This document outlines the ideal grain size composition for plaster sand used in mortar machines. It recommends that the sand contain 5-10% particles smaller than 0.125 mm to aid pumpability. The majority of particles, 30-40%, should be between 2-4 mm in size. The ideal gradation falls between standard curves B4 and C4, with an emphasis on fines to improve pumpability while avoiding too much which could cause cracking from higher shrinkage.

1. Plaster sand – grain size composition
5-
< 0,125 mm (“dust”) dust is a must in the mixture in order to
10%
receive pumpable material
0,125 - 0,25 mm 5-
10%
0,25 - 0,5 mm 15 -
20%
0,5 - 1 mm 12 -
18%
10 -
1 - 2 mm 15%
30 -
2 - 4 mm 40%
PMM / Jochen Knecht 19.02.2010

2. Grain size composition of 4mm plaster sand
The ideal gradiation for mortar machines is between standard curves B4 and C4
100
Percentage Passing [%]
90
80
70
60
50
40
30
20
10
0
0 0,125 0,150 0,25 0,30 0,50 0,60 1 1,18 2 2,36 4 4,75
Particle Size [mm]
the content of fines (filler, clay, dirt) is very important for the
The contentthe more fine particles (fillers, clay, dust)
of the the better ! is very important for the
pumpability - B4 C4
pumpability! But, if it is too much, cracks may occure due to the higher shrinkage.
PMM / J. Knecht 19.11.2010