Abstract: Studies of quaternary ammonium chlorides containing long unsaturated hydrocarbon chains have shown their effectiveness in stabilizing soils primarily by waterproofing the clay fraction. The nature of the interaction between organic salts and Wyoming bentonite was studied by means of X-ray diffraction.
Treatment of bentonite with a dialkyl dimethyl ammonium salt in an amount less than the exchange capacity results in the appearance of water-stable spacings of 10, 13 and 19 Å, but only if the sample has been dry cured. Moist curing a bentonite paste results in a marked expansion of the lattice despite treatment. The necessity of dry curing may relate to orientation of organic cations around bentonite aggregates; grinding prior to rewetting destroys the waterproofing action, and the clay lattice again expands.
Additions of the quaternary ammonium cations close to or in excess of the exchange capacity of the bentonite waterproofs regardless of dry curing or grinding, or both. Clays treated in this manner show spacings of the pure crystalline chemicals and other spacings which relate to interlayer penetration by water. There is no direct evidence for interlayer penetration by the organic cation, perhaps because of the unwieldy tetrahedral arrangement of the organic molecule. The degree to which organic cations are held depends on the nature of the surface as the cations are readily leached from quartz powder but are held more strongly on kaolinite and bentonite.