POLISHING CHATACTERISTICS OF MINERAL AGGREGATES

A LABORATORY INVESTIGATION IS REPORTED WHICH WAS UNDERTAKEN TO OBTAIN A BETTER UNDERSTANDING OF SOME OF THE VARIABLES INVOLVED IN PAVEMENT SLIPPERINESS. THE FOLLOWING FACTORS WERE STUDIED: (1) THE POLISHING CHARACTERISTICS OF DIFFERENT MINERAL AGGREGATES IN BOTH PORTLAND CEMENT AND BITUMINOUS CONCRETE MIXTURES, AND THEIR RELATION TO BASIC AGGREGATE PROPERTIES, (2) THE EFFECT OF TEXTURE, AS DETERMINED BY GRADATION, ON THE ANTI-SKID CHARACTERISTICS OF BITUMINOUS MIXTURES, AND (3) THE EFFECT OF INITIAL AGGREGATE SHAPE, OR DEGREE OF HARSHNESS, ON THE SKID RESISTANCE OF BITUMINOUS MIXTURES. THE BITUMINOUS CONCRETE LABORATORY TEST SPECIMEN WAS AN OPEN-GRADED ASPHALTIC CONCRETE IN WHICH THE ASPHALT CONTENT WAS KEPT INTENTIONALLY LOW IN ORDER TO EMPHASIZE THE EFFECT OF THE AGGREGATE. THE POLISHING CHARACTERISTICS OF BITUMINOUS MIXTURES COMPOSED OF TWENTY- TWO MINERAL AGGREGATES FROM FIVE DIFFERENT STATES WERE DETERMINED IN THE AGGREGATE STUDY. THE PORTLAND CEMENT CONCRETE USED FOR THE STANDARD LABORATORY SPECIMEN WAS MADE WITH A FAIRLY WELL-GRADED AGGREGATE, A HIGH CEMENT FACTOR, AND A LOW SLUMP. AS IN THE BITUMINOUS STUDY, EACH TEST SECTION WAS COMPOSED ENTIRELY OF ONE AGGREGATE TYPE. THE SLIPPERINESS OF EACH MIXTURE WAS DETERMINED IN THE LABORATORY SKID-TEST APPARATUS WHICH SPUN THE TEST SPECIMEN AT 2500 RPM AND EVALUATED THE SKID RESISTANCE BY FORCING A RUBBER TESTING SHOE AGAINST THE WET SURFACE OF THE SPECIMEN. RESULTS SHOW THAT DENSE-GRADED BITUMINOUS MIXTURES WILL EXHIBIT SOMEWHAT BETTER ANTI-SKID CHARACTERISTICS THAN OPEN- GRADED BITUMINOUS MIXTURES COMPOSED OF IDENTICAL AGGREGATE, PROVIDED AN EXCESS OF ASPHALT DOES NOT OCCUR AT THE SURFACE. THERE APPEARS TO BE SOME JUSTIFICATION, BASED ON SKID RESISTANCE ALONE, FOR REQUIRING THAT ANY NATURALLY-ROUNDED COARSE AGGREGATE BE ENTIRELY CRUSHED IF IT IS TO BE USED IN THE PAVEMENT SURFACE. THE POLISHING CHARACTERISTICS OF AGGREGATES ARE SIMILAR BOTH IN PORTLAND CEMENT AND BITUMINOUS MIXTURES WHICH ARE COMPOSED ENTIRELY OF ONE AGGREGATE TYPE. RESULTS OF LABORATORY STUDY INDICATE THAT UNIFORM FINE-GRAINED OR OOLITIC LIMESTONES CONSISTING ESSENTIALLY OF PURE CALCIUM CARBONATE SHOULD NOT CONSTITUTE THE TOTAL SURFACE AGGREGATE OF HIGHWAY PAVEMENTS. SURFACES OF THIS NATURE POSSESS ONLY FAIR SKID RESISTANCE WHEN NEW, AND MAY BECOME DANGEROUSLY SLIPPERY AFTER A MODERATE AMOUNT OF TRAFFIC WEAR.

• Supplemental Notes:
  • Proc 1st InTL SKID PREV CONF, PART II, PP 509-537, 17 FIG,
• Corporate Authors:

  Virginia Highway Research Council

  Charlottesville, VA  United States 
• Authors:
  • Shupe, J W
  • Lounsbury, R W
• Publication Date: 1959

Subject/Index Terms

• TRT Terms: Asphalt concrete; Bituminous mixtures; Coarse aggregates; Laboratory tests; Mineral aggregates; Polished aggregates; Portland cement; Skid resistance; Skid resistance tests; Slipperiness; Test sections
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 00217593
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 18 1994 12:00AM