Volume 31, Issue 6 (November 2008)
Methylene Blue Surface Area Method to Correlate with Specific Soil Properties
Specific surface area (SSA) of soils is calculated by determining the amount of adsorbed substance such as methylene blue (MB), ethylene glycol monoehtyl ether (EGME), or water required to form a monolayer. Free swell index and liquid limit of soils, which are well correlated with each other, and with engineering properties of soils, can be used to check the relative advantage of determination of a specific area by different methods in geotechnical engineering. The water adsorption method yields different values depending on the relative humidity (RH) at which the soils are equilibrated with water and gives significantly high adsorption values at 100 % RH. The water adsorption method, comparatively simpler, gives more accurate values for kaolinitc soils but generally has lower values for soils with montmorillonitic mineral owing to insufficient saturation of exchangeable ions. The SSA values obtained by EMGE correlates reasonably well with free swell index. Improved correlation is observed in specific surface area values obtained by MB methods. The SSA values obtained by methylene blue titration (MBT) or as methylene blue spot method (MBS) are comparable.