The effects of ethylene oxide–propylene oxide–ethylene oxide block copolymers on the physical properties of soils

The impact of a series ethylene oxide–propylene oxide block copolymers upon the physical properties of a sandy soil has been investigated. Specifically the impact upon the saturated hydraulic conductivity, water retention and water imbibition was examined. It was shown that soils exposed to aqueous solutions containing these block copolymers have reduced hydraulic conductivities. It was concluded that this could be due to the dispersion of fine grained materials or through changes in pore size brought about by swelling. Imbibition into soils that had been exposed to the block copolymers was enhanced. However the effect of the block copolymers upon water retention was complex. These block copolymers are surface active and as such will reduce surface tension to some extent or another. This should result in reduced water retention. It was observed that some of the block copolymers investigated did lead to reduced water retention. However some actually increased water retention. It is proposed that this was due to the effect that the block copolymers have upon wetting.