Suitability of the methylene blue test for surface area, cation exchange capacity and swell potential determination of clayey soils

Abstract

Application of the methylene blue test methods in determining soil properties, including specific surface area (SSA), cation exchange capacity (CEC), swell index, and swell potential are investigated on clayey soil samples with widely different mineralogy. The results indicate that the MB methods yield accurate prediction of some soil index properties, and they are easy to apply with simple test equipment. The results also show that the testing methods can be applied for soils that have widely different mineralogy. External and internal surface areas of soils can be measured by the MB adsorption methods. Effect of particle size on the MB surface area measurement accuracy was also studied using samples passing 0.425 mm (No. 40) and 0.075 mm (No. 200) sieves. The results show that there is no significant difference in the amount of absorbed methylene blue of the soil samples passing the No. 40 and No. 200 sieves. The test results also indicate that the MB-CEC values are generally lower than those obtained by the ammonium acetate method. The correlation coefficient between the MB-CEC and NH4-Na results is 0.88 indicating that MB can be used effectively to measure CEC of soils. The results also show that swell index and swell potential of the soils can be estimated with MB methods accurately, economically and readily. Significant relationship is observed between the swelling potential and MBV (methylene blue value) for a wide range of soils. A new classification for swelling soils is proposed using MBV. (C) 2008 Elsevier B.V. All rights reserved.