On 28/04/2015 13:27, BlackSpot wrote:
On Fri, 17 Apr 2015 10:32:59 +0100, philgurr wrote:

B&Q can call it what they like, but there are precise definitions of
'sharp'
and 'soft' sand. Sharp sand is usually found in river systems where the
time for abrading the edges of the sand/grit particles is limited.
'Soft' sand is usually found in marine environments with prolonged
exposure to the rounding of the grains - any sandy beach will illustrate
this.
The best 'sharp' sand that I ever found was from a gravel pit in
Walton-on-Thames. They would crush the river gravel to make a 'sharp'
sand that was like a myriad of tiny razor blades.



I recall hearing that one of the reasosn so many buildings in Haiti
collapsed was the use of beach sand in the concrete - being rounded it
made a weaker material.


Not to mention the lack of steel reinforcement!