Particle Size Distribution

Determination of particle size distribution

Different techniques are available for the determination of particle size distribution of a sample. The hydrometer method, pipette method for the finer fractions and for the coarser fractions sieving with an automatic sieving machine, is still the most appropriate way. For the different determinations, the pre-treatments are particularly essential. These can vary considerably per standard or regulation. The drying preceding the determination can also differ. With dry sieving the sample is dried and crushed, weighed and put on the sieves. The sieving is conducted by shaking the set of sieves with a shaking machine. Subsequently, the material remaining on every sieve is weighed individually. This is the appropriate method for coarse pure sand samples. During a wet sieving, the sample is sprayed with water until only clean water flows from the bottom sieve (63 µm). Subsequently everything is dried and, in certain cases, sieved again and weighed.

Determination of particle size through sedimentation

For the determination of smaller fractions in this test, the sample is peptisated. After this, it is diluted with demi water and intensively stirred and possibly loosened further in an ultrasonic vibrating bath. Subsequently, the sample is separated in a fine sieve with flowing demineralized water. Of the fraction < 63µm, the particle size distribution is determined with the pipette method.

More modern methods such as a sedigraph or measuring with laser light is not conducted at MOS. These more modern methods can deviate slightly from the traditional methods. This is due to the shape of the particle.