INFLUENCE OF SHAPE, SIZE, AND SURFACE TEXTURE ON THE STIFFNESS AND FATIGUE RESPONSE OF ASPHALT MIXTURES

RESEARCH RESULTS ARE SUMMARIZED RELATED TO THE INFLUENCE OF SHAPE, SIZE (INCLUDING SIZE DISTRIBUTION), AND SURFACE TEXTURE OF AGGREGATES ON THE STIFFNESS AND FATIGUE RESPONSE OF ASPHALT PAVING MIXTURES. A BRIEF DISCUSSION IS PRESENTED OF MIXTURE STIFFNESS WHICH INFLUENCES THE FATIGUE BEHAVIOR OF ASPHALTIC CONCRETE. DATA ARE GIVEN TO ILLUSTRATE THE EFFECTS OF AGGREGATE CHARACTERISTICS ON THE FATIGUE RESPONSE OF ASPHALT PAVING MIXTURES. THE METHODS FOR DETERMINING FATIGUE RESPONSE ARE DESCRIBED AND DISCUSSED. THE METHODS USED TO DETERMINE THE FATIGUE RESPONSE ARE IMPORTANT TO INDICATE THE INFLUENCE OF AGGREGATE CHARACTERISTICS ON THE FATIGUE BEHAVIOR OF ASPHALT MIXTURES. THE DATA INDICATE THAT AGGREGATE CHARACTERISTICS AFFECT BOTH STIFFNESS AND FATIGUE RESPONSE OF ASPHALT PAVING MIXTURES. IT WAS DEMONSTRATED THAT STIFFNESS AND FATIGUE RESPONSE ARE INTERRELATED. FOR THICK PAVEMENT SECTIONS, IT APPEARS DESIRABLE TO UTILIZE ROUGH-TEXTURED MATERIALS WITH DENSE GRADATIONS AND TO PRODUCE WELL-COMPACTED MIXTURES BECAUSE ALL OF THESE FACTORS TEND TO INCREASE MIXTURE STIFFNESS. IN THIN PAVEMENT SECTIONS, IT APPEARS THAT MORE OPEN-GRADED AGGREGATES SHOULD BE UTILIZED BECAUSE FLEXIBILITY IS INCREASED WITH REDUCTION IN FINES CONTENT. THE EFFECT OF SURFACE TEXTURE IS NOT SO APPARENT IN THIN SECTIONS BECAUSE OF CONFLICTING DEMANDS FOR LOAD-CARRYING ABILITY. AT COMPARABLE ASPHALT CONTENTS, MIXTURES PRODUCED WITH SMOOTH-TEXTURED MATERIALS MAY BE MORE DESIRABLE BECAUSE THEY PRODUCE LESS STIFF MIXTURES. IF STABILITY IS NOT ADEQUATE FOR THE LOADING CONDITIONS, THEN THE ROUGH-TEXTURED MATERIAL APPEARS MORE DESIRABLE. IT APPEARS THAT THE RESISTANCE OF ASPHALTIC CONCRETE BASES WILL BE IMPROVED BY USING AS MUCH ASPHALT AS POSSIBLE RATHER THAN BY PRODUCING MIXTURES THAT TEND TO BE LEAN, AS IS CURRENT PRACTICE IN SOME AREAS. INCREASED ASPHALT CONTENT RESULTS IN INCREASED MIXTURE STIFFNESS WICH RESULTS IN IMPROVED PERFORMANCE.