CLASS I BITUMINOUS MIXTURES

EVALUATION WAS MADE OF BITUMINOUS SURFACE COURSE MIXTURES PRODUCED UNDER TWO GRADATION SPECIFICATIONS WHICH DIFFER ONLY IN THE LOWER GRADATION LIMIT BELOW THE NO. 16 SIEVE. COMPARISON OF THE TWO GRADATIONS SHOW THAT THE ONLY DIFFERENCE OF ANY MAGNITUDE IS IN THE DUST SIZES (- NO. 16 SIEVE MATERIAL). MEDIAN GRADATIONS FOR TYPE B AND TYPE A MIXTURES WHICH CONTAIN LIMESTONE AND NATURAL SAND FINE AGGREGATES ARE PRESENTED IN TABULAR FORM. THE LABORATORY MARSHALL ANALYSIS OF MIXTURES PRODUCED UNDER THE TYPE A SPECIFICATION REQUIREMENTS INDICATE THAT ON THE AVERAGE THE AVERAGE THE DENSITY OF THE MIXTURE IS TOO HIGH TO SATISFY ACCEPTED MIX DESIGN CRITERIA. LABORATORY ANALYSIS OF MIXTURES PRODUCED UNDER THE TYPE B (MODIFIED) GRADATION LIMITS INDICATE THAT THE AVERAGE MARSHALL PROPERTIES OF THESE MIXTURES SATISFY THE DESIGN CRITERIA. IT IS RECOMMENDED THE TYPE A GRADATION LIMITS BE AMENDED TO AGREE MORE CLOSLEY WITH THE TYPE B (MODIFIED) GRADATION LIMITS. IT IS RECOMMENDED THAT MARSHALL DESIGNS BE PERFORMED PREPARATORY TO SURFACING TO MINIMIZE THE CHANCE OF PRODUCING MIXTURES WHICH WILL BECOME SLICK AS A RESULT OF HIGH ASPHALT CONTENT AFTER A PEROID OF TIME UNDER TRAFFIC. IT IS RECOMMENDED THAT GREATER CONTROL AND CARE BE EXERCISED IN THE APPLICATION OF TACKING MATERIALS. THE REQUIREMENTS MADE IN THE 1965 STANDARD SPECIFICATIONS WITH REGARD TO MINERAL FILLER FEEDERS AND DUST-RETURN SYSTEMS HAVE MADE IT POSSIBLE TO CONTROL THE CRITICAL DUST FRACTION AT THE PLANT. THE ACHIEVEMENT OF GRADATION CONTROL HAS IMPROVED SURFACE APPEARANCE, INCREASED STABILITY, ACHIEVED HIGHER DENSITY, AND ENHANCED DURABILITY.

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Filing Info

  • Accession Number: 00211370
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Apr 28 1994 12:00AM