The water stability of natural clay aggregates containing polyvinyl alcohol

Abstract

The effect of the adsorption of polyvinyl alcohol (PVA) by natural clay aggregates on their ability to withstand rapid wetting and shaking in water has been determined. It was found for aggregates from the B horizon of the Urrbrae loam soil (60% of < 2 µ material and 0.74% of organic carbon) that between 1 and 2% by weight of PVA was sufficient to almost completely prevent breakdown into micro-aggregates. Separation of clay particles from the aggregates by abrasive forces was also largely prevented. Polymer adsorbed slowly from a dilute solution was more effective than an equal weight of polymer adsorbed rapidly from a concentrated solution. Analysis of the rate of breakdown curves enabled the initial breakdown due to rapid wetting, and the subsequent abrasive forces, to be distinguished. The results provide further support for the hypothesis previously advanced that soil aggregates are stabilized by polymer molecules that line the surfaces of the pores, binding together the clay domains which comprise the walls of the larger pores.