Chiangmai Concrete Beam Repair?

[cheeryble]

Hi

Problem is a blown (spalled), large concrete beam caused by water leaks from above probably combined with the bar being not as deep as it might be.

Over several feet the rebar has rusted and flaked out the concrete along the bottom and up the sides a little.

I checked the rebar, which looked very rusty but on scraping it turned out to be good shiny steel close to the surface.

Believe the source of damp , rain and other water, leaking through a deck from above, has been cured with a resurfaced deck (to be confirmed when rainy season starts proper).

I think I know what the cure is........chipping back, rust removal, epoxy or other treatment of the steel, and specialised mortar patching to fill, with no feather edging so edges cut in at 90degrees if necessary. I think Sika make products.

Preferably need a specialist company for this work.

Does such a beast exist in Chiangmai?

Else what would be a good way of finding one?

Thanks!

Edited June 10, 2013 by cheeryble

[keeniau96]

Any repairs you make will be only cosmetic, no way to restore the loss of strength.

[cheeryble]

Thanks for your answer.

Are you talking about tensile or compressive strength?

Here's how I see it.

At the bottom of the beam compressive strength isn't needed, the concrete (which is so essential at the top of the beam where it's compressive strength helps stop the beam bending) is really only holding the rebar (which does all it's work in this area, the bottom, of the beam) in place, so filling with a specialist replacement is appropriate. As for the rebar sure deep corrosion would lose tensile strength but surface rusting would be tiny compared to the built in sizing redundancy.

Edited June 11, 2013 by cheeryble

[keeniau96]

Concrete itself has about zero tensile strength but very good in compression. Thus bottom concrete spalling does not have effect on strenght; as you correctly noted the top is compressive load. If the top has maintained it's integrity should be no structural problem if the rebar is OK. However, given the water damage coming from the top I would be suspicious of the condition of the concrete there. Safest would be to add a parallel steel beam to take the load, but it would need supporting columns.

[cheeryble]

Thanks Keeniau

We are hoping to get access for an inspection.

Don't get me wrong. I'm not a concrete engineer, but hope I know more than the average bear.

Even if I was I still need a firm to do the job properly which is why I'm here.

The good thing about concrete is it always shows rebar damage by blowing so a good check is necessary. Even if there was a cavity and no blowing there would be strong rust stains from any meaningful corrosion. Chances are water would enter the join between the beam and the floor hooked into it.

Anyway we'll have a look.

Thanks!

Edited June 13, 2013 by cheeryble

[bbradsby]

Biggest red flag is that the concrete spalled with just surface rust to the rebar, indicating poor quality/strength concrete. The entire beam is suspect. Can you add a column or two to reduce the beam span? Also, how many lineal meters of spalling are we talking about? Concrete struct repair is possible via epoxy grouts, but a bandaid applied to a gaping, bleeding wound will only cover the problem.

[thaiarcher]

What has been said so far is all correct. But you were also asking for someone who could do the repair. The only company I know of, who has the products and who may also do the repair, is a shop called "Home Repair Shop". Coming from Huai Kaew Rd. on the Superhighway heading south, the company is on your left, in a one story building, approximately 200 meters before the road turning left to Mae Joe. The owner is knowledgeable and speaks English. I hope that helps!

[cheeryble]

I know that shop.

Thankyou!

I believe they specialise in keeping water out but it'd be worth a try.

To BBradsby......you know perhaps there was enough rust to spall but still was shallow enough for the steel to be more than adequate.

In any case will be speaking to owner tomorrow and try to get another look see soon.

Also thanks!

Edited June 19, 2013 by cheeryble

[cheeryble]

Wanted to keep this thread visible hoping for info.

Latest

Just found out our first choice.....a recommendation from the surveyor.....is apparently impolitic.

So it's back to finding a recommendation for a specialist concrete repair company.

(I shall indeed now go to the Home Repair shop also now)