Study On Mechanism And Technical Performance Of Crumb Rubber Modified Asphalt By Cracking-polymerizing

The waste tire rubber powdering is widely used in pavement engineering,which not only could solve the problem of waste tires,and also satisfy the requirementson pavement of modern highway transportation.This paper adopted the methods of theory,experiment and statistics analysis to explore and research the characteristic,production equipment and technology of rubber modified asphalt by cracking-polymerizing and its mixture,in order to provide the correct direction for the scientific production and use of rubbermodified asphalt over lapping,and corresponding reference to ensure the pavement performance and the project quality of rubber modified asphalt over lapping.The new rubber particles was produced by adding appropriate amount of cracking agent in rubber powder(0.3-0.45mm)and cracking granulation,which is less dust,easy mixing.The viscosity of rubber modified asphalt can be reduced by adding polymeric modifier in the production process.Through the polymerization,the partially cracked rubber particles forms a partially cross-linked structure in the asphalt,which can obviously improve the asphalt high temperature,low temperature performance,fatigue resistance and durability.Through the analysis of the influence of the shear rate,temperature,time and of powder content on the technical performance of crumb rubber modified asphalt by crackingpolymerizing.The results show that lower the shear temperature,and the greater the viscosity of rubber modified asphalt,and rubber powder is not easily dispersed in asphalt;high shear temperature can easily lead to asphalt aging,thus affecting the performance of asphalt;smaller the shear rate,more slowly powder particle refining,and it is not easy to form stable crumb rubber modified asphalt system;shorter the shear time,less dispersion effect of powder.Powder is easily degradation because of the long shear time,thereby reducing the using performance of asphalt.The processing technology of rubber particles modified asphalt by cracking-polymerizing was determined: firstly,the matrix asphalt is heated to 165?,then adding cracking rubber particles and the polymeric modifier,and shearing and heating to 185 ?,and shearing by the rate of 4500r/min about 60 min.Through the conventional test,Brookfield viscosity test,DSR and BBR test,the binder performance of different crumb rubber modified asphalt by cracking-polymerizing was evaluated,and the effect of cracking,polymerization modifier on the properties of rubber modified asphalt and the modification process was analyzed.The results indicate that with the increasing of the content of cracking rubber particles,the viscosity,penetration,softening point,ductility and elastic recovery of crumb rubber modified asphalt by cracking-polymerizing increased,and 20% rubber are added into the asphalt,and its comprehensive performance is the best.The performance at the high temperature of crumb rubber modified asphalt by cracking-polymerizing is up to PG76 in accordance with the requirements of SHRP grade,which has better high temperature stability.The viscosity of rubber particles modified asphalt by cracking-polymerizing has little difference with SBS modified asphalt.Compared with ordinary rubber modified asphalt and SBS modified asphalt,the comprehensive properties of crumb rubber modified asphalt by cracking-polymerizing is better.Through infrared absorption spectroscopy,differential scanning calorimetry and scanning electron microscope,the modified mechanism of crumb rubber modified asphalt by cracking-polymerizing was analyzed.The results showed that the rubber powder has obvious swelling phenomenon in asphalt,and after the process of cracking-polymerizing,and rubber powder is more evenly distributed in asphalt.What's more,the endothermic peak area of DSC curve is reduced,and the temperature sensitivity of asphalt is further improved.The chemical reactions produces in asphalt and rubber powder,which shows that compatibility between asphalt and rubber powder is better.Based on the comparative analysis of mix design of rubber modified asphalt mixtureat home and abroad,and mix design and road performance dense gradation(AC-16)and the gap gradation(ARHM-16)rubber modified asphalt mixture by cracking-polymerizing were studied respectively by dry-mixing method and wet-mixing method,and compared with SBS and common rubber modified asphalt mixture,it was concluded that the gap gradation was more suitable for mix design of rubber modified asphalt mixture,which fully reflected the elastic properties and anti-fatigue properties of rubber asphalt mixture.The high and low temperature performance,water stability performance of rubber modified asphalt mixture by cracking-polymerizing were more prominent,and the anti-fatigue performance was almost the same as SBS modified asphalt mixture.When using the dry process,the rubber particles included in the grading curve,which avoided interference effect between rubber particles and the aggregate,so the road performance was close to the wet process.Based on production equipment in the original SBS modified asphalt,production equipment of crumb rubber modified asphalt by cracking-polymerizing was transformed and upgraded.By laying in the batching tank wall surrounding heating pipe and cancel internal coil heating mode,rapid warming-up was achieved;The vortex mixing downwards and inwards forms by changing the form of the mixing blade into the arc blade,thereby making rubber particles adding more smoothly,and decreasing the stirring resistance,and reducing the energy consumption;Through setting the included angle between static millstones and moving millstones of colloid mill millstones to 90 degrees and setting the clearance of millstones adjusting,the characteristics of the grinding of crumb rubber modified asphalt by cracking-polymerizing with high viscosity were improved,and the crumb rubber modified asphalt by cracking-polymerizing was ground uniformly.The whole electrical system is optimized,and the automatic operation of the modified production equipment is realized.This paper made research on the construction equipment and technology of rubber modified asphalt mixtures by cracking-polymerizing combined with the test road in Gannan to the hills.Then it summarizes the construction control elements of pavement of crumb rubber modified asphalt by cracking-polymerizing.At last,the environmental impact analysis of rubber modified asphalt mixture by cracking-polymerizing and common asphalt mixture was analyzed and compared.The results shows that rubber modified asphalt mixture by cracking-polymerizing has more economic benefits in the whole life cycle.