Reinforced concrete footing cracks/ghosting

[lucy778899]

Hello all

We recently, started our side extention. Engineer specified a reinforced concrete footing with rebar and mesh. We poured concrete a few days ago and are seeimg the mesh squares telegraphing through to the top of the concrete now its dry. These are hairline in most case but a few are wider and more prounced but dont appear deep.

Builder says its normal and due to recent heat and settlement.

Would anyone know if this is normal or should we worry?

Any thoughts will be appreiated. I'll get some.pics up later.

TIA

 

[noseall]

Hello all

We recently, started our side extention. Engineer specified a reinforced concrete footing with rebar and mesh. We poured concrete a few days ago and are seeimg the mesh squares telegraphing through to the top of the concrete now its dry. These are hairline in most case but a few are wider and more prounced but dont appear deep.

Builder says its normal and due to recent heat and settlement.

Would anyone know if this is normal or should we worry?

Any thoughts will be appreiated. I'll get some.pics up later.

TIA

Foundation concrete is usually thick enough for this to not be a concern. Floor slabs etc, are different in that respect (thinner) and need more care when laying in extreme temp's.

 

[stevie888]

Well he's correct to the extent that it;s normal if the concrete is placed too wet, not properly compacted and not covered for curing.

The excess water migrates upwards washing cement particles with it which leaves a dusty surface. The aggregates settle to take up the space now available but are impeded by the mesh so you typically see the surface curve up at the bar location from each side with a. tapering crack. Ironically it's worse if the mesh has been properly fixed as it then won't move whereas if it was just thrown in mid pour then it will partially at least settle with the concrete.

It's a sign of poor workmanship.

It's not normal to have reinforcement in conventional deep strip footings though. Drop edges slabs or ground beams yes. Be interstingto see your pictures.

 

[^woody^]

If the concrete has patterns of the reinforcement, then the reinforcement may be too near to the surfaces

Reinforced strip foundations are not normal, so if it's unnecessary design, then there may be nothing to worry about

 

[lucy778899]

Thanks you all for the responses, all valuable insights.

Just to add, we have a reinforced concrete footing (where mesh pattern is showing), this will support a reinforced concrete retaining wall, with block/brick each side. This goes up to dpc and then normal facing bricks.

We had a tree nearby and a slope which is the reason why we have this design.

 

[lucy778899]

A few pics, this is probably the worst section

 

[noseall]

A few pics, this is probably the worst section

Deep pour shrikage in thisty ground is normal. We have seen as much as 10mm down the pegs. What isnt normal is the proximity of the mesh to the surface of the concrete. Mind, having said that, with floors, 40mm cover is acceptable.

 

[lucy778899]

Thanks, the heat and drought didnt help i thibk. 50mm was specified and marked out with spacers, so should be not be far off that level. Would this be ok to build on or does it need fixing, crack filler, epoxy, additional concrete?

 

[noseall]

Thanks, the heat and drought didnt help i thibk. 50mm was specified and marked out with spacers, so should be not be far off that level. Would this be ok to build on or does it need fixing, crack filler, epoxy, additional concrete?

50mm is more than enough to prevent (oxygen) exposure. I guess what folk are looking at are the surface cracks. It's unlikely they'll penetrate all the way down to the reinforcement though.

 

[lucy778899]

Thanks noseall. Thats reassuring confirmation. Aligns with builder and what I researched elswhere.

Waiting to get a SE opinion as well so want to be prepared before carrying on. Thanks

 

[stuart45]

Why did the SE specify all that steel in a strip foundation?