in the wibau dustless (sl) asphalt plant the binder is added to the aggregate before it is dried and heated in contrast to a conventional plant in which the sequence of events is reversed. this new process virtually eliminates the discharge of dust into the atmosphere without the need to provide expensive dust collecting equipment and has other possible economic advantages deriving from its ability to carry out production in two stages. a group representing the department of the environment's transport and road research laboratory and engineering intelligence division, and the asphalt and coated macadam association have visited five plants in western europe in order to assess their ability to produce satisfactory bituminous materials. it was found that a wide range of dense materials containing penetration grade bitumen binders was being produced satisfactorily on the wibau sl plant at output temperatures above 120 degrees c. this suggests that the process could be employed to manufacture many of the dense bituminous mixtures used in great britain. although the limited evidence available suggested that materials produced by the sl process should have an adequate road performance, for full acceptance further evidence of the performance under traffic is required. the use of the process for a wider range of materials and its use in the two-stage form requires further investigation. (a)

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