Investigation of Pindan soil modified with polymer stablisers for road pavement

Road failures are often caused by structural weaknesses, and particularly unsealed roads are vulnerable to water as water easily flows into road structures. Moisture susceptibility of materials is an important aspect when pavements are designed as moisture can weaken bonds between aggregates. Pindan soil is a red soil, known as a soft and moisture sensitive soil. Polymer stabilisers have been proved that they can improve soil mechanical properties by providing an internal waterproofing. Studies of the polymer-Pindan soil stabilisation have been focused on engineering performances, but literature shows little information on the fundamental information of Pindan soil. This project focuses on fundamental information of Pindan soil and its improved performances using polymer stabilisers. Plastic index, specific gravity and particle size distribution were tested to obtain the basic properties. Compaction, Unconfined Compressive Strength and California Bearing Ratio tests were performed to determine the mechanical properties. The chemical property was examined using X-ray diffraction. Furthermore, the waterproof effect of the polymers on the stabilised Pindan soil was investigated from capillary rise tests. In addition, the mechanical properties of individual soil grains were investigated using nanoindentation tests. The materials used for this investigation primarily consisted of Pindan soil collected in Broome, Western Australia, and three polymer products manufactured in Australia. Based on the results, it is evident that the failure behaviour, strain and strength as well as the basic properties of the soils are affected and changed by the Polymer stabilisers. The type of polymer influenced the optimum moisture contents and strengths rather than the amount of polymer. Similarly, Nanoindentation technology provided various information such as elastic modulus, hardness, packing density, stiffness, cohesion and fracture toughness of soils at nano-scales. Polymers can reduce water ingress and minimise moisture in the pavement structures. Thus, the structures can maintain its strength and prevent deformation, which will increase the lifetime of unsealed pavements.