Effect of Bitumen Content on the Mechanical Properties of Composite Geotextile Produced with Hemp and Bitumen

Abstract

In order to maintain sustainability in construction, using natural materials instead of synthetic materials obtained from limited raw materials in nature is becoming increasingly widespread. In this study, the usability of natural hemp fiber with bitumen as a geotextile was investigated. Accordingly, it was aimed to investigate the effect of bitumen quantity on the mechanical properties of hemp fiber-bitumen composite geotextile by combining hemp fiber with bitumen at different ratios (1×, 1.5×, 2×, 2.5×, 3×, 3.5×, and 4× the weight of hemp fiber). Furthermore, samples with two different hemp amounts (40.95 and 81.9 g) were produced. While studying the mechanical properties, the wide-width tensile strength test was utilized to determine the maximum tensile strength, strain at breaking, breaking toughness, and tensile modulus parameters. Additionally, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy were used to observe the chemical structure, thermal degradation, and morphology of bitumen-coated hemp fiber, respectively. The study concluded that the optimum amount of bitumen for producing hemp-fiber bitumen composite geotextile is 3.5 times the weight of hemp fiber, and samples with 81.9 g hemp fiber perform better than samples with 40.95 g hemp fibers. For the composite geotextile produced at this bitumen content, the highest tensile strength was 9.65 kN/m, the breaking tensile load was 1,952.3 N, the strain at breaking was 187.2%, the breaking toughness was 24,040 J/m2, and the initial tensile modulus was 7.4 kN/m. Geotextiles are generally used as reinforcement elements to reduce settlement and increase bearing capacity, as well as for various purposes such as separation of soil layers, drainage, filtration, and insulation of the ground and prevention of erosion on slope surfaces. Plastic fibers are generally used in these materials, which can be produced as woven and nonwoven. Despite the superior performance of geotextiles produced with plastic fibers, the environmental damage caused by the fact that they are unsustainable and nonbiodegradable increases the tendency towards natural fibers. This study presents a sustainable geotextile alternative to those produced with plastic fibers by coating natural hemp fibers with bitumen. Within the scope of the study, hemp fibers were placed in a mold as nonwoven, and geotextile was obtained by pouring bitumen on them. During the production phase, the bitumen was increased by keeping the hemp fiber constant by weight, and the material with optimum bitumen content was obtained. The study results showed that the material with 3.5 times the bitumen weight of hemp shows the best performance. This material might be an alternative to geotextiles produced with plastic fibers in environments where high mechanical performance is not required.