Study On The Key Technology Of Thermal Regeneration Of Old Asphalt Mixture In Cold Area

China’s highway construction has shifted from a simple large-scale construction to a stage of equal emphasis on new construction and maintenance.The reuse of waste asphalt mixture has become a problem that every province and region must face and solve.Therefore,how to make better use of the waste asphalt mixture to make it play a greater role is an important issue for the maintenance and renovation of old roads.Developed provinces have done a lot of research in the field of thermal regeneration;for the relatively lagging development of Inner Mongolia in the severe winter,the experience of other places cannot be copied due to its special climate.Therefore,relying on the reconstruction and upgrading project of the first-class highway from Nierji to tengke of Hulunbuir National Highway 111,this paper makes a systematic study on the hot recycled asphalt mixture,in order to provide theoretical basis and guidance for the research and application of the hot recycled asphalt mixture in the cold area.This article first addresses the problem of large variability in recycled asphalt and aggregates.The RAP variability is well controlled by pre-processing the RAP and dividing the RAP into three grades of reference material,and using an extraction-microporous membrane vacuum filtration-distillation device.Second,the specific test method for the four-component analysis of asphalt by solid phase extraction was explored and determined.Then,fourcomponent and structural analysis of asphalt with different aging pathways were performed by solid phase extraction combined with ultraviolet spectroscopy and infrared spectroscopy.It was found that during the aging process of asphalt,oxidation reactions mainly occurred,the saturation content decreased,the aromatic content was converted into gum,and the gum was transformed into asphaltene,and polar functional groups such as carbonyl group and sulfoxide group were formed.Thirdly,according to the characteristics of cold area,the asphalt regenerator was developed.The performance of the regenerator and the regeneration performance of different recycled asphalt were studied through experiments.The results show that the developed regenerator can not only recover the performance of aging asphalt,but also the 10 ℃ ductility index is far better than raw asphalt,so it has good applicability to cold areas.A qualitative and quantitative analysis of the regeneration mechanism of the developed regenerant was performed by solid-phase extraction-ultraviolet spectroscopy and infrared spectroscopy.A certain dissolution reaction occurred between them,dispersing and dissolving the asphaltene molecular groups in the aged asphalt,and reducing the carbonyl and sulfoxide groups to a certain extent.Fourth,the target mix ratio design and road performance tests were carried out on the recycled asphalt mixtures with different RAP contents.The tests showed that the recycled asphalt mixtures with regenerant had good road performance.Finally,according to the climatic characteristics of cold regions,the applicability of recycled asphalt mixtures was studied,and the low-temperature crack resistance and freeze-thaw cycle resistance before and after longterm aging were proposed as the key control indicators of recycled asphalt mixtures in cold regions.