What is Concrete injection?
Concrete injection is a repair method aiming to return concrete structures to their original or near-original condition. It enhances strength, stiffness, density, and the concrete's protective barrier against aggressive agents and is used where there is a need to consolidate a structure or exclude water and air from contact with reinforcement.
This method involves injecting specific materials into cracks or voids to seal leaks, repair damage, and make structures watertight, preserving or restoring structural integrity.
What is Concrete injection used for?
Corrosion and Expansive cracks in special conditions in combination with other repairs.
How does Concrete injection work?
Concrete injection is a specialized repair method designed to address and remediate structural damage and water ingress in concrete structures.
Injection materials for cracks and voids in concrete fall into three main categories: force transmitting fillings, which bond surfaces and transmit forces to restore load bearing capacity; ductile fillings, offering flexibility to withstand minor movements; and swelling fitted fillings, capable of expanding through water absorption for repeated use.
The procedure utilizes two main types of materials: Hydraulic Injection Materials (HIM) such as grout and mortars, which are ideal for bonding concrete surfaces to restore structural integrity, and Polymeric Injection Materials (PIM) such as epoxy or polyurethane, versatile in addressing various repair needs including force transmission, accommodating minor movements, and sealing against water through swelling.
The selection between HIM and PIM is guided by the specific repair objectives, whether to restore the structural capacity compromised by cracks or to seal the structure against environmental elements and is influenced by the crack characteristics, desired repair outcomes, and environmental conditions surrounding the structure.
The aim of concrete injection is to not only address immediate repair needs but also to ensure the long-term durability and functionality of the structure by choosing the most effective method and materials that cater to both structural improvements and surface sealing against environmental ingress.
How do I carry out and control Concrete injection for concrete structure?
Concrete injection based on BS EN 1504-5 and BS EN 1504-9 uses the following procedures:
Asses the structure to determine the extent of damage, its likely causes and the repair requirements i.e. regain structural integrity, block water ingress or both.
Select the appropriate injection material based on your repair requirements. HIM for force transmitting fillings, especially where high structural strength is needed. PIM for all categories, including ductile and swelling fillings, allowing for flexibility or water swelling properties.
Prepare the crack/void for injection. First clean the area thoroughly to remove loose material and contaminants that may impair the bonding of the injection material. For wider cracks or significant voids, consider installing injection ports at regular intervals to ensure full penetration of the repair material.
For HIM, mix the material according to the manufacturer's specifications. Use a suitable pump to inject the material into the crack or void until it is fully filled.
Similar to HIM, prepare and inject the PIM, ensuring it is suitable for the intended repair category (force transmitting, ductile, or swelling).
Allow the injected material to cure as recommended by the manufacturer.
Once cured, remove any protrusions or injection ports and finish the surface to match the surrounding area.
Perform tests to ensure the injection has achieved its intended purpose, such as water tightness tests for ingress protection or load tests for structural strengthening.
Document the repair process, materials used, and any testing results.
Develop a maintenance plan to monitor the repair area and adjacent sections for future preventative measures.
What equipment and expertise are required for Concrete injection of concrete structures?
An injection pump suitable for the selected material type (HIM or PIM).
- Injection packers, ports and couplers for sealing and injecting into concrete cracks.
Cleaning equipment such as brushes, air blowers, or vacuum cleaners for preparing the crack or void.
Mortar, grout, epoxy or polyurethane filling materials.
What are the advantages of Concrete injection for concrete structures?
Concrete injection is a cheap, cost-effective repair solution offering a preventive approach to further damage, thus saving money in the long term.
Allows rapid repairs requiring no excavation and creating minimal disruption.
Concrete injection allows for precise application of the repair material directly into the cracks or voids, ensuring that the repair material is exactly where it's needed for optimal strengthening and sealing.
Repairs are extremely durable, capable of lasting years and preventing future damage.
Concrete injection is a versatile method that can be utilized for various repair types, including cracks of different sizes and depths, and in both interior and exterior settings.
Concrete injection can be more environmentally friendly compared to other repair methods that may require significant demolition and waste.
By addressing and repairing cracks and voids, concrete injection enhances the structural integrity and safety of the building or structure. It prevents minor damages from escalating into major structural failures, ensuring the safety of occupants and user.
What are the disadvantages of Concrete injection for concrete structures?
Concrete injection alone is not effective for repairing concrete affected by Alkali-Aggregate Reaction (AAR), Internal Sulphate Attack (ISA), or corrosion. Additional protective measures like chloride extraction, concrete replacement or coatings might be necessary.
High injection pressures required for fine cracks can sometimes cause additional fracturing of the concrete if not carefully controlled. This could potentially widen existing cracks or create new ones, especially if the injection is not properly executed.
What are the limitations of Concrete injection for concrete structures?
Injection of corrosion cracks or expansive cracks is only effective if the initial cause of the cracking is addressed by other repair techniques, ensuring no residual reactivity remains.
The effectiveness of concrete injection is limited for cracks wider than 0.2 mm; narrow cracks are more suitable to be repaired with this method.
The success of concrete injection also hinges on the compatibility of the injection grout with the original material. Selection of the appropriate type of grout (polymer, fiber-reinforced, cement-sand, gas-forming, or sulpho-aluminate) is crucial based on the specific repair work requirements. Not all injection materials are suitable for every type of crack or environmental condition. For example, certain resins may not perform well under UV exposure, high temperatures, or in wet conditions, potentially limiting the effectiveness of the repair over time
In cases where cracks are subject to ongoing movement or loading, the injected material may not provide a lasting solution. The repaired area might fail under continued stress, requiring further intervention.
Ancillary information
Service disruption: No
Preliminary works: Yes
Posterior works: Yes
Time consumption: Low (< one hour)
Cost: Low