EFFECT OF AGGREGATE GRADATION ON MEASURED ASPHALT CONTENT. NCAT REPORT

It is necessary to control the asphalt content closely in hot mix asphalt (HMA) mixes to obtain optimum serviceability and durability. However, coarser mixes (binder and base courses) made with larger maximum particle-sized aggregate tend to segregate. The resulting variation in the aggregate gradation of the sampled HMA mix can significantly affect the measured asphalt content. The objective of this research was to evaluate the effect of aggregate gradation on the measured asphalt content. Actual mix composition (asphalt content and gradation) data from a major interstate paving project were obtained and analyzed. A total of 547 binder course and 147 wearing course mix samples were obtained behind the paver and subjected to extraction analysis. A substantial amount of segregation was observed in the binder course mix which provided the opportunity to correlate the aggregate gradation with the measured asphalt content. Some of the deviation in the measured asphalt content of the binder course mixes from the job mix formula (JMF) was determined to be the result of the change in gradation of the mix from the JMF. The percentages of material passing the 4.75 mm (No. 4) and 2.36 mm (No. 8) sieves are correlated with measured asphalt contents. For segregated binder course mixes evaluated in this study, equations were developed to adjust the measured asphalt content to account for the change in gradation from the JMF as measured on the 12.5 mm (1/2 inch) and either 4.75 mm (No. 4) or 2.36 mm (No. 8) sieves.

Language

  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 14 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00666277
  • Record Type: Publication
  • Report/Paper Numbers: NCAT Report No. 93-1
  • Files: TRIS
  • Created Date: Sep 26 1994 12:00AM