Study On Performance Of Rubber And Polyvinyl Alcohol Fiber Composite Modified Cement Stabilized Macadam

Semi-rigid base pavement is a kind of pavement widely used in our country.As the most important semi-rigid base material,cement stabilized macadam has the advantages of low cost and excellent integrity,but it also has some problems and defects.In order to solve the problem that cement stabilized macadam is easy to crack due to its poor shrinkage performance.By improving the material properties,that is,two kinds of polymer(rubber powder and polyvinyl alcohol)were added into cement stabilized macadam.Under the premise of ensuring strength,the road performance of cement stabilized macadam could be improved effectively.In this paper,the properties of rubber powder and polyvinyl alcohol fiber composite modified cement stabilized macadam were studied systematically through a large number of laboratory tests,such as compressive strength,splitting strength,flexural tensile strength,dry shrinkage,temperature shrinkage and fatigue properties.The main contents and results of this study include:(1)The mix ratio of the rubber and polyvinyl alcohol fiber cement stabilized macadam was designed by orthogonal test.Firstly,the influencing factors and level of this paper were determined as follows:polyvinyl alcohol fiber length,fiber content,rubber particle size),rubber powder content,respectively.According to the orthogonal test table,nine groups of mixing ratio were determined,and the 7d unconfined compressive strength and splitting strength were carried out as the evaluation index.Through the range analysis of test results,finally,the optimum mix ratio of the four factors was determined as follows:polyvinyl alcohol fiber length was 18mm,fiber content was 0.9kg/m3,rubber particle size was 40 mesh,rubber powder content was 0.5%.(2)The basic mechanical tests were carried out on the seven groups of mixture of ordinary cement stabilized macadam,rubber powder cement stabilized macadam,rubber and polyvinyl alcohol fiber cement stabilized macadam with different fiber length,including unconfined compressive strength,split strength and flexural tensile strength.The variation law of seven groups of mixture was studied under the different ages(7d,14d,28d,90d,respectively).The results showed that the mechanical properties of cement stabilized macadam could be reduced by adding rubber powder alone,but the strength of cement stabilized macadam could be improved to some extent by adding rubber powder and polyvinyl alcohol fiber.The fatigue resistance of ordinary cement stabilized macadam and rubber polyvinyl alcohol cement stabilized macadam with 18mm fiber cured for 90 days was tested.The results showed that rubber powder and polyvinyl alcohol fiber could improve the fatigue performance of cement stabilized macadam.(3)The dry shrinkage tests and temperature shrinkage tests of ordinary cement stabilized macadam,fiber cement stabilized macadam and rubber polyvinyl alcohol fiber cement stabilized macadam were carried out at different ages(3d,7d,14d,28d).The results showed that the shrinkage of cement stabilized macadam single-doped fiber,mixed with fiber and rubber powder were improved compared to that of the common cement stabilized macadam,but the improvement effect of the mix-doped polymer material was more obvious.