AbstractThe effect of sodium carboxymethycelluloses (CMC) on soil aggregation, plasticity, moisture equivalent, fifteen‐atmosphere‐percentage, and water permeability was investigated in the laboratory. These compounds contained different degrees of substitution of sodium carboxymethyl groups, ranging from 0.32 to 1.28 substitutions per anhydroglucose unit. In general, increasing the degree of substitution resulted in greater soil aggregation, increased water permeability and larger plastic limits. Varying rates of CMC up to 0.5% concentration also resulted in significant increases in these soil characteristics. None of the compounds had any effect on the moisture equivalent and fifteen‐atmosphere‐percentage. The duration of aggregates stabilized by the 0.70 substitution was found to be much less than those aggregates stabilized by the higher‐substituted types.