Types of Grading7•Dense-or well-graded aggregate–Has gradiationclose to the FWHA maximum density grading curve.•Gap-graded aggregate–Has only a small percentage of particles in the mid-size range.•Uniformly graded aggregate–Composed mostly of particles of the same size.•Open-graded aggregate–Contains only a small percentage of small-size particles.

As water is added to a soil ( at low moisture content) it becomes easier for the particles to move past one another during the application of the compacting forces. As the soil compacts the voids are reduced and this causes the dry unit weight ( or dry density) to increase. Increased compactive effort enables greater dry unit weights to be achieved

The main groups of soils for engineering purposes are coarse-grained soils — sand and gravels — and fine-grained soils — silts and clays. It is important to know the differences between fine-

The Unified Soil Classification System is based on the airfield soil classification system developed by Casagrande during World War II. With some modification it was jointly adopted by several U.S. government agencies in 1952. Additional refinements were made and it is currently standardized as ASTM D 2487-93. It is used in the U.S. and much

The AASHTO Soil Classification System classifies soils into seven primary groups, named A-1 through A-7, based on their relative expected quality for road embankments, sub-grades, sub-bases, and bases. Some of the groups are in turn divided into subgroups, such as A-1-a and A-1-b. Furthermore, a Group Index may be calculated to quantify