The performance of rock ballast, when subjected to the physical stresses of loading and to the chemical and physical stresses of weathering environment, depends to a great extent on the mineralogical, chemical, textural, and structural properties of the material. Because these properties can readily be identified by petrographic analysis, useful predictions of ballast performance can be made by the experienced petrographer. However, because of the difficulty of assessing these properties quantitatively and the large number of variable factors involved, petrographic evaluation of ballast remains, at this stage, largely a subjective process. Mineralogy is a major factor in determining overall rock hardness and physical durability, chemical weathering potential, composition and quantity of derived fines, and degree of susceptibility to wetting and drying. Rock texture also affects hardness and is important in influencing toughness, relative susceptibility to freeze-thaw degradation, and mechanical stability in track. Most of the standard tests commonly applied to ballast materials essentially provide a measure of a combination of petrographic properties; consequently, the results of the tests can be predicted to within certain limits. Numerous techniques, including the use of microscopes and X-ray diffraction equipment, can be applied in the study of the fines fraction of track samples to determine the nature and source of the material. Three ballast types in use by Canadian Pacific (CP) Rail (Kimberley Float, Walhachin, and Prairie gravels) are discussed to demonstrate the influence of petrographic properties on performance.

Media Info

  • Media Type: Print
  • Features: Appendices; Figures; References; Tables;
  • Pagination: pp 45-63
  • Monograph Title: Performance of aggregates in railroads and other track performance issues
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00469504
  • Record Type: Publication
  • ISBN: 0309045150
  • Files: TRIS, TRB, ATRI
  • Created Date: Jul 31 1988 12:00AM