AN EVALUATION OF THE RELATIVE STRENGTH OF FLEXIBLE PAVEMENT COMPONENTS

THE PRIMARY PURPOSE WAS TO DETERMINE THE COEFFICIENTS OF RELATIVE STRENGTH FOR BASE AND SUBBASE MATERIALS COMMONLY USED IN SOUTH CAROLINA. THESE COEFFICIENTS ARE OF PRIMARY IMPORTANCE FOR THE FLEXIBLE PAVEMENT DESIGN PROCEDURE WHICH IS BASED ON THE "AASHO INTERIM GUIDE FOR THE DESIGN OF FLEXIBLE PAVEMENT STRUCTURES." PROTOTYPE PAVEMENT MODELS WERE CONSTRUCTED IN 8 FT X 12 FT TEST PITS. TWENTY-FOUR COMBINATIONS OF BASE, SUBBASE AND SUBGRADE WERE INCLUDED IN THE TESTING PROGRAM. TWO THICKNESSES OF EACH OF THE BASE AND SUBBASE MATERIALS WERE USED AND EACH MODEL WAS CONSTRUCTED OVER TWO SUBGRADES. THE SUBBASE MATERIALS TESTED WERE BITUMINOUS STABILIZED MACADAM, TYPE 2 MACADAM (CRUSHED GRANITE-GNEISS), SAND-ASPHALT, SOIL STABILIZED AGGREGATE, FOSSILIFEROUS LIMESTONE, AND A CRUSHED LIMESTONE SIMILAR TO THAT USED IN THE AASHO ROAD TEST. THE AASHO LIMESTONE WAS TESTED FOR THE PURPOSE OF CORRELATING RESULTS WITH THE AASHO ROAD TEST. ALL PAVEMENTS MODELS WERE SURFACED WITH A 3-INCH LAYER OF TYPE 1 ASPHALTIC CONCRETE. THE PAVEMENT MODELS WERE TESTED REPETITIVE APPLICATIONS OF LOAD BY DUAL 10 X 20 IN. TRUCK TIRES ACTUATED WITH A HYDRAULIC CYLINDER AND REACTION BEAM. THE LOADS REQUIRED TO PRODUCE A DEFLECTION OF 0.01" AND 0.02" WERE MEASURED AND RECORDED AFTER THE COMPLETION OF THE REQUIRED NUMBER OF CYCLES. EACH PAVEMENT MODEL WAS TESTED AT FOUR DIFFERENT COMBINATIONS OF TEMPERATURE AND MOISTURE. THE TWO TEMPERATURE LEVELS WERE 90 F. (HOT) AND 60 F. (COLD) AS MEASURED AT THE MID-DEPTH OF THE 3-INCH SURFACE COURSE; WHILE THE TWO LEVELS OF MOISTURE WERE ESTABLISHED AS DRAINED (DRY) AND SATURATED (WET) WITH THE WATER TABLE RAISED TO THE TOP OF THE BASE COURSE. BASED ON THE AASHO ROAD TEST VALUE 0.34 FOR BITUMINOUS TREATED BASE, THE RELATIVE STRENGTH COEFFICIENTS OF EACH BASE MATERIAL WERE COMPUTED BY COMPARING THE STIFFNESS MODULUS (CHANGE IN LOAD CAPACITY PER INCH OF THICKNESS PER INCH OF DEFLECTION) OF EACH MATERIAL WITH THE AVERAGE STIFFNESS MODULUS OF THE BITUMINOUS STABILIZED MACADAM. THESE CALCULATIONS WERE MADE ON THE BASIS OF LOADS MEASURED AT 0.01" AND 0.02" AND RESULTS IN COEFFICIENTS WHICH ARE PROPORTIONAL TO THE ACTUAL LOAD-CARRYING CAPACITY OR STIFFNESS, AT LIMITED DEFLECTION, FOR ANY PARTICULAR TEST SECTION OR CONDITIONS FOR ANY MATERIAL TESTED. THE RELATIVE STRENGTH COEFFICIENT OF UNBOUND GRANULAR BASE MATERIALS WHICH HAD NO CEMENTING CHARACTERISTICS DECREASED WITH THE THICKNESS OF THE LAYER WHILE THE CEMENTED MATERIALS GENERALLY SHOWED AN INCREASE IN STRENGTH WITH THICKNESS. VARIATIONS WERE ALSO NOTED FOR REASONS OF ENVIRONMENT AND SUPPORT. THE RELATIVE STRENGTH VALUES FOR ALL BASE AND SUBBASE MATERIALS WERE INTERPOLATED FOR VARIOUS THICKNESSES AND APPLICATIONS AND THE VALUES REPRESENTING THE BEST JUDGEMENT OF THE INVESTIGATORS WERE RECOMMENDED FOR DESIGN PURPOSES. THE RECOMMENDED VALUES ARE BASED ON ELASTIC DEFLECTION. /AUTHOR/

  • Corporate Authors:

    Clemson University

    Clemson, SC  USA  29634

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  USA  20590

    South Carolina State Highway Department

    State Highway Building, Drawer 191
    Columbia, SC  USA  29202
  • Authors:
    • Busching
    • Roberts
    • Rostron
    • Schwartz
  • Publication Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 00205383
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: Study No 522
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Feb 15 1972 12:00AM