The point is made that different plants make their subbase differently according to plant flow design, gradation requirements of the using agencies, quantities etc. In the southern states, bases and/or subbases are pugmilled. Pugmilling results from a combination of coarse and fine aggregate gradations which may or may not conform to standard aggregate sizes. In a recent Georgia project, 3 sizes of aggregates were blended utilizing a 3;4" aggregate, 1 1/2" crusher run and screenings. In West Virginia, 3/4" stone and 1/2" screenings were found to be unsuitable and the screenings were split on a 4 1/2 mesh screen; this gave better control at the pugmill. In New York state, all subbase and/or base material is produced through the aggregate plant and the resulting gradation is that which is eventually shipped to a construction site. The New York subbase specification permits a graded aggregate having a top size which is suitable for the construction of the project. The aggregate producer determines what top size is needed, develops a gradation band for that material, and then is held to a tolerance band on this material. The material can be no more than 1 1/4 inch or less than 3/4 inch where the subbase material is crusher run stone at a job site. For pit run blended or processed materials other than crashed run stone, the top size is based on the type of work to be performed and how the material is to be used. The point is made that in some states graded aggregate is used only as subbase, beneath bases that are stabilized with asphalt or other additives; in such cases, gradation control is not required to be as close as where the materials are designed to serve as a heavy duty base course. Subbase material is distinguished from quality controlled base materials as described in ASTM Specification D 2940.

  • Supplemental Notes:
    • Proceedings from a conference on Utilization of Graded Aggregate Base Materials in Flexible Pavements, March 25-26, 1974, Oak Brook Hyatt House, Oak Brook, Illinois.
  • Corporate Authors:

    National Crushed Stone Association

    1415 Elliot Place, NW
    Washington, DC  United States  20007

    National Sand and Gravel Association

    900 Spring Street
    Silver Spring, MD  United States  20910

    National Slag Association

    300 South Washington Street
    Alexandria, VA  United States  22314
  • Authors:
    • Martin, J P
  • Publication Date: 1974

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00127536
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 7 1976 12:00AM