INVESTIGATING SOURCES OF VARIANCES IN BITUMINOUS CONCRETE TESTING

AVERAGE GRADATIONS AND VARIANCES ARE PRESENTED THAT OCCURRED WHEN SAMPLES WERE TESTED AT NUMEROUS POINTS OF CONTROL IN THE PRODUCTION OF HOT BITUMINOUS PAVEMENT. IN AN ATTEMPT TO MEASURE WHERE FLUCTUATIONS OCCUR AND THEIR MAGNITUDE, SAMPLES FROM COMPOSITE HOT BINS WERE COMPARED WITH MIX SAMPLES OBTAINED FROM SPECIFIED AREAS IN THE TRUCK BODY. THESE RESULTS WERE THEN COMPARED WITH RESULTS OBTAINED FROM CORES CUT FROM THE ROADWAY. EFFORT WAS MADE TO FOLLOW THE SAME MATERIAL AS IT PASSED FROM STEP BY STEP IN THE PROCESSING. THE RESULTS OF THIS STUDY INDICATED THAT THREE STATISTICALLY DIFFERENT POPULATIONS EXISTED. OBSERVATIONS INDICATED THAT THE COMPOSITE GRADATIONS OF THE HOT BIN SAMPLES AND PLANT SAMPLES AND CORRESPONDENCE WERE SIMILAR, BUT THE VARIANCES WERE QUITE DIFFERENT. THE COMPOSITE HOT BINS ANALYSIS SHOWED A LOW VARIANCE OCCURRED ON THE COARSE SIZES. THE TRUCK AND CORE SAMPLE SHOWED A MUCH GREATER VARIANCE ON THE COARSE SIZES. THE VARIANCE IN THE FINES IN ALL CASES WAS ABOUT THE SAME. THE CONCLUSION OF THIS STUDY WAS THAT SEGREGATION OCCURRED WHEN THE MIXTURE WAS DUMPED INTO THE TRUCK. A MINOR STUDY CONDUCTED AT THE SAME TIME CONSISTED OF TESTING EVERY SECOND TRUCK SAMPLE WITH A VACUUM EXTRACTOR AND COMPARING THESE RESULTS WITH THE RESULTS OBTAINED WITH A CENTRIFUGAL EXTRACTOR. IT WAS ANTICIPATED THAT MORE FINES WOULD BE RETAINED USING THE VACUUM EXTRACTOR, THUS A LOWER ASPHALT CONTENT WOULD BE COMPUTED. THIS ASSUMPTION WAS FOUND TO BE TRUE. /AUTHOR/

  • Corporate Authors:

    Maine State Highway Commission

    Materials and Research Division, Bureau of Highways
    Augusta, ME  USA  04330

    Bureau of Public Roads /US

    400 7th Street, SW
    Washington, DC  USA  20590
  • Authors:
    • EDWARDS, B
    • Rand, D
  • Publication Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 00214507
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Report/Paper Numbers: 70-2p
  • Files: TRIS
  • Created Date: Jul 27 1970 12:00AM