THE EFFECTS OF MIXTURE VARIABLES ON THERMALLY INDUCED STRESSES IN ASPHALTIC CONCRETE AND DISCUSSION

AN INVESTIGATION HAS BEEN CONDUCTED TO EVALUATE THE EFFECTS OF MIXTURE VARIABLES ON THERMALLY INDUCED TENSILE STRESSES IN ASPHALTIC CONCRETE AND TO DETERMINE TO WHAT EXTENT, IF ANY, THESE STRESSES CHANGE WITH THERMAL CYCLING. THE VARIABLES WERE ASPHALT VISCOSITY, ASPHALT CONTENT, AND AGGREGATE ABSORPTION. ASPHALT CONTENT WAS FOUND TO HAVE A CRITICAL EFFECT ON THERMALLY INDUCED STRESSES IN ASPHALTIC CONCRETE. IN PRISMS HAVING A CONTENT CORRESPONDING TO THE MARSHALL DESIGN OPTIMUM ASPHALT CONTENT A HIGH RATE OF STRESS CHANGE WITH TEMPERATURE REDUCTION AND HIGH MAXIMUM STRESS UNDER THE TEMPERATURES TESTED OCCURRED. THIS EFFECT PRODUCED A HIGH BOND WITHIN THE MATRIX AND A RESULTING HIGH INTERNAL RESISTANCE TO THERMAL STRESSES. IN PRISMS HAVING A BELOW OPTIMUM ASPHALT CONTENT, THE RATES OF STRESS CHANGE WITH TEMPERATURE AND MAXIMUM THERMAL STRESSES WERE LOW INDICATING A LACK OF BOND DUE TO A THIN FILM THICKNESS AND HIGH VOID CONTENT. ON THE OTHER HAND, PRISMS HAVING AN ABOVE OPTIMUM CONTENT AND EXCESS FILM THICKNESS ALSO PRODUCED A LOW RATE OF STRESS CHANGE WITH TEMPERATURE AND LOW MAXIMUM STRESS INDICATING A STRESS RELAXATION WITHIN THE PRISMS. IN THIS INVESTIGATION, BOTH HIGH AND LOW VISCOSITY ASPHALTS SHOWED A HIGH INTERNAL RESISTANCE, PROVIDED AN OPTIMUM ASPHALT CONTENT WAS USED. THE PRISMS HAVING THE LOW VISCOSITY ASPHALT COMBINED WITH THE ABSORPTIVE AGGREGATE SHOWED A HIGHER INTERNAL RESISTANCE BY PROVIDING A HIGHER RATE OF STRESS CHANGE WITH TEMPERATURE REDUCTION. IN GENERAL, THE THERMALLY INDUCED STRESSES INCREASED WITH THERMAL CYCLING IN ALL THE PRISMS WITH DIFFERENT MAGNITUDES DEPENDING ON THE MIXTURE VARIABLES USED. THE AVERAGE INCREASE OF ALL MAXIMUM THERMALLY INDUCED STRESSES OVER THE INTERVAL TO 100 TEMPERATURE CYCLES WAS 3.3 PSI. THE RATE OF CHANGE OF TEMPERATURE INDUCED STRESSES IN THE PRISMS WITH TEMPERATURE REDUCTION DID NOT CHANGE WITH TIME AND TEMPERATURE CYCLING BUT DIFFERED IN MAGNITUDE ACCORDING OF THE MIXTURE VARIABLES USED. /AUTHOR/

• Supplemental Notes:
  • Vol 39, pp 703-744, 28 FIG, 22 TAB, 18 REF, 1 APP
• Authors:
  • Tuckett, G M
  • JONES, G M
  • Littlefield, G
• Conference:
  • Association of Asphalt Paving Technologists Proc
• Publication Date: 1970

Subject/Index Terms

• TRT Terms: Absorption; Asphalt concrete; Asphalt content; Bituminous aggregates; Bituminous mixtures; Tension; Thermal stresses; Viscosity
• Uncontrolled Terms: Tensile stress
• Old TRIS Terms: Thermal cycling
• Subject Areas: Highways; Materials;

Filing Info

• Accession Number: 00211674
• Record Type: Publication
• Files: TRIS
• Created Date: Jul 25 1971 12:00AM