Optimisation of natural fibre surface on soil-fibre morphology and geomechanical performance of reinforced soil

Information from the abstract

Incorporating natural fibres into soil reinforcement offers a low‑cost, environmentally friendly approach towards ground improvement. A significant limitation of these fibres, however, is their tendency to change dimensions when wet: their hydrophilic character causes them to absorb moisture, which undermines the mechanical properties and longevity of fibre‑reinforced soils. To mitigate this issue, the present work investigates how surface modification affects the mechanical response of soil–fibre systems, focusing on a polyaniline coating applied to sisal fibres to limit water uptake. Single‑fibre pull‑out experiments were conducted in soils with varying moisture content and density to characterise the fibre–matrix interfacial behaviour. In addition, unconfined compressive strength tests were performed on soil mixtures containing 100 mm coated fibres at a volume concentration of 0.75%. At the optimum moisture content after three days of curing, coated fibres exhibited lower interfacial shear strength (IFSS) than untreated fibres, an outcome attributed to a thin moisture layer at the interface that impeded adequate adhesion and mechanical interlock and promoted creep. Increasing the composite density through precompression markedly increased the IFSS for both treated and untreated fibres, due to greater frictional resistance at the interface. Composites with polyaniline‑treated fibres also lost moisture more rapidly, consistent with the hydrophobic character imparted by the coating. A shear‑lag formulation was used to model axial load transfer along the fibres, with predictive accuracy governed by the materials’ properties, geometry, and interfacial friction. Overall, the findings indicate that polyaniline surface treatment substantially improves the durability of natural‑fibre soil composites.

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Related topics: Natural Fiber Reinforced Composites · Geotechnical Engineering and Soil Stabilization · Innovative concrete reinforcement materials