THE EFFECT OF MIX VARIABLES ON THE FATIGUE STRENGTH OF BITUMINOUS MATERIALS

This report covers work carried out at the University of Nottingham from November 1968 to October 1972 on a contract awarded by the Transport and Road Research Laboratory to investigate the effect of mix variables on the fatigue properties of bitumen- and tar-bound road materials. Fatigue testing was carried out in controlled stress rotating bending machines. Measurements of dynamic stiffness were also made to enable the results to be analysed on the basis of applied strain. During the four years of testing, a considerable number of different mixes were investigated under a variety of test conditions. Both basecourse and wearing course mixes of the gap graded and continuously graded type were used. The effects of such mix variables as binder content, binder type, aggregate grading and aggregate type and the use of filler were studied. The report is divided into four main sections. Firstly, the method of testing, specimen manufacture and presentation of results are described. Secondly, the four annual reports are reviewed individually, indicating the main conclusions. Thirdly, the roles of the various mix variables in relation to fatigue performance are discussed. Finally, a statistical analysis is carried out in order to determine the most significant mix variables, and use is made of the analysis in proposing a method for the prediction of laboratory fatigue performance. The main conclusions are that fatigue performance on the basis of applied strain is primarily influenced by binder volume content and binder type. Binder type appears to be most conveniently represented by an equiviscous temperature in the region of the ring and ball softening point. The effect of such other mix variables as aggregate grading and type are apparently accounted for by their effect on the dynamic stiffness of the mix, and only when the relative binder volume is affected do these mix factors indirectly influence fatigue performance on the basis of applied strain. It is shown that the laboratory fatigue performance can be reasonably predicted using merely binder volume content and the ring and ball temperature of the binder. /Author/ /TRRL/

  • Corporate Authors:

    Transport and Road Research Laboratory (TRRL)

    Wokingham, Berkshire  United Kingdom 
  • Authors:
    • Copper, K E
    • Pell, P S
  • Publication Date: 1974

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 69 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00096169
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: TRRL LR 633
  • Files: ITRD, TRIS, ATRI
  • Created Date: Jul 24 1975 12:00AM