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.
