Opinions Please on Sub Base

[wozza]

Hi All,

 

Looking for your opinions on the sub base that we have had laid.

 

We asked the contractor to excavate the area to the side of the drive (so it can be eventually extended) - and to then to lay the sub base approximately 100mm lower than current drive with a ramp upto the drive and new garage so it can be used until we are ready to lay the block paving.

 

He said he has used "Crushed Concrete" as the sub base "as approved by the local council"- the problem is that it has not compacted very well at all as there is a lot of large material and also a lot of very fine material - and it consists of concrete, tarmac, blocks, bricks, tiles etc. He gave up trying to rake it level before compacting it and he admitted that "there is a lot of big stuff in it"

 

He now wants to try spread some "fines or tarmac planning's" over the top to try compacting it again.

 

We need to be able to drive over it and use the garage (which he was told)

 

What do you think? should we let him try using "fines" over the top? The tape is set at 400mm for scale.

 

 

 

 

 

 

[tonyshouse]

I would like to see him use road planings - fines could mean black sand so you want to see a sample 0.5m2 trial patch first 

[Marvin]

I understood to make a good surface the crushed concrete should be mixed fines, small and large items. The maximum size of the crushed concrete should be no more than half the thickness of the layer to be compacted and the fines should fill all the voids when compacted avoiding the fines in the ground below rising up to fill the voids causing the area to sink.

I usually compact the filling until no more fines will go in. the fines hold the larger pieces from moving.

 

Good luck.

 

M

 

[wozza]

I have just done loads of reading - it looks like the material he has used is 6F2 which is sized from 75mm to dust - all the suppliers websites say it should be topped with a type 1 size material. He also used a lightweight Wacker plate and didn't compact in layers.

[Marvin]

If the surface is to be left exposed then the areas of fines will wear away easily. Like driving on a beach. The mix is important. In Ministry of Transport type 1 fill the different grades are blended at source for maximum when compacted. This material is known as subbase.

[Marvin]

8 minutes ago, wozza said:

topped with a type 1 size

Yup MOT type 1

[Marvin]

My light weight compactor will handle type 1 ok, but not bits 100mm by 200mm as in your photo.

M

Edited August 1, 2021 by Marvin
Add info

[nod]

4 minutes ago, Marvin said:

My light weight compactor will handle type 1 ok, but not bits 100mm by 200mm.

If your going to be using it as a temporary drive 

He needs to hire a drive on roller 

It will crush the big stuff like eggs 

 

Our hardcore was just like yours I hired a ride on roller 50 quid dropped off at 8 collected at 12

I used a couple of ton of 20 mil to dust to fill in the any. It

It was used for van and 20 ton lorrys for twelve months before we paved it 

I had to use a breaker to put the gate boxes in 

 

Edited August 1, 2021 by nod

[Onoff]

My Evolution electric whacker seemed to cope OK with the hardcore I graded through a piece of mesh to give 40mm down to dust. That's only 5kN from memory.

 

Saint-Nazaire was a good sub base btw...I'll get me coat!