How To Repair Spalling Concrete
Spalling concrete appears as round or oval depressions along surfaces or joints. Spalling is normally found in cold climates while using de-icing chemicals or if the concrete is damaged by seasonal freeze-thaw cycles.
Reasons of Spalling and Preventive Measures
Spalling occurs when the rebar is uncovered & the rebar is affected with rust due to water penetration & humidity. Another reason is the concrete joints are created imperfectly. Due to change in weather, the concrete extends and as a result spalling occurs that causes further deterioration. To get rid of spalling, a strong water sealant should be applied to finished surface so that the water can't enter into the concrete.
Spalls are also controlled when the concrete is managed properly and correct methods are applied for pouring of concrete. For example arranging adequate concrete cover (embedment) of rebar and placing joints at the exact position and distances. Special concentration should be given to the edges and corners of uncovered concrete to retain sufficient concrete cover as per suggestions of the structural engineer or the ACI. The concrete mix is another vital factor for spalling since excess water content results in spalling.
Some Vital Tips to Repair Spalled Concrete
Remedies for spalling are dependent on intensity of the issue, the type, and position of concrete structure, and other factors.
- If the spalling damage is smaller than 1/3 of the thickness of the concrete, the concrete normally needs a surface repair. If the damage remains more than 1/3 of the depth, steel bars should be installed and a full depth restoration is necessary.
- Rotten rebar, because of exposure, should be cleansed initially of the restoration method. As soon as the rebar is cleansed fully (normally with a wire brush) and all corrosion is eliminated, the rebar should be covered with a shielding coating of rust inhibitor to get rid of future erosion.
- Damage on driveways, walkways, and other horizontal surfaces should be restored with a cementitious overlay. Once the overlay is set fully, a waterproofing membrane should be provided to avoid further spalling.
- Patching is another useful repair option for random or localized damage. Patches should be expanded minimum four inches beyond the spalled areas. To obtain a perfect result, the surface is saw-cut in the patch area to allow contain and secure the patch.
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- Surfaces to be patched should not contain debris and fine particles and should be entirely dry prior to use patching material. It will be perfect when the old concrete surface is rough to arrange tooth for superior bonding. The best patching materials range from Portland-cement-based or epoxy and should be mixed instantly before application.
- The air temperature should be more than 40 F for patching or other renovation work to maintain perfect bonding and curing of the repair material.
- Repair materials should contain an expansion coefficient close to that of the original concrete.
- Any joints which are repaired should permit the extension of the concrete slab.