Sustainable Utilization of Synthetic Nonwoven Waste Materials (NWM) for Improving Clay Soils in Rural Road Construction in Tanzania: A Review Paper

The rapid growth of plastic production and consumption has significantly increased the generation of synthetic nonwoven waste materials, creating serious environmental and waste management challenges. In parallel, the need for sustainable ground improvement techniques in geotechnical engineering has intensified. This study presents a structured literature review evaluating the potential application of synthetic nonwoven waste materials as soil reinforcement agents. Following the PRISMA 2020 framework, 54 publications were initially identified, of which 15 studies met the inclusion criteria for detailed analysis. The reviewed studies consistently demonstrate that incorporating small percentages (0.2–1.5% by dry soil weight) of synthetic nonwoven fibers significantly enhances key geotechnical properties. Reported improvements include increases in unconfined compressive strength of up to 64%, substantial gains in California Bearing Ratio (CBR) values, reductions in plasticity index, and notable decreases in swelling potential. These improvements are primarily attributed to mechanical interlocking, frictional resistance, and crack-bridging mechanisms provided by randomly distributed fibers within the soil matrix. The findings indicate that synthetic nonwoven waste materials offer a technically viable and environmentally sustainable alternative to conventional chemical stabilizers, particularly for subgrade and embankment applications. Moreover, this approach aligns with circular economy principles by diverting textile waste from landfills while enhancing soil performance. Although global studies confirm the effectiveness of synthetic fiber reinforcement, limited research has examined its application within the Tanzanian context. Therefore, further experimental investigations are recommended to evaluate locally available nonwoven waste materials and establish design guidelines for practical implementation.