Study On Soda Lignin As An Asphalt Modifier And Its Pavement Performance

Increasing cost,complex preparation process,low compatibility and poor storage stability of traditional modified asphalts have encouraged to develop environmentally friendly,renewable,cost-effective modified asphalt without compromising its performance.To overcome the above-mentioned shortcomings of the conventional modified binders introduction of an alternative source of modified binder for flexible pavement is essential.In recent years,lignin has been receiving more coverage as an asphalt modifier because of its wide range of sources,low price,renewability,and its potentiality to enhance the performance of asphalt pavement.However,thorough investigation regarding performance,storage stability and chemical characterization of modified asphalts by utilizing different lignin types is still lacking.This research aims to develop lignin modified asphalt that can overcome some drawbacks of traditional modified asphalt by utilizing soda lignin powder in different proportions.A series of tests including penetration,softening point,ductility,viscosity,rutting factor,fatigue,low-temperature cracking,storage stability and chemical tests were performed to find out the influence of soda lignin on asphalt binder.In addition,Molecular Dynamics simulation of asphalt and lignin were carried out using Materials Studio 8.0 software.The stable molecular structural model system of both lignin and asphalt were built and the rationality of the models were verified.Subsequently,the Cohesive Energy Density,solubility parameter and FloryHuggins parameter were determined in order to evaluate the compatibility of the mixture molecular level.Moreover,aging test were conducted including short-term,long-term,and ultraviolet aging to investigate the anti-aging ability of lignin modified asphalt.Ultraviolet aging was conducted by using Xenon Lamp Aging Test Chamber in such a way that the total amount of ultraviolet radiation during indoor aging is equal to the total irradiance of 6 months of outdoor aging.The general properties test results of lignin modified asphalt revealed that the addition of lignin helps to reduce the temperature sensitivity of the asphalt by increasing its hardness and decreasing its ductility.At the same time,the incorporation of soda lignin powder also increased the viscosity of base asphalt with the increase in lignin content.The simulation results recommend that the compatibility of lignin and asphalt is best when the mixing temperature is at 155°C and with the lignin content of 20%.The chemical test results suggest that the soda lignin and bitumen can be mixed physically without the formation of new chemicals.The analysis of aging index showed that soda lignin has good anti-aging ability,which helps to delay the oxidation and slows down the aging process of the asphalt.Rheological performance test results revealed that addition of soda lignin significantly enhanced the rutting resistance and fatigue performance for all the dosages incorporated.However,a slight reduction in lowtemperature cracking performance was found.In addition,storage stability test result depicted that the dispersion of lignin powder in asphalt was comparatively uniform and stable indicating great thermal storage stability for all the lignin amounts incorporated.