Raising concrete paving slabs - what material to use?

[Bensonville]

Hi, new here, hoping to get some advice.
I'm extending the paved seating area in our garden with additional slabs (plain, 60x60 concrete).

Upon digging out the area where the new slabs will go, I hit on a concrete layer at about 15cm depth. Before putting down the new slabs, I need to raise that area by about 8cm, so that the new slabs (30mm thick) come up level with the old ones, once set in mortar.

Now I'm not sure what material to use to raise the ground. Can I just put a few centimetres of sub-base material on top of that concrete and compact it or will that cause me an issue as the sub-base won't bond with the concrete layer below, and things will just move around?

Thanks,
Ben

 

[Nige F]

Hi, new here, hoping to get some advice.


Now I'm not sure what material to use to raise the ground. Can I just put a few centimetres of sub-base material on top of that concrete and compact it or will that cause me an issue as the sub-base won't bond with the concrete layer below, and things will just move around?

Thanks,
Ben

Welcome, Ben - I think you're right that it won't bond - Maybe a screed would work.

 

[lonner]

Well you have 150 mm to play with.
You can either lay a 130mm sand cement bed or 75-80 mm weak mix then 50 mm for the slads.