By Gert Schmidt
Restoring cracked concrete is a job best left to concrete repair specialists. This is considering that, if left untreated or repaired in an inappropriate manner, cracks can cause major damage.
Experienced concrete repair specialists, such as Hindle Mason Projects, are knowledgeable in a variety of crack repair methods. This includes tried-and-tested crack-injection. We are an expert in both polyurethane and epoxy crack injection methods.
Crack injection provides many benefits. Firstly, it is a more cost-effective and practical method of undertaking structural repairs. This is in addition to all leak-sealing applications in concrete by providing a permanent watertight seal.
Epoxy crack injection entails injecting an epoxy resin into cracks. Once the cracks have been filled, the system hardens to create a strong bond. This method is typically used for larger cracks and those that are not actively leaking water.
Polyurethane crack injection entails injecting a liquid polyurethane resin into cracks. This resin then expands to fill cracks and creates a seal. Therefore, this method is suited to repairing small cracks that are actively leaking water.
Concrete repair specialists remediate cracks
Concrete repair specialists know how to use both technologies to remediate cracks. This is not only to restore the integrity of structures but to also prolong their lifecycles. For Hindle Mason Projects, this is the ultimate measure of the success of any concrete repair project. It should be yours too considering the high costs involved in undertaking major concrete repairs or replacing defunct infrastructure.
A key to successfully restoring cracks is first selecting the correct injection material. Its viscosity, flexibility and behaviour when in contact with water are especially important considerations. These can significantly influence the effectiveness of the injection.
Epoxy provides a stronger and more robust repair. This is considering that it is a much stronger and durable material than polyurethane. However, it is not as flexible and, therefore, does not expand with movement in the structure as does polyurethane. Rather, epoxy forms a hard, rigid bond with concrete. Therefore, if there is movement in cracks, polyurethane may be the better choice.
Because it is a rigid material, epoxy crack injection is ideal for structural applications. For example, concrete repair specialists use it to repair cracks in load-bearing concrete structures. These include foundations, walls and beams. The tensile and compressive strength of cured epoxy is much greater than that of even concrete. Most non-flexible epoxies have a compressive strength of no less than 68MPa. Typically, concrete has a compressive strength of 20MPa. High performance concretes can have a compressive strength of at least 34MPa and upwards. Meanwhile, concrete’s tensile strength is about 10% of its compressive strength. Alternatively, epoxy has a much higher tensile strength. In some instances, its tensile strength can be up to 10 times more than standard concrete.
Concrete repair specialists bring experience
Concrete repair specialists bring many years of experience working with these materials to the professional team. This practical knowledge is harnessed by engineers during the repair design process. It is then again deployed to successfully execute the design, which is both practical and cost-effective.
Having worked extensively with epoxy, we know that it provides better adhesion to concrete than polyurethane. Therefore, when injected into cracks, epoxy forms a strong bond with the concrete to create a seamless repair.
However, it does not adhere well to wet and saturated surfaces. Therefore, working with the repair system requires dry surfaces.
Meanwhile, we have successfully deployed polyurethane injection foams and resins in both wet and dry applications. This is regardless of crack conditions and whether they are narrow or wide, and actively leaking.
With its expanding properties when reacting with water, polyurethane is primarily a water-activated sealant or leak-seal grout. The cured product creates a compression seal of varying flexibility.
On the other hand, epoxy resin must be contained in cracks until it has cured sufficiently to achieve its full strength. By curing rapidly and expanding, polyurethane is better suited to filling voids within concrete that are leaking.
Epoxy is more resistant to chemicals and moisture than polyurethane. Therefore, we use the material to repair areas that are exposed to harsh chemicals or moisture.
It also provides a smoother and more seamless repair than polyurethane. This is considering that it hardens to a rigid finish. Therefore, it can be sanded and painted to match the surrounding concrete, providing a more aesthetically pleasing result.
Concrete repair specialists’ injection equipment
Concrete repair specialists’ injection equipment is another contributor to the success of crack repairs.
This ensures correct initial dosage and mixing; delivery from suitable pumps; and use of the right packers, ports and connectors.
Epoxy injections are typically performed at lower pressures of between 20 and 200 psi. On the other hand, polyurethane crack injection is usually executed at higher pressures. This is done with special injection pumps and packers that have been installed into drilled holes. In this way, the expanding foam can be moved through the cracks, filling the entire thickness of the structure. This prevents water from entering cracks.
Concrete repair specialists undergo training
Concrete repair specialists undergo regular training in the correct application of these techniques. Hindle Mason Projects has access to the best crack-injection technology as an approved applicator of a leading manufacturer [Injections (sika.com)]. This means that our workmanship comes with a performance warranty.
We are well-versed in the application of the following crack-injection systems, having applied them in many applications:
- Low viscous, elastic and solvent-free polyurethane-injection resins. They cure in both dry and wet conditions to form an elastic, watertight filling and sealing material [https://zaf.sika.com/en/construction/waterproofing/injection-systems/sika-injection-203.html]. This solution is ideal for permanent watertight sealing.
- Polyurethane flexible injection resins. This two-part, polyurethane, low viscous, fast-foaming, water-reactive injection resin, cures in dense flexible foam. https://zaf.sika.com/en/construction/waterproofing/injection-systems/sika-injection-101rc.html is ideal for temporary water stopping.
- Polyacrylic elastic injection resin for permanent watertight sealing. This three-part acrylate-based injection resin has a very low viscosity and adjustable reaction time [https://zaf.sika.com/en/construction/waterproofing/injection-systems/sika-injection-307.html]. It is ideal for watertight sealing.
- A very low viscous, elastic and solvent-free polyurethane injection resins. It forms a uniform, closed and, therefore, watertight pore structure which is elastic and flexible when reacting with water. https://zaf.sika.com/en/construction/waterproofing/injection-systems/sika-injection-201ce.html provides a permanent watertight seal.
- A colourless liquid that accelerates the reaction and curing times of polyurethane injection resins even at low temperatures. [https://zaf.sika.com/en/construction/waterproofing/injection-systems/sika-injection-ac-20.html].
Schmidt is a Director of Hindle Mason Projects
