Mechanical Properties and Image-Based Crack Analysis of Hydrogenated Cup Lump Natural Rubber-Modified Asphalt Mixtures

Abstract

Researchers have explored the effects of incorporating cup lump natural rubber as an asphalt modification to promote rubber utilization and enhance pavement performance. However, cup-lump natural rubber treatment affects the performance of asphalt mixtures. This study investigates how cup-lump natural rubber treated via non-catalytic hydrogenation to create hydrogenated cup-lump natural rubber (HCLNR) affects the mechanical performance of asphalt mixtures. Asphalt mixtures were prepared by incorporating HCLNR at 2.5%, 5.0%, 7.5% and 10% by weight of bitumen. The performance was evaluated through Marshall stability, indirect tensile strength, and tensile strength ratio (TSR) tests, complemented by a MATLAB-based digital image analysis to quantify surface cracking and pattern. Results indicate that all HCLNR-modified mixtures comply with Malaysian Public Works Department specifications. The 5.0% HCLNR dosage was identified as the optimum content, achieving a peak Marshall stability of 13.1 kN and tensile strength of 862.08 kPa. Furthermore, the optimal dosage enhanced moisture resistance, with a TSR of 87.09% and the lowest crack ratio. Higher rubber contents increased bitumen stiffness and led to poor dispersion and brittle fracture patterns. This study confirms that HCLNR at moderate dosages serves as a sustainable and high-performance modifier, effectively improving the durability and crack resistance of asphalt pavements in tropical climates.