| With the rapid development of automobile industry,the annual production of waste tires in China exceeds 10 million tons,and is increasing at an annual rate about 10%.The chemical composition of waste tires is very complex,and the structure is relatively stable,so it is difficult to degrade.The environmental contamination turn out to be increased arising from the accumulation of waste tires.Using waste tires to prepare crumb rubber modified asphalt(CRMA)can not only reduce environmental pollution,but also effectively improve the road performance of asphalt pavement.Although the rubber asphalt pavement had been applied in China,the influence of waste tire components on asphalt performance was not systematically studied.This paper studied the influence of component of waste crumb rubber(CR)on the performance of asphalt.It is helpful to explore the interaction mechanism of rubber and asphalt,improve the performance of asphalt pavement effectively.And it is important to popularize the application of rubber asphalt pavement.In this study,three typical waste tires from bicycle(B),passenger-car(P)and truck(T)were collected and ground into the crumb rubber with three different particles sizes(40/60 mesh,60/80 mesh and 80/100 mesh)for the preparation of CRMA and the properties test of CRs.Two kinds of asphalt(SK-70 and SK-90)and 9 kinds of CRs were mixed respectively.18 kinds of CRMA samples were prepared by wet process for the performance test.The chemical composition,surface morphology,elemental content and thermal stability of different rubber samples were analyzed by thermogravimetry-mass,scanning electron microscope and energy disperse spectroscopy,respectively.The differences in properties of the waste rubber powder with different composition were investigated.And the effects of CRs with different components on the properties of asphalt were investigated.The results showed that the truck tires were mainly based on natural rubber,and its network structure was clearly visible.The sedative styrenebutadiene rubber was the mainstay of the passenger-car tires.Bicycle tire contained more butyl rubber,and the degree of vulcanization was the highest.The apparent viscosity of different asphalt samples was tested by Brookfield Viscometer.The dynamic shear composite modulus and phase angle of different asphalt samples were tested by dynamic shear rheometer frequency sweep test.After master curve was re-utilized by MHS model,the dynamic rheological properties of different asphalt samples were analyzed.The creep properties of different asphalt samples at low temperature were analyzed by a bending beam rheometer.The results showed that the dynamic shearing complex modulus of passenger car tire rubber modified asphalt was 7.6 times higher than that of the base asphalt,and the phase angle was 33% lower than that of the base asphalt at high temperature,so passenger car tire rubber modified asphalt had better resistance to rutting at high temperature and lower temperature sensitivity.The creep modulus of truck tire rubber modified asphalt was 73% lower than that of base asphalt at low temperature,and the creep rate was 30% higher than that of base asphalt,so truck tire rubber modified asphalt had better deformation ability and strong crack resistance at low temperature.The fatigue performance of each asphalt samples was analyzed by fatigue test using dynamic shear rheometer.The self-healing properties of each asphalt samples were studied by fatigue-healing test.The results indicated that truck tires contained more natural rubber powder,which could form a dense network structure in asphalt,and its modified asphalt had better fatigue resistance.The car tire rubber powder modified asphalt showed better self-healing performance,due to the good reswelling effect during the self-healing process.The content of sulfur elements in the bicycle tire rubber powder was 32% higher than that of car tire rubber powder,and 35% higher than that of the truck tire rubber.So its vulcanization degree was highest,as a result of the worst compatibility of the rubber powder with asphalt and the worst modification effect. |
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