Road planings laid over concrete slab

leafy211

Im resurfacing my driveway and part of is currently a concrete slab.  I wondered if i can lay road planings over the concrete slab (to avoid having to dig it out and get rid of it)?  

Section62

leafy211 said:

Im resurfacing my driveway and part of is currently a concrete slab.  I wondered if i can lay road planings over the concrete slab (to avoid having to dig it out and get rid of it)?  

It depends how thick the layer of road planings will be.

If you lay granular material (such as planings) in a too thin layer over a hard surface like concrete, they are more likely to move around and rut, and in the extreme will turn the concrete area into a skating rink.

Thinner layers need more fines to help bind the larger pieces together.  The makeup of road plannings can vary quite widely from load to load, so if you are aiming for a thin layer you'll need to take extra care, or else consider breaking the concrete up.  On the plus side, the company delivering the planings may give you a good rate for taking the concrete away if it is clean and you make it easy for them to pick up with a grab at the same time as they deliver the planings.

leafy211

Thanks Section62.  Ill ask the builder what depth he was planning for the planings, if on top of the concrete.  Is there a minimum you would advise? The drive is on a slope so the last thing Id want is for it to become slippery.  

Section62

leafy211 said:

Thanks Section62.  Ill ask the builder what depth he was planning for the planings, if on top of the concrete.  Is there a minimum you would advise? The drive is on a slope so the last thing Id want is for it to become slippery.  

On the flat I'd be concerned about anything less than about 150mm.  On a (significant) slope I wouldn't do it at all as the material is quite likely to migrate downwards at every opportunity.

How much of a slope is it?

leafy211

righty ho - many thanks for that advice.  I did have a niggle about just putting on top of concrete, as couldnt figure out how planings would 'stick'. Roughly 50% of the driveway is on steady incline... having a really random guess id reckon on around 8-9% elevation. Landscaper assured me it would be absolutely fine and wouldnt slide/move on the slab.