Flue gas composition of waste rubber modified asphalt (WRMA) and effect of deodorants on hazardous constituents and WRMA

Interaction of composite fume suppression and odor elimination agents with crumb rubber modified asphalt: Inhibition behavior of volatile organic compounds (VOCs) and inorganic fume

The production and construction of crumb rubber modified asphalt (RMA) at high temperatures can produce a large amount of toxic fume, which is detrimental to human health and environment. In this study, a series of composite fume suppression and odor elimination agents (CSEAs) with both physical adsorption and chemical capture functions were adopted to reduce the emissions of volatile organic compounds (VOCs) and hydrogen sulfide (H2S). The material composition, microstructure, and specific surface area of CSEA were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and N2 adsorption-desorption isotherm (BET). The inhibitory effects of adding CSEA on toxic fume emissions from RMA at high temperatures were investigated through a combination of fume emission tests, H2S gas detection, gel permeation chromatography (GPC), and gas chromatography-mass spectrometry technology (GC-MS). The adsorption behavior of CSEA on H2S was analyzed through adsorption dynamics. Results showed that the physical and chemical properties of CSEA are stable while chemical adsorption dominates the CSEA's effect on H2S. ZnO and Ca(OH)2 exhibit good crystallization effects on the surface of the carrier by forming mesoporous structures mostly above 3.4 nm in size. The incorporation of CSEA significantly reduced the total emissions of RMA fume and the main components of VOCs in which the average inhibition rate of H2S can reach 44 % at an initial 30 mins.

A comprehensive review on asphalt fume suppression and energy saving technologies in asphalt pavement industry

Based on the environmental issues of high energy consumption and high emissions of asphalt fumes that are associated with hot mixing asphalt pavement construction, especially with modified asphalt mixtures such as waste rubber modified asphalt (WRMA) mixtures, significant environmentally-friendly new technologies have been successfully applied in the field of asphalt pavement materials. These include fume purification equipment, fume suppression or flame-retarding asphalt mixture, and warm mixing or cold mixing asphalt mixture. This paper provides a comprehensive review of the latest technology in this area regarding both asphalt fume suppression and energy conservation within the last six years. Firstly, asphalt fume suppression technologies in production, laying, and combustion scenarios of an asphalt mixture are identified, and asphalt fume purification equipment utilized in the production process is thoroughly examined. The impacts and mechanisms of various fume suppressants and flame retardants of asphalt fumes regarding their influence on the performance of asphalt pavement are discussed. Secondly, from the perspective of reducing asphalt mixture temperature, different mixing techniques such as cold mixing asphalt (CMA), warm mixing asphalt (WMA), and warm mixing based retarding viscosity asphalt (WM-RVA) are introduced and evaluated utilizing energy consumption and carbon emission evaluation models. These results show that the combination of advanced oxidation and traditional purification methods is critical for promoting the green production of asphalt mixtures. In-depth research on nanomaterials and composite-type asphalt fume suppression materials, WM-RVA, and effective combinations of high-performance modification, recycled materials, fume suppression functional materials, and WMA or CMA hold great promise for future development in this field.

Study on the effect of different aldehyde modifiers on the fume suppression effect, mechanism and road performance of SBS modified asphalt

In order to curb asphalt fume emissions during the heating process of styrene-butadiene-styrene (SBS) asphalt, three aldehyde modifiers [vanillin (X), citral (N) and amyl cinnamaldehyde (J)] were blended into SBS-modified asphalt to prepare aldehyde-modified asphalt in this paper. By collecting solid particles and volatile organic compounds (VOCs) in asphalt fumes to conduct relevant experiments, we have analyzed the fume suppression effect and suppression mechanism of aldehyde modified asphalt, and finally examined the road performance of aldehyde modifiers with the best fume suppression effect. It was found that the average VOCs concentration of aldehyde modified asphalt was reduced by about 78 % after 30 min. Aldehyde modifiers significantly reduce the compositional type and content of VOCs in SBS asphalt and reduce the risk of carcinogenicity by curbing the emission of substances such as benzene and phenol. J asphalt reduced solid particle emissions from SBS asphalt fume by 31.4 % and outperformed both X and N asphalt in inhibiting the escape of solid particulate matter and carcinogens from asphalt fume. Polymer networks and the cross-linking of chemical molecules are the main reasons for inhibiting the escape of asphalt fume molecules. In addition, the J modifier enhanced the high-temperature stabilization and water-stability properties of asphalt mixtures, but slightly reduced the low-temperature cracking resistance. The results showed that the three aldehyde modifiers were effective in inhibiting the volatilization of fumes from SBS modified asphalt. Among them, with the best effect of curbing fume emissions and a better road performance, J-modified asphalt is promising for the application in asphalt fume prevention and emissions reduction, and provides a new solution to reduce construction pollution and physical harm caused by asphalt fume in the construction process.

Effect of heating history on the emission of volatile organic compounds from asphalt materials

Asphalt binders release hazardous fumes during high-temperature heating that severely endanger human health and pollute the environment. In this study, a volatile organic compound (VOC) generation and detection device comprising a portable VOC detector was developed, and two heating modes (intermittent and continuous heating) were established to explore the influence of heating history on the VOC emission behavior of five asphalt samples. The changes in the VOC species and content, as determined by the heating history, were analyzed via gas chromatography-mass spectrometry (GC-MS). Finally, the key factors affecting the emission of VOCs from asphalt are discussed based on the four components of asphalt materials. The results indicated that the emission of VOCs from asphalt materials under intermittent heating conditions decreased significantly with increasing heating history (significantly fewer VOCs, including 13 common components such as alkanes, benzenes, and hydrocarbon derivatives, were emitted under this condition than under continuous heating conditions at the same temperature point). Compared with continuous heating, intermittent heating is more conducive for studying asphalt VOCs. Under intermittent heating, different asphalt materials exhibited similar VOC emission curves; the VOCs were mainly emitted during the first two heating stages (200 and 180 °C, respectively). Thus, it can be deduced that asphalt VOC emissions were induced by the synchronized actions of the four components of asphalt materials. Therefore, different components can contribute to the emission of several VOCs of the same composition. The heavy and light components mainly facilitate the emission of common components with carbon atomic numbers <18 and > 18, respectively.

Investigation into the Rheological Properties and Microstructure of Silt/Crumb Rubber Compound-Modified Asphalt

Near the coast of China, a large amount of sediment is produced during construction work. In order to mitigate the environmental damage caused by sediment and enhance the performance of rubber-modified asphalt effectively, solidified silt material and waste rubber were prepared to modify asphalt, and its macroscopic properties, such as viscosity and chemical composition, were determined via a routine physical test, DSR, Fourier Transform Infrared Spectroscopy (FTIR), and Fluorescence Microscopy (FM). The results show that, with the increase in powder particles and the addition of a certain amount of hardened mud, the mixing and compaction temperature of modified asphalt can be significantly increased-still reaching the design standard. In addition, the high thermal stability and fatigue resistance of the modified asphalt were clearly better than those of the ordinary asphalt. From the FTIR analysis, rubber particles and hardened silt only exhibited mechanical agitation with the asphalt. Considering that excessive silt might result in the aggregation of matrix asphalt, the addition of an appropriate amount of hardened solidified silt material can eliminate the aggregation. Therefore, the performance of modified asphalt was optimum when solidified silt was added. Our research can provide an effective theoretical basis and reference values for the practical application of compound-modified asphalt. Therefore, 6%HCS(6:4)-CRMA have better performance. Compared to ordinary rubber-modified asphalt, the composite-modified asphalt binder has better physical properties and a more suitable construction temperature. The composite-modified asphalt uses discarded rubber and silt as raw materials, which can effectively protect the environment. Meanwhile, the modified asphalt has excellent rheological properties and fatigue resistance.

Rapid and Direct Assessment of Asphalt Volatile Organic Compound Emission Based on Carbon Fiber Ionization Mass Spectrometry

Due to the complicacy of asphalt fumes, the analytical methods for investigating volatile organic compounds (VOCs) are very limited. In this study, a direct and real-time analysis method based on carbon fiber ionization mass spectrometry (CFI-MS), an ambient mass spectrometric technique, was established and successfully applied in the analysis of asphalt VOCs. The asphalt VOCs can be directly detected in the open atmosphere without the collection step of asphalt fumes, and the mass spectra of one asphalt sample can be obtained in a few seconds in both positive and negative ion modes. By investigating the mass spectral changes of asphalt fumes at different heating temperatures ranging from 50 to 200 °C, the temperature factor of asphalt fume emission was demonstrated in this work. The research results demonstrate that the complexity of asphalt fumes is positively related to the applied temperature. Moreover, the VOCs of saturates, aromatics, resins, and asphaltenes fractions were also analyzed by the direct analysis method. The result shows that aromatics contribute most to the emission of VOCs. In addition, the obtained mass spectra combined with the principal component analysis method show the great potential to quickly screen VOC inhibitors of asphalt materials.

Recycled plastic modified bitumen: Evaluation of VOCs and PAHs from laboratory generated fumes

A key aspect when investigating the use of recycled plastics in bitumen relates considerably to the issues relating to occupational, health and safety for humans and the environment from a fuming and emissions perspective. This research investigates laboratory-generated fumes in the forms of volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs) generated from producing polymer modified bitumen using five different types of recycled plastics. A comparative analysis of recycled plastic modified bitumen fumes was conducted based on a series of optimized parameters, including working temperatures (160 °C, 180 °C and 200 °C) and polymer contents (1%, 2%, 4% and 6% by weight of bitumen) against neat bitumen and polymer-modified bitumen. Forty-eight volatile organic compounds (VOCs) and sixteen polycyclic aromatic hydrocarbons (PAHs) were quantified using gas chromatography-mass spectrometry (GC-MS). The results from the comparative analysis revealed that the incorporation of recycled plastics could reduce overall emissions from both VOCs and PAHs perspectives. The reduction in emissions can be attributed to the enhancement in thermal stability of the bitumen blend when recycled plastics are added. The reduction rate is heavily dependent on the type and source of recycled plastics used in the blending process. Furthermore, a specific compound concentration analysis of the top-four weighted compounds emitted reveals that the total concentration of emissions can be deceiving as specific compounds can spike when adding recycled plastics in bitumen despite a reduction trend for the overall concentration.