EFFECT OF OPTIMIZED TOTAL AGGREGATE GRADATION ON PORTLAND CEMENT CONCRETE FOR WISCONSIN PAVEMENTS

Most state paving specifications for portland cement concrete pavement allow a broad range of total aggregate gradation for concrete mixes. It has long been debated whether special efforts to control total aggregate gradation provide concrete improvements that justify potential increased costs. The results of an investigation examining the effect of optimizing total aggregate gradation on the properties of concrete used for paving in Wisconsin are reported. The investigation used concepts presented by Shilstone to optimize gradations consisting of carefully selected proportions of locally available aggregate. Unit weight, shrinkage, change in the water-to-cement (w-c) ratio at constant slump, change in slump at a constant w-c ratio, compressive strength, and possible segregation under vibration were measured in field test sections and laboratory mixes. This investigation showed that use of optimized total aggregate gradations instead of near-gap-graded gradations in pavement resulted in an increase in compressive strength of 10 to 20%, reduced water demand by up to 15% to achieve comparable slump, air contents achieved with 20 to 30% reductions in air entraining agent, potentially higher spacing factors in the air void system of hardened concrete, and reduced segregation following extended vibration (1 to 3 min). Not all efforts at gradation optimization in this study yielded measurable improvements in performance and the availability of local aggregates may still limit, to varying degrees, the ability to optimize. However, a reasonable effort to optimize gradation can lead to significant mix benefits.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 100-106
  • Monograph Title: Concrete and concrete pavement construction
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00711786
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 19 1995 12:00AM