Decreasing Moisture Susceptibility of Gravel Road Surface Aggregate by Hydrophobic Treatment Agent

Abstract

The use of a special hydrophobic treatment agent to reduce the moisture susceptibility of gravel road surface aggregate was studied. A treatment agent and dosage were chosen on the basis of positive results from earlier studies concerning different base course aggregates of paved roads. Laboratory pretesting samples from a chosen test site confirmed that, for example, in tube suction tests the dielectric value of the aggregate treated with the chosen agent and dosage was lowered remarkably as compared with untreated aggregate. This result indicated improved water resistance. The treated aggregate also showed increased abrasion resistance and was less density-susceptible as compared with the untreated aggregate. As a result of the encouraging results from the preliminary tests, a 500-m unpaved test section was constructed in 2009. Ordinary bitumen stabilization machinery was used for simultaneous spreading and mixing of 1% resin-based treatment agent emulsion to the gravel surface aggregate. Although the water content was lower than expected, the construction of the test section succeeded; it will be monitored regularly by falling weight deflectometer measurements and visual inspections.