concrete crack repair

Concrete cracks can compromise the integrity and durability of structures, making timely repair essential to maintain their performance. Among the various methods available, epoxy and polyurethane injection have emerged as popular techniques for effectively addressing concrete cracks. In this article, we will explore the benefits and applications of epoxy and polyurethane injection, highlighting their effectiveness in repairing and restoring cracked concrete.

epoxy injection


Application Conditions and Objectives:

Epoxy Injection: Suitable for structural crack repair and restoring structural strength. It works on dry substrates and is not recommended for actively leaking cracks.

Polyurethane Injection: Ideal for sealing active leaks, preventing moisture migration, and protecting structures from water damage. It works well on wet and actively leaking substrates.

Characteristics of Epoxy and Polyurethane:

Epoxy: It is a strong adhesive that does not expand during curing. It forms a strong bond with the concrete substrate, providing high compressive and tensile strength properties. Epoxy is a two-component system consisting of epoxy resin and hardener.

Polyurethane: It is a water-activated sealant or leak-seal grout that expands during reaction. The cured product creates a flexible compression seal. Polyurethane resins can vary from rigid and strong to flexible and rubbery elastomer compositions. Polyurethane foam resin often requires an activator or accelerator.

polyurethane injection


Injection Techniques:

Epoxy Injection: Typically performed at lower injection pressures with surface-mounted ports. It is applied to penetrate cracks and fine fissures, making it suitable for structural repair. In most cases, surface-mounted entry ports are sufficient for addressing cracks. However, socket-mounted ports are employed when dealing with blocked cracks, such as those obstructed by calcified concrete.

Polyurethane Injection: Often performed at higher pressures using injection pumps and packers installed into drilled holes. Polyurethane injection is suitable for wet and dry applications, regardless of crack condition and weather. The polyurethane resin reacts with moisture present in the crack, creating a closed-cell foam that effectively blocks water infiltration.

The selection of the appropriate viscosity of epoxy depends on factors such as the size of the crack, thickness of the concrete section, and access for injection. For cracks with widths of 0.010 in. (0.3 mm) or smaller, a low-viscosity epoxy (500 cps or less) is recommended. In cases of wider cracks or limited access for injection from one side, a medium to gel viscosity material may be more suitable.

Epoxy and polyurethane injection methods have proven to be reliable and effective for repairing concrete cracks. Whether it is the high strength and durability of epoxy or the flexibility and waterproofing properties of polyurethane, these techniques offer robust solutions for maintaining the structural integrity of concrete elements.

It’s important to choose the appropriate injection method based on the specific conditions, objectives, and properties of the concrete crack. Consulting with a professional can help determine the most suitable method for your concrete crack repair project. Contact us today to learn more about our comprehensive services!