Concrete spalling, also known as concrete cancer, is caused by corrosion of the steel reinforcement embedded within a concrete structure. As steel reinforcement corrodes it expands, causing cracking of the surrounding concrete. Spalling has the potential to be extremely detrimental to concrete structures and if left untreated, could result in complete structural failure.
There are a number of reasons why concrete spalling occurs; some of the more common causes, which can act in combination, are listed below:
* Poor quality or poorly compacted concrete
* Insufficient concrete cover to the embedded reinforcement
* Exposure of the reinforcement to the atmosphere through concrete cracking
* Carbonation of the concrete
* The existence of chlorides or dissolved salts within the concrete
The Remediation process
Typically the first step involves a comprehensive site inspection together with a detailed structural report outlining relevant observations. The report will advise on the likely cause of the observed detriment and would be the basis for the subsequent scope of works and repair specifications created for tendering purposes and the remediation Work.
We take a holistic approach to spalling remedial works by considering the entire building, not just patch repairing the most obvious detriment and disregarding adjacent areas vulnerable to future spalling. This approach generally provides a significant longer-term benefit. The costs associated with access are often considerable for rectifying a similar problem that appears in a untreated area, close to previously rectified works.
We typically use a combination of onsite cover meter survey’s and Schmidt Hammer testing to determine the insitu condition of the complete structure. Where considered appropriate, laboratory concrete testing may also be recommended.
The physical concrete data is then used in conjunction with the building, structural drawings (if available) and Australian standards requirements to verify why the observed areas have spalled and determine the zones of concrete likely to spall in future. This approach also assists to determine zones of concrete less likely to require remediation work, preventing costly and un-necessary works.
We have over 15 years experience with concrete spalling remedial works and have developed a number of tailored repair procedures and identified a range of products, including primers and corrosion inhibitors with specific attributes designed to provide the most comprehensive and permanent solution available for concrete spalling detriment.
MJ Civil also offer a tender issue, review of contractors returns and recommendation service as well as a superintendent service for supervision of the ongoing site works for certification purposes.