Concrete Cover

[ataman]

Hi,

I have a situation where a concrete beam has been poured without the specified cover for reinforcing steel stirrups on one side. I have checked shear and torsion and one leg of the ties would be sufficient. Can one consider rendering the beam with a 3:1 sand:concrete mortar to provide the necessary cover?

Thanks

 

[dik]

It could be OK... small diametre main bars? Is bond an issue? and any problem with fire resistance?

Dik

 

[csd72]

Render is quite porous, so I dont think it will have any benefit at all.

You should use a concrete repair mortar and bonding agent made specifically for patching spalled concrete. Google it.

 

[JAE]

Could you simply paint it with intumescent paint?

 

[ataman]

JAE

I am more concerned about corrosion since the structure is close to the sea. Any comment about the render?

Thnx

 

[csd72]

A few examples of products to do it the correct way.

http://www.lsepoxies.com/

http://www.sikaconstruction.com/con-dealer-repairing.htm

http://www.chemmasters.net/RepairMortars.htm

Use of anything else would be neglecting your duty of care for your client. And it is no more work than putting on a render.

 

[swivel63]

there are placement tolerances for cover and stuff like that. chapter 4 or 5, i think. depends on how much you have in the first place.

 

[Tomfh]

If you are going to bother fixing it then use a proper product such as the ones mentioned. You generally need a bonding agent too so it sticks properly.

 

[archeng59]

what is the cover?

 

[ataman]

Hi

We have about 15mm right now

 

[archeng59]

I agree with csd's recommendation for a repair-type mortar with a corrosion inhibitor included in the material.

 

[swivel63]

what's the cover per plan?

 

[ataman]

swivel,

I don't know what you mean exactly but we have 15mm cover to one side of the stirrups in the worse case and have the required cover for the bottom and top bars.

thx

 

[swivel63]

what do the plans say the cover has to be?

 

[ataman]

Swivel

40mm

 

[swivel63]

if memory serves me correctly, i think ACI has tolerance....but i don't think anything that'll take as low as you have. chapter 7 or something like that.

 

[henri2]

ACI 318 Section 7.5.2.1 has cover tolerances...

(1) for effective depth d> 8 in (203 mm), tolerance is -1/2 in(13 mm)

(2) at beam soffits (which does not apply in this case), tolerance is -1/4 in (about 6 mm)

(3) cover tolerance must not be gretaer than -1/3 specified cover. in your case this will be 40 mm/3 = approx 13 mm

So I guess minimum acceptable cover will be 27 mm if you go by ACI 318 requirements...almost twice the actual cover.

Just curious...was there a concrete inspector before and during concrete placement?

Is the beam fire-rated or not?