In geotechnical engineering, the activity number (A) of a soil is the ratio of the plasticity index to the mass percentage of the clay fraction.
See also Atterberg limits, consistency number, liquid limit, plastic limit, plasticity index, shrinkage limit.

Skempton (1953) defines clay activity, or the colloidal activity of clay, as the ratio of the plasticity index to the percentage of the clay-size fraction. According to Skempton, three types of activity can be determined: inactive (activity <0.75), normal (activity 0.75 to 1.25) and active (activity > 1.25).
See low-activity clay, high-activity clay

An obsolete term for muscovite.

An atom attached to a substrate.
Syn., adsorbed atom

Adhesion refers to the attractive forces between two or more chemically dissimilar molecules or surfaces of different materials (e.g., glass vs. water, clay vs. sand). Thus, wet-clay and dry-clay particles tend to adhere to different surfaces.
Cf., cohesion

A micelle structure adsorbed to a surface.
See micelle.

Durable, sun-dried, hardened bricks made from mixtures of water, clay, silt, sand and straw, or other fibrous organic materials

Any substance which, in molecular, atomic, or ionic form, will penetrate into and be retained by another (liquid, solid, gel, etc.) material.
Cf., Solid-state diffusion, adsorbent

H₂O molecules attracted to and adhered to by atomic forces at internal or external surfaces of a phyllosilicate or other material in thicknesses of one or more molecules. The term “water” (rather than “H₂O”) is not precisely used here because “water” is a (liquid) phase.

The process of attraction and adherence of atoms, ions, or molecules from a (gas, liquid, etc.) solution to a surface.