Study On Durability Of High Modulus Asphalt Mixture Pavement

The durability of asphalt pavement is a common concern of road workers.Inorganic binder stabilized base asphalt pavement is one of the most typical pavement structures of Expressway in China.Its durability mainly focuses on permanent deformation and fatigue damage of asphalt mixture layer.As a new pavement material with high mechanical strength,good water stability,excellent permanent deformation resistance and fatigue resistance,high modulus asphalt mixture is widely used in road traffic construction at home and abroad.In this paper,high modulus asphalt mixture was prepared by adding PR-Module modifier,and its preparation process and pavement performance were studied through laboratory tests.Relying on the construction project of Fuji Expressway in Jiangxi Province,taking temperature and axle load as the key factors,and based on rheological theory,superposition principle and Palmgren-Miner criterion,the finite element numerical model is established.The permanent deformation prediction method of high modulus asphalt mixture pavement based on superposition principle and the service life prediction method of high modulus asphalt mixture pavement based on fatigue cumulative damage are proposed.The main research results and conclusions are summarized as follows:(1)The modification mechanism of high modulus additive PR-Module was analyzed.The mixing process parameters of PR-Module high modulus asphalt mixture are determined by Marshall test.The optimum dry mixing time is 20 s,the optimum wet mixing time is 180 s,the optimum indoor mixing time is 200 s,the optimum mixing temperature is 175℃,and the compaction temperature is controlled from 162℃ to 163℃.The optimum asphalt-aggregate ratio of high modulus asphalt mixture AC-20 and AC-25 in humid and hot environment is recommended.(2)PR-Module high modulus asphalt mixture has excellent strength and water stability.Considering the road performance and engineering economy,it is suggested that the PR-Module content should be 0.5%.The dynamic modulus principal curve of PR-Module high modulus asphalt mixture was established.The dynamic modulustemperature distribution curve of PR-Module high modulus asphalt mixture is proposed to provide data support for the durability prediction of high modulus asphalt pavement.(3)PR-Module high modulus asphalt mixture has excellent permanent deformation resistance.Based on the triaxial repeated load permanent deformation test,the basic relationship between the permanent strain of high modulus asphalt mixture under different temperature conditions,the number of loading repetition and the deviating stress is established.Based on the modified Burgers model,a modified viscoelastic model of high modulus asphalt mixture is established,and the fitting results are good.The constitutive equation of viscoelastic model parameters,temperature and deviation stress of high modulus asphalt mixture is constructed,which lays a foundation for solving the permanent strain of high modulus asphalt mixture under arbitrary temperature and load.(4)PR-Module high modulus asphalt mixture has good fatigue resistance.The higher the temperature or stress ratio,the greater the fatigue life growth rate of high modulus asphalt mixture than that of ordinary asphalt mixture.When the content of PR.M varies in the range of 0.3%-0.5%,the growth rate is 50%-380%.The stress and strain fatigue equations of PR-Module high modulus asphalt mixture at different test temperatures are established.The fitting effect is good,and the correlation coefficient is above 0.95.The fatigue life of HMAM-0.5-AC-25 asphalt mixture is 2-5 times that of HMAM-0-AC-25 asphalt mixture,which indicates that high modulus asphalt mixture is suitable for hot and humid environment.(5)Based on superposition principle and considering pavement stratification,temperature distribution and axle load classification,the permanent deformation prediction method of high modulus asphalt pavement is established.A calculation method of permanent deformation of inverse calculation of the number of cumulative superimposed loading repetition in the temperature range and A calculation method of the linear superposition of layered strains among the temperature intervals are presented.The distribution curves of asphalt pavement annual temperature distribution frequency and axle load grade distribution frequency and cumulative contribution rate of permanent deformation of asphalt mixture layer of asphalt pavement are established.Taking Fuji Expressway as an engineering example,the deviation stress distribution curve of asphalt mixture layer is established.Based on the measured rutting depth,the prediction of permanent deformation of Fuji high-speed asphalt pavement was revised.According to the inverse algorithm,the service life of ordinary asphalt pavement structure and high modulus asphalt pavement structure of Fuji Expressway are calculated to be 10 years and 16 years respectively.(6)Based on fatigue cumulative damage,a life prediction method of high modulus asphalt mixture pavement is established.Based on Palmgren-Miner criterion,the modified equation of Miner criterion and the calculation formula of fatigue cumulative damage degree of asphalt pavement structure are deduced.Taking fatigue cumulative damage degree as the evaluation index,the concrete calculation method of life prediction of high modulus asphalt mixture pavement based on fatigue cumulative damage is proposed.Taking Fuji Expressway as an engineering example,the fatigue cumulative damage life of ordinary asphalt mixture pavement is 11.5 years,and that of high modulus asphalt mixture pavement is 14.2 years,increasing by 23.4%.This shows that PR-Module has a significant effect on improving the fatigue life of asphalt pavement.