Effects of Drying Treatments on Porosity of Soil Materials
1985
Thompson, Michael L. | McBride, John F. | Horton, Robert
The effects of three drying techniques on total porosity and pore size distribution of soil materials were studied by Hg intrusion porosimetry. The three soils investigated had different clay contents (21%, 35%, and 44%), but the clay fraction of each was dominated by montmorillonite. Some samples were dried in an oven at 40°C for 7 d; some samples were quick-frozen in liquid N and lyophilized; some samples were dried by acetone vapor exchange and immersion, followed by evaporation of the acetone. Both undisturbed and compacted samples were investigated. The three drying techniques caused a reduction in sample total porosity ranging from 3 to 52%. Freeze drying usually caused the least change in total porosity. Although materials highest in clay shrank the most, there was no other discernible relationship between shrinkage and clay content. Freeze-dried samples had the greatest volume of porosity in the 0.2- to 2- µm equivalent pore radius (epr) range, whereas acetone-dried samples had the greatest volume of porosity in the 0.02- to 0.2- and 0.2- to 2-µm epr ranges. Pore size distributions of oven-dried samples varied from soil to soil. The consistency of pore size distributions in freeze-dried materials strongly suggests that pores were deformed by ice crystals either during or after freezing of the samples. In the epr range of 0.002 to 0.02 µm, acetone-dried samples had porosities similar to oven-dried samples.
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