Investigating the performance of bitumen containing hydrogel microcapsules with industrial waste oil core

In this study, hydrogel-based microcapsules containing industrial waste oil were developed and added to bitumen. Bitumen-microcapsule composites were prepared at various dosages of 2 wt %, 3 wt %, 4 wt %, and 5 wt % (by mass of bitumen), and their mechanical and self-healing performance was evaluated using Fourier-transform infrared spectroscopy (FTIR) and tensile strength testing. FTIR analysis showed that the bitumen-microcapsule composite with 4 wt % microcapsules exhibited the highest self-healing efficiency. Furthermore, tensile test results indicated that while the incorporation of microcapsules increased the binder's strength, it reduced its flexibility; the composites containing 3 wt % and 4 wt % microcapsules showed the most favorable mechanical performance in terms of balancing strength and elongation. Based on these results, the bitumen-microcapsule composite with 4 wt % microcapsules was selected as the optimal formulation, and further testing was conducted at this level to assess its thermal and physical properties. Thermal behavior was evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and morphological characterization was performed using scanning electron microscopy (SEM). the rheology of the bitumen-microcapsule composites was evaluated using the MSCR (Multiple Stress Creep Recovery) test. Furthermore, the self-healing behavior in the asphalt mixture was assessed using the ITS (Indirect Tensile Strength) test. The thermal results indicated that the modified binder exhibited thermal stability comparable to that of base bitumen, suggesting its suitability for high-temperature pavement applications. SEM images confirmed that the microcapsules retained their original shape and structural integrity after mixing and were uniformly dispersed throughout the bitumen matrix without noticeable agglomeration.The MSCR test results showed improved rutting resistance. Additionally, the ITS test results showed an improvement in self-healing performance in the asphalt mixture containing 4 wt % microcapsules compared to the mixture without microcapsules, particularly under aging conditions. These results also confirmed the self-healing properties observed in the FTIR test on the bitumen samples.