drdawg said:Believe me, it is 1000X easier to mix ANYTHING with sand than with pure clay (thick, heavy molasses when its wet, brick-hard when its dry). 
... the clay was so heavy, that each shovel-full weighed in around 25 lb.!
... a commercial, extra-heavy duty tiller, a real monster of a thing.
... It would only till 2-3" deep at most.
... large back-hoe, ... a double-size dump truck (and filled it twice), and it was money well-spent.
Yeah, I know wh'acha mean.
There might be one tiny, narrow window of moisture where the clay is soft enough that it doesn't need a pick, each shovel only weighs 10 pounds, and it isn't QUITE as sticky as it is at all other times.
it is hard to move yards of wet clay: the density must be greater than stone.
The only way I could mix the clay was to dry it a little more than ideal shoveling wetness, then sift it through 1/4" screening along with compost, sand, bark and "topsoil".
I crushed it through the hardware cloth with the back of a shovel, and pushed it around with the back of a steel rake and my hands. Some mixing occurred during screening and more occurred in the heap.
This way, I also removed a lot of pebbles and stones, big clay-clods, and some very hardy weed roots. VERY hardy!
A lot of it, I re-screened after the first pass, with more compost.
I let the screenings build up to a cone so the worst "clay balls" rolled down and settled at the bottom-edge of the pile . Those, I shoveled up and threw away into a "some day" pile along with small pebbles.
I collected screened, amended clay in piles and aged them there while adding small amounts more compost. Eventually I got it to a state like "heavy clay loam", but probably with more compost than silt or sand.
It really likes to revert to clay pudding in the raised beds, but adding more compost than I want to buy helps. I think the main structure comes from roots pushing into it before it digests its compost and reverts to pudding.
(I was able to do this because my legs are much weaker than my upper body. I found ways to sit for around 30% of the time while shoveling, raking, screening and wheelbarrowing.
Here's the heck of it: now I have several square yards of raised beds with half-decent heavy clay "loam". Now the weeds have somewhere they can grow! I didn't mind cultivating the soil until I fell down, but I HATE weeding!
