Concrete cracking and repair
Concrete slab foundation settlement is often the result of changes in moisture content and density of the soils beneath the slab. For example, soils beneath a concrete slab can dry and shrink over time due to extended drought-like conditions or leaking sewer or stormwater systems. Loosely compacted fill soils can consolidate beneath a slab causing floor cracks.These types of conditions create a void under a slab. If the slab isn’t strong enough to span the void, the slab will crack, break, and settle into the void.
Repair of concrete takes many forms; cracks in concrete, corrosion of reinforcement,( cancer) in concrete causing spalling, concrete settlement such as in footings, concrete deterioration such as weathering or wear.
Vertical Foundation Movement Repairs include grout pumping to stabilize soils or elevate slabs, slab jacking to stabilize or lift settled slabs over deeper unstable soils, the use of driven steel pins to stabilize settling foundation walls or footings,and the use of helical or “screw piers” and concrete mini piles.
The type of concrete repair we’re looking at here [below] is concrete footing problems, basement wall problems that require the services of an underpinning specialist.
Concrete footing jacking is done to repair sinking concrete footings. These can be applied internally or externally to the wall footings.
Tie Backs (helical anchors) provide lateral stability to foundation walls and retaining walls with unbalanced earth pressures. Helical anchors can be installed with hand-held equipment, mini-excavators, skid steers so the anchors can be installed in almost any application. This versatility, along with the ability to immediately load and test the anchors, make helicals a convenient and economical solution for a wide variety of projects including concrete basement wall repairs.
The following photo shows a helical pier being used to Jack, a concrete foundation that needs supporting. The pier is usually driven to a predetermined hydraulic pressure so you are given a known load-bearing capacity and then the bolts are tightening over the pier head to cause an uplift force on the concrete footing.
Repairing foundation cracks which are not traced to building movement, structural problems, site problems, or other conditions which require site or structural repairs may be attempted for cracked foundations and other cracked concrete structural elements using a variety of products and materials such as masonry repair epoxy or sealant products if cracks are small.
This type of product, some of which include even structural repair epoxies, might be used to seal against water leakage as well, and may be used for repairing certain cracks in concrete foundations following evaluation and advice from a foundation professional. An evaluation of the presence, absence, or condition of reinforcing steel in cracked concrete foundations should be a part of an inspection.
Shrinkage cracks, which are not normally a structural defect in a building, may nonetheless need to be sealed against water entry. Common repair methods include chipping out the crack and applying a masonry patching compound to the surface, use of epoxies, or other sealants.
Water entry leaks at foundation cracks: Polyurethane foam sealant is used for foundation crack repairs to stop water entry.Particularly important for basement walls/floors. Or you can do a full on external wall seal if cracks are severe as shown in the following video. Bitumen with layers of plastic.
Guide to concrete repair – Australian Concrete Repair Association: www.acrassoc.com.au/index.php/publications/guide-to-concrete-repair