The bin manufacturer's foundation drawing comes first
A grain bin is not a generic slab with a tank set on top of it. The manufacturer publishes a foundation drawing sized to that specific bin, its diameter and the grain load it carries once it is full, and that drawing sets the ring diameter, the edge thickness, the rebar spacing and the anchor bolt pattern the concrete has to match.
We build to that drawing the same way we build a thickened pad under a vehicle lift to the lift manufacturer's requirements. If you have the drawing, bring it to the estimate. If you do not have it yet, the bin size and its rated capacity gets the conversation started, and we firm up the concrete once the drawing is in hand.
This is different from most of the concrete we pour, where the customer owns the whole decision and we sketch it out together on site. On a bin, the engineering has already been done by the manufacturer before we ever get involved. Our job is building precisely to those numbers, not choosing our own.
Base prep and the ring or edge that carries the wall
Underneath the drawing's numbers is the same base work every slab needs. We strip topsoil and soft spots out down to firm subgrade, then bring the grade back up with crushed stone compacted in lifts as it goes in. A bin full of grain is a steady, heavy load sitting in one place for months at a time, and settled or uneven ground under it shows up as a tilted bin, not just a cracked floor.
Most bin foundations carry the bin wall on a thickened ring or edge around the perimeter rather than a flat slab of one thickness throughout. That ring gets formed and set with rebar to the drawing's spacing, because it is doing the structural work of holding the wall up, not just covering the ground.
Getting the diameter and the level right before we form matters more here than on ordinary flatwork. A bin is a manufactured, round structure that has to sit on a true circle at the elevation the drawing calls for, not a shape we adjust on site the way we might square up a garage pad.
Anchor bolts set on layout while the concrete is still wet
The bin's anchor bolts get set into the concrete on the manufacturer's bolt pattern while the ring is still plastic, on the layout the drawing calls for, not drilled into cured concrete after the fact. Getting that pattern right on the pour is a small amount of care at the time, and it is what lets the bin bolt down exactly where it is supposed to on installation day.
Once the ring or slab is placed, cured and the anchor bolts are set to the drawing, the concrete side of the job is done. What goes up on top of it from there is between you and the bin installer.
Access for a bin site out past the driveway
Bin sites often sit past where a ready mix truck likes to go, out on a farm lane, on a graded pad off to the side of the working yard, sometimes with soft ground around it from grading work. Our own trailer line pump runs 2.5 and 3 inch line, so the truck can stay on solid ground while the hose reaches the ring itself.
That matters on a job where the concrete has to land on an exact circle at an exact elevation. Placing it steadily off the pump, rather than trying to chute it in from wherever the truck can get closest, is what keeps the ring true to the drawing all the way around.
It is the same reason we would run the pump on a foundation pour anywhere else on the farm. Once the ring is being placed, it needs to go in without stopping and starting while a truck repositions, and hose lets us keep pace with that instead of fighting the site.