The physical properties of modified bitumen and the performance of SMA mixtures with the inclusion of cup lump natural rubber

Pavement distresses, such as rutting and thermal cracking, adversely affect road performance and service life, highlighting the need for more durable and sustainable methods of binder modification. Although conventional polymer modifiers can enhance performance, their petrochemical origins raise significant environmental concerns. Cup lump natural rubber (CLNR), a renewable resource plentiful in Malaysia, presents a sustainable alternative with potential performance advantages. This study aims to establish the optimal CLNR content for modifying bitumen and to assess the performance of stone mastic asphalt (SMA) mixtures incorporating treated CLNR through both wet and dry mixing methods. CLNR was pre-treated with toluene at a 1:2 ratio to improve dispersion, and bitumen was modified with CLNR at concentrations of 2.5%, 5.0%, and 7.5%. SMA samples were subsequently prepared using a 5% dosage to determine the optimum binder content (OBC). The results demonstrated that CLNR-modified bitumen exhibited a substantial increase in softening point and a reduction in penetration, indicating enhanced rutting resistance and reduced temperature susceptibility. Furthermore, storage stability remained excellent, with temperature differentials below 2.5 C. The determined OBCs were found to be 5.8% for the dry mix and 5.6% for the wet mix. In conclusion, the incorporation of treated CLNR significantly enhances the performance of both bitumen and SMA mixtures while fostering environmental sustainability, thereby supporting progress in sustainable pavement engineering practices.