Asphalt fumes released at high temperatures significantly impact human health and the natural environment. This study systematically investigated the microstructure and compositional characteristics of tea stalk biochar (TB) from pyrolysis at different temperatures (300℃, 400℃, 500℃, and 600℃) and its adsorption capacity for asphalt fumes. Scanning electron microscopy and Brunauer-Emmett-Teller analysis indicated that increasing pyrolysis temperatures enhanced the porosity and BET surface area of TB, transitioning its structure from dense and low-porosity to highly porous. Fourier-transform infrared spectroscopy and elemental analysis revealed that higher temperatures promoted biochar graphitization, reduced oxygen-containing functional groups, and increased hydrophobicity and aromaticity. Analysis of asphalt fumes demonstrated that adding 1 % TB significantly reduced asphalt fume emissions, including VOCs, H₂S, SO₂, and NOₓ. TB prepared at 500℃ (500TB) exhibited optimal adsorption, reducing VOCs by 68.6 % and H₂S by 87.5 %. GC-MS analysis further revealed that 1 % 500TB reduced aliphatic hydrocarbons, aromatic compounds, oxygen-containing compounds, and sulfur-containing compounds in asphalt VOCs by 63 %, 69 %, 67.2 %, and 63.3 %, respectively. The superior adsorption performance of 500TB was attributed to its larger surface area, diverse mesoporous structure, and high aromatic carbon content, enhancing its affinity for pollutants. Physical tests indicated that biochar enhances the thermal stability and deformation resistance of asphalt by increasing its softening point, viscosity, and penetration index, while maintaining acceptable ductility. These findings demonstrate the effectiveness of TB for mitigating asphalt fume emissions.

Despite biochar has a good ability in suppressing asphalt fumes, the relationship between the structure of biochar derived from different plant sources and its performance in adsorbing fumes has not yet been explored. In this study, biochar with varying structures and compositions was prepared from cellulose-rich (tea stalks and poplar sawdust) and lignin-rich (coconut shell fiber and loofah sponge) biomass and used as asphalt fume suppressants. Structural characterization revealed that all biochar developed abundant pore structures. Specifically, cellulose-rich biochar featured macro-/mesoporous structures with relatively oxygen-rich surfaces, while lignin-rich biochar exhibited micro-/mesoporous structures with enhanced π-conjugated graphitic frameworks. Asphalt fume adsorption tests showed that, cellulose-based biochar was more effective in adsorbing H₂S and NOₓ, whereas lignin-rich biochar exhibited superior adsorption of VOCs. GC-MS analysis confirmed that cellulose-rich biochar facilitates the adsorption of polar pollutants due to its higher oxygen-rich surfaces, while lignin-rich biochar enhances the adsorption of aromatic pollutants through π–π interactions. Physical property tests of asphalt showed that the macropores of cellulose-rich biochar absorbed more light fractions and promoted an increase in asphaltenes content, significantly enhancing high-temperature performance but having an adverse effect on asphalt ductility.

9,10-Dihydro-9-oxa-10-phosphorophenanthrene-10-oxide (DOPO), recognized for its role as an efficacious fume suppressant, has been shown to mitigate the emission of noxious vapors emanating from asphalt. However, the comprehensive influence of DOPO on the composition and properties of asphalt had remained unexplored. This study embarked on an in-depth examination of the effects of various DOPO dosages on the chemical composition of asphalt, employing hydrogen nuclear magnetic resonance spectroscopy (¹H NMR) alongside an exhaustive analysis of asphalt components. Furthermore, the investigation elucidated the consequences of different DOPO dosages on the physical, rheological properties, and aging resistance of asphalt. The results of ¹H NMR and component analysis of asphalt disclosed that DOPO engaged in chemical reactions with the unsaturated groups within the asphalt, catalyzing a metamorphosis of saturates into aromatics and resins. Such chemical transformations were instrumental in augmenting the softening point, viscosity, and rutting propensity of the asphalt while imposing a minimal impact on its penetration and ductility. Post exposure to the thin film oven test (TFOT), pressure aging vessel (PAV), and ultraviolet (UV) aging, the DOPO modified asphalt (DMA) exhibited a diminution in the increment of softening point and viscosity aging index relative to the control asphalt. Furthermore, the DMA showcased enhanced retention rates of penetration and ductility, coupled with substantially reduced shifts in complex modulus and phase angle post-aging, underlining its superior aging resistance. Fourier transform infrared spectroscopy analysis revealed a comparatively slower rate of change in carbonyl and sulfoxide groups in DMA after aging, as opposed to the control asphalt. Notably, DMA exhibited enhanced resistance to UV aging relative to TFOT and PAV aging scenarios, a trait attributable to remarkable UV absorption capabilities of DOPO. Fundamentally, DOPO enhanced the high-temperature performance and aging resistance of asphalt while simultaneously diminishing the emission of noxious fumes.

Asphalt fumes released during pavement construction posed a threat to human health and environment. In this study, 9,10-dihydro-9-oxa-10-phosphorophenanthrene-10-oxide (DOPO) was used as a reactive fumes suppressant to reduce the asphalt fumes emission. The volatilization behavior of DOPO modified asphalt (DOPO-Asphalt) was investigated through thermogravimetric analysis, volatility test and thermal destruction gas chromatography mass spectrometry, and effect of DOPO on the chemical structure and composition of asphalt was explored through nuclear magnetic resonance hydrogen spectroscopy, Fourier transform infrared spectroscopy, and asphalt component testing. The results indicated that 1.0 wt% DOPO reduced the fume content of control asphalt by 1.1% from 120 ℃ − 200 ℃ and the H₂S and VOC content by 96.9% and 84.2%, respectively, at 180 ℃. Moreover, 1.0 wt% DOPO reduced the content of aliphatic hydrocarbons, hydrocarbon derivatives, aromatics, and sulfides in control asphalt fumes by 86.8%, 89.7%, 90.7%, and 93.5%, respectively, which may be attributed to electrophilic and nucleophilic reactions between DOPO and volatile substances in asphalt. Chemical structure and composition changing of DOPO-Asphalt confirmed that P-H bond in DOPO was chemically reacted with components in asphalt, generating stable aromatic hydrocarbons and resins. The results provided a novel method for inhibiting the volatilization of harmful substances in asphalt.