Why Rust Stains Appear on Concrete Seawalls

‍This post is part of the Seawall Repair Network series, featuring views, news and case studies written by the Seawall Repair Network. 

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Rust on Concrete Seawalls & Bulkheads is a Sign of Decay

Once the steel reinforcement inside of a seawall begins to rust, it expands inside of the concrete and results in spalling (aka cracking). Horizontal cracks (span-running) will then occur as the steel reinforcement of the seawall cap begins to rust and expand inside of the seawall cap. Spalling causes the seawall cap to expand from within itself, which in turn causes the concrete to further break and come apart. Spalling by itself (if allowed to progress) will destroy a seawall by displacing the wall panels. The overall seawall structure relies on the seawall cap to hold everything together.

Repairing the Damage Caused by Rust on Seawalls & Bulkheads

Traditionally, contractors and handymen who perform concrete repair work on seawall caps simply cut through and remove the entire section of seawall cap in need of repair. They then pour new concrete in that section of removed concrete. This form of remediation compromises the integrity of the steel reinforcement of the entire seawall cap.

In order to maintain as much of the original seawall structural integrity as possible, the Seawall Repair Network has created a surgical concrete repair process:

• We identify the extent of the spalling by cutting away the damaged concrete.
• We avoid cutting through any of the original steel reinforcement.
• We continue cutting and grinding the concrete until the extent of the spalling is fully exposed.
• We remove as much rust as possible.
• We add steel rebar as needed to replace severely damaged rebar.
• We install zinc anodes to both ends of the steel being repaired. Zinc anodes are designed to protect buried or submerged metal structural components by sacrificing themselves to prevent the steel reinforcement from rusting. In other words, the zinc anodes corrode instead of the steel rebar. This process is called cathodic protection.
• We then coat the entire service area with a balanced formula of phosphoric acid, dichromates, wetting agents, and extenders. This product is environmentally safe and non-flammable. It seals out moisture and prevents future rust from forming.
• We then install stainless steel screws into the service area to act as structural reinforcements.
• We then utilize forming boards to form and prepare the pouring of the concrete repair material.
• We then pour and form a high-strength concrete repair material to reconstruct the parts of the wall that were damaged by spalling.

End Result: The Best Seawall Cap Repair in the Industry

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