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The paper outlines recent investigations concerning the Polished Stone Value (PSV) test method. Although the research is limited to greywacke aggregate from Northern Ireland the results indicate that the standard PSV test may not adequately predict the ultimate level of skid-resistance reached by the aggregates assessed. Extending the duration of polishing further decreases skid-resistance. Modifying the apparatus to simulate cornering situations using angled polishing produced significant reductions in skid-resistance. It was also shown that results may alter when the aggregate size is decreased. The paper concludes that further research is necessary in order to predict the in-service performance of aggregates in the laboratory.

This paper considers the assessment of highway surfacing aggregate wear using the Aggregate Abrasion Value and micro-Deval test methods. Their historical development is discussed. The influence of test sample preparation and number of chippings assessed is compared. Data for both methods are presented for a range of rock types. Dry, wet and soaked versions of the micro-Deval test are compared. The use of a density correction to modify the micro-Deval test value is proposed. The ability of the Aggregate Abrasion Value and micro-Deval test methods to assess heterogeneous aggregates is assessed.

& Currently, in the UK, there is considerable interest in the fact that a German bituminous surfacing mixture known as stone mastic asphalt may possess levels of in-service performance that resist the growing incidence of premature failure experienced by traditional materials such as hot rolled asphalt. A high stone content grading requires the use of a stabilizing additive to ensure long-term performance. The most common type of additive is cellulose ®bre. This paper assesses the eect that the addition of diering types of this ®bre has on measurable bituminous mix properties.

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