Since the summer of 1954, it has been the practice of the Department to require only natural. sand or slag as the fine aggregate in high-type (Class I, Type B) bituminous surface mixtures. This, of course, was done in order to build skid resistance into the mixture, i.e. by use of polish-resistant fine aggregate. At first, this was specified by means of plan notes; and, during 1957, an Amendment was made to the Standard Specifications. While this has apparently reduced the slickness problem it has created problems relating to the durability and, at times, the stability of the surface course.

Report Date


Report Number

No. 184

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