MORTAR THEORY FOR USE OF UNGRADED AGGREGATES IN BITUMINOUS MIXES

THE DEVELOPMENT OF A MEANS OF UTILIZING UNGRADED LOCAL AGGREGATES IN BITUMINOUS MIXTURES WOULD REDUCE THE COST OF SECONDARY ROAD CONSTRUCTION SINCE EXISTING THEORIES OF DESIGN AND MIXING PRACTICES FOR BITUMINOUS PAVING MIXTURES DO NOT LEND THEMSELVES TO THE USE OF UNGRADED AGGREGATES, IT IS NECESSARY THAT A NEW CONCEPT OF DESIGN BE FORMULATED AND A NEW MIXING METHOD DEVISED. THE EFFECT ON CLAYS AND THE STABILIZING EFFECT OF DAMP CLAYS ON UNGRADED NATURAL AGGREGATES GERMINATED AN IDEA UPON WHICH A MORTAR THEORY FOR BITUMINOUS MIXES MIGHT BEBASED. THIS MORTAR THEORY, STATED BRIEFLY, IS THE FORMATION OF THIN FILMS OF BITUMINOUS BINDER UPON THE MINUTE PARTICLES OF A MINERAL DUST TO FORM A BITUMINOUS MORTAR, AND THE MORTAR SO PREPARED TO BE USED TO BOND AGGREGATES TOGETHER INTO A BITUMINOUS MIXTURE SUITABLE FOR PAVING PURPOSES. IN ORDER TO TEST THE VALIDITY OF THE MORTAR THEORY AS QUICKLY AS POSSIBLE, KNOWN METHODS OF PRODUCING SUCH THIN FILMS WERE STUDIED AND THE IMPACT PROCESS SELECTED FOR THIS PURPOSE IN FURTHER TESTS. IN THE IMPACT PROCESS THE BITUMINOUS BINDER IS INTRODUCED INTO A SLIGHTLY MODIFIED PUGMILL MIXER IN AN ATOMIZED FORM DURING MIXING. IT WAS FOUND THAT VERY THIN FILMS OF A BITUMINOUS BINDER COULD BE FORMED ON INDIVIDUAL PARTICLES OF DUST AND AGGREGATES. MINERAL FILLERS TESTED INCLUDED LIMESTONE DUST, PULVERIZED LOESS CONTAINING UP TO 40 PERCENT CLAY, AND FLYASH. UNGRADED AGGREGATES TESTED INCLUDED COMMERCIAL AGRICULTURAL LIMESTONE, AND NATURAL SANDS RANGING FROM A BLOW OR DUNE SAND HAVING PARTICLES BETWEEN THE NO. 40 AND NO. 80 SIEVES UP TO COARSE SANDS HAVING PARTICLES BETWEEN THE NO. 10 AND NO 40 SIEVES. MIXES WERE PREPARED CONTAINING VARIOUS COMBINATIONS OF SAND AND DUST WITH SOFT ASPHALT CEMENT AND TESTED FOR HUBBARD-FIELD STABILITY. SINCE THE LOESS USED AS THE DUST CONTAINED CLAY, ALL MIXES WERE SUBJECTED TO FREEZING AND THAWING TESTS. TEST RESULTS BASED ON HUBBARD-FIELD DESIGN CRITERIA INDICATE THAT MANY OF THESE MIXES POSSESS CONSIDERABLE PROMISE FOR APPLICATION IN BITUMINOUS PAVEMENTS CARRYING MODERATE TRAFFIC. TO DETERMINE FIELD BEHAVIOR AND CONSTRUCTION CHARACTERISTICS OF THESE MIXES A TEST ROAD WAS LAID. DURING THESE OPERATIONS COMMERCIAL PROCESSING OF PULVERIZED LOESS WAS DEVELOPED. MIXES WERE MADE IN SMALL CONSTRUCTION MIXERS MODIFIED TO THE PROCESS AND LAID BY HAND. DURING ONE YEAR IN SERVICE UNDER TRAFFIC OF ABOUT 3,000 VEHICLES PER DAY, THESE MIXES PERFORMED VERY SATISFACTORILY. THE VARIOUS TESTS PROVE THAT THE MORTAR THEORY AS PROPOUNDED IS SOUND AND CAN BE USED IN PREPARING BITUMINOUS PAVING MIXTURES CONTAINING UNGRADED AGGREGATES. /AUTHOR/

Media Info

  • Monograph Title: BITUMINOUS PAVING MIXTURES-FUNDAMENTALS FOR DESIGN
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00211389
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jul 7 1994 12:00AM