Experimental Study On Diatomite And Lignin Fiber Composite Modified Asphalt Mixture In Seasonal Frozen Area

The climate of Liaoning Province is characterized by large temperature difference between day and night,high temperature in summer,low temperature in winter and serious freeze-thaw cycle.Asphalt pavement in Liaoning Province is easy to produce cracks,ruts and loose diseases.In order to improve the comprehensive performance of asphalt pavement,extend the service life of asphalt pavement in seasonal frozen area and reduce the project cost,the thesis carried out the experimental research on Diatomite lignin fiber composite modified asphalt mixture.This thesis analyzes the causes of diseases of asphalt pavement in seasonal frozen area,and studies the problems of insufficient low-temperature and high-temperature performance of asphalt mixture,insufficient fatigue performance under freeze-thaw and poor frost resistance.Diatomite lignin fiber composite modified asphalt was proposed,and its basic performance test and micro test were carried out.It is found that when the diatomite content is 11%-13%and the lignin fiber content is 1%-2%,the composite modified asphalt has the best low temperature performance,the most obvious improvement of softening point and the best adhesion performance.Fluorescence microscope test result shows that when the content of diatomite exceeds 15%,the phenomenon of stacking and agglomeration of diatomite appears in asphalt.SEM test results shows that lignin fiber had strong adsorption on diatomite,and diatomite attached to the fiber surface to form graft structure",which improved the interfacial strength.This thesis studies the road performance,fatigue performance and frost resistance of composite modified asphalt mixture.The results of low-temperature bending test show that diatomite has no significant improvement in low-temperature crack resistance,but the synergistic effect with lignin fiber can further improve its low-temperature performance.The rutting test shows that diatomite can significantly improve the high temperature performance of asphalt mixture.Four point fatigue bending test shows that the fatigue life of the composite modified asphalt mixture has been greatly improved,and the loss rate of fatigue life after freezethaw is small.The frost resistance test shows that the frost resistance of the composite modified asphalt mixture is improved.It is found that diatomite can enhance the adhesion between asphalt and aggregate after freeze-thaw,which is beneficial to improve the frost resistance of asphalt mixture.Lignin fiber interpenetration in asphalt mixture plays the role of preventing and overlapping cracks,dispersing and transferring frost heaving stress,and relieving stress concentration at crack tip.Due to the coordination of diatomite and lignin fiber,the frost resistance of composite modified asphalt mixture is further enhanced.