Concrete Near the Water in Hervey Bay

The problem is the steel

Concrete itself copes well with salt air. The weak point is the steel mesh or reinforcing bar inside it. Salt carried in the air off the water settles on surfaces, and over time chloride can work its way into concrete. When it reaches the steel, the steel can rust. Rust takes up more room than steel, so it pushes the concrete apart from inside, which shows up as cracking, rust stains and pieces breaking away, often called concrete cancer.

Why location matters here

Hervey Bay homes along the Esplanade, from Point Vernon round through Torquay to Urangan, sit very close to the water. The Australian concrete structures standard, AS 3600, classifies exposure partly by distance from the coastline, and sites closer to the coast are treated as more aggressive environments. For engineered work such as house slabs, the engineer sets the concrete strength and the cover to the steel for the site’s exposure.

What helps

Cover. The depth of concrete between the steel and the surface is the main protection. Bar chairs hold the mesh at the right height so it does not end up near the surface or at the bottom of the slab.

A suitable mix. Denser, stronger concrete lets salt in more slowly. Your concreter or engineer can tell you what mix suits the site.

Curing. Well-cured concrete is denser at the surface, which matters most where salt lands. See when you can drive on new concrete for why curing is worth the wait.

Sealing. A sealer on driveways, paths and pool surrounds keeps salt and water out of the surface, as long as it is maintained.

Questions to ask

• What concrete strength is quoted, and why?
• How will the mesh be supported at the right height?
• Will the surface be sealed, and with what?

Next step

For homes near the water, read about house and extension slabs and pool surrounds, or call 0489 955 511 to be put onto a licensed local concreter.