Study On The Design And Performance Of Foam Asphalt Mixture With Recycled Concrete Aggregate

At present,with the gradual improvement of the national highway network,a large number of road maintenance projects will produce huge amount of old road materials.Therefore,how to recycle old road materials and carry out the "green highways maintenance" become one of the research hotspots.Besides,there is often the phenomenon of long-distance transportation and even shortage of natural sandstone due to the need of engineering construction in the developed areas of our country.At the same time,more and more construction waste is produced in developed areas because of the rapid expansion and expansion of buildings.So the disposal of construction waste has become one of the problems in big cities.The recycled aggregates from broken construction waste can be used in paving of road bed,road base and subsurface layer,which include construction and demolition waste,recycled road materials,scrap ceramics,etc..This way can not only alleviate the problem of environmental pollution caused by the disposal of construction waste,but also solve the problem of lack of natural sand in some areas,especially for large cities with no natural sand,and areas requiring long-distance transportation.Considering that there is no research on the application of recycled aggregate in foamed asphalt mixture in China,and the existing methods of recycled aggregate utilization are faulty,this paper focuses on the utilization of recycled aggregate in foamed asphalt mixture.Firstly,three kinds of asphalt were used for foaming test,and the results show that the temperature of foaming and the water consumption of foaming were significant to the effect of asphalt foaming.In practice engineering,foaming test should be carried out.The best foaming conditions of asphalt should be determined according to the results of foaming test of alternative asphalt.Secondly,the mixture ratio of recycled aggregate foam asphalt mixture was studied.The results show that due to the low density of regenerated aggregate and strong absorption,the maximum dry density decreases with the increase of the amount of regenerated aggregates,but the optimal water content of the mixture increases with the increase of the amount ofregenerated aggregate.And the optimum asphalt content of foamed bituminous mixture increases with the increase of the amount of regenerated coarse aggregate.The addition of recycled fine aggregate will further increase the optimum asphalt content.Thirdly,the properties of regenerated aggregate foam asphalt mixture are studied further.The test results show that,under the optimum asphalt content,the properties of different recycled aggregates content mixture are excellent,such as tensile,compressive,water stable and high stability,which basically meet the use requirements of surface layer materials(except 100% aggregates content mixture).Fourthly,by using the method of single factor variable,the effect of different factors on Indirect Tensile Stress(ITS)and dry wet Indirect Tensile Stress Ratio(TSR)of foamed asphalt mixture are studied.The test results show that,the internal factors determines the final strength level of the mixture which include mineral aggregate gradation,dosage of recycled aggregate,cement and asphalt,asphalt grade,mixing water and the dosage of red brick.And external factors affect the strength formation process of the mixture and have a certain effect on the max Indirect Tensile Stress which include curing time,curing temperature and compactness.The research results provide the experimental data support for optimal design of regenerated aggregate foam asphalt mixture.