Pop-outs on my concrete ceiling ..

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Pop-outs on my concrete ceiling ..

Postby groucho » Mon Oct 28, 2013 10:26 am

Hello,

On the top floor (4th) of my house the ceiling is riddled with many areas where the rebar has rusted causing the cement to pop out, leaving the exposed rusty rebar and rather deep crevice around it. To repair these pop-outs I want to dig out/expose the rusted rebar, get rid of the rust by using a spray on rust remover, and wire brush. I will then use some paint I have to cover the rebar, then use the Kangaroo mortar (forgot the name, but has Kangaroo on the bag), after hardening I want to use a TOA Fibermesh, before using a final finishing product to smooth the areas.

Is there any technique that I should use for patching the deeper areas, say 1 1/2 inches to make sure these areas don't somehow hold?

Thanks,

Groucho
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Re: Pop-outs on my concrete ceiling ..

Postby schuimpge » Mon Oct 28, 2013 1:45 pm

I think you should start with finding the cause of it.
Otherwise you will one day see much bigger problems.
Regards,
Luc
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Re: Pop-outs on my concrete ceiling ..

Postby Mike Judd » Mon Oct 28, 2013 2:03 pm

Hi there ! You should read my post about Concrete Cancer., You don't give enough details for a remedy if possible. Is it your roof or as you said the top floor. If it is open to the weather on it's top side you have a big problem as it means the moisture has reached the steel which then proceeds to expand and blow off the concrete. Most concrete is Not waterproof and needs a protective coating of some sort.
If it is completely inside it's a strange one, unless the steel was displaced when the slab was poured (which is a common occurrence ) and ended up only M.M. from the surface and rusty to start with. Anyway the normal procedure is as you said, to bare the steel ,treat as much of the steel as possible that you can get at, then patch it using Cemstic or something similar in the mix. Don't use too strong a mix cement from the original as they tend to expand differently over time. All concrete should have a min of 10m.m. cover, other wise you will have problems later. It's better to have more than less. Good luck.!
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Re: Pop-outs on my concrete ceiling ..

Postby groucho » Mon Oct 28, 2013 4:13 pm

The pop-outs are on the ceiling of the fourth floor, above is the uncovered roof of the building. Yes water seeped down through the roof to the rebar, and rusted it expanding the steel until the concrete blew out. Shortly I will be getting a Bluescope steel roof covering the old roof. After which I will treat the mould on the original roof, apply a sealant/barrier, then pour a new waterproof concrete layer. I am planning a thirty day dry out period for no water on the roof before treating the pop-outs on the ceiling below.

I was just wondering if I have to stuff any wire mesh up into the bigger divots around the exposed rebar to make sure the patch work holds?

-groucho
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Re: Pop-outs on my concrete ceiling ..

Postby Mike Judd » Tue Oct 29, 2013 6:03 am

That sounds like your roof slab is stuffed, so it all depends on how much, whether it will stay there once you protect it with a new roof over. Are you going to use that slab to support your new roof or have it completely independent .? If there is a danger of the slab falling later if it has a lot of rusted steel not seen yet, it might be wise to demolish it . That would require a scaffold under the spans to catch the concrete as it's broken up. Other wise if it is all O.K. structurally it will dry out pretty quickly once the new roof is on so as to repair the blow outs. Cemstik or similar cement adhesive in the mix will make sure the patch stays there. You would have to fix any mesh or steel that you put in there to the original steel to do any good in that regard. Could be a big job that you have there.
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Re: Pop-outs on my concrete ceiling ..

Postby thailazer » Tue Oct 29, 2013 8:02 am

If the concrete is popping out, wouldn't that suggest that the roof is under stress? Worth evaluating that prior to patching.

For patching, I wonder if just using epoxy putty wouldn't be the easiest. Plug the hole, put a pile on a plastic covered plate and wedge the plate against the ceiling.
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Re: Pop-outs on my concrete ceiling ..

Postby geordie » Fri Nov 01, 2013 11:28 am

Fist the kangaroo mortar is for aaac block laying ??? or maybe the BM sold me the wrong stuff
The pop outs could well be caused by the original builder using rusty steel or poor quality in the mix either way you have to remove the rust as best possible physically not just a spray with a paint as steel rusts it will expand causing the concrete to blow very well documented problem in theUK 60,s and 70,s ) in the UK it was the demise of a lot of constructions known then as concrete cancer usually the damage will extend beyond what you see as you are seeing only the worst of it I would be inclined to use a small drill with Kango attachment to investigate beyond the visible damage and same process physically wire brush and sand as best you can to remove rust then when repairing use a waterproofer in the mortar
Rresin would be an excellent solution but a very expensive one if the holes are deep chicken wire can be stuffed into them it will aid the filling but its the rebar you need to save ?? After you repair it keep a close eye on it and see if the problem re occurs I have seen a listed building repaired in the UK which had the same problem
Uxbridge underground station which is in fact a surface station in that instance resin was used cement mortar on smaller area,s and also cutting through the original roof
and replacing / paching really bad area,s the problem there was cause by High Alumina Cement rapidly reaching full strength it had the negative of being porous more so than conventional cement/concrete it was also fond of cracking particularly when poured in large areas slabs beams walls
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: Pop-outs on my concrete ceiling ..

Postby groucho » Fri Nov 01, 2013 3:47 pm

Yes geordie the kangaroo mortar is for aaac block, as you know it sticks to everything and is very difficult to get off. I want to use a small amount to cover the rebar after a primer, and before using a patching product. And yes I will look for a epoxy resin filler to patch the divots around the rebar.

As these pop outs are only on my top floor I will allow plenty of time to observe before doing the actual finish painting. As you know these blow-outs are quite common in Thailand. My building is about 25+ years old, and except for the top floor ceiling is in pretty good shape. I will try to follow up with a photo of the problem ceiling, and the repair work.

Many thanks for your advice,

-groucho
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Re: Pop-outs on my concrete ceiling ..

Postby pattayapope » Fri Nov 01, 2013 4:21 pm

This reminds me of a very funny story a few years back in my old town house I was watching a horror movie and a piece of cement dropped from the concrete planks used to support the upper floor and fell onto the plasterboard ceiling, I think I jumped about 2 feet in the air as I did not know what it was until I removed part of the plaster board ceiling. Same thing as you found caused by rebar in planks corroded and bust open the concrete. :lol: :lol: :lol:
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Re: Pop-outs on my concrete ceiling ..

Postby groucho » Mon Jul 21, 2014 1:43 pm

It's been more than a year from my original post on this subject. The ceiling pop outs of exposed rusted rebar was treated as mentioned above then rendered with a combination of gypsum, concrete and sand. The high ceilings and beams are exposed, as I prefer the height, and style for this converted shophouse. I have pained the 4th floor ceiling using matt ceiling paint, and although the coverage was very good, a couple of observations:

1. Standing directly under the ceiling there is a no visible inconsistency in the look of the painted surface.

2. When you look at the ceiling at an angle with reflected light coming in from the front windows, there are varying degrees of surface inconsistencies.

When I inspect the visible surface inconsistencies, I can see the blemishes caused by the finished render. I have decide that I can live with it, as later in the day when the sun is not directed through my windows the troublesome areas all but disappear.

As I have four more ceilings to paint this is my delima. The 3rd, and 2nd floor ceilings are perfectly finished and are white and crisp looking, at this point they have no visible surface distortion from any direction. I would like to leave them in their natural finish, but I want to apply some kind of clear protective coat to seal them without changing the appearance.

Does anyone have a comment or suggestion regarding a product that provides surface protection from, discoloration, dirt, moisture, etc.

Thanks,

groucho
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Re: Pop-outs on my concrete ceiling ..

Postby Sometimewoodworker » Mon Jul 21, 2014 5:37 pm

groucho wrote:It's been more than a year from my original post on this subject. The ceiling pop outs of exposed rusted rebar was treated as mentioned above then rendered with a combination of gypsum, concrete and sand. The high ceilings and beams are exposed, as I prefer the height, and style for this converted shophouse. I have pained the 4th floor ceiling using matt ceiling paint, and although the coverage was very good, a couple of observations:

1. Standing directly under the ceiling there is a no visible inconsistency in the look of the painted surface.

2. When you look at the ceiling at an angle with reflected light coming in from the front windows, there are varying degrees of surface inconsistencies.

When I inspect the visible surface inconsistencies, I can see the blemishes caused by the finished render. I have decide that I can live with it, as later in the day when the sun is not directed through my windows the troublesome areas all but disappear.

As I have four more ceilings to paint this is my delima. The 3rd, and 2nd floor ceilings are perfectly finished and are white and crisp looking, at this point they have no visible surface distortion from any direction. I would like to leave them in their natural finish, but I want to apply some kind of clear protective coat to seal them without changing the appearance.

Does anyone have a comment or suggestion regarding a product that provides surface protection from, discoloration, dirt, moisture, etc.

Thanks,

groucho

A water based polyurethane would probably do the job. The best I've found is only available from home pro.
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Re: Pop-outs on my concrete ceiling ..

Postby groucho » Mon Jul 21, 2014 10:50 pm

Thanks, I'll take a look.
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Re: Pop-outs on my concrete ceiling ..

Postby Sometimewoodworker » Tue Jul 22, 2014 10:47 am

groucho wrote:Thanks, I'll take a look.

I'll get the name for you later when I get back home from work
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Re: Pop-outs on my concrete ceiling ..

Postby Sometimewoodworker » Tue Jul 22, 2014 7:05 pm

Sometimewoodworker wrote:
groucho wrote:Thanks, I'll take a look.

I'll get the name for you later when I get back home from work


Here you go

image.jpg
Water based poly
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Re: Pop-outs on my concrete ceiling ..

Postby groucho » Tue Jul 22, 2014 8:54 pm

Many thanks.
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