Study On Crack Resistance Of Cement Stabilized Macadam Mixed With Waste Rubber Powder And Fiber

Semi-rigid base has become the main structural form of high-grade highway in China,which main shortcomings is that it is easy to produce shrinkage cracking,and the crack can cause the surface layer cracking to form reflective crack.The new standard has refined and promoted the base design strength of the high grade highway,thus increasing the dosage of cement inevitably.In view of this situation,it is necessary to ensure that the asphalt pavement base has certain structural strength,and also to reduce the cracking.On the basis of the research results at home and abroad,the paper mainly study mechanical properties and road performance of cement stabilized macadam blended with rubber powder and polypropylene fiber.(1)According to the relevant test regulations,the performance indexes of all kinds of raw materials needed in this study are tested,and the test gradation is determined.According to the relationship between 7d unconfined compressive strength and cement dosage,the cement dosage is determined to be 5.2%.The mixture ratio of mixture was studied based on orthogonal experimental design(four factors and three levels).The main inspection factors for the test are the size of rubber powder,the amount of rubber powder,the length of fiber and the amount of fiber.From two aspects of strength index and crack resistance index,the influence of various factors on the index is obtained,and the optimal mix ratio is determined: 30 particle size of rubber powder,1% of rubber powder,6mm fiber length,and 0.8‰ fiber content.(2)Laboratory tests were carried out to verify the mechanical properties and road performance of the composite material.The addition of rubber powder and fiber enhances the strength of cement stabilized macadam and reduces the rigidity.At the ages of 28 d,the compressive strength has increased by 4.9%,the compressive resilience modulus has decreased by 13.2%,and the increase of splitting modulus of 90 d days has increased the most,and the growth rate was 22.5%.(3)The fatigue equation of this special cement stabilized macadam base material is also studied,the results show that the fatigue life of the cement stabilized macadam was improved.The addition of rubber powder and fiber makes the cement stabilized macadam more resistant to erosion during each period.The improvement of the rubber powder and fiber against freezing performance is 23.26%.The dry shrinkage of the material also perform well.The results show that,on the whole,the performance of cement stabilized macadam with waste rubber powder and fiber has been greatly improved compared with the ordinary cement stabilized macadam.(4)Through the analysis of the economic benefit of the material,the result shows that its economy is better and the material has the feasibility to be popularized.The research achievements can solve the cracking problem of cement stabilized macadam base with high cement doses in high grade highway,and has influential engineering practical value.