Hardcore size

[RichS]

I'm looking for quotes, other than the silly answers I got from Network Rail, for hardcore.

Hilliard has specified 30-50 dia. so I'm assuming that I just want clean with no fines, would anyone agree with this assumption.

[jack]

The network rail stuff is, as far as I know, what some including me have used as a replacement (with Hilliard's blessing) for the specified 28-50 (from memory) angular no fines material.

 

It's been a while, but I seem to recall that this is an unusual spec in the UK, which is why recycled rail ballast became of interest. 

 

If you can find a source of hard, angular, no fines material with a slightly different size range, I'd just give Hilliard a call and ask whether he's happy with it as a replacement. Not sure whether a revised formal spec will be required - worth checking with your building inspector.

[Jeremy Harris]

I'm pretty sure the spec for ours was clean, washed, no fines, 18 - 35, which is not that easy to get here.  I seem to remember we paid a fair bit for ours, as we weren't aware of the railway ballast option.

[jack]

1 minute ago, JSHarris said:

clean, washed, no fines, 18 - 35

 

Just checked our spec and it's actually 30-50mm. Not sure where I got the 28mm lower number from!

 

[RichS]

Half the area of what will be the new house footprint is where I have just knocked down my original garage. This area already has a 300mm layer of 40mm down MOT1. Obviously  with the price of hardcore I am reluctant to just dig this out and skip it. What are the views on using this as a base layer over the complete area and then topping it up with 20-40 clean. Or alternatively trying to mix this material in with 20-40 clean so you end up with a hybrid mix.

[RichS]

And another question

I've just spoken with two local quarries. The first one is charging just over £15 + VAT per ton for 40mm washed limestone, the other is charging just under £10 + VAT per ton for 40mm washed hard chalk.

Obviously the latter is the favourite but is hard chalk acceptable??

Edited September 18, 2017 by RichS
Spelling

[Gone West]

42 minutes ago, RichS said:

Half the area of what will be the new house footprint is where I have just knocked down my original garage. This area already has a 300mm layer of 40mm down MOT1. Obviously  with the price of hardcore I am reluctant to just dig this out and skip it. What are the views on using this as a base layer over the complete area and then topping it up with 20-40 clean. Or alternatively trying to mix this material in with 20-40 clean so you end up with a hybrid mix.

Under my PH slab I have 250mm type 1 compacted and on top of that 50mm granite fines then the insulation. What you need must surely depend on the ground conditions.

[jack]

46 minutes ago, RichS said:

Half the area of what will be the new house footprint is where I have just knocked down my original garage. This area already has a 300mm layer of 40mm down MOT1. Obviously  with the price of hardcore I am reluctant to just dig this out and skip it. What are the views on using this as a base layer over the complete area and then topping it up with 20-40 clean. Or alternatively trying to mix this material in with 20-40 clean so you end up with a hybrid mix.

 

I doubt mixing is going to be the way forward, as it will affect the way loads are transmitted. As I understand it, no fines means that the larger pieces will lock together under load. 

 

I wouldn't speculate about something as literally fundamental as this. Hilliard is a really helpful guy. He knows your house and your ground conditions. Give him a call and I'm sure he'll set you straight within a couple of minutes. 

[RichS]

9 minutes ago, PeterStarck said:

Under my PH slab I have 250mm type 1 compacted and on top of that 50mm granite fines then the insulation. What you need must surely depend on the ground conditions.

Hi @PeterStarck, Thanks for that, I assume you mean 5mm granite fines??

[Gone West]

@RichS I can't find the spec. at the moment but 5mm max. sounds about right.

[RichS]

So the digger man started today. The existing MOT1 hardcore that I mentioned earlier, I am digging down 150mm deeper than required and then going to spread this MOT1 to form a sub-base for the 30-50 clean. The slab will still end up with the 300mm of clean as required but sat on a MOT1 sub base.

Just to re-ask a question that no one took up on, has anyone used hard chalk for their hardcore??