Coated chippings applied to a rolled-asphalt surfacing sometimes fail to adhere. One reason for this is "coking" or burning of the bitumen coating to a very hard layer which is no longer tacky, even at temperatures of 100 C and above. Laboratory investigations showed that no coking occurs during the mixing process, even at high temperatures, but only during storage. When the storage temperature is kept low (150 degrees C), prolonged storage has no deleterious effect on the binder, but at higher temperatures (e.g. 200 degrees C) coking can occur in about four hours. Some limited tests showed no differences due to type of binder or of aggregate. Coking can occur when chippings which were mixed under the recommended conditions are stockpiled while still hot. Full-scale stockpiling experiments have shown that with conical stockpiles the temperature can remain high or even apparently increase over a period of many hours, during which time cohesive properties of the binder are destroyed. Chipping trials on two trunk roads have shown that laboratory tests can be used to check the quality of chippings. Experience of commercial work where partially coked chippings were used conforms the need for a specification which will exclude chippings of inferior quality. Recommendations are made for coating and testing to facilitate production and control of high quality chippings. /Author/

  • Corporate Authors:

    Transport and Road Research Laboratory (TRRL)

    Wokingham, Berkshire  United Kingdom 
  • Authors:
    • Green, E X
    • Montgomery, F V
  • Publication Date: 1972


  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 32 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00081937
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: No. LR 456 R&D Rpt.
  • Files: ITRD, TRIS
  • Created Date: Apr 8 1975 12:00AM