Correct concrete mixture/ratio for levelling basement floor
I'm going to be leveling an approx 300 sq feet section of my basement slab in my 1920s 2 story. Finished surface will be cork plank on vapour barrier.
My initial plan was to get 30 odd bags of concrete pre-mix from the big box store, rough level it to within a half inch or so, and then use self-leveler for the surface. I'm rethinking this, as self-leveller is pricey, and the premix is meant for jobs 2" or deeper, so I'd have a large portion of the floor that's 0-1" out of level to do with the SLC.
I'm thinking it might be better to mix my own sand + portland mixture for the top layer (5:1?), sort of a poor man's SLC, but sand isn't any cheaper than premix, at least at my local Home Depot (Toronto, Canada).
Is this mix common? I'm thinking I could use premix for the deeper parts and switch to a sand mix for the top inch or so, then fine tune with a smaller amount of leveler.
A 3 or 4 to 1 flooring sand/cement is normally used as a finishing screed over concrete here. You can feather it down, although once it gets down to an inch there is the possibility of it cracking. There are some specialised screeds that can go thinner than this.
Sandmix won't make a good wear-surface but it will do okay as a filler.
You can also mix pea gravel in SLC to stretch it out but regular SLC also isn't intended for a wear surface for very long. There are SLC's that are made for wear however.
As far as mixing your own it wouldn't be flow-able without adding a lot of water and too much water will weaken and basically ruin the mix. SLC's have some kind of secret pixie dust in them that makes them flow-able.