How To Repair Spalling of Concrete?

In this article, we will discuss how to repair spalling of concrete.

Concrete is the composite material that is composed of a mixture of fine and coarse aggregates bonded together with biding material which hardens over time.

The binding material mostly includes fluid cement paste, lime putty, lime, etc. In simple language, Concrete is a mixture of cement, sand, aggregates, and water.

Spalling of concrete is the surface failure in which concrete breaks off from the concrete object or structure. Concrete Spalling is also called Concrete Cancer.

Spalling of concrete affects a broad variety of structures like jetties, bridges, framed structures, bunds, tanks, etc. Generally, a spall of concrete may be 150mm or more in diameter and 25 mm or more in-depth.

  1. How To Repair Spalling of Concrete?  

As soon as spalling occurs it must be cured because the size of the spall goes on extending over time which may lead to difficulties in repair/ maintenance, exposure of rebars to the atmosphere and sometimes it may lead to failure of the structure or structural member.

It also distorts the aesthetic view/appearance of the structure.

Repair work of spalling of concrete varies based on the location of the concrete structure and the severity of the damage. The answer to how to repair spalling of concrete is noted in steps.

1. Clean the spalled area

Clean the spalled area to eliminate the bond breaker agents by hand or pressure washer.

2. Remove Loose Concrete 

✔ Use hammer and chisel to remove loose and broken concrete.

✔ The removal of 3.81cm deep of concrete is recommended for better repair.

✔ Tapping the surrounding area of spalled area with the hammer is advised to check the future deterioration.

✔ Hollow sound represents deteriorated concrete. Such concrete should be eliminated to prevent the need for future repair work.

✔ It is suggested to cut the spalled area in regular shape (i.e. either in square or in a rectangular shape). This makes patching easy and effective.

✔ Finally, remove dust and debris using a vacuum.

3. Cleaning and Coating rusted steel bars

Clean the surface of the steel bar from dust and rust using the wire brush and apply the anti-rusting coating or paint.

4. Apply repair material mixture

✔ There are various materials for spalling and repair of concrete. Select the materials according to the size of the repair required.

✔ If the depth of spalling is less than 1/3 of the concrete thickness; surface repair is done.

✔ If the depth of spalling is more than 1/3 of the concrete thickness; Installation of steel bars and full depth restoration may be required.

✔ Apply an adhesion agent on the affected surface to increase the strength of bonding.

✔ After that, patch the area using a suitable admixture.

✔ Epoxy or Portland cement-based materials are recommended for patching.

✔ Selected material for patching should have a close thermal expansion value to that of existing concrete.

✔ Ambient temperature during patching should be considered as it affects the patching material.

✔ The ambient temperature should not be less than 4.5ºC.

✔ Repair of driveways, walkways and other horizontal surfaces can be done using cementitious.

5. Finishing

Finishing of the surface is done by providing leveled surface using a trowel or other means.

6. Curing

Curing is done to provide maximum strength and durability to the applied concrete.

A minimum of 7 days of curing is recommended if surface repair is done and 28 days for full depth restoration.

7. Coating or Application of Paint

After the material is set; the application of paint or the application of a waterproofing membrane is done to avoid future spalling.