Regarding concrete: I don't have much level ground in these Wisconsin hills so I sunk free telephone pole sections for my corral posts, used some RR ties to wall up the low corner and used a layer of "breaker" (6"-) to build up the low spots, then a layer of "gravel" then a layer of "screenings" all local limestone to fill to a final surface.

A key thing I have found is drainage in the corral - the entire surface has a 2% slope in one direction.

With the screenings on top and a very good operator on the skidsteer (not me) matching my chalk lines, I find no need for concrete. The tub, alley section with scale and chute with palp cage all sit directly on this screenings surface. As long as the surface is finished "flat" on my 2%, everything sits very nice and solid.

I did make and level a couple 2x8 treated boards for the feet of the scale loadbars but everything else sits directly on the screenings. A heavy enough reinforced concrete slab the size of the corral or even just under the tub, alley and chute would cost a fortune. 

A three stage breaker-gravel-screenings base properly compacted and leveled works just fine. I would not just set a permanent tub-alley/scale-chute on most soils which can be mud at times. The screenings also make a very good final surface for the cattle's hooves.  jmho.

Jim at Dawn