Compaction and strength properties of road subbase infused with a latex copolymer

There are significant challenges to the design and construction of roads and highways worldwide. There are many contributors to these challenges, including weak subgrade soil. This paper investigates the potential to stabilise and improve the compaction and strength characteristics of a road base through infusion with a non-hazardous latex copolymer dispersion. Brunei Darussalam was selected as a case study for this research due to the abundance of soft clay and peat in a large part of the country. In recent years, major serviceability issues, including undulating pavement surfaces due to differential settlement, have emerged on several local roads and highways built on these weak grounds. Standard laboratory tests were conducted to evaluate the short-term improvement in engineering properties of the stabilised soil-aggregate mixture. Five cylindrical specimens were prepared in standard compaction molds with polymer contents of 0% (control), 0.5%, 0.75%, 1%, and 2% concentrations by mass. The particle size distribution of the soil-aggregate mixture was first determined using standard laboratory sieve analysis, before the compaction characteristics (i.e. optimum moisture content and maximum dry density) of each specimen was determined using Proctor compaction tests. Further specimens were prepared under their respective optimum moisture content to be tested using unconfined compression test. Results indicated that the maximum dry density of the subbase-polymer mixture decreases with increasing polymer content. Adding 0.5% polymer doubled the strength of control mixture in terms of unconfined compressive test results. However, increasing the polymer content beyond 0.5% did not significantly increase the compressive strength any further. This can help to produce guidelines for application of the polymer to achieve a cost effective design alternative that may improve surface conditions and ride quality of roads on weak subgrade soil.