SPECIFICATIONS AND STANDARDS FOR UNBOUND AGGREGATES AND THEIR USE IN ITALY. UNBOUND AGGREGATES IN ROADS. PROCEEDINGS OF THE 3RD INTERNATIONAL SYMPOSIUM, UNIVERSITY OF NOTTINGHAM, APRIL 11-13, 1989

This paper describes the characteristics and use of unbound aggregates in roads and highways, according to Italian practice, together with quality and construction requirements, established by official Authorities (CNR Italian Institute of Research) and Autostrade SpA. The final section briefly reviews a special aggregate, lightweight expanded clay, (expanded lightweight aggregate, LECA). This aggregate can be manufactured in various different grades, and is chemically inert, durable, and unaffected by water even though it has a high degree of water retention and absorption. Such aggregates are used in Italy in road construction, as fill for embankments over very soft soils, as backfills beyond structural elements to avoid excessive earth pressures, and whenever stability problems occur. The material used as fill for embankments is generally 0/20 or 3/20 mm size, and the bulk density normally considered in theoretical calculations is 600-700 Kg per cubic metre (twice as high as the dry bulk density on delivery). Compaction methods are quite different from those usually used. The material has to be "densified" using a light vibratory roller operating on a sandy layer binding the top of the light aggregate. Settlement during compaction is not large. Details of relative density tests, large triaxial compression tests, and consolidation tests are provided, as well as the average angle of internal friction. For the covering abstract of the conference see IRRD 827698.