Research On The Emission Behaviour And Inhibition Of Organic Emissions From Asphalt Materials

The use and service of asphalt materials,asphalt mixtures,and asphalt pavements not only produce greenhouse gases that contribute to global warming,but also result in the organic emissions.These organic emissions are at the forefront of atmospheric pollutants and play a significant role in the formation of ozone(O3)and secondary organic aerosols(SOA),which can lead to the frequent outbreaks of photochemical smog.This can have detrimental effects on the growth and development of plants and animals,threaten human health,and damage the ecological environment.To address these issues,a research project was carried out to investigate the emission behavior and inhibition of organic emissions from asphalt materials.The study being conducted is situated in the era of "carbon peak and carbon neutrality".It is grounded in the widely accepted social consensus that "green mountains and clear waters" hold equal value as "gold and silver".The research is aligned with the development concept of "green highways" and is being supported by the National Natural Science Foundation of China as well as the Natural Science Foundation of Chongqing.This study aimed to investigate the organic emissions of asphalt material and explore from four key aspects:composition analysis and quantitative evaluation,emission behavior and evolution law,emission mechanism and performance deterioration,as well as emission reduction mechanism and its effectiveness.The research aims to advance environmental protection and sustainable development by promoting the use of clean paving technologies for asphalt pavements.Ultimately,the research seeks to contribute to the goal of achieving green and sustainable development and " carbon peak and carbon neutrality ".The main research and findings of this study are as follows:(1)Composition analysis and quantitative evaluation.A method for qualitative analysis of organic emissions from asphalt materials was developed using headspace-gas chromatography-mass spectrometry(HS-GC-MS).The accuracy of the qualitative analysis was improved by utilizing the selective ion scanning method(SIM),retention time,qualitative and quantitative ions,and mass spectrometry comparison.This allowed for more precise identification and characterization of the organic compounds present in the emissions.Meanwhile,the discussion and analysis determined the typical organic emissions of asphalt materials and the characteristic emissions of crumb rubber modified asphalt.Then,based on the HS-GC-MS qualitative analysis method,a quantitative analysis method for organic emissions from asphalt materials was established using an internal standard method for standards,selective ion scanning method(SIM),and calibration curve.The accuracy,precision,and reliability of the HS-GC-MS test method for asphalt materials were evaluated through spiked recovery and substitution recovery tests.Finally,the organic emissions from base asphalt,SBS modified asphalt,and crumb rubber modified asphalt were quantitatively evaluated using the HS-GC-MS qualitative and quantitative analysis method.The results showed that the incorporation of styrene-butadiene-styrene(SBS)modifier resulted in a significant decrease in the overall emission concentration of diverse compounds.Specifically,the SBS modifier demonstrated an effective inhibitory effect on organic emissions.On the other hand,the introduction of crumb rubber caused a substantial increase in the emission levels of certain compounds.Specifically,the addition of crumb rubber resulted in a 12.68% increase in n-alkane compounds and a50.60% increase in polycyclic aromatic hydrocarbon(PAH)compounds.Moreover,the crumb rubber modified asphalt exhibited higher concentrations of characteristic emissions associated with the crumb rubber.(2)Short-term emission behavior and evolution laws.The HS-GC-MS analysis method was employed to study the short-term emission behavior of organic emissions from asphalt materials.The quantitative evaluation index used was the ratio of peak area of the target compound to the peak area of the internal standard reagent.The study analyzed the variation law of organic emissions from asphalt materials concerning the amount of asphalt samples,heating temperature,heating time,and stirring rate to reveal the emission evolution law.The analysis results indicated that the amount of asphalt sample significantly influences the concentration of organic emissions released from asphalt materials.Additionally,the emission of organic compounds from asphalt materials exhibits a temperature dependence.Furthermore,the heating time and stirring rate are critical factors that affect the concentration of organic emissions released from asphalt materials.That is,the amount of asphalt sample,heating temperature,heating time,and mixing rate all contribute to large differences in the emission concentrations of organic emissions from asphalt materials.Finally,based on the fundamental principle of the diffusion of gaseous substances,the emission behavior of organic emissions from asphalt materials with the amount of asphalt samples,heating temperature,heating time,stirring rate and other factors were successfully explained by using Fick’s law of gas diffusion,as well as the flux theory of gas at the gas-liquid interface and other relevant theories.(3)Long-term emission behavior and emission mechanism.The HS-GC-MS quantitative analysis method was used to investigate the emission regulation of organic emissions from asphalt materials before and after undergoing ultraviolet aging test(UV)and pressure aging vessel test(PAV).The results demonstrated that the concentration of organic emissions from asphalt materials significantly decreased after PAV aging,suggesting that asphalt pavements in service release a considerable amount of organic emissions.Additionally,the concentration of organic emissions from asphalt materials significantly reduced after UV aging,indicating that asphalt pavements in areas with high UV radiation also release a significant amount of organic emissions due to the impact of UV radiation.Then,the aging mechanism of asphalt materials was revealed by analyzing the effects of long-term emission behavior of organic emissions on asphalt composition and microscopic properties by Fourier transform infrared spectroscopy(FTIR)test,differential scanning calorimetry(DSC),and fluorescence microscopy(FM).Finally,the long-term emission behavior and emission mechanism of organic emissions from asphalt materials were analyzed and explained based on the aging mechanism of asphalt materials.Specifically,aging increases the emission probability of organic emissions from asphalt materials,resulting in higher emissions during the aging process.Therefore,the concentration of organic emissions detected after aging of asphalt materials is reduced.(4)Emission reduction effect and emission reduction mechanism.Firstly,the emission reduction agents for organic emissions from asphalt materials were selected through HS-GC-MS tests.The results indicated that the High-performance activated carbon powder had the most effective reduction effect for emissions,followed by expanded graphite.Secondly,the emission reduction effect of emission reduction agent modified asphalt was evaluated based on HS-GC-MS analysis.The results indicated that the best emission reduction effect was achieved by adding 4.5% SBS to the base asphalt,1% expanded graphite to SBS modified asphalt,and a composite emission reduction agent consisting of 1.5% SBS and 5% High-performance activated carbon powder to crumb rubber modified asphalt.Then,the engineering performance of the emission reduction agent modified asphalt was assessed using dynamic shear rheology test(DSR),DSC analysis,and surface free energy test(SFE).The results revealed that the SBS modifier significantly enhanced the high-temperature performance,moisture stability,low-temperature performance,compatibility,and thermal stability of the asphalt.Conversely,the emission reduction agents High-performance activated carbon powder and expanded graphite improved the high-temperature performance of the asphalt,but resulted in poor moisture stability,low-temperature performance,compatibility,and thermal stability of the asphalt.Subsequently,the composition and microscopic properties of the emission reduction agent modified asphalt were investigated with the help of FTIR and FM.The results indicated that the interaction between SBS modifier,crumb rubber,High-performance activated carbon powder,and expanded graphite with the asphalt was predominantly a physical reaction,and no significant chemical reactions were observed.Finally,the emission reduction effect and performance evaluation results were considered comprehensively and the emission reduction recommendations were provided accordingly.The results showed that for the base asphalt,the combination of4.5% SBS dosage exhibited the best emission reduction effect and performance improvement.In the case of SBS modified asphalt,the use of 0.15% expanded graphite or 1% High-performance activated carbon powder resulted in a good emission reduction effect with minimal damage to asphalt performance.For crumb rubber modified asphalt,the recommended options include using a composite emission reduction agent consisting of 1.5% SBS and 1% High-performance activated carbon powder or using 3%SBS dosage.