Research On Mechanical Properties And Mesoscopic Structure Of Cement Stabilized Macadam Material Based On Vibrating Compaction

Cement stabilized macadam base material is widely used in our national road construction,which has the feature of high early strength,fine water-stability and well antifreezing.However,with the development of highway construction technology,the traditional heavy compaction test and static pressure forming method have been proved unable to guide the indoor design and engineering application of cement stabilized macadam.An increasing number of scholars have launched on going effort to study the vibration test methods of cement stabilized macadam,having accumulated abundant research results and rich engineering practice experience.At present,there are still no clear specifications for mixture design standards and construction guidelines that can be promoted in the whole country.In this paper,combined with the engineering construction in Jilin Province,the research and application of cement stabilized macadam vibration method were carried out,which is of great significance to improve bearing capacity of road bases,reduce shrinkage cracking decrease and promote the vibration test methods.In the meantime,both the static pressure test and the vibration methods guide the design and engineering construction of mixture by macro test and analysis.With the continuous penetration and application of X-Ray CT and digital image processing technologies in road engineering,digging for the meso-structure information of the mixture,and exploring the correlation between the meso-structure and the macro properties have become the hotspot and frontier.In view of the above two problems,the laboratory vibration test method of cement stabilized macadam mixture is researched in this paper,while the microstructure differences are explored by industrial CT scanning and digital image processing technologies.The main research contents and results are summarized in the following:Firstly,according to previous research,analyze the compaction mechanism of cement stabilized macadam base material and construction field compaction characteristics of the base course,and determine the indoor vibration test method and the operating parameters of the vertical vibro-compression testing equipment.On the basis of gradual filling theory and the Interference Theory,a skeleton dense gradation with good skeleton-compact structure was proposed by the vibration molding test.This paper compared and analyzed the difference between the vibration compaction test and the heavy compaction test.The increasing rule and the factors of mechanical strength of cement stabilized macadam base material under two molding conditions(vibration and static pressure compaction).The variation rule of mechanical property of GM-mixture specimen using VVTM under different freeze-thaw cycles were studied and analyzed,attempting to measure the measures' frost resistance.Secondly,the X-Ray CT was utilized to scan the cement stabilized macadam including vibration test piece,static pressure test piece and pavement core samples.Combined with digital image processing technology to process and analyze the scanned image,the three-dimensional void ratio of the mixture was obtained.Through the analysis and description of the internal void distribution characteristics of the mixture and the skeleton characteristics of the coarse aggregate,it shows that the void distribution characteristics of the VVTM specimen are closer to the pavement core which are both more uniform;the uniformity of the static pressure specimen is the worst;meanwhile,as the vibration time increases,the contact degree of the coarse aggregate inside the mixture increases,the coarse aggregate changes to a small deflection angle,and the overall arrangement tends to be uniform.At last,based on the experiment section built,key parts and control points of cement stabilized macadam base construction under the guidance of vibration test method were studied.The relevant detection results demonstrate that the vibration compaction test is more reasonable to calculate the base compactness;the compressive strength and cleavage strength of the VVTM specimen and the pavement core are close to each other,which are larger than those of the indoor static pressure specimen.The reliability and accuracy of the actual mechanical properties of the field base simulated by the vibration test have been verified.