The use of specific surface area, pore volume, and pore area in evaluating the degree of weathering of fine particles: an example from Lauhanvuori, western Finland
AbstractSamples of weathered granite from the Lauhanvuori region, in western Finland have been collected in order to study the degree of weathering of the fine fractions in the weathering crust. Grain size distribution of the < 0.074 min diameter fractions has been determined by Sedigraph analysis. The nitrogen adsorption method has been used to determine the specific surface area of the fractions d < 0.02 min and < 0.074 mm, and the cumulative pore volume and pore area of the fractions < 0.074 min have been measured by using the mercury porosimeter test.
The results obtained have been compared with those from materials formed mainly by mechanical crushing by natural processes, such as the fine fractions present in silty till above the weathering crust in the Lauhanvuori area and a clayey vein filling in the regolith. They have also been compared with materials formed by artifical crushing, such as the powder from a granitic aggregate.
The fine‑grained material from the weathered deposits had specific surface area values of far greater than those corresponding from the silty till and the clayey vein. The results of the mercury porosimeter test showed a strong increase in the cumulative pore volume and pore area in pores with diameters < 1 um, as compared with the corresponding pore sizes in the finest powder of a similar grain size distribution from artificially crushed granite.