Investigating The Evolutionary Behavior Of Volatile Organic Compound Emissions From Road Asphalt

During the construction and service life of asphalt pavements,volatile organic compounds(VOCs)are emitted into the surrounding environment.However,the current understanding of the evolution of asphalt VOCs release behavior is inadequate.Firstly,the concentration of asphalt VOCs released is a complex mass transfer process,and there is a lack of research on the release model of asphalt VOCs concentration,leading to an absence of a scientific basis for predicting and controlling the release of asphalt VOCs concentration.Secondly,existing studies primarily focus on the release characteristics of VOCs components from newly built asphalt pavements,neglecting the influence of aging,regeneration,and other factors on the release characteristics of asphalt VOCs components.Furthermore,the unclear evolution characteristics of VOCs environmental hazards and health risks under different aging conditions have resulted in an unclear priority for controlling pollutants.To address these issues,research on the evolution of asphalt VOCs release behavior will be pursued from four aspects.The main research activities are as follows:(1)Rapid quantification of indoor asphalt VOCs concentration was achieved by developing an in-situ quantification device.Furthermore,the release characteristics of asphalt VOCs concentration under different influencing factors and its performance change trends were examined,and the experimental boundary conditions for quantifying asphalt VOCs concentration were established.Subsequently,an analytical solution for the asphalt VOCs concentration release model was derived based on Fick’s second law of diffusion.Concurrently,the in-situ quantification device was used to clarify the release characteristics of asphalt VOCs concentration at different times,enabling the inverse calculation of key parameters of the VOCs concentration release model and verification of the model’s reliability.Building upon the aforementioned research,a precise representation of the evolution of asphalt VOCs release concentration over time was achieved.(2)Dynamic headspace gas chromatography-mass spectrometry(HS-GC-MS)was utilized to elucidate the characteristics of asphalt VOCs emissions under different aging conditions.The findings revealed that the emissions of asphalt VOCs were significantly influenced by aging,and distinct aging methods exerted varying effects on their emission characteristics.Additionally,Pearson correlation analysis was employed to investigate the relationship between the emissions characteristics of VOCs during asphalt aging and their physicochemical properties,thereby providing a deeper understanding of the evolution mechanism of asphalt VOCs emissions from a physicochemical perspective.Furthermore,the study uncovered the emission characteristics of asphalt VOCs under different heating temperatures,offering insights into the construction temperatures during the regeneration of waste asphalt pavements with the aim of reducing VOCs emissions.(3)Three typical rejuvenators were selected as examples and utilized for regenerating aged asphalt.Through indoor experiments,an investigation was conducted on the rheological properties and VOC components characteristics of the regenerated asphalt.The findings revealed substantial differences in rheological properties and VOCs emission characteristics among the various regenerated asphalts.On one hand,distinct rheological properties were observed in the regenerated asphalts compared to the aged asphalt,with each exhibiting unique properties when restored to the characteristics of virgin asphalt.On the other hand,the number of VOCs components and their peak areas increased following the regeneration of aged asphalt.Recognizing the inadequacy of a single evaluation criterion for a comprehensive assessment of the rejuvenator’s performance,this paper considers the rheological properties and the VOCs emission characteristics of the regenerated asphalt to propose an evaluation indicator for the rejuvenator’s performance.(4)The study employed ozone formation potential(OFP),secondary organic aerosol formation potential(SOAFP),and carcinogenic and non-carcinogenic risk models to quantify the environmental and health risk evolution characteristics of asphalt VOCs components under different aging conditions,and identified the priority control components of asphalt VOCs.The findings indicate that the environmental and health risks of asphalt VOCs are jointly influenced by asphalt type and aging process.Following aging,the environmental risk of VOCs components in asphalt generally exhibits a decreasing trend,with different aging asphalt VOCs components contributing differentially to environmental risk.Analysis of the priority control components of asphalt VOCs components reveals certain similarities in the priority control components of VOCs in different asphalt types.To further mitigate the environmental and health risks of asphalt VOCs components,priority should be given to controlling high-carbon alkanes(such as nonane,decane,undecane),aromatic compounds(such as 1,2,3-trimethylbenzene,1,2,4,5-tetramethylbenzene,),nonanal and decanal.In conclusion,the study elucidated the evolution rule of environmental and health risks of asphalt VOCs components under aging conditions.