Concrete spalling is a common problem that affects a wide range of structures, from frame buildings and multi-storey car parks to bridges, jetties, tanks and dams. When spalling is detected, it's essential to take action and repair the concrete surface as soon as possible. Otherwise, the integrity of the concrete will be compromised and the capacity of the element will be put at risk. Spalling can occur due to exposed reinforcing bars that have started to rust due to moisture or incorrect construction of concrete joints.
As the weather changes, the concrete expands and causes it to spall, leading to further deterioration. One way to prevent concrete spalling is to apply a good water sealant to the finished surface. This will help keep water out of the concrete and stop spalling from occurring. On horizontal surfaces such as driveways or pavements, spalling is not only an aesthetic issue but also a safety hazard. To repair spalling on these surfaces, it's best to resurface and seal them with a coating solution.
This will not only repair the spalled concrete but also help prevent future problems. Concrete spalling can be caused by a variety of factors, including poor installation, corrosion of rebar, freeze-thaw weathering, thawing and temperature fluctuations. If left unattended, damaged concrete can compromise the integrity of the entire structure. It can lead to increased water ingress, deeper spalling, crumbling concrete, exposed reinforcing bars and structural disintegration. In addition, spalling concrete can pose a serious safety hazard for people and property - especially if detached parts are located overhead such as balconies, parapets, entrances, arches and bridges. To repair spalled concrete, one technique is to mix one part Portland cement type 1 with one part fine sand by volume.
Add water until the mixture is the consistency of thick paint and brush it onto the wet concrete. Corroded steel can expand up to ten times its original volume which puts stress on surrounding concrete. However, despite best efforts concrete patch repairs often fail prematurely due to corrosion at the periphery of repairs. The repaired area should then be sealed to ensure that spalling does not recur. Symptoms of concrete spalling include flaking, spalling and large chunks showing on the surface of the concrete which expose coarse rocky aggregate.
It's important to use a bull float immediately but wait for the concrete to harden before using an edger and broom. Belzona 4141 is an epoxy compound designed for concrete repairs on overhead and masonry structures. Common mistakes when repairing spalled concrete include adding too much water to the mix for easier pouring; spraying the surface with water to prolong finishing time; and not curing the concrete properly after installation. The type of repair needed depends on where the spall is located, how deep it is, whether it's on a vertical or horizontal surface and whether there's any exposed rebar. Repairs must be carried out in accordance with European and British Standard BS EN 1504 for repair and protection of reinforced concrete. Concrete resurfacing is used to repair and revitalise surfaces that suffer from minor issues such as staining or light corrosion due to elements as well as more structural problems like spalling.
Another key factor to consider when repairing spalled concrete is the mix - too much water can also cause spalling.