of the RCC buildings built in last 100 years in developing countries have corrosion problem. Due to the poor grade of concrete, inadequate cover to concrete, poor quality of steel, such buildings are undergoing repairs, particularly in coastal and corrosive areas. To treat the corrosion is therefore a major challenge. The advents of new chemicals have however made it possible.
(a) Alkaline Rust Converting Primer:
It is applied on rusted steel surfaces to form a complex compound. During the application of primer, the deoxygenating agent is formed which makes rusted steel surface more corrosion resistant.
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It protects the surface from further corrosion. They are sometime referred as “rust remover” or “rust killer”.
Conventional rust converters are water based and free from mineral acids making it safer for application and for the environment. It gives no fumes and is ideal for use in enclosed spaces. They are alkaline in nature and hence safe to use with concrete and embedded steel in concrete.
(b) Corrosion Inhibitors:
Corrosion inhibitors by virtue of its high vapour pressure and affinity for the embedded metal diffuse through densest concrete to reach the corroding steel. The main advantage is that the Corrosion inhibitors reach the unexposed side of reinforcement, too and ensures protection even in the presence of high amount of chlorides.
The corrosion inhibitors can be added to water during concrete mixing to impart corrosion protection to the embedded reinforcement. Corrosion inhibitors are used in structures exposed to the saline atmosphere, coastal structures, sewage structures, and swimming pool, etc.
07. Repair Mortars:
When it comes to materials for repair of cracks in concrete structure, repairing mortar plays an important role. They are used in external face repairing work, Concrete patching work, and reinforcement protection. They are generally blended with super plasticizers, micro silica, and polypropylene fibres.
Repair mortars such as rapid hardening mortar, rapid drying mortar, slump-free mortar, patching and repairing mortar, fine finished mortar are easily available in the market.
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08. Protective Coatings:
(a) IPN Protective Coating:
It is a system, which is based on epoxy-phenolic interpenetrating polymer network (IPN). It is used for protection of concrete structures and anti-corrosive coating to steel bars.
These systems are chemical and weather resistant, have high elongation and hence have excellent crack bridging ability and compatible with concrete substrates.
(b) Acrylic Protective Coating:
They are concrete specific coating that provides protection against chloride ion penetration, carbonation, UV radiations and weathering effect. They have excellent crack bridging ability and excellent biological resistance. It can be used in the painting of external surface of concrete buildings.
(c) Super Plasticizer Modified Cement Paints:
Ordinary cement paints can be mixed a suitable melamine based super plasticizer to enhance the quality, durability and life of the paint. It is also used in the painting of external surface of concrete buildings.
The selection of materials for repair of the concrete structure is an intricate process which may put home owner in the difficult situation. Hence above are general guidelines which help to select right materials for repair of the concrete structure. It is advisable to appoint a consultant, if the repairing work is major.