This document is the Classes of Embedment and Backfill Materials Brochure. Various materials are charted with descriptions and photographs.

Classes of Embedment and Backfill Materials lists various types of materials such as crushed rock, clean, coarse grained soils, coarse grained soils, coarse grained materials with fines, inorganic fine grained soils, fine grained soils and organic soils. The ASTM D2321 classes are listed with description, major divisions, notation, AASHTO soil groups and visual descriptions with photographs.

An AASHTO M 43 Table 1 standard sizes of processed aggregate shows the values for size number, nominal size, square openings and 4 through Number 100 dimensions. A 2nd table lists the descriptions for clay and sand consistencies.

Gravel Terminology is defined by Bank run - the gradation as it exists in nature, with little processing; gravel with sand & clay present (Generally Class 2). Crushed gravel - oversized particles are crushed and fed back into the mixture (Generally Class 1 or 2). Dense-graded - all particle sizes are present, limited voids content (Generally Class 2). Open-graded - screened material with a narrow range of particle sizes and a large voids content (Generally Class 1 or 2 depending on screen size). Pea Gravel/River Rock/Creek Rock – generally rounded, small stones with potentially wide range of stone types 4 sizes (Generally Class 2).

A unified soil classification system table is provided with dimensions for gravel, sand and fine. Photographs for angular, sub angular, sub rounded and rounded aggregate is included.