Resurfacing Concrete

[petej42]

I have a raised concrete area about 25 square meters with a shed perched on top. The area is comprised of two slabs.
One is solid but has a crack running across it, the surface of the other slab is crumbling, but otherwise seem solid.
There is a manhole on one slab that sits between the septic tank and soakaway, the cover is badly rusted and needs replacing.

Water has been lying on the surface which I think over the years, has caused the crumbling and the damage to the manhole cover.

There doesnt seem to have been any recent movement on either of the two slabs.

I would like to tidy the area up, by resurfacing if possible, laying perhaps 50mm (?) of new concrete over the old.

Can anyone offer any advice on how to achieve this, for example, is it worth putting additional expansion joints to create additional slabs.
This would allow me to lay the new surface over several days but I dont know if this is a good idea. I also need to provide better drainage
than currently exists, perhaps by creating chanels between the slabs to a suitable run off point.

Any advice greatly appreciated

Pete

 

[r896neo]

If you want to overlay concrete 70mm is the minimum. Ideally you would have 90mm.

Less than 70 will almost certainly crack at some point.

You can break it up into sections if you like but you must maintain a joint of some sort where the join between the 2 slabs is.

Drainage wise you could do anything that suits? Simple concrete channels running off to the lawn? Aco channels collecting and discharging into your soakaway etc.

 

[nickjb]

When putting a thinner layer of concrete down on existing concrete I apply a slurry of sbr and cement first. Done this a couple of times now. To get maximum bonding you want a nice clean surface so do it soon after removing the loose and damaged bits. Seems to work OK but time will tell. No cracks at the moment.

 

[petej42]

Thanks for the suggestions

Ive just had some ballast and mastercrete delivered to start on the first slab, the back of the mastercrete says concrete should be at a ratio of 4:1 with the ballast, is this a good mix for this purpose?. Also, since my original post, I have pressure washed both slabs to remove the muck and crumbled surface both are now solid but there are a few more hairline cracks than I first realised. Do you think its likely that the slabs could be still moving. I reckon they have been down for at least 10 years. I think at the least I shall have to look at 90mm. I am also going to get some sbr. for the sake of a tenner and a bit of cement, it seems worth it.

 

[Ian H]

Could you go over them with slabs instead of concrete?