Water sorption isotherms and the associated length changes were determined for eight basalt aggregates from the Melbourne area. The isotherms of the non-vesicular basalts form hysteresis loops which close at the dry point. The desorption isotherms are reproducible and resemble type 1 isotherms of the bet classification. Features of the isotherms are attributed to the properties of the swelling clays in the basalts. Confined within the solid these clays, in general, are unable to expand beyond the double- layer state. The isotherms of the vesicular basalts show hysteresis loops at high relative humidities. The occurrence of these loops is attributed to differences between the mechanisms of filling and emptying of capillaries. An inelastic movement of the basalts was shown by the non-reproducibility of the length measurements. Plots of length change V. Water content for the non- vesicular basalts in the desorption of water comprised a steeply-falling portion followed by a roughly linear portion in which the loss of water produced a less marked shrinkage. The first portion covered the relative humidity range 1.0 to about 0.5 and overall involved the loss of about 20 per cent of the water held at saturation. The initial loss of water from the vesicular basalts led to little change in the length. Further loss of water to a relative humidity of about 0.5 led to a sharp contraction in length but the magnitude of the changes for the basalts from deer park and epping were small by comparison with that for the "near Melbourne" grey basalt. (Author/TRRL)

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 25-29
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00325304
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ITRD, TRIS, ATRI
  • Created Date: Aug 15 1981 12:00AM