Evaluation of Rheological and Microstructural Behavior of Modified Asphalt Binder with Chitosan Derived from Shrimp Shell Powder

Abstract

Chitosan derived from shrimp shells (SSPCH) was used for the first time as a biological biopolymer to modify the properties of bitumen across high, medium, and low-temperature ranges. Therefore, physical tests (penetration, softening point, and ductility) and rheological tests (RV, DSR, MSCR, LAS, and BBR) were conducted along with morphological and microstructural analyses, on modified bitumen with 2%, 4%, 6%, and 8% SSPCH. Chemical analysis revealed that bitumen and SSPCH interacted physically during the mixing process, while no chemical reaction was observed. Moreover, the thermal sensitivity of the modified bitumen was enhanced by decreasing the penetration degree and increasing the softening point. SSPCH improved the properties of modified bitumen as a result of its porous structure and asphaltene absorption, as well as its structural similarity to bitumen and ability to absorb the light components of bitumen with its heavy components. Increasing the SSPCH dose in bitumen improves its resistance to deformation and recoverability by increasing the viscous phase and decreasing the elastic phase, resulting in increased stiffness. The findings also revealed that the addition of 6% SSPCH yielded the best performance against rutting failures. Generally, SSPCH incorporation significantly improved bitumen performance in different temperature ranges. By adding 8% SSPCH, the highest resistance to rutting occurred. However, the phase separation between SSPCH and bitumen exceeded the suitable range. Hence, 6% SSPCH is useful in the bitumen mixture for areas at high temperature. Also, to prevent fatigue and cracking damage, it is recommended to limit the dose of SSPCH to 4-6%.