Compacting Hardcore

[mravant]

Hi,

My builders are in the process of digging down prep work for a concrete floor for a new extension they are building.
They have dug down around 400mm and have hit chalk due to the house being on a slope and lots of top ground already has been removed to get it level.
Speaking to them they said its not going to be necessary to compact the 150mm hardcore they fill as they have hit solid ground (chalk).

Is this correct?

 

[joinerjohn]

I'd get in touch with Dominic Littlewood off Cowboy Builders. I've never heard of a single case where hardcore doesn't have to be compacted.
If they don't compact the hardcore and it then settles after the concrete is poured, you'll end up with voids underneath the concrete.

 

[r896neo]

No that's rubbish. You don't compact hardcore in order to firm up the ground underneath?? You compact it to consolidate it.

Try spreading 150mm depth of MOT on the ground and then walk on it. your footprint will be at least 30mm deep.

 

[theoldun]

In a word NO..

If you lay 150mm of hardcore be it MOT, crushed concrete or hand pitched brick hardcore to either make up levels or to form an acceptable sub base, they all need blinding with sand ad whacking. The material of the sub grade has nothing to do with it
If no fill is required and sub grade is good firm chalk then just blind with sand, lay polythene to stop dewatering and then concrete. No whacking required.
oldun

 

[noseall]

If they happen to leave the hard core un-compacted that's ok.......

....so long as they trample over the entire area for the next couple of months whilst it self compacts.

Unrealistic me thinks.

Get the Wacker plate out.

 

[mravant]

Thanks Guys

I shall have a word with them tomorrow and tell them i would like it compacted trying not to put their nose out of joint.

 

[^woody^]

I'd get in touch with Dominic Littlewood.

And throw him in the trench before concreting. Please

 

[Nige F]

Surrey says it all