ADDITIONAL STUDY OF ASPHALT MIXING TIME /FINAL REPORT/

THE OBJECT OF THIS INVESTIGATION WAS TO OBTAIN FURTHER INFORMATION REGARDING THE REDUCTION OF SPECIFIED MIXING TIME REQUIREMENTS FOR HOT BITUMINOUS CONCRETE MIXTURES. STUDIES WERE CONDUCTED AT NINE BATCH PLANTS PRODUCING TOP, BINDER, OR BASE COURSE MIXTURES TO GIVE THE INVESTIGATION A STATE- WIDE SCOPE. THE REPORT PRESENTS THE RESULTS OF TESTS ON THE PERCENTAGE OF COARSE PARTICLES COATED, AS DETERMINED BY THE ROSS COUNT METHOD, FOR 84 BATCHES OF BITUMINOUS CONCRETE USING VARIOUS WET-MIXING TIMES. OTHER TESTS CONDUCTED INCLUDED AGGREGATE GRADATION AND ASPHALT CONTENT TO DETERMINE MIXTURE UNIFORMITY; AND PENETRATION OR VISCOSITY TESTS ON RECOVERED ASPHALT TO DETERMINE THE DEGREE OF HARDENING OF ASPHALT DURING MIXING. ALL MIXTURES CONTAINED CRUSHED LIMESTONE COARSE AGGREGATE, LIMESTONE SCREENINGS, NATURAL SAND AND 85-100 PENETRATION-GRADE ASPHALT. THE AUTHORS FOUND THAT /1/ BATCH PLANTS SHOULD BE EVALUATED INDIVIDUALLY TO ESTABLISH MINIMUM MIXING TIMES FOR SPECIFIC MIXTURES, /2/ FOR THREE-TON CAPACITY PLANTS, AGGREGATES IN TOP AND BINDER MIXTURES WERE ADEQUATELY DISTRIBUTED AND COATED WITH ABOUT 10 SECONDS DRY-MIXING AND 25 SECONDS WET-MIXING, AND FOR BASE COURSE MIXTURES, 10 SECONDS DRY-MIXING AND 35 SECONDS WET-MIXING, /3/ PLANTS OF LARGER CAPACITY MAY REQUIRE LONGER MIXING TIMES, AND /4/ EQUIPMENT IN MANY BATCH PLANTS WOULD PREVENT A REDUCTION IN MIXING TIME BELOW THAT NEEDED FOR ADEQUATE COATING AND DISTRIBUTION. ASPHALT HARDENING OCCURRED DURING THE FIRST 15 SECONDS OF WET-MIXING BUT NO ADDITIONAL HARDENING COULD BE ATTRIBUTED TO CONTINUED MIXING. THE REPORT INCLUDES NEW SPECIFICATION REQUIREMENTS WHICH WILL PERMIT REDUCTIONS IN MIXING TIME BELOW A MINIMUM OF 15 SECONDS DRY-MIXING AND 45 SECONDS WET-MIXING. /BPR/

  • Supplemental Notes:
    • Hps-hpr-1 /22/, BPR ITEM 17, STATE 20-2
  • Corporate Authors:

    New York State Department of Transportation

    1220 Washington Avenue
    Albany, NY  USA  12232
  • Authors:
    • THOMAS, J
    • DIXON, C
    • Clark, W H
  • Publication Date: 1966-11

Subject/Index Terms

Filing Info

  • Accession Number: 00210334
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Files: TRIS, STATEDOT
  • Created Date: Jan 1 1994 12:00AM