| In order to recycle the old asphalt pavement materials,environmental protection cost savings,since the fifties the last century renewable technology and engineering application of asphalt has been a focus.After decades of development,the use of recycled materials was 15-40% during the construction of the highway;while in some low-grade road base and the underlying layer,regrind usage reaches 50-100%.Obviously,how to more greatly improve the old material utilization resulting in costs reduction is one of the core issues of the asphalt recycling.This submitted dissert focuses on the regeneration of asphalt mixture using cold recycling techniques.Researches on old asphalt emulsion technology and performance evaluation of dissolved ability were carried out in order to improve the utilization of renewable materials,recycled mixtures without sacrificing their road performances.This dissert was sponsored by the fund of Guangzhou science and technology projects.Firstly,performance testing was conducted on recycled typical asphalt concrete materials in Guangzhou city,and then old asphalt was reclaimed using ABSON method.The national standard indicators of aging asphalt,such as penetration grade,ductility,softening point and viscosity and the rheological properties based on SHARP projects including multi-stress creep were evaluated.Completed penetration,ductility,softening point and viscosity test of the recycled asphalt binder,as well as the aging of the asphalt main curve and multi-stress repeat creep and so on.Results show that the old asphalt became hard and sticky,the overall stiffness modulus and the softening point became large,the extension of the penetration slightly.The complex shear modulus of the aged asphalt is several times larger than that of the unaged asphalt binder.At the same time,the multi-stress repetitive creep test at different temperatures shows that the asphalt becomes harder,it is difficult to deform under small load and its deformation is difficult to recover.The recovery of asphalt from the aged asphalt was increased from 14 to 65 when the amount of regenerant in the recovered asphalt was increased.With the increase of the regenerant,the variability of the test data was reduced from 7% to 2%,and the ductility of the recovered old asphalt increased from 11 to 95.With the increase of the regenerant,the variability of the penetration data became smaller and the softening point of recycled asphalt binder gradually decreases from 59 to 48 which indicates that 1-2% of the regeneration agent will recover different basic properties of asphalt restored to the new bitumen level.The rheological and repeated creep tests of aged asphalt were carried out.The complex shear modulus of aged asphalt at low frequency was higher than that of unaged asphalt by 10 times to 100 times according to main curve.The phase angle decreased with the increase of frequency.Lastly,this dissert proposed a new dissolved emulsifying regeneration method which could reject the utilization of new asphalt usually adopted in traditional methods.According to the cold recycled asphalt pavement method,the new asphalt is removed from the additive,the regenerant,the modifier and the emulsifier are added and the four cold recycled asphalt mixes are designed.They are excellent in volume index and have a splitting strength of more than 2 times that of the specification.The freeze-thaw and Marshall stability are greater than 5% to 10% of the specification and are excellent in water resistance and fatigue resistance.At the same time,the stability of the mixture reached 3300 times per mm higher than the general new mixture,fatigue performance close to the new mixture before regeneration.The cold reclaimed mixture used in this study can be used in upper surface and surface treatment of the level one and two roadway and the secondary roads of the city.And it can be used for the local cold regeneration and the plant cooling.The highway and the city main road can be carefully promoted after investigation and research. |
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