Evaluation of Particle Size Distribution Characteristics of Fine-Grained Soils by LSD and Hydrometer—A Critical Review

This paper describes a comparative study of the particle size distribution of fine-grained soils done by adopting hydrometer and laser diffraction (LSD) methods. In general, these analyses are adopted for fine-grained soils less than 75 μm are classified as silt (75–2 μm) and clay (< 2 μm). However, the methods are based on different methodologies they may not obtain the same results of clay and silt fractions. The hydrometer method is based on sedimentation analysis (up to 1 μm), whereas the LSD is based on laser diffraction analysis (0.4–2000 μm). Although the hydrometer was time-consuming, it is typically preferred for the particle size distribution of fine-grained soils. The obtained values of clay and silt fractions are uncertain due to the influence of factors such as temperature, particle shape, mineralogy, and predominant molecular weights of the elements in the soil. The results obtained from these methodologies are critically evaluated and presented in the study.