This paper presents results of a comprehensive investigation on the utilization of carpet waste fibers in reinforcement of clay soils. Effects of adding proportionate quantities of two different types of shredded carpet waste fibers to clay soils (i.e., 1, 3, and 5% by dry weight of the soil) were investigated and evaluated. The investigation was conducted on specimens prepared at their maximum dry unit weight and optimum moisture content, as well on specimens prepared at variable conditions of dry unit weight and moisture content. A comparison was also made on specimens prepared at the same fiber content by changing dry unit weight while moisture content was kept unchanged or by changing both dry unit weight and moisture content. The investigation revealed that inclusion of carpet waste fibers into clay soils prepared at the same dry unit weight can significantly enhance the unconfined compression strength (UCS), reduce postpeak strength loss, and change the failure behavior from brittle to ducti...

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.

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.

Research on the utilization of recycled concrete aggregate (RCA) in civil engineering applications is gaining popularity worldwide due to the increased efforts to promote preservation of the environment and sustainable development. Recycled concrete aggregate concrete is, however, presently still limited to nonstructural applications. Recycled concrete aggregate concrete can still be considered as a rigid pavement material when its flexural strength is improved adequately to sustain future traffic loads. In this study, polyvinyl alcohol (PVA), a water-soluble polymer, was used to improve the flexural strength of RCA concrete. The influence of PVA-to-cement ($p/c$ ) and water-to-cement ($w/c$ ) ratios on the compressive and flexural strengths of RCA-PVA concrete was investigated via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Polyvinyl alcohol films were found to retard the hydration process, resulting in the delay in initial and final setting times of cement-PVA paste, therefore reducing the compressive strength of RCA-PVA concrete. For all the $w/c$ ratios tested, the flexural strength increased with increasing $p/c$ ratios up to an optimum $p/c$ ratio that provided the highest flexural strength, followed by a subsequent decrease beyond this peak value. The optimum $p/c$ ratio tended to increase with an increase in $w/c$ ratio, being 0.5, 0.5, 1.0, and 1.5 for $w/c$ ratios of 0.3, 0.4, 0.5, and 0.6, respectively. Based on the requirements of the Department of Highways, Thailand, the $p/c$ $\le 1$ at $w/c$ $\le 0.5$ was found to be suitable for developing RCA-PVA concrete for rigid pavements. The outcome of this research confirms the viability of using PVA to improve the flexural strength of RCA concrete for usage as a sustainable rigid pavement material.