RELATIONSHIPS OF SPECIFIC SURFACE AREA AND CLAY CONTENT TO SHRINK-SWELL POTENTIAL OF SOILS HAVING DIFFERENT CLAY MINERALOGICAL COMPOSITIONS

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Abstract
Data for 22 samples from 17 pedons were analyzed for relationships of specific surface area and amounts and kinds of clay to coefficient of linear extensibility, as determined by the paste method (COLErod), and to free swelling index (FSI). The soils were divided into three main groups according to their clay mineralogy. The clay of the first group was micaceous, that of the second group kaolinitic, and that of the third group montmorillonitic. Both clay contents and specific surface areas of the combined first and second groups of soils were closely related to COLErod (r2 = 0.81 and r2 = 0.91) with specific surface area giving the higher correlation. The correlation of clay content with COLErod decreased markedly, however, when the montmorillonitic soils were included (r2 = 0.56). In contrast, the correlation of specific surface area with COLErod remained high (r2 = 0.97), indicating that for the soils used in this study, specific surface area was more basic with respect to shrink–swell potential than was clay content. Specific surface area was also highly correlated with FSI (r2 = 0.96) which was expected from the close relationship between COLErod and FSI (r2 = 0.95).