Use of wheat fiber and nanobentonite to stabilize clay subgrades

Since clayey soils naturally present low mechanical strength, they pose direct challenges for engineering applications. Finding appropriate soil stabilizers to address the challenges posed by clayey soils is crucial for ensuring that the soil meets the necessary geotechnical requirements and fulfills economic and environmental issues. To this end, this research uses several stabilizers and techniques in clayey soils to improve their suitability for construction. The main objective of this study is to assess the use of wheat fiber and nanobentonite (NB) in soil stabilization, estimate their behavior in practices, outline their obstacles and potential for soil improvement, and consider their ecological and financial effects. This research also evaluates the behavior of the soil by incorporating NB (0.4, 0.8, and 1.2 %) as a stabilizing agent. For this purpose, the randomly dispersed wheat fibers as a reinforcing agent at different dosages and lengths (0.3, 0.6, 0.9 %, and 5, 10, and 15 mm) were combined to the soil matrix. The soil was characterized by conducting compaction, unconfined compressive strength (UCS), direct shear (DS), California bearing ratio (CBR), indirect tensile strength (ITS), freezing-thawing (F-T) tests, and microstructural analysis. The data were used to assess the effect of wheat fiber and NB on the soil's geotechnical properties. The results revealed that incorporating 0.8 % NB into the soil led to the best enhancement in compressive strength. This improvement is attributed to the dehydration and formation of a viscous-like film between the soil particles. In addition, 0.6 % fibers with a length of 15 mm increased the interaction and bonding forces between the particles of soil, resulting in a maximum increase in compressive strength. Combining fibers and NB improved the shear strength, tensile strength, and bearing capacity. Besides, the stabilized soil exhibited superior resistance to freezing-thawing cycles compared to the unreinforced clay. Overall, the results indicate that using wheat fibers and NB is a cost-effective and eco-friendly solution for stabilizing clay subgrades. • Nano bentonite and wheat fiber increased compressive, shear, tensile, and F-T characteristics of soft clay. • Wheat fibers promote soil particle interlocking, whereas nano-bentonite's viscous gel increases cohesion by 81%. • Due to the anchoring impact, wheat fiber can bridge the gap between particles and improves tensile strength up to 178 %. • As environmentally friendly materials, nano bentonite and wheat fiber stabilize clay to minimize pavement thickness.