Study On Mechanical And Dry Shrinkage Characteristics Of Basalt Fiber Reclaimed Cement Stabilized Gravel

Cement stabilized macadam is widely used as the main material of Chinese high level highway pavement base,so it often produces huge volume of Old cement stabilized macadam（OCSM）milling material in the major pavement repair.It is necessary to carry out research on OCSM recycling for the purpose of protecting environment and saving resources.Basalt fiber is a kind of inorganic fiber with excellent comprehensive properties.It is widely used in concrete and road asphalt surface,but its application in OCSM needs further study.Therefore,the mechanical and dry shrinkage characteristics of Basalt fibre regeneration old cement stabilized macadam（BR-OCSM）were studied.Through the design and physical experiments,The basic properties of OCSM material,the optimal aggregate gradation and the optimal mixing process of BR-OCSM mixture were tested and analyzed.On this basis,the influence of the characteristic parameters（diameter,length,content）of basalt fiber on the mechanical and dry shrinkage characteristics of BR-OCSM and the mechanism of action were studied.The numerical model of asphalt pavement structure at the base level of BR-OCSM was established.Combined with the results of mechanical response analysis of pavement structure,the optimum fiber characteristic parameters of BR-OCSM were determined comprehensively,and a universal method for determining BR-OCSM mix ratio was established.The main achievements of the thesis are as follows:（1）The physical parameters of OCSM material can basically meet the specification requirements naturally.The active ingredients such as Si O₂and Al₂O₃exist in the cement mortar attached to the aggregate surface,which can participate in chemical reactions.In addition,the rough surface of recycled aggregate can enhance the friction between aggregates,which is conducive to the formation and improvement of material strength.At the same time,the optimal aggregate gradation of recycled materials was obtained,and the influence law of feeding order and mixing time on mixing effect was determined,and the optimal mixing technology of BR-OCSM was obtained.（2）The unconfined compressive strength and flexural strength of BR-OCSM showed a peak value at 20mm with the increase of fiber length,and a peak value at0.8‰with the increase of fiber content.The strength of the material with a fiber diameter of 15μm was higher than that of 20μm.The dynamic elastic modulus peaked at 15mm with the increase of fiber length,and decreased gradually with the increase of fiber content and tended to be gentle,but the diameter had no significant effect on it.The shrinkage coefficient reached a peak value at 20mm with the increase of fiber length,decreased gradually with the increase of fiber content and tended to be gentle,and was smaller when the fiber diameter was 15μm.The control of appropriate fiber characteristic parameters can effectively increase the strength and flexibility of the material and reduce the shrinkage deformation of the material.（3）Under traffic load,with the increase of fiber content,the road surface deformation gradually increases,the anti-deformation ability of the base decreases,and the vertical deformation of the road surface presents an increasing trend.With the increase of fiber length,the stress at the bottom of road base layer increases first and then decreases.The vertical deformation reaches the minimum value when the fiber length is 15mm,and the anti-deformation ability of road base layer is the strongest.The flexibility of the material can be enhanced and the mechanical properties of BR-OCSM base can be improved by controlling the appropriate fiber characteristic parameters.（4）Based on the results of physical test and numerical analysis,the optimal fiber characteristic parameters were determined as diameter 15μm,length 20mm and content 0.8‰.At the same time,the universal BR-OCSM mix ratio determination method and its operation flow were established.The thesis has 58 figures,38 tables,and 90 references.