The term “concrete cancer” is a broad brush phrase, usually loosely used to describe the deterioration of concrete due to corrosion of the reinforcing steel. Symptoms include corrosion stains, minor and major cracking, surface whitening, delamination and spalls. Industry professionals reading this article will know that these conditions are usually the result of a combination of factors, rather than any simplistic single cause.
Concrete cancer does have some similarities with its human counterpart.
- It usually develops slowly over an extended period, and obvious signs may not be seen until the condition is advanced.
- In its early stages, concrete cancer is often caused by a mutation of the concrete itself.
The deterioration cycle
As noted, concrete ‘cancer’ deterioration will usually result from a number of factors; but one key common element is the movement of moisture vapour and moisture-borne contaminants within the concrete’s own porosity.
These can set up reactive processes in the concrete itself (e.g. ASR), resulting in expansive forces which drive cracking. Further, the contaminants (e.g. chlorides) can destroy the natural protection of the steel and encourage corrosion.
This becomes a self-accelerating deterioration process: ASR creates small cracks, allowing increased moisture ingress. Moisture-borne contaminants reach the rebar zone, destroying the passivity and triggering corrosion of the steel. Corroding steel itself is very expansive and drives cracking from within, escalating the cycle.
At some point in the cycle, the cracks usually become evident, corrosion stains show on the surface, and so on.
(These signs are not always visually assessable – see separate article on Hidden ASR)
What is the answer?
With the key factor of moisture movement in mind, it becomes plain that immobilizing moisture will logically help to arrest the deterioration process.
This is where concrete silicate hydrogel technology comes to the fore – the advanced solution to a broad spectrum of concrete deterioration issues.
- Initial moisture ingress can be prevented. This includes moisture vapour.
- Movement of moisture within the concrete porosity, including the rebar zone, can be prevented.
- Moisture-borne contaminants are therefore prevented from moving about the concrete.
- These contaminants are also robbed of the elements needed to drive deteriorating reactions.
Early action saves money!
Existing deterioration needs to be professionally assessed to ascertain its extent. The earlier treatment is applied, the more effective the long-term outcome will be. Advanced deterioration may require extensive restorative work, hence the value of early assessment.
And then there’s prevention! New and young concrete can be treated to protect the structure as early as possible – a pro-active approach to reduce long-term maintenance costs!
Have you diagnosed concrete cancer in a structure in your care? Talk to the Markham team today!