The Effect of Poly(vinyl Alcohol) on the Crust Strength of Silty Soils

Summary Fourteen samples of soils were collected from localities in England where crusting and consequent depression of seedling emergence had been recorded. Natural aggregates of these soils were sprayed with poly(vinyl alcohol) (PVA), subjected to simulated heavy rain, and dried under IR lamps. In most soils, aggregate stability was enhanced by increasing applications of PVA and crust formation was prevented. Some soils, however, were unresponsive to PVA and crusts formed whether or not it was applied. Responsive and unresponsive soils did not differ in particle size distribution, or porosity characteristics. Removal of iron oxides and organic matter did not alter their adsorption characteristics towards PVA. Unresponsive soils, however, were found to have the mineral chlorite as a major component and it is suggested that PVA is unable to bind particles together when the surfaces presented for adsorption of PVA consist of gibbsite, the interlayer material of chlorite.