Particles smaller than 0.075 mm are referred to as what?

Particles smaller than 0.075 mm are classified as "fines." This term encompasses particles that are predominantly clay, silt, or very fine sand, which are crucial in various engineering applications, especially in soil mechanics and geotechnical engineering.

Fines play a significant role in the behavior of soil, affecting its compaction, permeability, and overall stability. In appropriate conditions, these smaller particles can improve the cohesion of soil mixtures, enhance nutrient retention in agricultural settings, and influence the hydraulic properties when dealing with water flow through soils.

In contrast, cobbles, gravel, and sand refer to larger size categories of aggregate materials. Cobblestones are generally much larger, while gravel consists of particles that range from 2 mm to 63 mm, and sand falls within the size range of 0.075 mm to 2 mm. Understanding these classifications is fundamental for civil engineers who need to select suitable materials for construction and environmental projects.