Concrete Crack Repair and Reinforcement
Fortress Stabilization Systems Engineer and Contractor Resources
ENGINEER / CONTRACTOR
Concrete Crack Repair is something that all homeowners, construction workers, safety personnel and others will have to deal with at some point in time. The simple fact is that all cement structures will crack.
Foundations and other cement structures will often crack as a result of settling, soil pressure, water damage, drying shrinkage, thermal movement, or other causes. As most homeowners know, basement wall fractures are common and a fact of life. Most fractures are minor and cause few problems. However, other fractures can grow over time and cause structural integrity or, more commonly, water leakage. If the fracture is large or growing over time, simple injection techniques are not an appropriate or lasting fix. Under these circumstances, appropriate needs to stabilize the fracture, i.e., prevent it from expanding and getting larger. To accomplish this, reinforcement and stabilization is required.
Concrete crack repair employing the Fortress Stabilization Systems Carbon Fiber Countersunk Staples are designed to transfer load away from the fracture, thus creating a long-lasting fix.
There are 6 ways in which a cement fracture in a below-grade poured wall generally moves:
- Tensile/inward: due to lateral loading
- Outward: due to shrinkage of soils
- Opening: due to thermal changes
- Closing: due to thermal changes, i.e. cold, wet, dry, etc.
- Shear: due to differential loading
- Combination: all of the above conditions, plus the added load of the structure
Concrete crack repair using Fortress Stabilization Systems’ materials and techniques address all 6 of these movements.
Concrete crack repair using the Fortress Stabilization System involves, after surface preparation, a standard injection technique to fill all voids with a specially formulated epoxy mixture. After the voids are filled, staples are installed across the fracture in a fashion that relieves and dissipates both lateral and vertical movement. Staple placement is critical for proper fix and is usually engineered into the project plan. Staples are usually placed no more than 24 inches apart for effective reinforcement.
When a fracture is caused by differential loading (shear), the fix is considered structural. The staples in this case are crisscrossed at a 30 degree angles that will load the carbon in tension, allowing function in shear. The result is not only a fracture fix, but restoration of the structural integrity of the wall.
When carbon-fiber sheet staples are anchored into the cement, fewer loads are exerted on the weak surface substrate and transferred into actual cement. This improves its entire inter-workings with the material of choice.
Concrete crack repair and stopping shifting walls with Carbon-fiber is a proven application and technology that works as well in your home as in commercial buildings, bridges, mines, road surfaces, and in any other applications where reinforcement and reparation are need.
Look in our Case Studies for many more examples of how Fortress Foundation Repair can fix and add structural reinforcement and stability to a variety of structures.
Repairing Minor Concrete Cracks and Holes
Here are some tips and suggestions on how to patch and repair minor concrete flaws that are not structural. You should not attempt to make a repair on any wall that may be structural as you could further hinder the structural integrity of the wall. Additionally, if a concrete crack reappears after repair, then there exist an underlying condition and the repair should be done professionally and with reinforcement.
Hairline Cracks and Concrete Repair
- You can repair hairline cracks in concrete with grout made of Portland cement and water, much in the same way as repairing a crack in drywall. Add enough water to the cement to form a thick paste.
- Thoroughly clean around and in the crack as much as possible and remove all dust. After the crack has been cleaned, moisten the concrete along the hairline crack with water for several hours. Moistening the concrete prevents it from drawing the water from the grout, which may dry out the grout mixture. Although the concrete should be damp, there should be no standing water on the surface when the grout is applied.
- After the hairline crack has been cleaned and moistened, apply the grout with a putty knife or pointing trowel, forcing the grout into the crack as much as possible. Smooth the hairline crack area off so it is level with the original concrete.
- Allow the repaired area to dry about two hours and then cover the area with a piece of plastic sheeting or a board. Keep the area covered for about five days, lifting the covering each day to keep the area moist (sprinkle the area with a little water).
- If the hairline crack reappears, then the crack will require reinforcement or the hairline crack will continue to expand.
Repairing larger Cracks and holes in Concrete
Larger cracks are generally structural, starting out as hairline cracks and increasingly getting larger. Such cracks should not be repaired as described below as you may further compromixe the structural integrity. However, if you have a larger crack that is not structural, it may be repaired as described below:
- Cracks larger than hairline cracks must generally be enlarged before they can be satisfactorily repaired. Enlarge the crack along its entire length with a cold chisel and hammer. Make the crack wider at the bottom than at the top (known as undercutting) that helps to bond the new concrete with the older concrete. The width and depth of the undercutting depends on the size and length of the crack. Undercut the crack to a minimum depth of 1″.
- After the crack has been widened and thoroughly undercut, remove all loose material and brush the area with a wire brush to completely clean the area. Do not over-clean as the rough surface created by the chiseling provides a good bond for the new concrete.
- The concrete patch will generally hold better if a concrete adhesive is used first. There are many types of concrete adhesives available in most hardware stores. Acrylic resin is one common type. Brush the adhesive into the undercut area and allow it to dry until it becomes tacky. If you do not use a cement adhesive, thoroughly moisten the area to be patched. Moistening the area prevents the old concrete from absorbing all the moisture in the concrete patch. Although it should be moist, no water should be standing on the area where the patch is to be applied. You can also prime the area with a thin, creamy mixture of Portland cement and water.
- For small patching jobs, use a pre-mixed concrete patch. If you use ready-mix concrete patch, all you need to add is water. To mix your own concrete patch, use one part Portland cement to two-and-a-half parts of fine, clean sand.
- Force the mixture into the cutaway area with a pointing trowel. Be sure to use enough pressure to force the patch mix into all the cutaway areas in the crack.
- Keep the area covered for about five days. Lift the cover once each day to wet down the repaired area, permitting the new concrete to cure correctly.