Concrete spalling is one of problematic damages for concrete members. As you can see in the figure below, when it happens, concrete member becomes more expose and vulnerable to erosion. As a result, it is highly important to find out what causes spalling, and how can we prevent it.
Generally, we can mention three main reasons for concrete spalling including:
- The presence of sodium chloride, which may exist in the aggregate. Moreover sodium chloride is a substance used for melting snow on the frozen concrete pavements in the winters.
- Inappropriate curing process is another cause of concrete spalling
- Another factor is carbon dioxide which is either in the air or trapped inside the concrete mixture. This substance can truly cracks the body of concrete and starts the spalling process.
- Thermal stress expands the steel pars inside the concrete body. If thermal stress exceeds the tolerance of concrete cover, it results in spalling.
- Las but not least is the excessive amount of water in concrete mixtures. Remembers, in any concrete damage, water can be the main culprit. In other words, water is the biggest enemy of concrete mixture.
Tip: in some countries, the old foundations are made of bricks which makes them highly potential to absorb salt. As a result these foundations and the structure above are usually in danger of spalling.
BS EN 1504 introduces some requirements for repairing damaged concrete in details. Here we summarize the main points of concrete repairing.
- The material used to repair damages must be compatible with the host concrete. some materials can be placed by hand while can flow and fill the cracks.
- Repairing can postpone the corrosion process but it usually fails to stop it permanently. So instead of leaving the repaired member alone, we should use enough sacrificial anodes in the area to reduce the rate of corrosion. In other word cathodic protection is an essential part of repairing operation.