Mechanical Properties And Microstructure Analysis Of AC-25 Asphalt Mixture Based On Vibration Forming Method

With the development of transportation in our country,the requirements for road loading capacity have also increased.But the traditional Marshall Compaction method has been proved unable to guide constructions of heavy traffic asphalt pavement in many investigation and research.Some studies demonstrate that gyratory compaction test can match actual road conditions,however,the compaction method can not be widely used for its high cost and technology issues.The vertical vibration forming method is based on the principle of simulating road vibrating compaction,and the cost is less than that of gyratory compaction,which can be tried to guide constructions.At present,there are no exact specification used in the guidance on construction methods and design standards for vibration molding.While,AC-25 asphalt mixture was the subject in this paper.The macro-mechanical properties and mesoscopic internal structure of the VVTM and Marshall molding mixtures were compared and linked.Combined with the actual engineering,the design standards and mineral aggregate gradation of the AC-25 were studied,which can provide reference and basis for indoor molding methods of AC-25 mixture and related engineering design specifications.The main research contents and results are summarized in the following:From macroscopic,this paper firstly studied the volume parameters and mechanical properties of the AC-25 asphalt mixtures by Marshall method and VVTM under different compaction effort and asphalt-aggregate ratio.The results show that the asphalt-aggregate ratio 3.8% of VVTM is smaller than the Marshall methods' 4.1% corresponding to their own peak mechanical performance,and the mechanical strength of VVTM-AC25 mixture increase on average by 14.25% compared to Marshall method under the same compaction work.Then,divide the mixture into three parts: coarse aggregate,fine aggregate and asphalt mortar to optimize the mixture gradation.Finally,based on the AC-25 mixture mechanical performance optimization,an attempt was made to put forward construction methods anddesign standards for mixture vibration molding by fitting the relationship between volume parameters and mechanical properties.On the mesoscopic research,industrial CT was utilized to scan asphalt mixture in this paper.The 3-d reconstruction software VG Studio MAX 2.2 was used to analyze the difference between the calculated void ratio and the measured void ratio,as well as the void pore distribution,horizontal and vertical distribution of the specimen with different molding methods or core samples.Then,study the contact numbers of aggregates and the contact point distribution of the specimen and core samples.Comparing the compaction state and the influence on the gradation change of the indoor test and the actual road surface,it showed that the 60 s vibration molding specimen is the closest to the core samples.Finally,the correlation between mesoscopic structure of AC-25 mixture and its mechanical properties were studied.Build and detect the test road on the Fu Yu connecting line belonging to the Yu Song Expressway.The 60 s vibration molding method was used to control the AC-25 mixture production quality as a guideline.Study and record the test road construction process.The high temperature properties,low temperature performance and water stability of the specimen that were made from the mixture at the construction site and the core samples was compared.The results demonstrate that the 60 s vibration molding method can match the construction of AC-25 mixture in the test road well.