Narrow Channel Against Wall Needs Filling

[charliegolf]

Context: Daughter is about to lease a space for a yoga studio, and I've been helping. In what is a storage area (out of sight and against an internal masonary wall) there is an approx 3" wide by 2" deep by 2 m long channel*. It needs filling for a 20mm rubber gym flooring made up of metre squares to cover it.

Can I :

a) fill it with sand and cement, given it's too close to the wall to be trodden on; or have anything heavy placed on it?
b) or do I have to use concrete.
c) don't hate me- post mix?
d) other

Thanks.

*I think it was chased out to accommodate a sink waste, then covered with chippings. But not abso sure on that.

 

[Deluks]

Sharp sand and cement would work ok.
Throw a couple of handfuls of pea shingle in it and it's effectively concrete.

 

[Ivor Windybottom]

Agree with the above. Standard ballast/concrete would be too chunky.

1 part cement
2 parts sharp sand
2 parts 10mm (pea) gravel
A bit of plasticiser or washing up liquid if you don't have any

Normal concrete would be 3 or 4 gravel, but you want something with more paste to get into the edges. The plasticiser will hold it together so you can work with it. Washing up liquid is fine as you don't have any steel reinforcement.

Obviously check the building owner's happy with the idea!