SPECIAL STUDIES

SPECIAL STUDIES CONDUCTED DURING THE AASHO ROAD TESTS ARE SUMMARIZED. NUCLEAR TESTING EQUIPMENT WAS DEVELOPED FOR MEASUREMENT OF IN-PLACE DENSITY OF THE SEVERAL COMPONEMTS OF THE PAVEMENT STRUCTURE. AN EXTENSIVE PROGRAM OF DYNAMIC TESTING OF THE PAVEMENT STRUCTURE MAKING USE OF THE SHELL ROAD VIBRATION MACHINE WAS CONDUCTED. SOME CONCLUSIONS DRAWN FROM THIS STUDY WERE: (1) THE STIFFNESS OF THE ASPHALT PAVEMENT IS GREATLY INFLUENCED BY SEASONAL CHANGES, (2) SEASONAL RECOVERY OF THE PAVEMENT STRUCTURES INDICATED THAT DEGREE OF RECOVERY REQUIRED FURTHER INVESTIGATION, AND (3) THE STIFFNESS OF PAVEMENT SECTIONS WITH BITUMIMOUS-TREATED BASES IS VERY HIGH. A STUDY WAS CONDUCTED TO TEST THE ALERTNESS OF PERSONNEL ENGAGED IN FATIGUING AND MONOTONOUS DRIVING. ALERTNESS WAS MEASURED ON AN HOUR-BY-HOUR BASIS FOR ONE GROUP OF DRIVERS IN ORDER TO OBSERVE THE LEVEL AND SCOPE OF PERFORMANCE. ANOTHER GROUP OF DRIVERS WERE ADMINISTERED A VARIETY OF PSYCHOLOGICAL TESTS AND MEASURES IN AN ATTEMPT TO PREDICT INDIVIDUAL DIFFERENCES IN ALERTNESS. AN INVESTIGATION WAS CONDUCTED OF THE RESISTANCE TO SKIDDING OF WET AND DRY FLEXIBLE AND RIGID PAVEMENTS OF KNOWN DESIGN AND TRAFFIC TREATMENT. THE EXPERIMENT INCLUDED 80 TEST SECTIONS OF DIFFERNET DESIGN. A PAVEMENT PERFORMANCE STUDY WAS CONDUCTED ON THE TWO- AND SIX- KIP AXLE LOAD LOOP. THOSE SECTIONS WHICH SURVIVED THE OVER 1 MILLION LOADED AXLE APPLICATIONS WERE SUBJECTED TO REPETITIVE APPLICATIONS OF 32-KIP TANDEM AXLE LOADS. ONE GROUP OF MILITARY TRACTOR, SEMITRAILER UNITS WAS EQUIPPED WITH LOW PRESSURE-LOW SILHOUETTE (LPLS) TIRES AT 35 PSI AND THE OTHER WITH CONVENTIONAL MILITARY TIRES AT 70 PSI. APPROXIMATELY 16,500 AXLE APPLICATIONS WERE APPLIED. COMPARISONS OF THE RELATIVE EFFECTS OF THE TIRE DESIGN AND PRESSURE, FOR THE FLEXIBLE SECTION, WERE MADE ON THE BASIS OF SERVICEABILITY LOSS, INCREASED IN AREA OF CRACKING AND PATCHING, AND INCREASED IN RUT DEPTH. FOR THE RIGID SECTIONS, THESE COMPARISONS WERE ON THE BASIS OF SERVICEABILITY LOSS, INCREASE IN CRACKING AND PATCHING, AND INCREASED IN PUMPING SCORE. A TIRE PRESSURE AND DESIGN STUDY WAS CONDUCTED TO DETERMINE POSSIBLE EFFECTS OF CHANGES IN TIRE PRESSURE AND DESIGN ON THE DYNAMIC MEASURE- MENTS ASSOCIATED WITH PAVEMENT STRUCTURES AND BRIDGES. AN INVESTIGATION WAS CONDUCTED TO DETERMINE THE DYNAMIC EFFECT ON BRIDGES AND PAVEMENTS OF COMMERCIAL CONSTRUCTION EQUIPMENT, AND RELATE THE DYNAMIC EFFECTS OF THESE VEHICLES TO THOSE OBSERVED FOR CONVENTIONAL DUAL-TIRE UNITS. ONE MEDIUM AND ONE SMALL 2-AXLE TRACTOR-SCRAPER UNIT WERE OPERATED OVER PAVEMENT SECTIONS ON WHICH DYNAMIC MEASURENETS WERE MADE OF STRAIN, DEFLECTION, TRANSMITTED EMBANKMENT PRESSURE, AND DYNAMIC LOAD EFFECT. A STUDY WAS CONDUCTED TO DETERMINE THE DYNAMIC EFFECTS ON PAVEMENTS AND BRIDGES OF VEHICLES EQUIPPED WITH SPECIAL SUSPENSION SYSTEMS. THREE TRACTORS AND TWO SEMITRAILERS EQUIPPED WITH SPECIAL SUSPENSION WERE USED. FOR THE BRIDGE STUDY, RESULTS SHOWED THAT: (1) THE MEAN AMPLIFICATION FACTORS FOR THE CONVENRIONAL SINGLE-AXLE VEHICLE WERE HIGHER THAN THOSE FOR THE TANDEMAXLE VEHICLE, (2) THE MEAN STRAIN AMPLIFICATION FACTORS FOR ALL SPECIAL VEHICLES WERE APPRECIABLY HIGHER THAN THE FACTORS FOR THE CONVENTIONAL UNITS AT 30 MPH.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/sr/sr73/73-010.pdf
• Supplemental Notes:
  • pp 166-172 Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Corporate Authors:

  Highway Research Board

  2101 Constitution Avenue, NW
  Washington, DC    20418

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Leathers, R C
  • Perry, Clyde H
• Conference:
  • Highway Research Board Conference on the AASHO Road Test
  • Location: St Louis MO, United States
  • Date: 1962-5-16 to 1962-5-18
• Publication Date: 1962

Media Info

• Monograph Title: THE AASHO ROAD TEST - PROCEEDINGS OF A CONFERENCE HELD MAY 16-18, 1962, ST. LOUIS, MISSOURI
• Serial:
  • Highway Research Board Special Report
  • Issue Number: 73
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Asphalt pavements; Driver performance; Drivers; Dynamic tests; Flexible pavements; Highway bridges; In place density; Nuclear tests; Pavement layers; Pavement performance; Personnel performance; Rigid pavements; Seasons; Skid resistance; Stiffness
• Identifier Terms: AASHO Road Test
• Uncontrolled Terms: Pavement structure; Seasonal variations
• Old TRIS Terms: Nuclear testing
• Subject Areas: Highways; Pavements;

Filing Info

• Accession Number: 00207114
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Aug 26 1970 12:00AM