I need a base for some large log stores. One solution is to place them
on 440x220x100 concrete building blocks. This could be achieved fairly
quickly, and allows for straightforward relocation at a later date.

The site is disturbed ground - so this may not provide uniform support
and I can expect some settlement. However I can make adjustments at a
later date as and when the stores are empty.

Concrete blocks seem to come in 2 main types - dense and medium density.
Both types are available for a compression load of 70 N/mm2. The
medium density blocks weigh about 14.5kg as opposed to 18 kg for the
dense blocks but cost approximately 10% more.

I am willing to pay the extra premium on the medium density blocks in
return for the easier handling. But will the medium density blocks be
more fragile and liable to break in my application where the variable
nature of the ground support may give rise to shear stresses across the
blocks?

Any comments appreciated.

Andrew