Dunno in detail. Our foundation concrete came from Eastern Concrete https://www.easternconcrete.co.uk/ who happen to have their head office in Stowmarket and who also seem to have a depot in Cambridge. They do mix-on-site, which we got, so there's no waste. They were contracted by our groundworkers/foundation builders (Mead https://www.meadplantandgrab.co.uk/ ) and Michael was very keen on the eco-nature of our project. I believe it was a GGBS mix but I'm no expert in the specifics. Mead were on a fixed price contract so I don't know the concrete cost.

Posted By: jms452Did you ask for low carbon concrete or did they offer it?

You probably don't have these but just in case...:
Was there a spec in either carbon intensity or GGBS/cement quantity?
Was it called CemFree any any chance?

I'm afraid the answer to all three questions is 'sorry I don't remember' !

It's dependent on where you are in the country and what is being used in the mix instead. As I understand it the GGBS for instance is subject to availability and demand. For a while it was very hard to find as we gradually reduce the industries that create it as a waste stream.

Depending on use you can also look into void former solutions for things like floors ( e.g. BubbleDeck) which physically displace the concrete, but I think options are more limited for foundations.

Posted By: djhOur slab has quite a complicated shape underneath. There's a flat slab 150 mm deep and on the underside there are strengthening ribs another 100 mm deep spaced 1200 mm (one sheet of EPS) apart. I believe that's designed to allow a thinner slab that's still sufficiently strong, so as to minimise the amount of concrete and rebar. A bit like BubbleDeck and suchlike do.

That's very cool Dave - As far as you are aware is this a carbon reduction measure or typical practice?

Q for everyone:
There seem to be lots of established methods of reducing the CO2 emissions from concrete elements out there.
How widely used are these on real projects?

Posted By: jms452As far as you are aware is this a carbon reduction measure or typical practice?

As I remember it's to reduce the amount of concrete, both for carbon and cost reasons. The slab was originally going to be 100 mm but had to be increased to 150 mm to meet NHBC guidelines. I don't know how widespread the idea is.

There seem to be lots of established methods of reducing the CO2 emissions from concrete elements out there.
How widely used are these on real projects?

I think they're becoming quite widely used especially by any project trying to meet one of the 'project excellence' rating schemes. But whether they've made it to e.g. large housing estates yet, I've no idea.