Study On Preparation And Preformance Of Lignin Fiber In Asphalt Mixture

Fiber asphalt mixture is widely used in asphalt pavement engineering because of its excellent high temperature stability,low temperature crack resistance and water damage resistance.At present,there are many types of fibers that can be used in asphalt mixture,the preparation process is complicated,and the manufacturing cost is high.Lignin fiber is a complex natural polymer compound rich in nature.Blending with polymer materials can increase the mechanical properties,thermal stability,aging resistance and flame retardancy of polymer materials.In order to solve the problem of waste of lignin fiber resources and environmental pollution,it is of great practical significance to explore the available value of lignin fiber and explore the preparation and performance evaluation of new road lignin fiber.In this study,based on the composition and technical characteristics of the raw lignin residue,the lignin residue raw material was extracted and prepared by acid hydrolysis method,alkali extraction method and acid precipitation method,and its morphological characteristics,extraction rate,functional group and molecular weight were characterized.And we analyzed its road performance and enhancement mechanism.The main conclusions are as follows:The lignin residue raw materials were pretreated by acid hydrolysis method,alkali dissolution method and acid precipitation method,and the extraction conditions were optimized to obtain lignin fibers of different treatment methods and their yield,structural characteristics and thermal properties were carried out.The alkaline extraction method had better selectivty at extraction time 1 h,solid-liquid ratio 1:110;the mass ratio of hydrochloric acid lignin has little effect on lignin extraction;the highest yield of lignin extracted by acid hydrolysis method is 90.6%.The basic structure of lignin fibers obtained by different extraction methods is intact and has good thermal stability.Among them,the lignin structure obtained by alkali dissolution method has the most damage,and the acid-settled lignin has the best thermal stability.Using raw material lignin residue,JRS lignin fiber,straw,and lignin extracted by acid hydrolysis method,alkali extraction method,acid precipitation method as raw materials,high-speed shearing machine is blended with asphalt to prepare different amounts and different fiber types asphalt mortar.As the blending amount increases,the softening point and penetration of the asphalt mortar increase,and the ductility decreases.The six fibers all showed the same pattern,indicating that the incorporation of lignin can enhance the high-temperature stability and shear resistance of asphalt mortar.Dynamic shear rheology and bending beam experiments show that lignin can enhance the high temperature rutting resistance and low temperature crack resistance of asphalt mortar.The optimal fiber content of lignin is 3%,and the performance of acid precipitation lignin at high and low temperature optimal.Finally,through the asphalt component model,FTIR,scanning electron microscope and DSC test,the performance mechanism of lignin reinforced asphalt mortar was analyzed.The FTIR spectrum shows that after lignin is added to the asphalt,no chemical reaction occurs to generate new functional groups,and the mixing between lignin and asphalt is physical.The results of SEM and DSC experiments show that lignin has good adsorption performance,excellent dispersibility and compatibility in asphalt,and an interface structure between the two phases is structured asphalt.The increase of structured asphalt can improve the viscoelasticity of asphalt and strengthen the high temperature stability,and low temperature crack resistance performance of asphalt mortar.