STRIPPING OF ASPHALT CONCRETE - CHEMICAL TESTING. FINAL REPORT

Although it is generally felt that the mechanism of stripping is the displacement by water or moisture of asphalt films from the aggregate surfaces, the action of water in stripping is still not entirely explained. Various methods have been developed and used to prevent stripping in asphalt-aggregate mixtures. Common practice is to use chemical antistripping additives. The objectives of the present investigation were to develop a better understanding of the nature of adhesion and stripping phenomena, to relate stripping propensity with aggregate characteristics, to identify the fundamental properties of additives that are primarily responsible for effectiveness, and to develop criteria for selection and use of antistripping additives. The boil test was chosen for studying the stripping process. An UV spectroscopic method to detect polyamine type antistripping additives was used successfully. Also a definitive method for quantifying the additives in asphalt cement by using a tracer metal was developed. Aggregates which impart a relatively high pH value to contacting water and/or which have relatively high surface potential show higher stripping propensity. The effectiveness of an antistripping additive can be determined by observing the contact angle of an asphalt drop on an aggregate immersed in water. Additive dosage level was more important than the type additive, and 0.5 to 1.0% was the typical dosage for desired performance. It was found from their IR spectra, that all proprietary additives tested were amines or chemical compounds containing amines. All additives tested were thermally unstable at temperatures above 300 deg F. The effectiveness of an antistripping additive could be maximized when applying it directly to the aggregate and could be improved considerably by storing the asphalt-aggregate mixture at a high temperature (about 300 deg F) for several hours. The addition of most antistripping additives softened asphalt and reduced age-hardening. Certain organometallic additives, however, increased the age-hardening of asphalt.

• Corporate Authors:

  Auburn University

  Engineering Experiment Station
  Auburn, AL  United States  36849

  Alabama State Highway Department

  Bureau of Materials and Tests, 1409 Coliseum Blvd
  Montgomery, AL  United States  36130

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Tarrer, A R
• Publication Date: 1987-1

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 190 p.

Subject/Index Terms

• TRT Terms: Adhesion; Age hardening; Aggregates; Amines; Antistrip additives; Asphalt concrete; Boiling; Chemical tests; Dosage; Measures of effectiveness; pH value; Stripping (Pavements); Tests; Tracers (Chemistry); Ultraviolet spectroscopy
• Uncontrolled Terms: Effectiveness
• Old TRIS Terms: Aggregate characteristics; Boil test; Tracers
• Subject Areas: Geotechnology; Highways; Materials; I31: Bituminous Binders and Materials;

Filing Info

• Accession Number: 00481033
• Record Type: Publication
• Report/Paper Numbers: FHWA/AL-105B/88, HPR 105B
• Contract Numbers: 930-111
• Files: TRIS, USDOT, STATEDOT
• Created Date: Mar 31 1989 12:00AM