Abstract
Many roads that were initially designed for relatively low traffic volumes need re-surfacing or partial replacement of the unbound granular material to satisfy current traffic demand. Significant research efforts based on laboratory studies have been seen in the literature to characterize the suitability of virgin materials, which is relatively expensive and unsustainable. Therefore, the object of this study is the in situ recycling of existing materials in two road sections by improving their properties with a suitable additive. A hydrophobic synthetic polymer was chosen for two trials due to the high plasticity of fines of the in situ materials and a high chance of water intrusion in the low-lying plains in Adelaide. The extensive laboratory characterization shows that hydrophobicity is imparted in capillary rise tests, improved drainage in permeability tests, and greater matric suction at the same moisture content. Furthermore, the unconfined compressive strength was increased. The repeated loading triaxial testing showed higher stiffness and lowered permanent strain to withstand higher traffic volume. In general, in situ recycling is adaptable and considered to be cheaper and sustainable. The estimated current costs and carbon footprints are presented for re-construction and in situ recycling with dry powder polymer, or solely with lime, to help construction planning.
Highlights
IntroductionAustralia has a large network of local roads, which has been built at relatively low cost, using materials which do not meet current specifications for major road pavements [1]
Australia has a large network of local roads, which has been built at relatively low cost, using materials which do not meet current specifications for major road pavements [1].these roads were initially designed for relatively low traffic volumes and so many of these roads have a low structural capacity for the increased traffic volumes over time
This paper reports laboratory studies into two Polyroad dry powder polymer (DPP) products, arising from separate field trials on local government roads in the northern suburbs of Adelaide, the capital city of South
Summary
Australia has a large network of local roads, which has been built at relatively low cost, using materials which do not meet current specifications for major road pavements [1]. These roads were initially designed for relatively low traffic volumes and so many of these roads have a low structural capacity for the increased traffic volumes over time. Re-surfacing or partial replacement of the unbound granular material (UGM, referred to as “aggregates”) with asphalt is a common but relatively expensive solution. One attractive solution is to re-use the existing pavement material after milling the road base/subbase to the required depth (usually 200 to 250 mm). An additive or stabilizer is spread evenly over the re-worked pavement surface, and it is intimately mixed using the milling equipment and compacted to provide a reconditioned pavement layer (Figure 1)
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