Mechanical behaviour of polymer-coated sands

Abstract

The water repellent behaviour of polymers such as polydimethylsiloxane enables them to be utilized as coatings in grains to control wetting, with potential applications in barriers and fills. However, little exists on the mechanics of the polymer-coated soils. Here, the mechanical behaviour of a polymer-coated sand subjected to two mass ratios of dimethyldichlorosilane (0.05% and 3%) was investigated at the macro scale via the triaxial tests. Dimethyldichlorosilane is used to treat the particles surfaces and produce the water repellent polydimethylsiloxane coatings. Selected results from the triaxial tests show that when the mass ratio of dimethyldichlorosilane is low (i.e. 0.05%), the stress-strain behaviour is similar to that of natural sand. Therefore, the effect of the thin polymer-coatings on the mechanical behaviour is negligible. While when the mass ratio of dimethyldichlorosilane is high (3%), the reduction of shear strength is evident. Furthermore, quantification of the particle surface topologies prior to and after the triaxial tests clearly reflects the damage and crush of the polymer-coatings when the polymer-coated particles are subjected to relatively high stresses.