USE OF AIR-BLOWN ASPHALT CEMENTS TO REDUCE THERMAL CRACKING

In recent years, several studies have shown that low temperature transverse cracking of asphaltic concrete is a function of the stiffness and temperature susceptibility of the asphalt. If the stiffness can be kept below a critical value at the lowest of in-service temperatures, cracking will not occur. These considerations have led to greater use of so-called "soft-asphalt", i.e., high penetration asphalt cements or sc-6 cutback asphalts, for thin asphaltic concrete surface courses. The success of soft asphalts in limiting transverse cracking has led to a desire to use them in relatively thick full-depth pavement structures. However, the fear that these mixes will excessively distort at high temperatures under traffic has prevented designers from using them. An optimum asphalt is one that would have A stiffness lower than that for cracking at low temperatures but higher than that for deformation at high temperatures. Studies have indicated that air-blown asphalt cements might have the thermal and structural characteristics to satisfy these performance requirements. A full scale test section was constructed in central Saskatchewan in 1973 to evaluate the performance of air-blown asphalt cements in full-depth structures. A 400-pen stock asphalt was air-blown to provide 100-pen and 150-pen asphalts to be used in comparison with a standard 200-pen Saskatchewan ac-5 asphalt in a seven and a half inch full-depth structure. The paper outlines design and construction details of the test section, reports changes in consistency of each asphalt over the first 6 months in service, and summarizes general performance to date. /TRRL/

• Corporate Authors:

  Canadian Technical Asphalt Association

  174-2417 Main Street
  West Kelowna, British Columbia  Canada  V4T 2H8
• Authors:
  • Clark, M F
  • CULLEY, R W
• Publication Date: 1974-11

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 5-23
• Serial:
  • Canadian Technical Asphalt Association, Proceeding
  • Volume: 19
  • Publisher: POLYSCIENCE PUBLICATIONS INC.

Subject/Index Terms

• TRT Terms: Air; Asphalt cement; Asphalt pavements; Bituminous mixtures; Cracking; Deformation; Experimental roads; Full-depth asphalt pavements; Liquid asphalt; Oxidation; Pendulum tests; Railroad engineering; Stiffness; Surfacing; Temperature; Test sections; Transverse cracking; Ventilators; Workability
• Geographic Terms: Canada
• Old TRIS Terms: Air blowing; Det eisenbahntechnik
• ITRD Terms: 6714: Air; 4967: Bituminous mixture; 8018: Canada; 5211: Cracking; 4983: Cut back bitumen; 5595: Deformation; 2778: Experimental road; 2922: Full depth asphalt pavement; 7157: Oxidation; 6285: Penetration; 5931: Stiffness; 2972: Surfacing; 6722: Temperature; 5941: Workability
• Subject Areas: Design; Highways; Materials; Pavements; Railroads; I22: Design of Pavements, Railways and Guideways; I31: Bituminous Binders and Materials;

Filing Info

• Accession Number: 00137953
• Record Type: Publication
• Source Agency: Transportation Association of Canada (TAC)
• Report/Paper Numbers: Analytic
• Files: ITRD, TRIS
• Created Date: Nov 9 1977 12:00AM