A solid slab of concrete weighs *150 pounds* per cubic foot. A cubic foot
of broken concrete weighs 75 *pounds*. Cost could be close to zero.
All of these schemes are really good, and I certainly have used several.
WHen you glue up 2 surfaces together( especially face to face as in
veneering) the issue is to spread out the force if the weight over the
entire surface. (Using a wrong example: face  glue 2 sheets of plywood
together using a single lead weight. If the single weight is 4x8 feet it
all works well. If the same weight is 1x1 foot, you are not applying
pressure to the other 31 sq ft. It does not work.
I think a more useful discussion on how to distribute pressure/  weight
might help more folks.
My veneering teacher had us make up 2 matched torsion boxes. About 6x18x24.
They were made from melamine  barf board. Pit your boxes on sawhorses, with
project inside, and clamp with weights, lots of clamps, etc. worked like a
champ.
-- 
Frank Filippone
BMWRed735i@g...