COMPARISON OF AGGREGATE GRADINGS FOR HIGHWAYS BASED ON THEIR VOIDS CHARACTERISTICS

The grading of aggregates for road construction can differ widely from one agency to the next. In an effort to identify a specific parameter for the design of gradings, the packing and voids characteristics of aggregates of different sizes were studied. It was observed that the voids structure in an aggregate mixture depends on the size ratios and volumetric proportions of the aggregates contained in the mixture. The voids structure was defined as "composite" or "filler" type depending on the size ratios of the components. The components were further subdivided into "balanced", "abundant in fine aggregate" and "abundant in coarse aggregate". It was found that aggregate grading can be analysed for its voids structure if the size ratios and proportions of consecutive aggregate size fractions are known. An experimental investigation was carried out to compare three standard specified gradings with skip gradings possessing the same voids ratios as standard grading, but with their components proportioned at or near the balanced stage. The Marshall characteristics of such skip-graded mixtures were observed to be superior to those of the standard continuously-graded mixtures. This shows that the strength characteristics of a pavement mixture are influenced by the voids structure as well as the voids volume. Aggregate grading can therefore be designed by selecting the sizes of aggregate groups so as not to lose the composite structure and by selecting them in balanced proportions. For the covering abstract see TRIS 450963. (TRRL)

  • Availability:
  • Supplemental Notes:
    • Indian Roads Congress, Highway Research Bulletin N23, Rigid and Flexible Pavements, 1984.
  • Authors:
    • Sharma, R P
    • RAO, S K
  • Publication Date: 1984

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Filing Info

  • Accession Number: 00450967
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Aug 27 2004 9:57PM