APPLICATION OF DESIGN CALCULATIONS TO BLACK BASE PAVEMENTS

DORMENS METHOD OF PAVEMENT DESIGN BASED ON THE THREE-LAYER ELASTIC SYSTEM HAS BEEN EXPANDED TO INCLUDE FATIGUE CRITERIA MAKING THE METHOD APPLICABLE FOR DIFFERENT TRAFFIC VOLUMES. THEORETICAL DESIGN CURVES SHOW COMBINATIONS OF THICKNESSES OF ASPHALT LAYERS AND GRANULAR LAYERS AT WHICH THE STRAIN VALUES IN THE PAVEMENT ARE WITHIN ACCEPTABLE LIMITS. BECAUSE THE METHOD INVOLVES THE RELATIONSHIP BETWEEN THE SEPARATE LAYERS, IT PROVIDES THE BASIS FOR THE PREPARATION OF EQUIVALENT DESIGNS. THESE OFFER INFORMATION BY WHICH SPECIFIED THICKNESSES OF GRANULAR MATERIAL CAN BE REPLACED BY SMALLER THICKNESSES OF BLACK BASE. DESIGN FOR AN 18,000- LB. AXLE LOAD ON A WEAK SUBGRADE /CBR EQUALS 2.5/ REQUIRES 4.1 INCH OF ASPHALT SURFACE ON A 21-INCH GRANULAR BASE. SUBSTITUTION OF A FOUR-INCH BLACK BASE REPLACES 11-INCHES OF GRANULAR BASE. THE COMPLETE 21-INCH GRANULAR BASE CAN BE REPLACED BY A 5.8-INCH BLACK BASE. INVESTIGATION OF ALTERNATE DESIGNS PROVIDES ADDITIONAL INFORMATION ON EQUIVALENCY RATIOS BETWEEN ASPHALT AND GRANULAR MATERIALS. CURVES DEMONSTRATE THAT EQUIVALENT RATIOS DO NOT REMAIN CONSTANT BUT THEY VARY ACCORDING TO THE THICKNESS OF ASPHALT LAYERS AND THE STRENGTH OF THE SUBGRADE . CALCULATIONS SHOW THAT BLACK BASES HAVE THEIR GREATEST ECONOMIC ADVANTAGE IN AREAS OF WEAK SUBGRADES. IN ADDITION, MAXIMUM EQUIVALENCY RATIOS ARE DEVELOPED BY COMPLETE REPLACEMENT OF GRANULAR BASES BY BLACK BASES. THERE ARE OTHER ADVANTAGES IN THE USE OF BLACK BASES, HOWEVER. ONE OF THESE INVOLVES THE REDUCTION IN TENSILE STRAIN VALUES IN THE ASPHALT LAYER. THESE REDUCED STRAINS GREATLY DIMINISH THE RISK OF FAILURE BY CRACKING. CHARTS OF TENSILE STRAINS FOR DESIGN SECTIONS DISCLOSE THE REDUCED RISK OF CRACKING. /NAPA/

• Supplemental Notes:
  • Vol33, Pp221-240
• Authors:
  • Lettier, J A
  • Metcalf, C T
• Conference:
  • Assoc Asphalt Paving Technol Proc
• Publication Date: 1964-2

Subject/Index Terms

• TRT Terms: Asphalt; Base course (Pavements); Bituminous aggregates; Design; Economic benefits; Flexible pavements; Granular materials; Pavement cracking; Pavement design; Pavement layers; Plant mix; Reduction (Chemistry); Subgrade (Pavements); Tension; Theory
• Uncontrolled Terms: Design features; Tensile stress
• Old TRIS Terms: Dormens method; Layered system mechanics; Reduction
• Subject Areas: Design; Economics; Highways; Materials; Pavements;

Filing Info

• Accession Number: 00210285
• Record Type: Publication
• Source Agency: National Asphalt Pavement Association (NAPA)
• Files: TRIS
• Created Date: Mar 24 1994 12:00AM