The chloride attack mechanism – deterioration by stealth!
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 initiate electrochemical corrosion of 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.
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How can we halt the process?
It is a proven fact that controlling free moisture will significantly extend concrete life. This is because moisture is the vehicle by which contaminants enter and move through the concrete.
Chloride ingress and corrosion activity can be prevented by providing a penetrating 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 the concrete by spray or admixture.
- The catalyst reacts with the free lime (CaOH) in the concrete.
- This hydrophilic reaction draws in the concrete’s moisture (H2O) content, penetrating deep into the 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?
Looking after a deteriorating concrete structure? Get in touch!
For more on this topic, try our on-demand webinar, “The Marine Concrete Experience“.
