I asked the same question a few years ago, was told it’d need ripped out and redone as opposed to concrete if over.
Concrete over concrete thickness
- Thread starter SLM
- Start date
Awesome. Thanks. Did you mesh within the 2”?
goldeneagle
Member
If the sub base under the existing is sound will be less of an issue. the problem if new pour is too thin a section and there is a bit of give in the original sub base then it will crack or delaminate from the original concrete.
The thickness of concrete is always debated, think the Americans/Canadians put in stuff at 10 -12", guys on clay on here go with 6-8". Anything i have laid has been C35 at either 5" or 6" thick and seems to be holding up well with no cracks. control joints are important in achieving this. Even on green concrete it takes a minute to get them marked out and cut in.
- Location
- Ardrossan Ayrshire
- Location
- Ardrossan Ayrshire
Depends why the concrete failed, if its acid erosion or it cracked and now settled it would be fine, if there are voids under the concrete or soft spots then these need dealt with.
Current slab has been down 25 years. There’s a bit of a extension going on the back so thinking rebars drilled into existing slab, tied onto 10mm mesh and then pour 8” to finish level with the 2” cover on old slab
RWG Contracts
Member
- Location
- Samlesbury, Lancashire
Personally I wouldn’t lay as thin as 2”. it’s not just the strength of the concrete when it’s in use but it’s the curing time, thinner concrete will cure very fast so there’s a greater risk of it cracking like crazy paving.
We’ve just laid a car park floor over a concrete floot, laid on a fall to an aco so it’s 190mm to 75mm. The 75mm end felt very thin when laying it
We’ve just laid a car park floor over a concrete floot, laid on a fall to an aco so it’s 190mm to 75mm. The 75mm end felt very thin when laying it
RWG Contracts
Member
- Location
- Samlesbury, Lancashire
The other problem with 2” Concrete and mesh, what are you putting your mesh on?
As far as I know the smallest spacer I can get is 35mm, then you use say A193 mesh which is 7mm bars so top of mesh is now at 42mm, except on the corners where the mesh meets which is nearly double that height.
Having this little cover to the top of the mesh is nearly worse than not using mesh I’d say
As far as I know the smallest spacer I can get is 35mm, then you use say A193 mesh which is 7mm bars so top of mesh is now at 42mm, except on the corners where the mesh meets which is nearly double that height.
Having this little cover to the top of the mesh is nearly worse than not using mesh I’d say
Skintagain
Member
- Location
- Perched on the Pennines
i would estimate opc 70/80 newton stuff I bet it’s blue if you try peck it
- Location
- South West
Not with current access as the only proper access is to one side so would mean which ever way I split it I’d have to drive on it at some point, and I’d rather pull the plaster off quick and do it in one slab / pour if possible.
Skintagain
Member
- Location
- Perched on the Pennines
Call a local conc company explain what you want to do
They will offer additives etc
I’d go 70 newton mix OPC cement 250mm deep 10mm mesh top and bottom
- Location
- Ardrossan Ayrshire
Skintagain
Member
- Location
- Perched on the Pennines
Can’t see 2 inch holding tbh and I can bodge at times
- Location
- Welshpool Powys
Best fix for a poor silage pit floor rather than break out and relay is asphalt.
Have a word with your local tarmac contractor.
Have a word with your local tarmac contractor.
designanddetail
Member
If it is just pitted and a bit damaged but no major cracks right through it then maybe look at getting it ground down and polished.
These chaps are the nuts, Martin runs a very good operation
https://www.concretepolishing.co.uk/project/industrial-polished-concrete-gloucestershire/
These chaps are the nuts, Martin runs a very good operation
https://www.concretepolishing.co.uk/project/industrial-polished-concrete-gloucestershire/
Forever Fendt
Member
- Location
- Derbyshire
Concrete designed on the basis it reaches its design strength in 28 days but many factors will vary how soon it reaches its strength in ideal conditions it will be a lot sooner the curve of the strength flattens out after a few days ,Concrete panels are lifted from the beds next morning having been poured the afternoon before I'm sure I was told they reach 50kn from 70kn in less than 24hrs ,You can test the strength with a Schmidt rebound hammer tool
Forever Fendt
Member
- Location
- Derbyshire
Have a huge slab to do outside 225 mm thick with 2 layers 8mm mesh what do you think of using mesh with flying ends
Jd Everytime
Member
- Location
- lanarkshire scotland
I've just laid a new concrete floor over old silage pit floor that was all rough and corroded but not cracked and unstable. It's used as general purpose shed now with the provision for possible cattle pens in future with sockets in floor. 6" over top to 8" at door way. A did wash it completely clean before hand.