All Topics / General Property / Advice Requested: Rust in Concrete Reinforcements

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  • Profile photo of parismyloveparismylove
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    @parismylove
    Join Date: 2006
    Post Count: 7

    Hi All

    Wanting some advice.

    I am looking at an apartment near a beachside suburb.

    The floors have been done with a fancy concrete rendering, they have been sealed with a resin. However in 2 places there is concrete reinforcing that has been exposed and appears to be rusting.

    Could this be indicative of anything more serious?

    Is it worth still considering the apartment less the amount it would cost to fix this, or should I just avoid the apartment altogether. It is built around the 1970s.

    Any opinions greatly appreciated.

    Paris.

    Profile photo of jhopperjhopper
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    @jhopper
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    Hi Paris,

    Can you give me a few more facts. Is it internal or external (balcony or inside the unit), is ist exposed because concrete is missing, ie a crater in the concrete so the reinforcing is exposed. How rusty are we talking about, a bit of brown flakey dust or is the steel pitted (looks like the steel has been eaten)? What City are you in out of curiosity?

    All depends on circumstances really. If the cover to reinforcement was inadequate and the concrete is spalling, could have an issue but hard to say without more info.

    Profile photo of parismyloveparismylove
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    @parismylove
    Join Date: 2006
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    Hi Jhopper

    Thanks for the quick reply.

    It is inside the unit, it is in Sydney near one of the popular Eastern beaches.

    It seems to be exposed as when the ground down the concrete, they hit the reinforcements. But there is a resin layer of sorts – apparently polyurethane. So some reinforcements were exposed due to the polishing, and they are rusting to a certain degree.

    It looks brown but not pitted.

    I am not bothered about it from a cosmetic perspective, but rather if this could mean something more serious.

    Any help appreciated.

    Thanks
    Paris.

    Originally posted by jhopper:

    Hi Paris,

    Can you give me a few more facts. Is it internal or external (balcony or inside the unit), is ist exposed because concrete is missing, ie a crater in the concrete so the reinforcing is exposed. How rusty are we talking about, a bit of brown flakey dust or is the steel pitted (looks like the steel has been eaten)? What City are you in out of curiosity?

    All depends on circumstances really. If the cover to reinforcement was inadequate and the concrete is spalling, could have an issue but hard to say without more info.

    Profile photo of jhopperjhopper
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    @jhopper
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    Hey Paris,

    My immediate reaction would be it spells trouble. If th reinforcing was exposed through polishing it could throw into question how much concrete cover they provided to begin with, and when they polished how much concrete did they take off. Also, how long ago did they do the polishing?

    Failure of reinforced concrete can occur when moisture has access to the steel. This in turn rusts the steel and reduces it strength over time. Can also cause concrete to spall (pops out blocks of concrete causing craters.)

    Like I said, immediate thought would be concern, however having said that, I would have to see it first. Sorry, based in Perth so bit of a long haul to check it out. A builder should be able to give you a quick assessment.

    As for the current rust, not a big issue as the brown residue dosn’t sound structural. Can certainly lead to more strucutal issues though.

    Profile photo of parismyloveparismylove
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    @parismylove
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    Thanks for the quick response.

    I did get a builder to check it out, and his response was:
    “A well bonded cement topping over the slab may be required at some stage.”

    The polishing was done very recently apparently.

    My next question is if this will sort out the issue, is this an expensive exercise? Will it solve the problem?

    Just trying to work out if it is worth securing the property at a good price – this issue may scare away other buyers – allowing me to get it at a good price, and factor in some repairs.

    You have been helpful, thank you. :)

    Paris

    Originally posted by jhopper:

    Hey Paris,

    My immediate reaction would be it spells trouble. If th reinforcing was exposed through polishing it could throw into question how much concrete cover they provided to begin with, and when they polished how much concrete did they take off. Also, how long ago did they do the polishing?

    Failure of reinforced concrete can occur when moisture has access to the steel. This in turn rusts the steel and reduces it strength over time. Can also cause concrete to spall (pops out blocks of concrete causing craters.)

    Like I said, immediate thought would be concern, however having said that, I would have to see it first. Sorry, based in Perth so bit of a long haul to check it out. A builder should be able to give you a quick assessment.

    As for the current rust, not a big issue as the brown residue dosn’t sound structural. Can certainly lead to more strucutal issues though.

    Profile photo of jhopperjhopper
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    @jhopper
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    Hi Paris,

    Ok, a well bonded topping probably means you will have to scabble the concrete surface (roughen it up so you can get a good connection). Normally for a topping you would use a self levelling cement mix like Ardit.

    What he is trying to achieve is increasing the cover of concrete so that moisture won’t get to the reinforcing as concrete is porous. All seems to make sense and believe it should solve the problem

    Not sure on costs to do this but your builder should be able to give a guesstimate.

    Profile photo of Dave LDave L
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    @dave-l
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    Hi Paris,

    Like jhopper says it’s hard to tell without looking at it but it does’nt sound too serious. Reo is frequently installed in slabs of concrete these days already rusty. Builders buy so much for the job and it sits there in the weather until it is used. Usually you would have at least 30mm coverage of concrete over it but when it is poured things get trodden on and moved so less coverage sometimes occurs. Get an engineer to have a look if in real doubt. You could still haggle with the price subject to building inspection like you say it could work in your favour.
    Good luck

    Dave

    Profile photo of parismyloveparismylove
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    @parismylove
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    Thanks for all the feedback. Never ceases to amaze me how there is always so much to learn. :)

    Paris

    Profile photo of jhopperjhopper
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    Hey Paris,

    The only reason I have any vague idea about this is because I work as an Engineer for a reinforcing supplier. I would think this really is an unusal case for investing so don’t be too hard on yourself! :)

    What have you decided? Going to go for it or not?

    Profile photo of depreciatordepreciator
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    I did get a builder to check it out, and his response was:
    “A well bonded cement topping over the slab may be required at some stage.”

    Given the apartment has obviously been renovated, you wouldn’t want to consider the above. Putting a topping on would require doors to be removed and trimmed etc.
    At least with the clear topping you can see and monitor the steel.
    If the whole block has been renovated, have you knocked on any doors to see if any other owners have problems?
    You’re right to be wary of rust at that location.
    Scott

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