Ballast question

[petej42]

I want to lay a thick concrete slab(600mm in places) as a shed base and intended to use a maxibag of ballast and cement. Many builders merchants seem to offer only ballast with small stones. More like a very coarse concreting sand, such as this from Travis Perkins
https://www.travisperkins.co.uk/Travis-Perkins-Sand-and-Stone-Ballast-Bulk-Bag/p/938169
Is this really as strong as sand and gravel, I was always under the impression that it was the gravel that gave the concrete it's strength.

 

[Notch7]

The ratio of large aggregate to smaller fines in concrete affect its strength.

Ballast should have a good mix -usually with bigger stones upto Id guess 40mm and small stuff.

I n the context of a shed I cant see it making much difference.

Pumped concrete only contains small stones.

 

[Ian H]

The Travis one will be 20mm stone which is pretty standard.

 

[scbk]

I want to lay a thick concrete slab(600mm in places) as a shed base

Is it a typo or am I missing something? 2ft deep?

 

[petej42]

No, 600mm is correct. It's a foundation for a telescope pier. Most of the shed base will be around 100mm thick. But part of it will be 900x900x600

 

[petej42]

Thanks for the replies everyone, probably going to go for the Travis Perkins one