The characterization and analysis of the cementation properties of novel biopolymer binders in soils are essential for their potential application in geotechnical engineering. This study investigates the cementation effect of a novel zein biopolymer binder on sandy soils. Soil specimens are mixed with various contents of zein biopolymer ranging from 0 to 5%. The mechanical and microscopic characteristics of the treated specimens are evaluated using unconfined compression tests and scanning electron microscopy, respectively, after curing for 3, 7, and 28 days. The results show a consistent increase in compressive strength and elastic modulus of treated soils with increasing curing periods and biopolymer contents. A small amount (1%) of zein biopolymer increases soil strength and elasticity regardless of gradation. Additionally, the bonding force between the soil–zein biopolymer increases linearly with soil uniformity. Therefore, the application of zein biopolymer can be potentially used as a binder for fine- and coarse-grained soils in geotechnical engineering considering its stabilization and sustainability properties.

The curing condition and solvent composition of biopolymer binders may impact their efficacy for soil stabilization. This study introduces a novel hydrophobic biopolymer, zein, and investigates the effects of solvent and curing conditions on the mechanical properties of zein-treated soils. The zein biopolymer is used to prepare cohesionless soil with various ethanol contents. Unconfined compressive strength and microscopic tests are used to investigate the treated specimens under two different curing conditions. The mechanical properties of the treated specimens are evaluated in terms of compressive strength and the secant elastic modulus. The experimental results show that the compressive strength and elastic modulus increase with the curing period under both curing conditions. Higher curing temperature improves the compressive strength of biopolymer-treated specimens. The linear relationship between compressive strength and the elastic modulus of zein-treated soils shows higher strength and a lower elastic modulus compared to rock. Furthermore, the zein biopolymer shows significant strength improvement compared to the existing biopolymers, including casein and lignin. Thus, the effects of solvent and curing conditions on the mechanical properties of zein-treated soil should be considered for its application to soil stabilization.

Repeated wetting–drying cycles accelerate scouring and deteriorate soil structure by increasing pore-water pressure. This study examines the durability of sand treated with zein biopolymers subjected to wetting–drying cycles and compares its uncycled condition with that of xanthan gum (XG). The treated specimens are prepared with biopolymer contents of 1% and 3% by mass of sand. The specimens are cured for an initial period of 7 days under atmospheric conditions, whereafter they are subjected to a series of wetting–drying cycles. Subsequently, the dimensions and mass of the specimens are measured to evaluate bulk density-related changes during the cycles. The strength and degradation characteristics of the specimens are evaluated through unconfined compression tests after being subjected to different numbers of cycles. The bulk unit weight after the drying phase remains nearly constant, whereas that after the wetting phase increases with both the number of cycles and biopolymer content. Overall, specimens with higher biopolymer content exhibit lower bulk unit weights. The XG-treated specimens show earlier strength improvement than the zein-treated specimens due to the faster curing-related strength development associated with water-based gelation. Moreover, the XG-treated sand rapidly fails after the first wetting phase, while the compressive strength of the cycled zein-treated specimens is lower than that of the uncycled specimens. Zein-treated sand with 3% biopolymer content shows a higher durability index after 10 cycles than sand treated with 1% biopolymer content. Therefore, a higher zein content can be used to enhance the durability of sand subject to frequent wetting and drying cycles.