The enhancement of mechanical, physical, and thermal properties of modified asphalt mixture with lignin from mahogany sawdust in the presence of diphenylmethane 4,4′-diisocyanate

Abstract

The road infrastructure condition, which can be easily damaged by the occurrence of potholes due to the weak adhesion between asphalt and aggregate, disrupts economic activity and requires high maintenance costs. This problem needs to be overcome by adding adhesive to modify the asphalt. Lignin is a sustainable biopolymer that can serve as a natural asphalt binder. Lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate has never been used to modify asphalt mixtures. This modification can improve the properties of the asphalt mixture, which is very important in road pavement engineering. This study aims to modify asphalt mixtures with lignin isolated from mahogany sawdust combined with diphenylmethane 4,4′-diisocyanate and investigate their physical, mechanical, and thermal characteristics. The isolated lignin was prepared for a modified asphalt mixture by reacting with diphenylmethane 4,4-diisocyanate and adding asphalt. Next, the asphalt mixture was mixed with sand aggregate in an extruder at 150 °C. The results showed an improvement in mechanical, physical, and thermal properties. The optimum composition of asphalt and lignin was 60:40 with a compressive strength value of 3.107 MPa, a water absorption value of 0.246%, and a melting point of 238 °C. The Fourier-transform infrared spectroscopy (FT-IR) spectrum showed a small band at 1715 cm−1, indicating the CO carbonyl group of the NH–CO–O urethane bond. The morphology showed that the surface structure of the modified asphalt mixture becomes more homogeneous due to the interaction between asphalt and polyurethane, which is the result of the reaction of lignin isolate with diphenylmethane 4,4′-diisocyanate.