All buildings are prone to cracks over time, even if they have undergone excellent workmanship during construction. This is due to the number of natural forces that act on their structure over time. These natural forces include:
- Excess heat leading to expansion of materials inside of the concrete slab
- Exposure to wind or sunlight during the drying stage, leading to a crusty and weak surface.
- Excess weight being placed on top of the building’s structure.
- Upward forces from the ground beneath the concrete structure.
- Overly wet concrete mixes drying and leaving behind voids the slab.
When cracks are found within your structure, it is crucial that you immediately get in contact with a professional concrete repair company who can help you to investigate the structure. At times, surface cracks may merely be an eyesore and pose no danger to the structure. Other times, major cracks may be masked by the surface, posing a risk to the structural integrity of your building.
Ideally, when cracks are found, a full replacement of the cracked section of the concrete slab is carried out. This approach should renew the lifespan of the concrete’s structure’s lifespan. However, it can be costly in terms of both resources and time. As such, most building owners opt for crack injection to serve as a short to medium term solution.
Crack injection involves the filling the cracks with grout or resin, which when dry help to stabilize the structure. Furthermore, injection grout also helps to provide waterproofing and corrosion protection.
Depending on the type of crack at work, different types crack injection material are recommended. Each type of grout has varying characteristics and properties. This makes the selection of grout type a confusing task for industry newcomers. Generally, grouts should have low viscosity, high bond strength, high stability and low shrinkage.
Common grout materials used for crack injection include:
- Cementitious grouts
- Epoxy resins
- Polyurethane resins
- Acrylic resins
Cementitious grouts are composed from a mixture of cement, water, admixes and additives. This includes:
- Pure cement mixes (PCMs)
- Admixed cement mixes (ACMs)
- Additive cement mixes (ADCMs
Epoxy resins are a mixture of resin and hardener, which when mixed together react chemically to form a nonfoaming elastic grout. They are typically used to adhere to metals, concrete and ceramics, showing little change in volume during and after its curing stage. Importantly, epoxy resins are mechanically strong and resistant to chemicals.
The properties of polyurethane resins vary markedly between its liquid and hardened phases. In particular, its viscosity, thixotropy, foaming reaction and mechanical strength is altered between its states. In general, polyurethane resins cure rapidly and are flexible, making them suitable for structures with movement or for sealing against water inflows.
Acrylic resins can be formed form a polymerization reaction between a resin and hardener. The result grout is a permanent gel that has both low adhesive, high tear strength and compressive strength properties.
Choosing the Right Grout for Crack Injection
The right choice for grout material for crack injection is highly dependent on the type of crack suffered as well as the surrounding conditions. It is critical that professional advice is sought when selecting the grout material.