Research On Material Composition Design Of Highway Cement Stabilized Macadam Base Based On Crack Resistance

At present,the cement stabilized macadam base is the bearing layer of asphaltpavement structure in most of China’s expressways.But in the actual use of cementstabilized macadam base,there are still some shortcomings,such as easy cracking,surface erosion and so on.A lot of traffic survey,can not meet the design life of service life of highway in our country,especially in some heavy traffic road,some highway project after paving effect is not ideal,on the base of the cement stable macadam base material composition design is not perfect,just the way by strengthening paving compaction makes the compaction degree of super best,change the original gradation by rolling over,skeleton structure are also damaged,there is still a early cracks in the process of keeping in good health.The crack resistance of cement stabilized macadam base mainly depends on how to design the base material with good skeleton stability and crack resistance.Based on the existing research base,the graded optimization,the different molding methods,design factors impact on the performance of the mixture,study crack resistance on the base of the cement stable macadam mixture ratio design method,grading of mesoscopic structure skeleton evaluation,the influence of the vibration molding against cracking resistance,the compaction method to the effect of mixture and crack resistance of cement stabilized macadam road base shrinkage performance research.The research results are as follows:(1)In terms of graded optimization,this paper establishes the three typical discrete element model of grading,the numerical simulation of cyclic loading with different loading plate test,track and monitor the mixture chain internal contact stress.the force distribution and stress transfer figure such as monitoring project,analysis the load in the process of three kinds of gradation mesoscopic structure mechanics response patterns.By putting forward the stress transfer rate,the stress distribution rate of the main skeleton and the variation coefficient of the stress distribution inside the mixture,it is concluded that the skeleton structure effect of the skeleton void structure and the skeleton dense structure grading group is better than that of the suspended dense structure.(2)the gradation design USES the coarse aggregate gradation blending method,fine aggregate gradation design,I determine the classification of blending vibrated income ZD-1 grading test group and other 13 different mixing ratio of the crack resistance of cement stabilized macadam mixture gradation,and through the discrete element numerical simulation to evaluate skeletal structure does not match at the same level,recommend the size distribution of the four groups of JS-5,7,9,zd-1 can be used as a grading optimization design the crack resistance of cement stabilized gravel base.Based on above analysis results,the design gradation in this paper was obtained,and through 7d unconfined compressive strength,the cement dose of the design gradation was finally determined to be 4%.(3)In the aspect of laboratory test,the influence of different molding methods on the performance of the mixture was explored.Combined with the literature,the principle of vibration forming is synthetical analyzed,and the disadvantages of heavy compaction method in practical engineering are expounded.The mechanical properties and shrinkage properties of the mixture were compared by different compaction methods and different molding methods.The results show that the change of particle size distribution caused by heavy compaction is higher than that caused by vibration compaction,which is 2.4 times of the crushing degree of vibration compaction.The test results of unconfined compressive strength and splitting strength of vibration forming specimens are 1.14 times and 1.53 times of those of static forming specimens.Compared with static compression molding,the dry shrinkage strain of vibration molding decreased by 8%,and the average dry shrinkage coefficient of vibration molding decreased by 18.5% in the first 7 days of test monitoring,indicating that the vibration molding method can effectively reduce the dry shrinkage of the mixture in the early stage.(4)Taking different cement dosages,gradations and ages as the research elements,a series of laboratory tests were conducted on cement stabilized macadam mixture specimens to comprehensively analyze the changing rules of mechanical properties and shrinkage properties with the increase of cement dosages and ages.Finally,by analyzing the mechanism of dry shrinkage and temperature shrinkage,the evaluation method of crack resistance was put forward.The experimental results show that the design gradation is superior to the specification gradation in every performance.