Dredged sediments excavated or removed from reservoirs are classified as waste materials. The reuse of dredged sediments as road materials is an interesting solution to environmental problems. However, only the compaction technique without treatment by admixtures is insufficient to improve the strength and stiffness of the dredged sediments for use as standard road materials. This research presents the mechanical and microstructural properties of dredged sediments treated with ordinary Portland cement (OPC) and fly ash (FA). A large amount of FA was utilised for the purpose of cost-effectiveness. The dredged sediments were mixed with 1.5%–5% OPC and 5%–20% using exclusively OPC, exclusively FA and a combination of OPC and FA. The experiments in this study consisted of unconfined compressive strength, splitting tensile strength, California bearing ratio, resilient modulus, and ultrasonic pulse velocity tests. The results showed that the mechanical properties were improved by the addition of FA and that the maximum values of these properties were observed with a combination of 5% OPC and 10% FA. In addition to evaluating the mechanical properties, microscale analyses were also conducted using scanning electron microscopy and energy-dispersive X-ray spectroscopy to understand the behaviour of the dredged sediment with respect to the OPC and FA contents. Finally, stabilised sediments were assessed for possible reuse as road materials based on the Department of Highways of Thailand standard as well as the recommendations of the AASHTO Mechanistic-Empirical Pavement Design Guide and Austroads (2017)

This research studies the unconfined compressive characteristics of cement-treated sand reinforced with palm fiber. Type 1 Ordinary Portland cements with 3, 5, and 7% dry sand weight were mixed with sand and different amounts of water to produce cement-treated sand. Palm fiber contents of 0.5, 1, and 2% volume and fiber lengths of 10, 20, and 40 mm were utilized. Three performance parameters were considered to assess the performance of the cemented sand reinforced with palm fiber: peak strength, strain ratio, and toughness. The results showed that incorporating palm fiber elements could improve the peak strength and ductility and reduce brittleness by increasing the fiber content and length. All palm-fiber-reinforced samples showed a softening behavior and changed the behavior of cement-treated sand from brittle to semi-ductile or ductile. The compressive strength of reinforced cemented sand increased when the fiber length was 40 mm, and the compressive strength was reduced as the fiber content exceeded 1.0%. Palm fiber was the most efficient at increasing the toughness of the cemented specimen because of its rigidity and bridging ability. The optimum fiber content and length for the cement–treated sand were 1.0% and 40 mm, respectively.