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THE AASHO ROAD TEST: REPORT 7 - SUMMARY REPORT

A SUMMARY IS PRESENTED OF THE AASHO ROAD TEST ON THE STUDY OF THE PERFORMANCE OF PAVEMENT AND BRIDGE STRUCTURES OF KNOWN CHARACTERISTICS UNDER MOVING LOADS OF KNOWN MAGNITUDE AND FREQUENCY. THE AASHO ROAD TEST WAS CONDUCTED NEAR OTTAWA, ILLINOIS, OVER A 2-YEAR PERIOD TO PROVIDE RESEARCH DATA USEFUL IN THE DESIGN OF EFFICIENT HIGHWAYS OF ECONOMICAL COST FOR HIGHWAY ENGINEERS. THE ROAD TEST WAS COMPOSED OF THE FOLLOWING MAJOR EXPERIMENTS: RELATING TO FLEXIBLE PAVEMENT WITH ASPHALT CONCRETE SURFACING, RIGID PAVEMENT WITH CONCRETE SURFACING, SHORT-SPAN BRIDGES WITH STEEL BEAMS AND SHORT-SPAN BRIDGES WITH CONCRETE BEAMS. ONE OF THE BASIC CONCEPTS OF THE EXPERIMENT WAS TO STUDY AND EVALUATE THE PERFORMANCE OF PAVEMENTS AND BRIDGES THROUGH FAILURE. CONSTRUCTION OF THE TEST PAVEMENTS WAS VERY CAREFULLY CONTROLLED. PAVEMENT RESEARCH WAS CONDUCTED TO ESTABLISH RELATIONSHIPS SHOWING HOW PERFORMANCE OF PAVEMENTS IS INFLUENCED BY STRUCTURAL DESIGN, REPRESENTED BY COMPONENT THICKNESSES OF THE PAVEMENT STRUCTURE, AND LOADING, REPRESENTED BY THE MAGNITUDE AND FREQUENCY OF AXLE LOADS, FOR BOTH RIGID AND FLEXIBLE PAVEMENTS OF CONVENTIONAL DESIGN. TEST RESULTS ARE PRESENTED IN THE FORM OF EQUATIONS AND GRAPHS SHOWING THE RELATIONSHIPS SOUGHT. AN IMPORTANT BY-PRODUCT OF THE AASHO ROAD TEST WAS THE DEVELOPMENT OF A NEW CONCEPT FOR THE EVALUATION OF PAVEMENT PERFORMANCE. OTHER IMPORTANT FINDINGS FROM THE PAVEMENT PERFORMANCE STUDY INCLUDE INFORMATION ON THE EQUIVALENCIES OF SINGLE AND TANDEM AXLE ARRANGEMENTS. FLEXIBLE PAVEMENTS LOST SERVICEABILITY THROUGH THE DEVELOPMENT OF RUTS AND ROUGHNESS IN THE WHEEL PATHS AND BY CRACKING IN THE ASPHALTIC CONCRETE SURFACING, EVENTUALLY REQUIRING PATCHING OF THE SURFACE. FOR THE ROAD TEST CONDITIONS, THE TESTS SHOWED THAT IN THE DESIGN OF FLEXIBLE PAVEMENT 1 INCH OF ASPHALT CONCRETE WAS EQUIVALENT TO 3 INCHES OF CRUSHED LIMESTONE BASE, OR 4 INCHES OF SAND-GRAVEL SUBBASE IN THEIR LOAD-CARRYING ABILITIES. FLEXIBLE PAVEMENT BASES TREATED WITH BITUMINOUS MATERIAL OR CEMENT WERE FAR SUPERIOR TO UNTREATED CRUSHED LIMESTONE OR GRAVEL BASES IN RESISTING LOSS OF SERVICEABILITY UNDER LOAD. RIGID PAVEMENTS LOST SERVICEABILITY BY THE DEVELOPMENT OF ROUGHNESS ALONG THE WHEEL PATHS, BY SLAB CRACKING OR BY THE NECESSITY OF PATCHING THE PAVEMENT SURFACE DUE TO SEVERE CRACKING AND ROUGHNESS. IN THE RIGID PAVEMENT EXPERIMENT, THE USE OF SAND-GRAVEL SUBBASE INCREASED THE LIFE OF THE PAVEMENT APPRECIABLY WHEN PAVEMENTS WITH SUBBASE WERE COMPARED TO PAVEMENTS WITH NO SUBBASE. THE COMBINED DEFECTS OF TRAFFIC AND WEATHERING ON PAVEMENT SURFACE SKID RESISTANCE WERE STUDIED. AN IMPORTANT PART OF THE AASHO ROAD TEST WAS A STUDY OF THE SHORT-SPAN HIGHWAY BRIDGES. REPEATED APPLICATIONS OF OVERSTRESS WERE MADE TO THESE STRUCTURES TO DETERMINE FATIGUE LIFE AND THE MANNER IN WHICH DISTRESSES CAUSED BY REPEATED STRESSES. THE DYNAMIC EFFECTS OF MOVING VEHICLES WERE DETERMINED ON THESE STRUCTURES AND THESE DYNAMIC EFFECTS CORRELATED WITH THOSE PREDICTED BY THEORETICAL COMPUTATIONS. THE OBSERVED DISTRESS CAUSED BY REPEATED APPLICATIONS OF A STRESS INDICATED THAT THE LIFE OF HIGHWAY BRIDGES CAN BE PREDICTED WITH REASONABLE ACCURACY ON THE BASIS OF SIMPLE LABORATORY TESTS, IF THE HISTORY OF STRESSES IN THE BRIDGE IS KNOWN.

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    • Part G, 66 PP, 23 FIG, 7 TAB, 57 PHOT 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
  • Publication Date: 1962

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  • Accession Number: 00207037
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 15 1994 12:00AM