INFLUENCE OF AGGREGATE SHAPE ON BASE BEHAVIOR

A re-examination and simplification of the original rut index concept for predicting rut susceptibility in aggregate bases is presented to eliminate some of the disadvantages of the original approach. The rut index can be determined from the results of a single cyclic load triaxial test performed at a confining stress of 6 psi, rather than at two confining stresses as originally proposed. The principal stress ratio to be used in the test varies from 2 to 6, depending on the structural strength of the pavement section. The resilient and permanent deformation characteristics of river gravel, granitic gneiss, shale, limestone, and quartzite aggregates were determined using the cyclic load triaxial test. Variables investigated included density, gradation, moisture content, and aggregate shape and surface characteristics. The revised rut index concept was used to evaluate and compare the relative permanent deformation behavior of these various unbound aggregates. The cubic-shaped, smooth rounded river gravel was found to be more than two times as susceptible to rutting as the crushed aggregates tested. The crushed aggregates were angular, blade, and disc shaped and had relatively rough surfaces. These aggregates generally performed similarly with respect to permanent deformation, although the visual appearance of the two blade-shaped aggregates was not as nice as the others. The use of a simple, slow triaxial shear test as a practical alternative to the conventional dynamic test was studied for evaluating the resilient and permanent characteristics of unbound base materials. The slow triaxial shear test was found to be suitable for evaluating the resilient modulus, but appeared not to be appropriate for evaluating permanent deformation characteristics.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1989/1227/1227-017.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=INFLUENCE+OF+AGGREGATE+SHAPE+ON+BASE+BEHAVIOR&author=R.+Barskale&author=S.+Itani&publication_year=1989
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0309048222
• Supplemental Notes:
  • This paper appears in Transportation Research Record No. 1227, Rigid and Flexible Pavement Design and Analysis: Unbound Granular Materials, Tire Pressures, Backcalculation, and Design Methods. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Barskale, Richard D
  • Itani, Samir Y
• Publication Date: 1989

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 173-182
• Monograph Title: Rigid and flexible pavement design and analysis: unbound granular materials, tire pressures, backcalculation, and design methods
• Serial:
  • Transportation Research Record
  • Issue Number: 1227
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Aggregate gradation; Aggregates by shape and surface texture; Alluvium; Base course (Pavements); Deformation; Density; Gneiss; Limestone aggregates; Modulus of resilience; Moisture content; Quartzite; Repeated loads; Ruts (Pavements); Shale; Shear stress; Stress ratio; Test procedures; Triaxial shear tests
• Uncontrolled Terms: Aggregate shape; River gravel; Rut; Susceptibility
• Old TRIS Terms: Gneisses; Triaxial shear
• Subject Areas: Design; Geotechnology; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I36: Aggregates;

Filing Info

• Accession Number: 00495077
• Record Type: Publication
• ISBN: 0309048222
• Files: TRIS, TRB, ATRI
• Created Date: Jun 30 1990 12:00AM