CUTBACK ASPHALT PATCHING MIXTURES

ASPHALT PATCHING MIXTURES SHOULD BE SATISFACTORY FOR USE AT ALL SEASONS OF THE YEAR AND SHOULD HAVE SUITABLE STABILITY IF USED IMMEDIATELY AFTER MIXING OR AFTER STORAGE FOR LONG PERIODS OF TIME. THE ADDITIONAL REQUIREMENTS ARE THAT LOCAL MATERIALS MUST BE USED WHEREVER POSSIBLE AND THE MIXTURE SHOULD BE SATISFACTORY FOR PREPARING BY THE MAINTENANCE FORCES IN THE DISTRICTS. IN THE STUDY REPORTED, ONE AGGREGATE WAS CHOSEN FOR ALL PHASES OF THE PROJECT. THIS MATERIAL WAS A HARD DOLOMITIC LIMESTONE. TWO METHODS OF CURING WERE USED FOR ALL CUTBACK. THE FIRST METHOD WAS THAT OF CURING THE PREPARED MIXES IN OVENS AT A CONSTANT TEMPERATURE OF 140F. THE SECOND METHOD OF CURING WAS IN LENGTHS OF STOVEPIPE PLACED UPRIGHT ON SCREEN WIRE ON THE ROOF OF THE LABORATORY AND PROTECTED FROM RAIN. THUS, THE MIXTURE WAS EXPOSED TO THE AIR AT BOTH ENDS OF THE STOVEPIPE SERIES OF MIXES USING BOTH MC CUTTER STOCKS AND RC CUTTER STOCKS WERE USED. THE RATE OF CURING OF THE MC CUTBACKS INDICATED THAT THESE MIXTURES COULD BE STORED FOR LONG PERIODS OF TIME AND STILL BE USED, BUT THEY WOULD CURE SO SLOWLY IN A STOCKPILE THAT THEY WOULD NOT BE USEABLE FOR SOME TIME AFTER MIXING. MIXES USING THE RC CUTTER STOCKS CURED TOO RAPIDLY. A MARSHALL STABILITY OF 500 LB WAS CHOSEN AS THE DESIRABLE MINIMUM STABILITY SATISFACTORY FOR PATCHING. A COMPARISON OF THE DISTILLATION CURVES OF RC CUTTER STOCKS AND MC CUTTER STOCKS INDICATED THAT THE IDEAL CUTTER STOCK WOULD BE ONE HAVING THE CHARACTERISTICS OF THE LIGHTER ENDS OF AN RC WITH THE HEAVY ENDS OF AN MC. A BLEND OF 40 PERCENT OF RC, 50 PERCENT MC AND 10 PERCENT SC CUTTER STOCKS PRODUCED A DISTILLATION CURVE APPROXIMATING THE DESIRED CHARACTERISTICS. PATCHING MIXTURES PREPARED WITH BLENDED CUTBACK GAVE THE DESIRED RESULTS. FROM 30 TO 40 PERCENT OF THE VOLATILE MATTER WAS LOST DURING MIXING AND STORING. AT THIS POINT THE MARSHALL STABILITIES RANGED BETWEEN 400 AND 500 POUNDS. BEYOND THIS POINT THE RATE OF CURING WAS SLOW, THUS PROVIDING A LONG PERIOD OF STORAGE WHERE NEEDED. A TENTATIVE SPECIFICATION FOR CUTBACK SPECIFICATION VARIES FROM THE USUAL SPECIFICATION IN SEVERAL IMPORTANT POINTS AND IS VERY RESTRICTIVE. FIELD USE WILL BE REQUIRED FOR IMPROVEMENT OF THE SPECIFICATION. /AUTHOR/

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  • Accession Number: 00211395
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Apr 28 1994 12:00AM