Is Concrete Cancer repairable?

Concrete cancer may be a scary term. However, damaging as it may sound, it is repairable. Understanding what concrete cancer is and the importance of having an expert diagnose and prescribe the appropriate repair method is critical to a successful outcome.

So, what is it? Concrete cancer or concrete spalling, as it is also known, is generally caused by the corrosion of the reinforcing steel embedded within reinforced concrete building elements. As the steel corrodes, due to the presence of chloride salts or other contaminants, it expands causing the concrete surrounding it to crack and eventually spall off.  Whilst initially a minor problem, in time, if left unchecked, widespread spalling can lead to a loss of structural integrity and in severe cases structural failure. Spalling concrete becoming detached from buildings and structures can also poses a serious threat to the safety of the general public and property in and around them. Usually concrete cancer is attributable to the ingress of chloride salts from, marine environments or industrial processes, or carbonation due to prolonged exposure to carbon monoxide from vehicular traffic or other sources. Factors that can hasten the onset of concrete cancer include poor waterproofing, aggressive environments, poorly placed or finished concrete easing the path of contaminants through the concrete cover layer to the reinforcing steel, and poor design of the concrete structure.

Now that we know what concrete cancer is and the damage it can cause, let’s understand how to diagnose and do concrete cancer repair! A few tell-tale signs of concrete cancer will be cracking or crumbling concrete, rust stains, roof and internal wall leaks or bubbling concrete render. If you notice these, make sure you contact a professional (such as a structural engineer or remedial builder) to properly diagnose and correct the problem.

Minor instances of concrete spalling are generally addressed via patch repair procedures where concrete is repaired by breaking out the concrete at the repair site using jackhammers to expose the corroding reinforcing steel and them ‘chasing’ that corrosion until good, un-corroded steel is found. The corroded steel is then either cleaned or replaced and new steel is installed as per engineering requirements. Primer is then applied to steel and concrete surfaces and concrete repair mortar is then applied to reinstate the repair area to the original profile. Larger and more serious instances of spalling may necessitate more ‘heavy duty’ methods of removal, preparation and reinstatement. For example the use of hydro demolition techniques using water delivered at around 20,000PSI is  a highly effective method removing large areas of spalled concrete in an economical fashion. In such cases repair products are often spray applied using either wet or dry sprayed repair products or in larger flat areas repair products may be poured into prepared formwork. In all cases the repair of spalling concrete is a job for specialist consultants and contractors.

ACRA, the Australian Concrete Repair Association, is a good source of information and expertise on concrete cancer repair and other problems and its membership is vetted for quality and competence in the field. Structial Building are a member of ACRA and are happy to assist if you are concerned about spalling in your building or structure. https://acrassoc.com.au/