A laboratory study of soil stabilisation with an urea-formaldehyde resin

Abstract

The aim of this paper is to present laboratory results on the effectiveness of a proprietary urea-formaldehyde (UF) resin as a soil stabiliser. The Indirect Tensile Strength (ITS) was used to characterise the soil stabilising properties of the resin. A brown shale gravel with an ITS dry strength of 160 kPa was used as test soil. Treated samples were compacted at the optimum moisture content (OMC) of the soil (ca. 9,5%) using the Marshall apparatus. Dry strength was evaluated after the samples were left to air-dry for 7 or 21 days. The wet strength was determined following a 24-hour water-soak of the air-dried samples. In this system, cement and lime were ineffective soil stabilisers even at the 6% dosage level. In contrast, the addition of 2% UF resin was sufficient to raise the dry strength to 340 kPa but wet strength was still poor. This problem was solved by a further addition of a suitable bitumen emulsion. At a 2% dosage it increased both the wet and dry strengths to ca. 450 kPa. Unconfined Compressive Strength (UCS) measurements on this as well as other soil types confirmed the soil stabilisation utility of the UF resin. These tests also showed that the system performed better in siliceous than in calcareous aggregates.