RESEARCH INTO THE DURABILITY OF BITUMINOUS OVERLAYS AND WEARING COURSES IN TROPICAL ENVIRONMENTS

The early development of surface initiated cracking in bituminous surfacings has been shown to be a common form of deterioration in tropical environments. This thesis describes an investigation of the durability of asphalt wearing courses, overlays and samples manufactured in the laboratory with particular reference to the problem of surface cracking. Results of the investigations show that large increases in bitumen viscosity occur in the top few millimeters of asphalt surfacings. Where air voids were inter-connected, bitumen hardening occurred throughout the layer and a relationship was found between the viscosity of the bitumen, age, mix air voids and bitumen content. However, large increases in bitumen viscosity also occurred in the top 3mm of dense mixes with low air voids and high bitumen contents. In these mixes age was the dominant factor in determining the degree of hardening. Surface dressings were very successful in reducing the rate of hardening at the surface of the asphalt whilst also providing a crack resistant surface with good surface texture. Deflection curvature measurements and dynamic cone penetration tests were very effective for evaluating the existing pavement before overlaying. When used to assess the change in structural strength resulting from overlaying, deflection curvature measurements showed considerable scatter. These measurements did, however, reflect the stiffening effect with time caused by bitumen hardening. (A)

• Corporate Authors:

  University of Birmingham, Edgbaston

  School of Civil Engineering
  Birmingham,   United Kingdom  B15 2TT
• Authors:
  • Smith, H R
• Publication Date: 1989

Language

• English

Media Info

• Pagination: 236 p.

Subject/Index Terms

• TRT Terms: Aggregates; Bituminous macadam; Bituminous materials; Cracking; Curvature; Deflection; Developing countries; Durability; Fatigue (Mechanics); Mix design; Pavement design; Pavements; Properties of materials; Rolled asphalt; Seal coats; Strength of materials; Structural strengthening; Surfacing; Test procedures; Theses; Thickness; Tropics; Viscosity; Wearing course (Pavements)
• ITRD Terms: 4577: Aggregate; 4921: Bitumen macadam; 4955: Bituminous materials; 5211: Cracking; 5586: Deflection; 2870: Degree of curvature; 150: Developing countries; 5910: Durability; 5579: Fatigue (mater); 4714: Mix design; 3055: Pavement design; 5925: Properties; 4989: Rolled asphalt; 3096: Strengthening (pavement); 2984: Surface dressing; 2972: Surfacing; 6288: Test method; 8597: Thesis; 5933: Thickness; 2513: Tropics; 5936: Viscosity; 2980: Wearing course
• Subject Areas: Geotechnology; Highways; Materials; Pavements;

Filing Info

• Accession Number: 00604966
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• Files: ITRD, TRIS
• Created Date: Feb 28 1991 12:00AM