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This study examines the combined capacity of rubber powder inclusion and polymer treatment in solving the swelling problem of South Australian expansive soils. The rubber powder was incorporated into the soil at three different rubber contents (by weight) of 10%, 20% and 30%. The preliminary testing phase consisted of a series of consistency limits and free swell ratio tests, the results of which were analyzed to arrive at the optimum polymer concentration. The main test program included standard Proctor compaction, oedometer swell–compression, soil reactivity (shrink–swell index), cyclic wetting and drying, crack intensity, and micro-structure analysis by means of the scanning electron microscopy (SEM) technique. The improvement in swelling potential and swelling pressure was dependent on the rubber content, with polymer–treated mixtures holding a notable advantage over similar untreated cases. A similar dependency was also observed for the crack intensity factor and the shrink–swell index. The beneficial effects of rubber inclusion were compromised under the cyclic wetting and drying condition. However, this influence was eliminated where the rubber powder was paired with the polymer agent. A rubber inclusion of 20%, preferably paired with 0.2 g/l polymer, was suggested to effectively stabilize South Australian expansive soils.

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Fibres have been used in construction materials for a very long time. Through previous research and investigations, the use of natural and synthetic fibres have shown promising results, as their presence has demonstrated significant benefits in terms of the overall physical and mechanical properties of the composite material. When comparing fibre reinforcement to traditional reinforcement, the ratio of fibre required is significantly less, making fibre reinforcement both energy and economically efficient. More recently, waste fibres have been studied for their potential as reinforcement in construction materials. The build-up of waste materials all around the world is a known issue, as landfill space is limited, and the incineration process requires considerable energy and produces unwanted emissions. The utilisation of waste fibres in construction materials can alleviate these issues and promote environmentally friendly and sustainable solutions that work in the industry. This study reviews the types, properties, and applications of different fibres used in a wide range of materials in the construction industry, including concrete, asphalt concrete, soil, earth materials, blocks and bricks, composites, and other applications.

In this study, a series of multi-stage drained reverse direct shear tests were carried out on soft clay samples reinforced with 0.25% and 0.50% polypropylene fibers of 6 mm, 10 mm and 19 mm in length. Tests were carried out at different normal effective stresses and cumulative horizontal shear displacement of 1.17 times of the sample width. Results showed an increase of the shear strength with the increase of fiber content and length. However, the rate of improvement was capped with the normal effective stress applied during the shearing stage. At a high normal effective stress, the shear strength of the fiber-reinforced soft clay approached that of the unreinforced clay regardless of the amount of fiber inclusion. The rate of shear strength improvement decayed with the number of shear cycles. Fiber reinforcement also resulted in a reduction of the compressibility of the soft clay at consecutive consolidation and shear stages. Although the effective internal friction angle of the soft clay was not altered significantly with the fiber reinforcement, the effective cohesion of the soft clay improved significantly as much as 6.4 and 8.5 times with the inclusion of 0.25% and 0.50% of 10 mm long fibers, respectively.