House Information 04 – Spalling Concrete
Spalling concrete is the failure of concrete due to negative environmental impact(s) which stresses it as well as poor installation at the beginning stage of construction. Spalling concrete may result in structural damage as there are possibilities whereby the reinforcing bars are getting exposed. Therefore, it is important to deal with spalling as soon as there are signs of it.
When the surface of concrete becomes rough and seems breaking, it is starting to spall. For some cases, chunks of concrete may be loose and could fall off. This is repairable by replacing the damaged part of the concrete with cement fillings.
Uncoated steel reinforcing bars begins to corrode when rust is spreading on the surface of it and this will cause cracks near the interface of steel and concrete.
Preventive measures could be taken when concrete is first being poured such as:
- accuracy of measurement of water to be mixed,
- keeping the mixture dry,
- proper curing process,
- sealing of concrete with sealers like acrylics or epoxies,
- and quality finishes.
Whenever there are signs of spalling, actions has to be taken immediately to prevent serious damages. If the spalling concrete is structural in nature, it is best to seek assistance from professional or contractor to conduct the repair works.
Spalling concrete can be a headache when it occurs on decorative concrete as it may deface the concrete. It will be hard to get the patterned/ design standardised after the repair. Thus, it would be best to engage the original contractor or person whom installed the concrete to conduct the repair works.
Spalling Concrete Rectification Method
a) Scrap off carbonation, fragments cement and peeling plaster.
b) Cut a square around the spalling concrete about three-eighth inch deep using an electric cutter.
c) Use the chisel and hammer to break away the concrete contained in the cut area. Expose the reinforcing bars beneath the surface of the concrete and break away any concrete attached to the bars.
d) Brush rust away from the bars using a wire brush. Examine the ends of the bars still covered in concrete. If the rust continues, cut and clear away the concrete until you reach a no rust section.
e) The hacked concrete surfaces will then be washed and dry.
f) Paint the rust-cleared bars with an anti-rust paint. Two coats of paint will be applied 10 minutes apart to provide adequate rust protection.
g) Brush a layer of “W1” bonding agent to the cleared concrete surface. Allow the adhesive to dry until it’s tacky but not wet. The adhesive will help to create a bond between the old concrete and the new.
h) Mix a batch of non-shrink grout cement in a large bucket using an electric drill with a paddle bit.
i) Use the trowel to smooth the surface of the concrete patch with the surrounding surface of the soffits.