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Mix up in grade of concrete

Mix up in grade of concrete

Mix up in grade of concrete

(OP)
I had specified the contractor to lay down an M20 concrete slab for a two storey residential building but he layer down an M10 grade. Will it cause any problems and are there any precautions to take or any procedures to strengthen the concrete

RE: Mix up in grade of concrete

Is this the ground slab or an elevated slab?

The short answer: you need to check with your structural designer. It can cause significant problems in some cases (especially the elevated slab).

Typically any attempt to strengthen concrete that has already been poured is more expensive than just removing and replacing the concrete in question. In some cases, your engineer may be able to come up with a creative and cost-effective solution.

----
The name is a long story -- just call me Lo.

RE: Mix up in grade of concrete

(OP)
Thanks for the reply and It is an elevated slab for a 2 story residential building with an area of 1200 square feet layer down 2 days ago. Will it work or do shall we replace it .

RE: Mix up in grade of concrete

Shear and long term deflection are likely the issues. For small percentages of steel, flexure is not likely an issue. There is a large difference and if schedule is an issue, then replace it outright. Your EOR has to review the condition to see if acceptable.

Dik

RE: Mix up in grade of concrete

This FAQ (FAQ507-1575: How to Evaluate Concrete Tests per ACI 318) is the US sequence from ACI 318 for responding to possible low strength concrete tests.

In your case you know that the wrong mix was used but you will eventually get compression test information back and you can and should respond to those results.
Many times the actual test results (and resulting fc value) will come up higher than that intended.

It may be (based on Lomarandil's reference to the structural check of the slab) that the lower strengths still work. Just have to check.






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RE: Mix up in grade of concrete

Not sure if you are using ACI or not, but in ACI there are minimum strength requirements depending on exposure to sulfates, deicing chemicals, freeze thaw, etc. You may need to get approval from the AHJ to get around those requirements if they apply to you.

RE: Mix up in grade of concrete

If by M10, you mean 10 MPa, that is not structural concrete. Where I am, 20 MPa is not even considered to be structural concrete.

RE: Mix up in grade of concrete

Why are you asking the internet? Is there no engineer for this project who is responsible? Ask him or her.

Or replace it. Those are your options.

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