Performance of bitumen improved with coconut shell activated carbon additives

Abstract

The agricultural industry alone generates a wide range of waste materials, such as shells, palm oil, husks, leaves, and fronds. Because of the growing waste generation, researchers have investigated alternative methods to recycle waste materials for bitumen modification to improve road materials and reduce solid waste pollution. While the utilisation of agricultural wastes for activated carbon production has been reported, there is limited study on the potential use of activated carbon from Coconut Shells (CS) in bitumen mixtures for road construction purposes. Therefore, this study investigates the feasibility of Coconut Shell Carbon (CSC) and Coconut Shell Activated Carbon (CSAC) as additives for road construction. The CSC and CSAC were used to modify 80/100 penetration grade bitumen (80/100PEN) under three work phases. In phase one, the CS waste was converted into CSC and CSAC, followed by the production and characterisation of the additives using the Laser Particle Size Analyser (LPSA) and Elemental Analyser (EA) for proximate and ultimate analysis respectively. CSC and CSAC were then mixed in 80/100PEN bitumen at 5% to 25% to produce the modified binder. The physical, chemical, and rheological properties of the modified binder containing CSC and CSAC were evaluated in the second phase under various ageing conditions (unaged, short- and long-term aged). The laboratory tests include Fourier Transform Infrared (FTIR), softening point, penetration, storage stability, viscosity, and Dynamic Shear Rheometer (DSR). The best modified binder was determined and used to develop the modified Hot Mixture Asphalt (HMA). For the third phase, the study focused on evaluating the mechanical properties of the modified HMA in terms of Marshall stability, resilient modulus, dynamic creep, indirect tensile strength, and rutting potential. The performance of the modified HMA was compared to the control of 80/100PEN HMA and 60/70PEN HMA. According to the results, both CSC and CSAC are harder, more corrosion-resistant and lower in emissions than that of the controlled mixtures. Furthermore, the chemical activation process of CS produces CSAC with a smaller microporous pore structure than CSC. When applied as additives to the bitumen mixture, the physical and rheological properties of the modified binder have been significantly improved, including stiffness and rutting resistance. The addition of 10% CSC and 15% CSAC per weight of 80/100PEN bitumen was the best proportion for the formulation of the modified binding with optimal properties. Compared to the controlled mixtures, the 5.2% CSAC improved by 81%, 46% and 13% in rutting, fatigue, and permanent deformation resistance, respectively. It can be concluded that CSAC can be used as an additive to change the properties of bitumen, improve performance, and promote the element of sustainability in road pavement.