Eco-Friendly Stabilization of Coarse-Grained Soil Using Gum Rosin and Natural Fiber

Cement and its derivatives are frequently used as traditional construction materials for soil improvement. However, the most commonly used ordinary Portland cement can significantly affect the ecological environment. This study proposes an innovative alternative improvement method to stabilize soil by incorporating gum rosin (GR), a natural polymer, into the soil. For this purpose, the improvement of soil with different grain diameters (G1 and G2) by incorporating different proportions of sisal fiber (0.2%, 0.4%, 0.6%, and 0.8%) into different proportions of GR (5%, 10%, and 15%) was investigated. The focus of the study was the treatment of GR natural polymer to the soils by heating as an innovative method and to determine the characteristic changes in the strength and permeability of the soil. Firstly, the setting time of this method was determined. After that, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), and permeability tests were performed on the samples subjected to different curing times (1, 7, and 28 days). According to the results obtained from the experiments, it was determined that the setting time of the samples reached a stable state after one day of curing. The average strengths of G1 and G2 soils were 3.72 MPa and 2.48 MPa, respectively, and it was observed that the decrease in grain diameter contributed positively to the increase in strength. In addition, it was determined that both the strength and the failure stress increased with the inclusion of fiber. Moreover, a high coefficient of R2 = 0.9428 was obtained from the variation of the UPV test and UCS test, and the usability of the UPV test results in estimating the strength was evaluated. According to the permeability test results, a negligible decrease in permeability was observed after the treatment, and in this case, it was evaluated that this method could be used in many different engineering fields, such as permeable asphalt pavements. The findings suggest that this natural polymer may have potential in certain engineering applications, though its wider use requires further exploration. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.