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BLACKTOP PAVING MATERIALS INCLUDING MANUFACTURE AND LAYING ---PAPERS PRESENTED AT THE IHT CONFERENCE, 1986, LONDON

The author examines the relationships between the manufacturing process and the laying of blacktop materials to meet required highway standards. For satisfactory road performance, the same degree of control needs to be exercised over both the blacktop production and stone production. The requirements of machinery for blacktop manufacture are listed. The required quality control has been achieved through very accurate feeders, and the development of electronic and microprocessor technology, which allows corrective steps to be taken; but the mechanical movement equipment needs to be designed to accept such accuracy limits. In the laying process, it is forecast that through electronics, the rolling regimes will be properly matched to the speed of the paver. The paving machine needs to be carefully selected for the job, be it continuous lane width work, or variable country/urban work. Equipment developed for the European or American market, the high speed double tamping action available at the screed plate, may not be appropriate for UK circumstances. The microprocessor control of drum mixers allows more objective application of recycling, especially where raw materials are scarce, transport costs are high, and traffic light. The validity of the new design approach proposed by the transport and Road Research Laboratory report lr1132 (IRRD 280375) is accepted by the industry. Details are given of a pervious macadam developed by TRRL. The performance of the macadam is being monitored for spray, noise, and wear characteristics of the surface. Earlier work in 1982 showed that the dynamic stiffness of the road base built to BS 4987 can be improved by using 50 pen binder replacing 100 pen, and increasing the filler content from a specified range of 2 -8%, to a range of 5 -11%. Best results were achieved at 8%. This modified material has been monitored and preliminary results indicate that the modified road base was easier to handle and compact, and stiffness was improved by a factor of 2. Mention is made of the problems arising from the need to use 50 pen binder and a much higher filler content than the standard material. Full depth blacktop/bituminous substitution is discussed. Provided the subgrade level is of such CBR value that it could accept paving traffic, it is possible to substitute the bituminous bound for unbound stone and satisfactorily compact it. Stiffness testing has shown that an equivalence ratio of 0.3 in substitution of bituminous bound material for unbound stone is a valid proposition. The concept of equivalence values is seen as important for the future strengthening of roads to meet increasing traffic loads. The modification of binders is likely to be used more in the future, particularly alongside the concept of whole life costing, which takes into account the cost of delay caused by road works.

  • Corporate Authors:

    INSTITUTION OF HIGHWAYS & TRANSPORTATION

    6 ENDSLEIGH STREET
    LONDON,   United Kingdom  WC1H 0DZ
  • Authors:
    • Cook, J
  • Publication Date: 0

Language

  • English

Media Info

  • Pagination: 10 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00487721
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Sep 30 1989 12:00AM