|
Southwest Illinois | Footings and form height are two different things. A footing is how much concrete you have below the surface of the ground. Form height will determine how high your bin will sit off the ground.
Footings vary depending on location. In south central Illinois most will tell you around 30" deep, w/ rebar, 36" if you need peace of mind. A 8-12" wide footing works for smaller bins, less than 30' in diameter. Once you get to that size you probably need to consider a footing 12-18" wide for 30'-48' diameter. These are considering wide corrugated bins 6-8 rings high.
Form height varies by everyone. I like the 18-24" if you are going with a short aeration floor and a 10" unload. In this case the 10" unload will only be about an inch or two from the concrete floor. If you are going with a tall drying floor and an 8" unload the 12" forms will work as the unload is now more like 8" above the floor. We haven't put drying floors in for some time and go with the short aeration supports with a 10" tube. The 18" forms will work, but the 24" forms are nicer if you try to get a 12" truck auger under them. If you go with a vertical unload then you can get back to the 12" forms and be OK. My advice use the next size taller than you think you need. If you pour rock or sidewalks around the bin you'll be glad you did.
As far as thickness of concrete everyone will have an opinion. If you have a great base down and use 5/8 rebar on 12", 6" deep is plenty on smaller bins(up to 15K), we go 8" on the bigger bins. When I say good base, I mean a clean excavation followed by 6" of clean rock and 6" of pug mill or grade 8 compacted. On bigger bins I'd go 8-12" of rock under your pug or G8. I've seen guys pour concrete 12" thick only to see it crack because they used a poor base. I would also use rebar and not mesh. If you get a crack, water will rust that flimsy mesh apart in 5 years, rebar will hold together much, much longer. Remember, you can replace roof sheets, augers, floors, bolts, etc, but you only get one shot at the concrete. Do it right or hire it done.
Edited by Lookingglass 2/22/2007 23:22
| |
|
How Thick Should Concrete Be Under Grain Bin?
