What is Spalling?
Spalling is a term used to define the breaking of a large material body into smaller pieces in the form of chips and fragments.
What is concrete spalling ?
Concrete spalling is a defect that is commonly found in a hard concrete structure or blocks located in a colder climate region.
Here the concrete gradually disintegrates or breaks into smaller pieces from a large reinforced concrete body, these small pieces are called spalls or flakes.
Concrete spalling or Peeling is most often seen on a concrete slab or concrete layer in colder climates and may be exposed to the constant destructive forces of cyclic freezing and thawing (freezing and thawing cycle). The situation increases as salt is applied to the concrete surface because of the defrosting chemicals.
What causes Concrete Spalling?
Concrete spalling is mainly caused due to presence of salts, moisture, heat, and mechanical expansion within the concrete body that leads to cracking, peeling, and chipping of the concrete structure.
As we know concrete is a porous material, so any moisture or salt present on the concrete surface can seep into the concrete, and the chance of corrosion of steel reinforcement can occur in the presence of air and water.
Some other causes of concrete spalling:
- Freeze and thaw cycling
- Reingorcing steel covered with low qulaity concrete
- Expansive effects of Alkali Silica Reaction
- Inadequate depth of cover over reinforcement
- Joint spalls are often caused by improperly constructed joints lead to joint spalling
How to prevent spalling of concrete
- On concrete floor slabs, Saplling can be prevented by providing a dry cut at early entry level.
- Apply good waterproofing to the finished surface to prevent water from entering the concrete.
- Proper handling of concrete during pouring to ensure sufficient coverage and placement of joints in the correct positions.
- Avoid excess water in the concrete mix as this will lead to spalling of concrete.
Spalling of Concrete Repair Process
Repair of concrete splashes varies according to the severity of the damage, the type, and the location of the concrete structure. This should be done based on application code recommendations such as ACI Code and BS EN 1504.
The concrete spalling repair process involves 4 steps:
1. Clean and Remove Spalled Concrete Area
Clean the area to be repaired of all dirt to remove accumulated substances. If there are any heavy stains and dirt, a pressure washer may be required to thoroughly clean the surface.
Remove loose and broken concrete from the area with a hammer and chisel. Sometimes blasting or grinding may be necessary for proper surface preparation. For a successful repair, it is advisable to take about 3.81 cm deep concrete.
To make the plaster, it is advisable to cut off the rectangular part of the concrete spalled area and remove the concrete, which is located in the defined area.
2. Clean and Coating Corroded Steel Bars
Clean the corroded steel or other dirt with a wire brush and then apply a corrosion protection coating to the reinforcing steel.
3. Apply Repair Material Mixture to concerete spalling area
Different products are used depending on the size of the concrete spalling repair, its depth. If the spalling depth is less than 1/3 of the concrete thickness, then the concrete usually needs a be surface repair.
If the damage exceeds 1/3 of the concrete depth, then it may be necessary to install steel bars and restoration of the entire depth may be required. For a better and strong bonding, the surface must be roughened and a suitable adhesive must be applied.
Next, seal the area with a suitable admixture, The best-recommended material for patches is Portland cement-based epoxy. Patch material must be chosen with thermal extension almost to the existing concrete.
When patching, take the ambient temperature into account as this will affect the patch material. The ambient temperature should be above 4.5 C. Damage to walkways, driveways, and other horizontal surfaces can be repaired by a cementitious overlay. If the affected area is adjacent to a joint, make sure that it is properly restored to allow for member expansion.
4. Finishng and Curing
With the help of a trowel remove all the excess material and provide a finishing touch and level the surface. After that make sure to cure the repaired area adequately to attain the required strength.
At last, apply a waterproof or paint coat to avoid the re-occurrence of concrete spalling.
Also Read – Types of Concrete Mixers Machine