This was done last summer for a 60' 150,000 bushel bin.   I think its 23 rings high.  Soil engineering required we excavate 8' deep and 80' in diameter and then fill in 6" lifts up to grade.  I requested grade be 3" higher than original grade.  The pad was then built on top of that as is 24" thick.  5' wide footings were dugs around the perimeter, leveled with crushed concrete, and the had rebar put in on 12" centers.  The footing is 2' deep if I recall correctly.  Then on top of the footing they built 24" tall forms for the floor.  The attached pictures explain what they did better than I can write it.  225 yards of concrete for the entire project.

(IMG_6659 (full).jpeg)

(IMG_6668 (full).jpeg)

(IMG_6682 (full).jpeg)

(IMG_6686 (full).jpeg)

(IMG_6693 (full).jpeg)

(IMG_6697 (full).jpeg)

(IMG_6703 (full).jpeg)

(IMG_6715 (full).jpeg)

IMG_6659 (full).jpeg (183KB - 7 downloads)

IMG_6668 (full).jpeg (175KB - 7 downloads)

IMG_6682 (full).jpeg (233KB - 8 downloads)

IMG_6686 (full).jpeg (209KB - 7 downloads)

IMG_6693 (full).jpeg (151KB - 7 downloads)

IMG_6697 (full).jpeg (186KB - 7 downloads)

IMG_6703 (full).jpeg (149KB - 7 downloads)

IMG_6715 (full).jpeg (154KB - 7 downloads)