In Radika Kesavan wrote:
My memory from Colloidal Chemistry classes is that clay will form a
collodial suspension in water, and the one way to break this up is to
add electrolytes to the colloid. It is a memory from long ago. Also,
IIRC, this is the principle by which one washes leeks and spinach and
cilantro other muddy and leafy vegetables free of the clay and soil
that have coagulated on them as a thick colloidal suspension, by
adding a pich of salt to the wash water.

I have, from time to time, used a product called Groundbreaker on my
clay beds. It contains 'buffered polygnosulphates' or some such
gibberish. It's meant to change the structure of clay to allow root
penetration and aeration without digging.

Of course there's no way of measuring whether it works. You take it on
faith or not at all. Here's the blurb:

http://www.multicrop.com.au/soil.htm