"Chris Hogg" wrote in message
...
On Tue, 23 Jun 2009 14:22:35 +0100, "Spider"
wrote:

Not sure about all your rubble, but I have heard that it's not wise to put
brick dust or soft (old) brick on clay soil. This is because the bricks
were once clay and the brick dust returns to block the air gaps in the
soil,
making it more claggy and less aerated.

Spider

Bricks were indeed once clay, but after they've been fired there's no
way that they can return to clay (I assume that's what you meant). The
structural and mineralogical changes that take place during firing are
irreversible, except possibly on a geological time scale. However, I
suppose it's possible that a fine dust might clog pores in clay, in
which case it would also be true of any fine sand. Grit is usually
recommended to open up clay, and I vaguely recall reading that sand on
clay makes it go like concrete, especially when dry, so there may be
something in the second part of your post. But I can't see chips and
other bits of broken brick doing any harm at all, but not much good
either.
--
Chris

Gardening in West Cornwall overlooking the sea.
Mild, but very exposed to salt gales

E-mail: christopher[dot]hogg[at]virgin[dot]net


Indeed, larger chips of brick would be helpful until they, too, broke down
to dust... and you're right, of course, it is a small scale problem. I'm
inclined to think sand would be sharper and so less clogging, but the
principle is the same. We have, no doubt, both read somebody's pet theory
:~). Mind you, gardening on clay on an end-of-building-site plot, where all
the left over sand and grot was abandoned, I can see how 'your' theory may
have some merit :~(.

Had I been the OP, I would have been pleased for any information to guide my
decision-making, and this is the premise on which I replied. The OP is
perfectly free to embrace or ignore my post.

Regards,
Spider