Lobster wrote:

Out of interest, and for my possible future use, what's the rationale
behind the following:

Sand has a bulk density of between 1.4 and 1.6 kg/l (T/m^3)As you are
making a mortar, the higher value will apply.

If the sand is dry it will be 1.6 if a bit damp the sand tends to behave
like brown sugar and tends to "fluff up", hence 1.4. Wet (saturated)sand
has an overall density of 2 because of the water in the voids, however
the actual particle packing is almost exactly as for dry sand. I hope
this is clear enough.

John Schmitt