Cracks on Lean Concrete - Do these need to be repaired? 1

[Eduardo1982]

Dear Guys. I would appreciate your help with my next issue.
Just now I am working in a Project of a power plant. We already completed the backfilling and poured lean concrete. After three weeks we have seen some cracks on lean concrete of a main foundation. The lean concrete's thickness is 100 mm. and 10 MPa.
The engineering says that these cracks need to be repaired. Many people told me that lean concrete is just to have a clean Surface and start to mark and install rebars and embedded ítems. I consider these cracks are a minor point and should not carry out reparation.
However, my engineering insist (without any code or reference) about this point.
Do you (guys) know about any code, standard, reference or technical background about cracks on lean concrete and if these really need to be repaired?
I would appreciate your help!

 

[hokie66]

I assume you mean this is an unreinforced work mat or 'blinding' layer. Cracks in this type subgrade improvement are inevitable, and do not require repair. I would be dubious of engineering advice that required repair, and suggest you seek a ruling from an engineer with more experience.

 

[Eduardo1982]

I attach some pictures for a better understanding.
By the way, my engineering also noted me some parts of lean concrete (blind concrete) shows some breaks.
I would appareciate your comments!

 

[Eduardo1982]

Cracks!

 

[hokie66]

The first one appears to be a construction joint, the second one a drying shrinkage crack. But this is a non-structural concrete working surface, so it doesn't matter.

 

[KootK]

X2 for Hokie's sentiment. The litmus test is usually just "is it stronger and stiffer and more durable than the ground that we're using for bearing below?" And, usually, it is. As the owner or the contractor, I'd be pretty upset if I had to spend money repairing cracks in this.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[darthsoilsguy2]

Are we talking about a mud-mat??? Are we talking about an undercut to suitable bearing soils that was backfilled with lean concrete???

In both situations, you will have better luck finding a reference on training polka-dotted elephants the cha-cha.... then you will finding a reference to cite for when you have to repair this.

Does the engineering division freak out when they find a crack in the soil subgrade?.... Do they call HILTI to come look at it and sell them something???? I assume by power plant.. you meant nuclear power plant. (btw don't answer that question yes, putting photos on the net is a no-no) That industry allows people to be nth-level bureaucratic idiots. they can't see the forest for the trees.

 

[Brad805]

I wonder how they thought this might be fixed and what is the goal of the repair? No need to repair in my books.

 

[Eduardo1982]

Thanks guys for your cooperation and comments.
I just wanted to have some technical opinión regarding this issue (new for me) because in my previous experience I have seen many cracks and a poor quality of lean concrete and no one ever said something for rejection.
I am wondering if you (guys) have seen something similar in other projects without future problems.

 

[Duwe6]

"Is it better/stronger than the dirt under it?"