Cutting drainage groove into concrete slab?

[kxi]

Small surface water drainage design fail has come up that neither architect, SE, groundworker, or myself spotted before the slabs were laid, and now needs remedial work.

 

 

Rainwater falls on old slab A at the top, which is nicely V'd so water collects in the middle (you can see the mud collecting there).

Water then supposed to flow down new slab B and onto another V'd new slab C and into the drain bottom left of picture. I.e. along the blue line.

 

Sadly, no one picked up that slab B wasn't specified to have a V and so the water finds it's own path down slab B and veers off into barn D, along the red line. Oh dear. You can see mud collecting at the threshold.

 

My plan is to get a drainage groove cut in slab B to encourage the water to flow along the intended blue line. Perhaps a few 10mm saw cuts next to each other and any remaining material between them chiselled out? Any tips for this?

Slab B is 200mm thick, so I don't think a 10mm groove would be that much of a problem.

 

I want to re-route the water and not have to add a new ACO at threshold of barn. In theory could also add a drain at the water collection point at top of slab B, but a drainage groove seems simpler.

[Mr Punter]

Unfortunately the left hand side of the C slab is either level or has a fall towards the barn.  Have you tested it with a long level and then with a hose?

[Declan52]

You could try grinding a few mm of the concrete to create the channel needed. In effect all you would be doing is polishing the surface.  If that fails then your going to have to cut it out.

[kxi]

1 hour ago, Mr Punter said:

Unfortunately the left hand side of the C slab is either level or has a fall towards the barn.  Have you tested it with a long level and then with a hose?

 

Not tested it, but C looks nearly level at the top, then Vs down the bottom at the drain. But it has a central 'channel' made by tamping. I think might have a few bumps at the top that just send the water into the barn. So, yes looks like might need to do something about both B and C.

 

Clearly this isn't the best situation since everything should have a deeper V, but I'm hoping it could be remedied by encouraging the water down the middle of B with a groove, then perhaps more central and diagonal grooves in C to keep it on track until the V deepens.

 

Area A is about 35m2 so collects a fair bit in a storm.

[kxi]

So perhaps grooves like this:

 

 

Can you get something like a V 'router' bit for concrete? I suspect not, so a wide saw blade / multiple close cuts + chisel out?

 

 

[PeterW]

Diamond floor grinder on its edge would cut that but not sure how you would hold it at that angle. Some concrete floor saws can be set at angles but they aren’t cheap to hire and it’s only normally 5-10° you can move them by. 
 

What about a concrete wall chaser ..??

 

https://vevor.co.uk/products/wall-chaser-concrete-saw-electric-groove-cutting-machine-slotter-125mm-saw-blade

[kxi]

Or perhaps a crack chaser blade?

 

Bosch 'V-groove' looks like it creates an ideal groove for drainage:

 

 

Bosch V-groove blade