Study On Adhesion Performance Of Broken Pebbles And Asphalt

With the gradual increase in the mileage of highways in China,the amount of raw materials used has also gradually increased.In order to meet the requirements of ecological and environmental protection policies,the mining of high-quality stone materials has also gradually been limited,while the price of sand and stone materials has increased significantly.Tibet is rich in pebble resources.The composition of pebbles is complex and acidic aggregates.Acidic aggregates are generally considered to have poor adhesion to asphalt,which restricts the application of pebbles.If the acidic pebbles can be used in the construction of highways,it will undoubtedly have great economic and social benefits.Reasonable evaluation of the adhesion properties of broken pebbles and asphalt with complex components and the study of the adhesion mechanism between the two are of great significance to promote the application of broken pebbles in highway construction.X-ray fluorescence analysis,XRD and SEM were used to analyze the chemical properties and microstructure of the broken pebbles.It was concluded that the main elements of broken pebbles with different colors and different particle sizes were different,but the content of Si O₂was the most.The mineral composition of broken pebbles of different particle sizes was also different,but there were substances such as biotite,feldspar,quartz,etc.,thereby reducing the adhesion properties of asphalt and broken pebbles.Based on the theory of surface energy,the adhesion properties of broken pebbles and asphalt were studied.The surface energy of asphalt and broken pebbles were tested by the sessile drop method and the capillary rise method.It was concluded that the addition of anti-stripping agents would reduce the asphalt surface energy,increase the polar component and reduce the dispersion component.Factors such as composition,mineral composition,and surface charge lead to different surface energy of broken pebbles with different particle sizes.The resistance to water damage of the broken pebble and asphalt mixture was evaluated by calculating the adhesion and peeling power of asphalt and broken pebble under dry and wet conditions.The improved solvent elution method,infrared spectroscopy and gel permeation chromatography were used to study the mechanism of the interaction between the broken pebble and asphalt,and the mechanism of cement and mineral powder to improve the adhesion performance was explained.The results showed that the addition of mineral powder and cement would reduce the macromolecular substances in the eluted asphalt,and the adsorption of colloid and asphaltene on the surface of broken pebbles increased the adhesion properties of the mineral and asphalt.The Marshall test and freeze-thaw split test of the asphalt mixture were verified to improve the water stability of the broken pebble asphalt mixture by using SBS modified asphalt,adding anti-stripping agent,cement and mineral powder.It was proposed to use the method of Comprehensive Energy Ratio（CER）index to evaluate the water stability of broken pebble asphalt mixture,and the relationship between the surface energy index of raw materials and the macro performance of asphalt mixture was established to provide theoretical support for the application of broken pebble in highway engineering construction.