Study On Mesoscopic Characteristics And Freeze-thaw Damage Characteristics Of Cement-stabilized Macadam Base Using Non-destructive Techniques

Cement stabilized crushed stone base material is a composite material composed of graded crushed stone,water and cementitious material,which is compacted according to the embedding principle.Because of its low cost,high strength,good durability and bearing capacity,as well as excellent overall stability and other advantages,it has become the most used highway pavement base material.Therefore,the performance index of cement stabilized gravel base material has become the focus of research.The most intuitive research is the study of the strength and crack resistance of cement stabilized gravel.The properties of the material itself are influenced not only by its macroscopic properties but also by its internal microstructure.Different internal structures result in different properties of the mixed materials,so the importance of the study on the microstructure of cement-stabilized crushed stone base is highlighted.At the same time,the shortcomings of cement stabilized gravel base material are also very obvious: for example,the heavy load has a greater impact,serious shrinkage and cracking,poor drainage performance,significant freeze-thaw damage,etc.Especially in the tundra area,temperature difference obvious season after freezing and melting state of two different materials on the base of the cement stable macadam mixture,the durable performance,mechanics index,deformation characteristics will change,the change of cement stabilized base materials will effect the performance of actual use,serious will result in the crack of the pavement,produce immeasurable damage.Therefore,it is very important to study the freeze-thaw damage characteristics of cement-stabilized gravel base materials and to find out the freeze-thaw damage rules of cement-stabilized gravel base materials.In this paper,standard specimens were firstly prepared and kept healthy by different molding methods based on laboratory tests,and the specimens were scanned by industrial CT technology to obtain internal microscopic characteristics.The influence of forming mode and gradation form on the internal microstructure of cement-stabilized crushed stone base material was studied.Second,not under the static pressure molding method with form of freeze-thaw cycle test specimens,by acoustic emission testing technology and ultrasonic testing technology,the determination of the parameters of the specimens after freezing and thawing cycle changes,and deal with the test data analysis,the mechanical properties change rule and freeze-thaw damage change law of the specific work includes the following:(1)Analysis of internal microscopic characteristics of cement-stabilized crushed stone base materials at different levels in different molding methodsDifferent forming method were obtained through the compaction test is not at the same level with forms of maximum dry density and optimum moisture content of the specimens,and based on this specimen,standard curing 28 d,put more specimen,cut scan standard specimen,by industrial computed tomography(CT)scanning technology to scan of specimen,access to the internal structure of information,the forming method and forms of gradation of cement stabilized gravel base materials on the effect of mesoscopic structure within.(2)Study on freeze-thaw damage properties of cement stabilized gravel base materialFirst of all,the static pressure molding method of curing 28 d don't match in the form of a specimen at 0,5,10,15,20 times of freeze-thaw cycling test,and the compressive strength experiments respectively,the compressive modulus of resilience experiment,ultrasonic test,analysis of cement stabilized macadam specimen after freeze-thaw cycling test,the law of mass loss,strength loss law and the rule of the ultrasonic wave velocity loss.Secondly,acoustic emission technology was used to monitor the sound information of specimen compression failure after freeze-thaw cycle to obtain the trend of ringing count,cumulative energy,amplitude value and cumulative amplitude value changing with the relative stress level,and to find out the influence of freeze-thaw damage on the performance of cement-stabilized gravel base material.