Research On The Key Technologies For Application Of Rubber Asphalt And Its Mixture In Severe Cold Region

The northern severe cold region has the characteristics of large temperature difference,long winter temperature,large amount of rain and snow,and the remarkable phenomenon of freezing thawing cycles.Low temperature cracks become the main structural failure form in asphalt surface,the traditional modified asphalt and its mixture can not meet the performance requirements under the special usage environment.The coarse particle rubber asphalt produced by 30 mesh rubber from waste tyre has the advantages of low temperature crack resistance and excellent moisture resistance,which can not only prevent the early damage of asphalt pavement,but also avoid or reduce the low temperature cracks.However,the current research on coarse particle rubber asphalt used in cold region is almost blank.The evaluation index,production equipment,production process,process quality control and coarse particle rubber asphalt mixture composition design remain to be further researched.Directed against the environmental characteristics and low temperature performance requirements in the severe cold region,the coarse particle rubber asphalt evaluation indexes,which are composed of 180℃Haake viscosity,softening point,25℃cone、25℃springback recovery and 5℃ stretching flexibility,the permitted variation ranges of the corresponding indexes,the test instruments and the test methods are put forward.Based on the rubber powder production process and mechanism of rubber asphalt,the test results are comparative analyzed by using five rubber asphalt and sixteen rubber powder in five kinds of powder content,which verifie the applicability of the evaluation system.The influence rules of the rubber powder content,processing technology and developing temperature and time on the rubber asphalt performance are studied.The optimum formula and production parameters of the coarse granular rubber asphalt are obtained.Based on the grey correlation theory,the influence of different factors on the rubber asphalt indicators is analyzed,and the results obtained is consistent with indoor test,which verifies the applicability of evaluation index to the performance of coarse particle rubber asphalt.It provides theoretical basis for the rubber asphalt production quality control.The specification composition and quality control requirements of rubber asphalt equipment in the severe cold region are put forward.The rapid heating demand is met by improving the original matrix asphalt heating system,and the heat transfer model between the inlet temperature and velocity of the conductive oil and the outlet temperature of matrix asphalt is established.Based on the gray GM(1,1)and the CARIMA algorithm,the associated control online prediction model between the rubber powder and the matrix asphalt is established.The measurement deviation of rubber powder is reduced from 2.3% to 0.22%,which ensures the accuracy of mixing ratio.Based on the standard k-epsilon turbulence model,the solid-liquid two-phase flow numerical simulation of the mixing process in the stirring tank is executed.The influence rules of the parameters of the stirring tank on the distribution uniformity are obtained,and the better production parameters,which include blade diameter 800 mm,blade position 630~900mm,blade width 100 mm,and rotational speed 240~300 r/min,are acquired.It meets the technical requirements of rubber asphalt equipment in the severe cold region.In view of the existing defects of rubber asphalt performance detection,the relationship model between rubber asphalt production data and rubber asphalt production quality is established by the HOPLS algorithm.The key production parameters of rubber asphalt are monitored.The simulation analysis and test verification show that the performance indexes of rubber asphalt are relatively stable after monitoring,and they are basically consistent with the values in laboratory.Large amounts of data collected is statistically analyzed,and the dynamic quality control scope of the key parameters is obtained,which establishes the basis for the quality control of the rubber asphalt production process and improving the rubber asphalt performance.Aiming at the special application environment of the cold region,the technical performance requirements of the AR-AC-13 coarse rubber asphalt mixture are proposed.The influence of key sieve hole pass rate and oil film thickness on volume index and low temperture performance of rubber asphalt mixture is studied.Based on the different algorithms,the regression model of oil film thickness and asphalt dosage is established,and the suitable range of the oil film thickness of rubber asphalt mixture is 19~21μm in the cold region.The influence rule of the different Marshall specimen forming conditions and different aggregate gradations on the performance of rubber asphalt mixture is obtained,and the adaptability of the AR-AC-13 coarse rubber asphalt mixture to the low temperature performance in the severe cold region is verified.The production parameters of the mixture are gained.Based on Zhangcheng expressway maintenance project,the key technology of construction and quality control method of AR-AC-13 rubber asphalt mixture in the severe cold region is put forward.The adaptability of the coarse particle rubber asphalt and its mixture to the special use environment in the severe cold region is verified.After the freeze-thaw cycle,the physical engineering observations shows that the low temperature crack frequency is at least 25% lower than the traditional modified asphalt.The construction cost of the coarse particles rubber asphalt mixture is greatly reduced than that of the SBS modified asphalt SMA-13 mixture.The results of this paper provide theoretical support for the application of the coarse particles rubber asphalt and its mixture in the severe cold region,and also have reference significance for the quality control of other modified asphalt.