TnWildflower, in a way it's too bad you used to have good soil. It makes clay disappointing. (But after you amend it, clay makes some of the richest soils since it tends to buffer and hold, then gradually release, positively charged mineral ions.)
I've never had anything but heavy clay soil. So now, the discovery that I really can, reliably, cure that with enough compost and bark and grit, seems wonderful.
I find that, when I don't have enough compost, which is "always", that mixing the clay and compost very well through a fine screen and adding lots of bark fines and shreds, plus some grit, crushed stone and even some coarse sand helps the "not-enough-compost" act more like "enough-compost".
Not everyone agrees. At some point in the past, someone coined the phrase "clay plus sand equals concrete" and now few people think that sand (or grit, or anything BUT compost) is helpful in improving clay.
But the soil texture triangle and some people's experience contradict that. They indicate the truth behind the glitzy phrase:
"If you ONLY add sand to very heavy clay, you would have to add almost three parts of sand to one part of clay to get really well-draining sandy clay." Who can afford to import, spread and till in a TWELVE INCH LAYER OF COMPOST? Then renew most of that every year.
The lesson I take away from that is: "Don't rely ONLY on sand to improve clay!"
But if you don't HAVE enough compost to make your clay usable, try not-enough-compost plus some chunky stuff to improve aeration: bark fines, bark shreds, grit, crushed stone and coarse sand.
Some of that ADDED TO not-enough-compost gives better results. I "fluff the soil up" and then firm it down gently after doing this, and the aerated structure lasts for a year or two. After several years of adding compost and mulch, the "fluff and firm" dance seems less necessary.