What is the maximum concrete cover?

[ssbear]

Hi there,

Does any code specify the maximum concrete cover? It is the concrete embedding a turbine in a hydro-power plant. Due to some construction issues the contractor wants to lower the top rebar mat, which makes the concrete cover 120mm for the top rebar. I don't know if that would cause any cracking problems in the long run. The project design basis report required a minimum of 40-70 mm concrete for different locations but it didn't specify the maximum values. My thought is that the rebar should be close to the concrete face due to constant vibration from turbine and generator but I can't find anything documents to support it. The concrete has a strength of 35 MPa.

Thanks,

Alex

 

[jayrod12]

You would need to check the crack control parameter as well as any negative bending the slab may see.

moving it down an additional 50mm if it sees any negative bending would likely be a deal breaker.

 

[hokie66]

jayrod12 is correct. You can't lower top steel from the intended position without decreasing the bending strength. You should pose this question to the design engineer.