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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

RESULTS OF FATIGUE TESTS ON DIFFERENT TYPES OF BITUMINOUS MIXTURES

IN ORDER TO FIND THE FACTORS, WHICH HAVE THE GREATEST INFLUENCE UPON THE FATIGUE STRENGTH OF BITUMINOUS MIXTURES, A NUMBER OF FATIGUE TESTS HAVE BEEN CARRIED OUT ON A WIDE VARIETY OF MIXTURES. MOST OF THE TESTS WERE CARRIED OUT BY MEANS OF A BENDING MACHINE WITH FIXED AMPLITUDE, IN WHICH THE SPECIMENS WERE SUPPORTED AT THE ENDS AND LOADED IN THE THIRD POINTS WITH A SINUSOIDAL LOAD, WITH A FREQUENCY OF 50 CYCLES PER SECOND AT A CONSTANT TEMPERATURE. PLOTTING THE FATIGUE STRAIN AGAINST THE NUMBER OF CYCLES TO FAILURE, USING LOGARITMIC SCALES, THE POINTS SCATTER AROUND A STRAIGHT LINE, AS FOUND BY PELL IN HIS BENDING TESTS. FOR ALL THE MIXTURES, THE SLOPE OF THIS LINE IS THE SAME, ONLY FOR THE MIXTURE CONTAINING OXYDIZED BITUMEN, THE SLOPE IS A LITTLE LESS STEEP. THE SLOPE SHOWS THAT IF THE STRAIN IS REDUCED BY ONE THIRD, THE FATIGUE LIFE IS NEARLY INCREASED BY A FACTOR OF 10. ALL THE GRADES OF BITUMEN USED WERE FROM THE SAME SUPPLIER, AND NO DIFFERENCE WAS FOUND BETWEEN THE GRADES FROM PENETRATION 180/200 DOWN TO PENETRATION 40/50. STILL HARDER GRADES SHOWED A SLIGHT INCREASE IN FATIGUE STRAIN. THE BINDER CONTENT IS THE MOST IMPORTANT FACTOR, AND THE FATIGUE LIFE HAS BEEN FOUND TO BE DIRECTLY PROPORTIONAL TO THE BINDER CONTENT, AS STATED BY PELL, BUT ONLY AS LONG AS THE AIR VOIDS VOLUME IS SMALL, COMPARED WITH THE BINDER VOLUME. WHEN THE AIR VOIDS VOLUME IS LARGE, THE FATIGUE STRAIN IS FOUND TO BE RELATIVELY LARGER. NO EFFECT OF THE TYPE AND THE GRADATION OF THE AGGREGATE UPON THE FATIGUE STRAIN HAS BEEN FOUND. A FEW TESTS HAVE BEEN CARRIED OUT WITH ANOTHER FOUR POINT BENDING MACHINE WITH IMPULSE LOADING, WHERE THE TEST SPECIMENS WERE DEFLECTED TO ONE SIDE ONLY, AND WHERE THE LOADING HAD THE FORM OF HALF A SINE WAVE WITH A DURATION OF 0.02 SECOND, FOLLOWED BY A REST PERIOD OF ABOUT 0.5 SECOND. THE MOST IMPORTANT FINDINGS HERE ARE THAT THE FATIGUE STRAIN IS ABOUT 100 PERCENT GREATER WITH THIS TYPE OF LOADING THAN WITH SINUSOIDAL LOADING, AND THAT THE FATIGUE STRAIN WITH THIS LOADING INCREASES WITH INCREASING TEMPERATURE. THIS INDICATES THAT THE FATIGUE LIFE IS NOT DEPENDENT UPON THE MAXIMUM STRAIN IN A PAVEMENT BUT UPON THE DIFFERENCE BETWEEN THE MAXIMUM AND THE MINIMUM STRAIN, CAUSED BY A LOADING. /AUTHOR/

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Filing Info

  • Accession Number: 00210669
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 15 1994 12:00AM