Direct Shear Testing of a Hardening Oil–Silica Sand Mixture in Dry Condition

Cemented sands have great potential as construction materials compared with clean sand due to the higher strength, but they have insignificant environmental benefits such as high embodied energy and carbon footprint. To provide an environmentally friendly, cost-effective, and reliable solution to create an engineered soil, this study explored how Tung oil, a Chinese traditional vegetable hardening oil, affects the mechanical behavior of silica sand. Sand with different grain size is mixed with various concentrations (1–5%) of Tung oil. Heating can accelerate hardening of Tung oil when mixed with sands and may contribute to the increase of shear strength and dilatancy compared with clean sand. Therefore, direct shear box tests are performed on samples equilibrated at 60 °C. The Tung oil–sand mixture was found to exhibit (1) increasing shear strength and dilatancy with increasing Tung oil concentration, but excessive Tung oil concentration will weaken the stabilization efficiency of coarse sand; (2) the larger shear strength and stress dilatancy for host sand with grain size ranges from 0.063 to 0.3 mm.