For marine engineers and asset managers: why coastal patch repairs keep coming back, and what to do about concrete that still looks sound.
The inspection report lands: spalling on the jetty soffit, rust staining along the splash-zone beams.
Break out, clean the steel, patch, coat. Job done.
A few years later, new cracks appear. Not in the patches, but just beside them.
It’s rarely bad workmanship. More often, the repair dealt with the damage it could see and left the chlorides it couldn’t.
Why coastal repairs fail next door
Seawater carries chlorides into concrete through its pores, helped by wetting and drying in the splash and tidal zones. Once enough chloride reaches the reinforcement, it breaks down the protective layer that alkaline concrete normally gives steel, and corrosion starts.
- RELATED READING: Disrupting the Concrete Maintenance Cycle
Visible damage shows up long after contamination begins. By the time concrete spalls, chlorides have usually travelled well beyond it.
The patch is new. The concrete around it isn’t.
A patch repair replaces the worst concrete with clean material. The neighbouring concrete, which looked fine at breakout, may still hold enough chloride to corrode the steel.
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The new corrosion that forms around a repair is called an incipient anode, or the “halo effect”. Loughborough University research on UK structures points to residual chloride in the original concrete as one likely cause, alongside the quality of the bond between repair and existing concrete. (Christodoulou, Goodier & Glass, 2015)
New structures start the clock on day one
For new marine concrete, chloride exposure effectively starts from day one. Every tide and storm adds to the load. Good mix design and cover buy time; they don’t stop the ingress.
The MARKHAM approach
The alternative is to treat the whole element, not just the patch. Penetrating hydrogel treatments are sprayed on and set inside the concrete’s pores, rather than forming a surface film. That cuts the movement of water, and the chlorides it carries, through the concrete.
For marine work, MARKHAM frequently uses AQURON 7000, a spray-applied colloidal silica hydrogel for new and existing concrete. It is designed to limit further chloride ingress and help immobilise chlorides already present, reducing their availability to contribute to ongoing corrosion. It is particularly suited to aged concrete with deep contamination.
- FURTHER LEARNING: Extending the Life of Critical Concrete Infrastructure
Applied alongside patch repairs, it treats the concrete around the patch too, helping guard against incipient anodes. Colour, sheen and finish are unchanged.
On new marine structures, treatment can go into the structure before the first season of exposure, so protection starts before chlorides do.
In practice
AQURON 7000 has been used at Dublin Port for corrosion remediation and waterproofing.
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| You can download the Dublin Port Berth 34 case study here. |
Questions worth asking
- Has the condition survey measured chloride content at steel depth beyond the visibly damaged areas?
- What does the repair specification do about concrete that is contaminated but not yet cracked?
- Where did new damage appear after previous repairs on this asset?
- Which elements sit in the splash and tidal zones, and are they treated any differently?
- For new works, what protection is in place before the structure sees its first winter?
Talk to us before the repair specification is locked in
Scoping repairs to a pier, harbour wall, jetty or outfall, or designing a new marine structure? We can review your condition data and advise where treatment fits. Request a marine durability review with our team.
