How does Chloride Attack?
Early corrosion of reinforcing steel causes frustrating downtime and maintenance costs!
The cost of repair of chloride attack can be huge, inconvenient… and come as a shock!
And often, this is because deterioration goes undetected for years – hence the reason preventative treatment must be done before damage is manifest.
Chlorides are reactive chemicals that enter concrete through the constant movement of moisture in and out of the capillary pores. Chlorides, together with oxygen, reach the embedded steel and set up electrochemical corrosion in the rebar. Untreated steel corrosion will very often cause the concrete to break down well short of its planned service life.
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Chlorides are typically present in seawater, putting marine structures at particular risk. Other sources include salt-contaminated groundwater or de-icing salts in cold climates.
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How can we halt the process?
It is well established that controlling free moisture will significantly extend the life of concrete. This is because moisture is the vehicle by which contaminants enter and move through the concrete.
Chloride ingress and corrosion activity can be arrested by setting up a moisture barrier. This moisture barrier must be long-lasting and effective. A coating is not sufficient; moisture must be immobilised within the concrete itself to prevent the movement and action of the moisture-borne contaminants.
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What is an effective way to control moisture from inside and out?
You need a concrete treatment system that:
- penetrates the pores of the concrete,
- deals with the moisture currently in the concrete, and
- blocks the entrance of outside moisture.
In fact, you need a penetrating hydrogel treatment.
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How does it work?
- A catalytic silicate solution is applied to concrete by spraying or as an admixture.
- The catalyst reacts with the free lime (Ca(OH)2) in the concrete.
- This hydrophilic reaction draws in the concrete’s moisture (H2O) content, penetrating deep into its porosity.
- The result is calcium-silicate-hydrate (C-S-H) gel.
- The hydrogel maintains moisture in the concrete, aiding the entire hydration process.
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Intrigued?
The MARKHAM approach to remediation of existing concrete is called CIVIL-TECT®.
Looking after a deteriorating concrete structure? Get in touch!
For a deeper dive into the issues discussed here, try our on-demand webinar, “The Marine Concrete Experience“.
