A PROPOSED SECONDARY MINERAL RATING FOR BASALT ROAD AGGREGATE DURABILITY

A secondary mineral rating (denoted rsm) for the durability of basalt road aggregates is proposed. It is based on the amount (p), type (M) and distribution (tr) in the aggregate of clay and other secondary minerals. Rsm values are calculated from (sigma (p.m.))tr where p is a percentage, M ranges from 2 to 10, and tr ranges from 0.3 to 2.0. The secondary mineral rating correlates well with Washington degradation values, methylene- blue dye absorption data and surface area measurements. It is tentatively suggested that for basalts in victoria, rsm values of 140 or less indicate a durable material and that values greater than 140 indicate potentially unsound stone. An rsm value of 140 corresponds to a Washington degradation value of about 40, a methylene- blue dye absorption value of 3.1 ml/g, a total surface area of 97 m**2/g, and a secondary mineral content of 30 per cent. Basalts with these properties would only just satisfy Country Roads Board (Victoria) requirements for class 3 sub-base materials. The determinations of rsm values are seen as being essential for the initial investigation of a basalt quarry site and for identifying the reasons for aggregate failure in service. For day- to- day use, methylene- blue values and total surface area measurements could serve similar useful prediction purposes in addition to the normal mechanical tests required by the purchasing authority. (Author/TRRL)

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 27-37
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00330393
  • Record Type: Publication
  • Source Agency: ARRB Group Ltd.
  • Files: ITRD, TRIS, ATRI
  • Created Date: Aug 15 1981 12:00AM