Rebar rust staining on concrete soffit

[Joshie485]

Hi All!

I live in an apartment complex that was completed less than 10 years ago. Recently, I noticed what looks like reinforcement rust staining on the soffit of the concrete slab in certain areas of the underground carpark. I don’t have much experience dealing with this kind of issue, so I’m hoping to get some advice on what steps I should take.

My main concern is that the reinforcement may be actively corroding, which over time could reduce the effective steel cross-sectional area and potentially lead to structural failure. There's also the risk that corrosion could cause the concrete to spall.

If the steel is indeed corroding, I assume the typical approach would involve temporary propping, scabbling the concrete to expose the reinforcement (removing enough to assess the extent of corrosion), cutting out the affected steel, and patching the area with repair mortar. This assumes that no additional reinforcement is needed to restore structural capacity or serviceability.

Any guidance would be greatly appreciated! I’ve attached a PDF with some photos for reference.

 

[Enable]

I suppose on one hand I should commend you for being proactive on things. That's something most people do not do but should. On the other hand, if you are not an engineer you should not be deciding anything by your lonesome. If you are concerned about the problem then you should retain a local engineer who is specialized in restoration work and building condition assessments.

As for a quick assessment, some bar marks are apparent but that may have also been some sort of conduit laid against the surface for a time (or alternatively the contractor used chair bars on the form). The smaller, curly looking rust stains, might be from steel fibers being added to the mix. Odd choice for an underground though and may be something else. In any event, this is hardly something to be worried about today. Here's an example of one of my projects just so you know when you need to be worried! Being worried a dash before it gets like below would be good.





Edit - Here are some of the pictures in line for those that dont want to open the PDF

 

[Ants22]

Is it only locally on the slab? Or widespread throughout the slab? Photo 3 looks curious with the 'white'ish' staining on the side of the beam. Is at that location above the slab open to rain?

Some of the photos look like they didnt clean the formwork or had staining on the formwork before they poured concrete? Or at least didnt clean off the tie-wire (tie-wire) stains before pouring.

As Enable said, probably best to get a local engineer to have a look and provide advise. Monitor for signs of worsening.

Enable - Those photos are awesome haha.

 

[Brad805]

OP, ask management for a report to start and then go from there. If the owners do not take it seriously you can always plan to move at some point.

Enable, wow, now that was an idea.