ADHESION OF ASPHALT TO AGGREGATES IN THE PRESENCE OF WATER

RELATIONS BETWEEN COVERAGE WETTING AND ADHESION ARE DISCUSSED AND ILLUSTRATED. COVERAGE IS ESSENTIAL TO WETTING, BUT WETTING DOES NOT NECESSARILY FOLLOW COVERAGE. WETTING IS NECESSARY FOR ADHESION, BUT DOES NOT ASSURE IT. PROPERTIES OF VISCOSITY, SURFACE TENSION, POROSITY AND POLARITY ARE DESCRIBED WITH REFERENCE TO THEIR EFFECT ON ADHESION: (1) IN GENERAL, THE HIGHER THE VISCOSITY THE BETTER THE ADHESION BUT THE MORE DIFFICULT TO WET THE AGGREGATE, (2) THE HIGHER THE SURFACE TENSION OF A SOLID THE GREATER ITS WETTABILITY, (3) THE SMOOTHER THE SURFACE TEXTURE THE MORE EASILY WETTED AND THE ROUGHER SURFACE ONCE WETTED IS MORE LIKELY TO HAVE BETTER ADHESION, (4) POROUS AGGREGATES ONCE WETTED USUALLY SHOW BETTER ADHESION DUE IN PART TO MECHANICAL INTERLOCKING, (5) POLARITY OF AGGREGATE IS THE MOST IMPORTANT PROPERTY AFFECTING ADHESION. THE LIQUID WHICH SATISFIES THE GREATER ENERGY DEMAND WILL ADHERE MOST TENACIOUSLY. THE FOLLOWING CONDITIONS SHOULD BE MET: (1) USE DRY AGGREGATE, (2) USE DUST-FREE AGGREGATE, (3) SEE THAT PARTICLES ARE UNIFORMLY COATED WITH AS THICK A FILM AS COMPATIBLE WITH TYPE OF CONSTRUCTION, (4) USE ASPHALT OF AS HIGH INITIAL VISCOSITY AS CAN BE USED AND STILL OBTAIN WETTING, (5) PROTECT COATED AGGREGATES FROM PROLONGED CONTACT WITH WATER, (6) IN COOL WEATHER PREHEAT AGGREGATE TO ASSURE WETTING, (7) AVOID HIGHLY HYDROPHILIC AGGREGATE, AND (8) WHEN USE OF HYDROPHILIC AGGREGATE IS UNAVOIDABLE, USE ASPHALT THAT IS SPECIALLY TREATED FOR SUCH AGGREGATE. A SIMPLE STATIC IMMERSION TEST IS DESCRIBED.

  • Supplemental Notes:
    • Vol 18, ParT 1, PP 238-249
  • Authors:
    • Hubbard, P
    • Shuger, L W
  • Publication Date: 1939

Media Info

  • Monograph Title: Proceedings of the Eighteenth Annual Meeting of the Highway Research Board Held at Washington, D.C. November 28-December 2, 1938. Part I
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00210904
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 13 1994 12:00AM