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

THE MINIMUM POROSITY OF ASPHALTIC CONCRETE SURFACINGS (IN GERMAN)

THE SPECIFICATION, TV BIT 3/64, PRESCRIBES A CALCULATED RESIDUAL POROSITY OF 1 TO 5% BY VOLUME, AS A MEASURE OF THE AMOUNT OF BINDING AGENT IN ASPHALTIC CONCRETE. HOWEVER, EXCESSIVE GREASING AND POLISHING OF THE SURFACE MAY RESULT IF THE BINDING AGENT IS NO LONGER ABLE TO EXPAND AT HIGH TEMPERATURES, DUE TO THE POROSITY BEING TOO LOW. THE THERMAL CUBIC EXPANSION OF BITUMEN ON HEATING TO THE TEMPERATURE OF THE HOT 6 PLACEMENT HAS THE EFFECT OF CONSIDERABLY REDUCING THE POROSITY WHICH EXISTS AT 25C. HENCE, IN DETERMINING THE BITUMEN CONTENT, IT MUST BE CONSIDERED THAT EXCESSIVE GREASING OF THE SURFACE DURING PLACEMENT CAN ONLY BE AVOIDED WITH CERTAINTY, IF THE WHOLE POROUS SPACE IN THE BINDING AGENT IS STILL NOT OCCUPIED BY THE INCREASE IN VOLUME OF THE BINDING AGENT WHEN THIS IS AT THE TEMPERATURE OF THE HOT PLACEMENT. THE LOWER LIMIT OF 1% BY VOLUME FOR POROSITY, PRESCRIBED BY TV BIT, MAY NOT BE REGARDED AS APPROXIMATE AT WILL; POROSITIES BETWEEN 1 AND 2% INVOLVE THE DANGER OF EXCESSIVE GREASING THROUGHOUT. THE EXTENDED MINIMUM POROSITY OF 3% IN AMERICAN SPECIFICATIONS, IN THE CASE OF SURFACES MADE IN ACCORDANCE WITH THE CONCRETE PRINCIPLE, IS THEREFORE JUSTIFIED. THE ESTABLISHMENT OF THE MINIMUM POROSITY VOLUME FOR ASPHALTIC CONCRETE SURFACINGS IS EXPLAINED WITH THE AID OF SIX FORMULAS, A TABLE, AND A NOMOGRAM. /FG/RRL/

  • Supplemental Notes:
    • Vol 29, No 6, PP 156-159, 2 TAB, 2 PHOT, 1 REF
  • Authors:
    • Rose, D
  • Publication Date: 1967

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Filing Info

  • Accession Number: 00211101
  • Record Type: Publication
  • Source Agency: Road Research Laboratory /UK
  • Files: TRIS
  • Created Date: May 25 1970 12:00AM