ASPHALT CHARACTERISTICS IN RELATION TO ROAD PERFORMANCE AND DISCUSSION

TO ASSIST IN THE DEVELOPMENT OF MORE SIGNIFICANT SPECIFICATIONS FOR PAVING GRADE BITUMENS, TWO LARGE-SCALE ROAD TRIALS WERE LAID IN EUROPE IN 1963 AND 1964 INVOLVING IN EACH TRIAL EIGHT DIFFERENT BITUMENS OF DIFFERENT PHYSICAL CHARACTERISTICS WITHIN THE 70/100 PENETRATION GRADE RANGE. THE ROAD TRIALS WERE DESIGNED TO PROVIDE AN ESSENTIAL LINK BETWEEN RESEARCH STUDIES AND PRACTICAL PERFORMANCE. FOR THIS PURPOSE THE BEHAVIOR OF THE EIGHT BITUMENS WERE STUDIED IN DENSE TYPE HOT MIX (ASPHALTIC CONCRETE AND DENSE MACADAM) WEARING COURSES SUBJECTED TO MEDIUM TO HEAVY TRAFFIC IN TWO AREAS, ONE WITH A HOT AND DRY SUMMER (SE FRANCE), THE OTHER WITH A CONTINENTAL COLD WINTER WITH MUCH HEAVIER RAINFALL (S GERMANY). IN ADDITION TO THE DIFFERENCES BETWEEN THE BITUMENS, OTHER FACTORS INCLUDED IN THESE TRIALS WERE VARIATIONS IN AGGREGATE GRADING AND DIFFERENT BINDER CONTENTS AND AGGREGATE TYPES. DESPITE DIFFERENCES IN THE INITIAL CHARACTERISTICS OF THE BITUMENS, NO DIFFERENCES IN PERFORMANCE ATTRIBUTABLE TO THE BITUMENS HAVE BEEN FOUND ON THE ROADS SO FAR. THE TRIALS WERE LAID TO ALLOW FOR NORMAL PRACTICAL VARIATIONS IN THE SUB-BASE AGGREGATE, MIX TYPE AND BINDER CONTENT. PROGRESSIVE DETERIORATION ON THE TEST SECTIONS HAVE BEEN NOTED, AND THESE ARE IN LINE WITH THOSE GENERALLY EXPERIENCED IN PRACTICE. SOME VARIATIONS HAVE SHOWN UP DUE TO THE DIFFERENT MIX AND STONE TYPES EMPLOYED IN THE TRIALS. CHANGES IN THE BROAD CHEMICAL COMPOSITION AND THE RHELOGICAL CHARACTERISTICS OF THE BITUMENS HAVE BEEN STUDIED, AND ARE DISCUSSED IN THE PAPER. THE MAXIMUM CAANGES IN THE BITUMENS HAVE OCCURRED DURING THE MIXING/LAYING PROCESS, WITH LITTLE FURTHER CHANGE BEING OBSERVED DURING 5 YEARS SERVICE. /AUTHOR/