- Moisture permeates the tiny breaks in the concrete substrate and in colder climates enlarges them to full-fledged leaking cracks by expansion/contraction resulting from freeze/thaw cycle of the moisture.
- As the ground around the footing or foundation stabilises, any movement can cause the rigid concrete substrate to separate at these tiny breaks in the concrete, enlarging them to a water-leaking size.
Low and high-pressure injection
The repair of the concrete structures mentioned above is suitably accomplished using low-pressure injection of the damaged areas with a liquid polymer, which hardens with time. Other applications, such as those involving very thick-walled structures (e.g. dam repair) or where a high volume of water flow must first be stopped may be better suited for high-pressure injection.
Low-pressure injection, here defined as 20-40 psi, utilises surface ports placed directly on the surface of an otherwise sealed crack as the entry point of the liquid polymer. This technique can be utilised at up to 250 psi of injection pressure.
High-pressure injection at 250 psi -100 psi utilises injection packers which are typically placed in holes drilled at 45 degrees to intersect the interior of the crack. Until recently, this technique has traditionally been used in in commercial and civil projects, but as the technology is more readily available the use of polyurethane foam repair is preferred. The disadvantages of this approach is the extra cost of packers but it’s worth it in the long run.