In recent years the United States of America has seen a rapid increase in the use of the drum-mixing process for the production of bituminous materials. The process uses a simplified plant in which mixing takes place in a drum similar to the continuous dryer of a conventional asphalt plant. This report describes the findings from a study visit to the United States, in June 1974, by a small group representing the Department of the Environment's Transport and Road Research Laboratory and Engineering Intelligence Division, and a member of the staff of the Amey Roadstone Corporation Limited representing the Asphalt and Coated Macadam Association. The report indicates that: (I) the mixtures produced were well coated and handled in a normal way during paving operations; (II) the gradings of the mixed materials were uniform but the test results for binder content indicated some variability; (III) the recovered binder showed less hardening than obtained when mixtures have been conventionally mixed; (IV) the temperatures of the mixed materials were very uniform under the favourable operating conditions; (V) mixing and laying temperatures were similar to those used in the UK; (VI) the effect of the presence of any substantial quantity of residual water on the behaviour of mixtures during paving and rolling, and on the long-term performance of the laid material, has not been established; (VII) there was no evidence to suggest that the service life of the materials produced would be unsatisfactory; (VIII) the exhaust emissions could be restricted to very low levels; (IX) the capital and production costs were lower than for conventional plants; (X) the general requirements of the state specifications for coated materials were applied; slightly lower materials temperatures and higher residual water contents were permitted for drum-mixed materials; (XI) a provisional specification covering bitumen macadams, with penetration-grade bitumens, and rolled asphalt base and basecourse mixtures could be issued; (XII) further evidence was required of the suitability of the process for the production of wearing course rolled asphalt with bitumen and pitch/bitumen binders, tarmacadams and materials containing cut-back bitumens. /Author/TRRL/

  • Corporate Authors:

    Transport and Road Research Laboratory (TRRL)

    Wokingham, Berkshire  United Kingdom 
  • Authors:
    • Goodsall, G D
    • FERNE, B W
  • Publication Date: 1976

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: 73 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00137755
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Lab. Rpt. 691
  • Files: ITRD, TRIS, ATRI
  • Created Date: Apr 13 2000 12:00AM