Assessment of industrial waste lignocellulosic fibers as a sustainable additive for improving engineering waste mud

In response to the growing ecological issues caused by engineering waste mud and the lack of effective solutions. This study first examines the physical properties and the microstructure of raw waste mud. Subsequently, environmentally friendly and sustainable lignocellulosic fibers from industrial waste were incorporated to improve the waste mud soil, with an addition ratio ranging from 0% to 4%. The effects of fiber content on the strength reinforcement and stress-strain behavior of the reinforced soil specimens were evaluated through a series of direct shear tests and unconfined compressive strength (UCS) tests. The environmental properties were assessed through pH tests, and microstructure changes were analyzed using scanning electron microscopy (SEM). Finally, the reinforcement mechanism was revealed by combining mechanical performance and microstructural evolution. The results indicate that the addition of lignocellulosic fibers effectively enhances the mechanical strength and deformation resistance of the reinforced specimens compared to natural mud. The UCS of untreated mud soil is 144 kPa, while the UCS of the treated soil, with an optimal fiber content of 3.0%, increases to 304 kPa after 7 days of curing. The pH test results indicated that regardless of the fiber content, the pH remained approximately 8.8, suggesting that the incorporation of lignocellulosic fibers has minimal impact on the acidity or alkalinity of the specimens. The reinforcement mechanism of lignocellulosic fibers in mud primarily involves microparticle filling effects that compact pore spaces and bridging effects that connect soil particles. This study offers valuable insights into the use of fibers as additives for waste mud treatment and their potential for reuse in geotechnical engineering.