EFFECT OF PARTICLE SHAPE AND SURFACE TEXTURE ON THE FATIGUE BEHAVIOR OF ASPHALTIC CONCRETE

A LABORATORY INVESTIGATION IS REPORTED ON THE EFFECTS OF PARTICLE SHAPE AND PARTICLE SURFACE TEXTURE ON THE FATIGUE BEHAVIOR OF AN ASPHALTIC SURFACE MIXTURE. THE INVESTIGATION WAS LIMITED TO ONE MIXTURE TESTED IN A CONSTANT-STRAIN MODE. THREE AGGREGATES WERE USED IN SEPARATE MIXTURES FOR THE PARTICLE SHAPE FATIGUE COMPARISONS: ROUND GRAVEL, LIMESTONE, AN INTERMEDIATE-SHAPED AGGREGATE THAT WAS NEITHER ROUND NOR SLABBY, AND SLABBY SLATE. TWO MIXTURES, ONE CONTAINING UNETCHED LIMESTONE AND THE OTHER ETCHED LIMESTONE, WERE COMPARED IN THE PARTICLE SURFACE TEXTURE-FATIGUE STUDY. BEAMS DIMENSIONED TO 2.5 BY 3 BY 4 IN. WERE COMPACTED FROM EACH MIXTURE AND TESTED IN THE LABORATORY. THE FATIGUE LIFE WAS DEFINED BY CRACKING OF THE BEAM SURFACE AND MONITORED BY THE RESULTANT CRACKING OF FOIL STRIPS GLUED TO THE BEAM. THE RESULTS OF THE CONSTANT-STRAIN MODE FATIGUE TESTS SHOW THAT THE MIXTURE CONTAINING THE SLABBY-SHAPED AGGREGATES HAD A SIGNIFICANTLY SHORTER FATIGUE LIFE THAN THE MIXTURE CONTAINING THE ROUNDED GRAVEL. THERE WAS NO SIGNIFICANT DIFFERENCE BETWEEN THE FATIGUE LIFE OF THE UNETCHED LIMESTONE MIXTURE AND THAT OF THE ETCHED LIMESTONE MIXTURE. THE DATA ON RUPTURE MODULUS VERSUS NUMBER OF CYCLES INDICATE THAT A LINEAR RELATIONSHIP ON A LOG-LOG PLOT EXISTED FOR ALL MIXTURES CONTAINING AGGREGATES WITH DIFFERENT SHAPES AND SURFACE TEXTURES. THE CURVES ARE ESSENTIALLY PARALLEL FOR ALL MIXTURES, AND THE UNETCHED AND ETCHED LIMESTOME CURVES ARE ESSENTIALLY IDENTICAL. /AUTHOR/