Posted: 04/02/2015 at 10:53
"decent sharp sand is full of grit. with very little sand."
Well just buy grit...as you said above, sand is not "big enough to break the clay particles up, they just combine and can make things worse" Hence there is no reason to ever add sand to clay soil.
Sand is also good at keeping water, so terrible in winter when around roots - you can build sand castle with damp sand because of this property.
Gravel and bark and compost is best thing to break down clay soil.