Study On The Damage Of Pavement Cement Concrete Under The Interactive Effect Of Traffic Load And Freeze-thaw Environment In Seasonal Frozen Region

Cement concrete pavement has the advantages of high bearing capacity,long service life and green environmental protection,it is widely used in highway traffic construction in China.However,in the actual working environment,the cement concrete pavement is subjected to repeated traffic loads,at the same time suffered from frequent freeze-thaw cycles.Under the effect of traffic load and freeze-thaw cycle,the pavement concrete structure is damaged and the performance is deteriorated in short term,caused the serious inadequacy of cement pavement durability.For the problem of insufficient durability of pavement concrete in seasonal frozen region,this study based on the national natural science foundation,according to the typical damage environment of pavement in season frozen region,the macro performance attenuation and meso structure evolution of pavement concrete under the interaction of traffic load and freezing-thawing environment will be studied,and the damage mechanism of pavement concrete will be revealed,the results will lay the theoretical foundation for improving the durability of pavement concrete in season frozen region.Through the investigation of the traffic condition,climate environment and cement pavement disease in the seasonal frozen region,the interactive effect of traffic load and freeze-thaw cycle is determined as the typical damage environment of cement pavement.The four-stage damage test schemes of pavement concrete with the stress level of 0.5 and 0.8 is designed,which is composed of single-factor fatigue load effect,fatigue load and freeze-thaw cycles interactive effect.By testing the flexural strength and chloride diffusion coefficient of pavement concrete under the different effect,the deterioration laws of the macro mechanical properties and impermeability of pavement concrete were studied.The pore structure of pavement concrete were quantitatively characterized by mercury intrusion method,and the microstructure was observed qualitatively by scanning electron microscopy.Through analyzing change rules of six pore structure characteristic parameters,such as porosity,total pore area,average pore size,median pore size,pore size,pore spacing coefficient and pore size distribution under different test conditions,the damage evolution process of pavement concrete meso pore structure is studied.,and it is concluded that the pore evolution process can be divided into three stages: compaction,pore expansion and pore splitting.O n the basis of the above analysis,the correlation between macro properties and pore structure was analyzed by using grey correlation analysis method,and a mathematical relationship between macro performance attenuation and micro pore structure evolution was established.At the same time,the damage coefficient was defined by the chloride diffusion coefficient DRCM,through analyzing the damage effect of the interaction between load and freeze-thaw according to the damage coefficient,the damage mechanism of pavement concrete in seasonal region frozen under the practical application environment was put forward.Finally,the damage model of pavement concrete under the interactive effect of fatigue load and freeze-thaw cycle is established,and a damage model based on Weibull distribution is also discussed.The results of this study will fill the gaps about the study of pavement concrete damage caused by the traffic load and freeze-thaw environment in seasonal frozen region,and also can provide the theoretical basis for the durability design of pavement concrete.