Chlorides, Steel and Time

A spall is where concrete has already let go. Around it is a zone where the steel is corroding and the concrete is still attached, and nobody knows how large that zone is until it is opened and sounded. Any fixed price given before that is a guess with a number attached.

The uncertainty is not evenly distributed either. A garage that has been maintained and coated will usually come in close to the engineer's estimate. One that has been deferred for fifteen years can run well beyond it, because deterioration accelerates and the last few years did more damage than the first ten.

Removing to sound concrete means going past the delaminated material to concrete that is still bonded, which frequently means removing more than looks necessary. The exposed steel is then cleaned or replaced depending on how much section it has lost, and treated before anything goes back.

The repair mortar has to be compatible with the surrounding concrete and properly cured, which in Florida heat means protection from drying too fast. A repair that cures badly debonds at the edges and the same area is back on the list at the next inspection.

1. 01Sound the structure with the engineer before pricing.
2. 02Price on unit rates with an estimated quantity.
3. 03Measure and document every repair as it is opened.
4. 04Remove to sound concrete and treat or replace steel.
5. 05Report measured quantities monthly so nothing surprises you.

Chlorides travel further than the damage shows. A repair that removes only the visibly failed concrete leaves contaminated material against the steel, and the same area fails again within a few years — which is how owners end up repairing the same bay three times.

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