Add some bigger aggregate + plasticizer + fly ash + microsilica + some polymer for waterproofing. Optionally, add some reinforcement fibers. If you're pouring concrete, you might as well make it good. Concrete is a serious business and you can get so much more out of it compared to off-the-shelf solutions.
Very timely, my machine arrived last week, but doesn't have the new style drains. I am adding some that look similar to the new style.
I am wondering why you don't just fill the well with a RESIN and allow it to self level and harden. Why concrete?
Add some bigger aggregate + plasticizer + fly ash + microsilica + some polymer for waterproofing. Optionally, add some reinforcement fibers. If you're pouring concrete, you might as well make it good. Concrete is a serious business and you can get so much more out of it compared to off-the-shelf solutions.