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Recipe for strong concrete using ballast.


epsilonGreedy

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Once the sun burns off last night's frost I intend to fill a shallow trench across the entrance threshold of my drive. The dimensions of the trench are 5.5 meters long 300mm wide and 225mm deep. When the concrete is semi set I will bed down a line of granite kerb stones laid flat on the surface of the setting concrete, these kerb stones are 75mm thick by 150mm wide.

 

Given the vehicle traffic passing over I assume a strong concrete mix is recommend and I have a pile of 10mm ballast left over from the cavity fill operation. I understand that a strong mortar has a 3:1 mix but since the lumpyness of ballast equates to less aggregate surface area to bond, a strong concrete has less cement.

 

In another thread @PeterWsuggest a 4:1 mix was strong but I might not have mentioned I was using ballast. The advice at the site below suggests 1 part cement to 6 parts ballast will equate to a strong concrete for paths and drives. The same site also says 1 to 8 would be good for foundations which is counter intuitive to me.

 

https://www.allmix.co.uk/much-ballast-need-mix-concrete/

 

Anyhow after that preamble what does the panel recommend? I am thinking 5.5 or 6 to 1.

 

He is my other thread discussing the need for the driveway entrance "speed bump".

 

 

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1 hour ago, Mr Punter said:

Between 1:6 and 1:9 will be fine.  Make sure you dig down the trench to remove any soft material.  Backfill with type 1 and thoroughly consolidate.  If the sub base is not wide and solid the concrete will not hold up. 

 

 

Thanks. Having been mixing and filling for the last 30 minutes. I have mixed a touch stronger than 1:6, my theory is I am up against the clock and the freezing overnight weather so a stronger dryer mix makes sense to me. Not sure that is conventional building trade wisdom.

 

Got loads of hessian sacking to keep it snug and warm overnight.

Edited by epsilonGreedy
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