Optimum Design And Performance Test Of Cement Stabilized Macadam Base In Seasonal Frozen Region

Cement stabilized macadam base is widely used in road construction in seasonal frozen region in China because of its high strength,good water stability and good integrity.However,cement-stabilized macadam is easy to crack in application and has low early strength,which results in the decline of road performance and service life.As a typical representative of seasonal frozen region,northeast China has the characteristics of large temperature difference between morning and evening,early freezing but late thawing,long cold time and short warm period in a year.The strength of cement stabilized macadam base decreases after several freeze-thaw cycles,and the semi-rigid base is sensitive to the changes of temperature and humidity.It is easy to produce temperature shrinkage and drying shrinkage strain,which results in cracks in the base,which significantly reduces the strength and durability of the base.The reflection of cracks on the base to the asphalt surface causes crack damage to the asphalt pavement,which will reduce the overall performance of the road and reduce the road.Service life.This paper relies on the transportation science and technology project of Jilin Province,based on the systematic indoor test,literature review and field investigation,this paper studies the gradation selection,performance characteristics and dynamic and static modulus of cement stabilized macadam base.The main research work carried out in this paper is as follows:Firstly,the raw materials used in the test are tested to ensure that their performance meets the requirements.On this basis,combined with the climate characteristics of northeast cold region,a large number of performance tests of cement stabilized macadam materials with different gradations are carried out,including unconfined compressive strength test,dry shrinkage test,temperature shrinkage test,freeze-thaw test and static resilience modulus test.The effects of gradation type,age,water loss rate,content of gravel with key particle sizes and temperature on the strength,crack resistance and frost resistance of cement stabilized macadam base are obtained.Based on the analysis of the experimental data,a strength growth model with age was established,and the ratio of 4.75/13.2 to the pass rate of two key particle sizes was proposed.In this paper,the influence of this index on the strength of cement stabilized macadam base is analyzed,and the influence law of different gradation on crack resistance is given.At the same time,the application of comprehensive fuzzy analysis method to gradation optimization is proposed,the gradation range of cement stabilized macadam base in seasonal frozen zone is proposed.Secondly,the optimum gradation is used as the experimental gradation to determine the strength,crack resistance,freezing resistance and the range of design parameters of cement stabilized macadam materials under different cement dosages.The influence law of cement dosage on the properties of cement stabilized macadam material is obtained.The relationship between the maximum dry density and the optimum moisture content and the cement dosage is given.The functional relationship between compressive strength,splitting strength,flexural strength,maximum shrinkage strain,static modulus and cement dosage,the relationship between 7d compressive strength and 90 d flexural strength and 90 d splitting strength,and the relationship between 90 d dynamic and static modulus are established respectively.On this basis,the strength and crack resistance of cement stabilized macadam base are comprehensively considered,the optimum cement dosage for Northeast seasonal frozen zone is obtained.This paper provides a theoretical basis for road construction in the northeast seasonal frozen region.Finally,the optimum gradation of cement stabilized macadam is designed under the optimum cement dosage,the mixing proportion of aggregate is given,the recommended range of each performance index during construction of cement stabilized macadam base is suggested,the construction delay time is determined,the full thickness construction method of cement stabilized macadam base for road in seasonal frozen zone is recommended,and the implementation method is put forward.The key links of construction and the indexes to be controlled in construction provide reference for the construction of cement stabilized macadam base.