|This sandblasting sand is graded
from medium (about 1-2 mm) down to a very fine
powder. The varied grits, or different particle size
adds increased strength and crack resistance
When used in a cement basecoat for
high strength applications such as stucco floors or cement boats, the various grits can quadruple the compressive strength of Portland cement mortar.
The reason is that the smaller grains fill in the voids when the mortar is packed down.
This is what we usually use in our stucco finish coat.
|Q-ROK is graded quartzite,
which means crushed quartz or crushed
white sandstone. Sand like Q-ROK is used in
stucco finishes, but
the grading is different. Q-ROK comes in 3 grades, #1, or fine; #2, or
medium and #3, coarse. Fine powder is packaged as silica fines.
The main difference is that number 3 is all the same size (about 3 mm.) Number two is all medium, and number 1 is all fine.
When used as a stucco finish, different grades are usually mixed together to vary the size for improved strength and appearance.
What this means in human readable terms:
Silica sand (usually crushed quartz or sandstone) is
passed through various screen sizes and measured
as to the percentage of what size the grains are.
Everything above 4.75mm is thrown away. The sand
is then graded from less than 2.36mm (coarse or # 3)
down to a fine powder of 75 micrometers (µm) or
75 thousandths of a millimeter.
This chart is completely ambiguous if you do the math,
but the idea is that the sand is graded from coarse
down to fine powder.
Also, since the sand is irregularly shaped, larger width
particles can pass through the sieves.