Experimental Study On Metakaolin-slag As Quick Repair Material For Pothole Of Asphalt Pavement

In recent years,China’s transportation network has ushered in a period of great development.In the total mileage of highway,it has become the longest country in the world,with a total of 5012500 km.The density of highway reaches 52.21 kilometers per100 square kilometers.As a result,the maintenance mileage has reached 98.8% of the total highway,which is 4.9531 million km.Highway maintenance has become particularly important.Pit is one of the main diseases of asphalt pavement,which seriously affects the road service life and driving safety.At present,only 15% of phosphogypsum in the world is effectively utilized,most of which are stored in the form of open storage.It not only leads to the waste of land,but also pollutes the surrounding water,land and atmosphere,and brings serious environmental problems.In this paper,the application of phosphogypsum in GGBS-metakaolin geopolymer cementitious materials was studied.The flexural strength,compressive strength and water resistance of geopolymer were tested.The microscopic morphology was studied by SEM,the types of hydration products were studied by EDX and XRD,and the amount of hydration products was studied by chemical bonded water.The results show that,the major hydration products of GGBS-metakaolin geopolymer was C-(A)-S-H or N-(A)-SH gel.In addition,AFt was produced after adding phosphogypsum.When the replacement ratio reached 20%,the increasement rate of non-evaporation water was high.Meanwhile,the flexural strength of geopolymer containing phosphogypsum is significantly higher than that of control group;When the content of phosphogypsum reaches 20% and slag content is less than 32%,the compressive strength is significantly higher than that of the control group.Therefore,the appropriate amount of phosphogypsum is helpful to improve the mechanical properties of alkali activated geopolymer and solve various problems caused by phosphogypsum.In this paper,alkali activated geopolymer and emulsified asphalt composite cementitious material mixture were studied.The 4H and 1D strength of the mixture were tested by Marshall stability test,The water stability of the mixture was tested by immersion Marshall stability test,The high temperature stability of the mixture was tested by high temperature rutting test,The low temperature crack resistance of the mixture was tested by low temperature trabecular bending test.The results show that alkali activated geopolymer can significantly improve the early strength of emulsified asphalt mixture,It can improve the water stability of emulsified asphalt mixture.Because alkali activated geopolymer is a rigid material,it is not easy to deform,so it is not easy to produce rutting in high temperature environment.Therefore,alkali activated geopolymer and emulsified asphalt composite cementitious material mixture can meet the requirements of rapid repair of asphalt pavement pit.