Laying a concrete floor

[Bannon]

I'm in the process of laying a new concrete floor in the house and have just started to dig down to find my level before getting the old mixer going.

Question: What I am digging out consists of gravel, sand, chalk rocks and some sandy soil.... can I not just use this to mix with cement instead of sand and tip it all back in and if so, at what mix ratio?

Cheers, off now to lean on my shovel!

 

[condorman]

Hi Bannon, Not recomended matey, The composition of the mix you have in the ground may well cause the concete to crack,  I have done this myself on garden projects and there has been reactions between the mixed aggregates causing severe cracking,  It reely is best to use clean agregates that are for the job,,, I like to recycle and save a few euros but this could be costly in the long run, Chalk is no good in concrete,,  Have you ever heared of Mundic Block ?? concrete blocks and prefab slabs were made using a mix of cement and sand n agregates from river beds, the blocks were made in the 1950's using on site materials, they are fine untill they get damp, then the delitrious mineral agregates react and the blocks crack or crumble,, I bought a house built from this that i demolished,  I knocked the whole house down on my own using a sledge hammer, hit the blocks once and they would shatter into hundeds of individual agregates,,,,  there are still many houses around that were built from this, and as long as they remain damp free thelyle be fine.....  unless you know exacly what youve got ide steer clear of doing this, best of luck....condor

[Dave&Olive]

this should give you a hint .WASHED  sand and gravel

            dave

[Bannon]

Thanks guys, much appreciated, new gravel on order!