Cause: Excessively thick concrete layer dried out too quickly
Found on: Longitudinal cracks along or across the top reinforcement
Crack repair systems
A great deal of damage to concrete structures is caused by cracks and cavities that allow contaminants to penetrate the building fabric. These harmful influences impair the functionality of the concrete, significantly reducing the load-bearing capacity of the structure. The most common causes of cracks include:
- Shrinkage
- Hydration heat
- Inherent stress of the building element
- Changes in length due to heat
- Static overloading
Full usability and functionality of the concrete can be restored by injecting or saturating the defective areas with suitable crack fillers.
To define the objectives of crack repair, detailed knowledge is needed about the type and course of the crack, the moisture at the crack edges and the change in crack width. Remmers injection resins are optimally suited for producing frictional or flexible connections thanks to their excellent bond strength, high chemical resistance and constant viscosity during injection.
Polyurethane resin-based injection resins can be used to seal damp and water-bearing cracks. They are ideal for creating flexible connections.
For frictional sealing of cracks, on the other hand, injection resins based on epoxy resin or cement paste/cement suspension are used.
Classification of cracks
Intended use and workability
Crack fillers are categorised according to defined performance requirements in accordance with DIN EN 1504-5. These performance requirements contain essential information for potential areas of application. For instance, the CE classification describes the following performance characteristics:
U = Usage
W = Workability
- Minimum crack widths
- Moisture level of the crack
- Usage temperatures
- Changes in crack width (for frictional connections)
Using crack injection materials
Selecting a suitable crack injection material depends primarily on the repair objective and the existing moisture level. Epoxy resins are used for the frictional filling of cracks. On the other hand, the polyurethane group of substances is suitable for the limited elastic filling of cracks. Polyurethane foam resins can be used to create a barrier against flowing or pressing water. Remmers covers the entire field of application. We always have the perfect solution! The use of injection resins must be adapted to the condition of the structure.
Impregnation/pressureless filling of cracks and cavities: Cracks and crazing close to the surface in or on horizontal or slightly sloping surfaces can be permanently closed by casting. Only epoxy resins and cement-based fillers are used here.
Injection of cracks and cavities: Depending on the characteristics of the crack or cavity, the thickness of the component and the positioning of the reinforcement, crack injection can be carried out. This involves injecting crack fillers using injection equipment under controlled pressure via injection packers, with or without tamping. The choice of crack filler depends on the crack width, the expected crack width changes and the effects. The general conditions dictate whether drill packers or adhesive packers should be used. Cracks are injected from bottom to top until injection material emerges from the upper packers.
Using drill packers
There are two types of packer: high-quality, metal screw packers and cheaper, single-use plastic drive-in packers. Both are connected to the machine via an injection nipple with a non-return valve. Important parameters for use are the packer spacing and the structural arrangement.
Using adhesive packers
Adhesive packers are used whenever holes cannot be drilled in the component to be injected, e.g. in the case of small cross-sections or if holes cannot be drilled for design or structural reasons, such as in the case of pre-stressed reinforced concrete components. The adhesive packers are glued on in the centre of the crack. They should be spaced according to the component thickness.
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