We can characterise the pore size distribution of wet soils/porous materials using the Mercury Intrusion Porosimetry (MIP).
Description
To prepare samples for the MIP, water is removed from wet samples using the freeze-drying technique for minimal alteration of the pore structure. Soil is frozen in liquid isopenthan (-160°C melting point) in turn placed in liquid nitrogen (-189°C boiling point). Drying is carried out using a Coolsafe 110-4 PRO lyophilizer where water sublimation occurs under absolute gas pressure of 0.001 mbar with ultimate temperature of -110°C.
MIP tests are carried out using a Quantachrome Poremaster 60 capable of exploring entrance pore size in the range of 950 – 0.0032 μm. Blank tests are performed to correct errors associated with system compressibility and temperature effects.
An example of determination of pore size distribution is shown in the figure for Speswhite kaolin compacted at different water contents.