Aggregate Gradation Optimization - Literature Search

The objective of this research is to perform a literature search which summarizes the findings in various publications that involve aggregate optimization issues such as the effect of optimization on constructability, strength, smoothness, segregation and required water and air entraining agent dosage. Most reports of the use of aggregate optimization point out the benefits of using a more well-graded material, including less paste and hence less concrete shrinkage, greater strengths, better pumpability and enhanced finishability. Well-graded mixtures tend not to have as many problems as gap-graded mixes in terms of pavement edge slump, segregation during vibration, finishing, raveling at joints and wear resistance. One of the main benefits of characterizing the mix as a single point on a coarseness factor-type chart is the ability to adapt to changing gradations in a timely manner. Concern about the practicality of producing optimized aggregates centers on the difficulty in producing the gradations, especially coarser sands, in quantities large enough for typical jobs. Extra equipment may have to be purchased, extra handling may be involved, extra shipping costs may be present and some natural sources of materials may not be conducive to providing the missing sizes. One caution about trying to overcome a gap-graded mix by adding an intermediate size aggregate is that the particle shape must at least be compact and preferably rounded. If the intermediate aggregate is flat and elongated, the result may be quite far from what was intended. A brief analysis of current Missouri Department of Transportation specified limits on gradations was undertaken. Depending on which side (fine or coarse) the gradations were running in relation to the limits, various combinations of sand and coarse aggregates A, B or D were all over the coarseness factor chart, with behavior ranging from rocky to good to sandy.

Language

  • English

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: 102p

Subject/Index Terms

Filing Info

  • Accession Number: 01005739
  • Record Type: Publication
  • Report/Paper Numbers: RDT 05-001, RI 98-035
  • Files: TRIS, STATEDOT
  • Created Date: Oct 15 2005 10:26PM