Performance Of Asphalt Research Articles

Synergistic effect of surface modified nano-zinc oxide and organic vermiculite on long-term ultraviolet and thermal-oxidative aging resistance of different asphalt binders

Asphalt pavement will be subjected to the action of thermal, oxygen and ultraviolet during long-term service, which in turn causes the ultraviolet and thermal-oxidative aging of asphalt simultaneously. Based on the long-term aging mechanism, the double retarding effect of surface modified nano-zinc oxide (ZnO) and organic vermiculite (OEVMT) in different stages of long-term aging was utilized in the research. This work investigated the synergistic effect of ZnO and OEVMT on rheological properties and chemical structures of base asphalts (70# and SK-70) and polymer modified asphalts (SBS modified asphalt and SBR modified asphalt) after long-term ultraviolet and thermal-oxidative aging. Dynamic shear rheological (DSR), bending beam rheological (BBR) and Fourier infrared spectroscopy tests were utilized to study the DSR properties, BBR properties at low temperature and chemical structures, respectively. Meanwhile, the synergistic effect mechanism was analyzed. Results showed that the effect of 1 % ZnO to resist the long-term ultraviolet aging of 70# base asphalt approximates that of 3 % OEVMT, while the long-term thermal-oxidative anti-aging ability of 1 % OEVMT for 70# base asphalt is equivalent to that of 3 % ZnO. Besides, compared with 2 % ZnO or 2 % OEVMT, 1 % ZnO + 1 % OEVMT shows a better long-term ultraviolet and thermal-oxidative aging resistance for different asphalt binders, indicating its synergistic effect in strengthening the anti-aging performance of asphalt. Moreover, 1 % ZnO + 1 % OEVMT not only can effectively retard the oxidation rate of asphalt in the process of long-term aging, but also inhibit the degradation degree of modifiers in SBS modified asphalt. The research could propose a new design idea to effectively solve the long-term aging problem of asphalt.

Development of sustainable compound bio-oil rejuvenator and its rejuvenation mechanism on long-term aged asphalt

To develop a new sustainable compound bio-oil rejuvenator product and understand its rejuvenation mechanism on long-term aged asphalt, the castor oil vegetable asphalt (COA) was selected to react with epoxidized soybean oil (ESO) for preparing the compound bio-oil rejuvenator of long-term aged asphalt. The in-situ dynamic chemical reactions between COA and ESO, as well as the changes in basic properties, chemical compositions, molecular weight distributions and microstructures of aged asphalt were characterized before and after rejuvenation. Results indicate that COA and ESO undergo ring-opening reactions at 80 °C. These reactions still occur continuously during the rejuvenation process of aged asphalt. The compound bio-oil recovers the physical performance of long-term aged asphalt to its original level before aging. Under the combined action of COA and ESO, the sulfoxide index and carbonyl index of long-term aged asphalt samples are decreased. Molecular weight distribution of aged asphalt can be recovered with compound bio-oil. The lengths of catana phases of long-term aged base asphalt and SBS modified asphalt can be restored to their original lengths respectively. Although the average surface roughness of long-term aged base asphalt and SBS modified asphalt can be restored to the original level of base asphalt and SBS modified asphalt, it is difficult to accurately characterize the degree of asphalt rejuvenation due to the uncertainty of its changes. The developed compound bio-oil rejuvenator is suitable to restore the pavement properties of long-term aged asphalt. This is socially beneficial, economically viable and environmentally imperative.

Laboratory evaluation of different bio-oil recycled aged asphalts: Conventional performances and microscopic characteristics

The performance of diverse types of bio-oils varies greatly from each other, which makes it arduous to apply different bio-oils directly in engineering practice. This study is based on physical and microscopic properties, studying different types of bio-oil recycled asphalt and analyzing their differences. Five bio-oils (castor oil, straw oil, soybean oil, gutter oil, and vegetable oil) were used to regenerate asphalts after short-term and long-term aging to prepare recycled asphalts. The physical performances of recycled asphalts with different bio-oils were assessed, including penetration, softening point, and ductility tests. In addition, scanning electron microscopy was utilized to investigate the microscopic morphologies of recycled asphalts. Simultaneous thermogravimetry and differential scanning calorimetry were applied to determine the thermal stabilities of recycled asphalts. Finally, Gel permeation chromatography was employed to analyze the asphalt's relative molecular masses. The results revealed that vegetable and gutter oil have apparent adverse effects on temperature sensitivity and high-temperature performance of aged asphalt. In contrast, they have positive effects on low-temperature performance. All five bio-oils can repair cracks on the surface of aged asphalt. However, the surface wrinkles of vegetable oil-recycled asphalt and castor oil-recycled asphalt are relatively less and have an outstanding recycling effect. The slight thermal weight loss of recycled asphalts corresponding to castor oil, straw oil, and soybean oil at high temperatures positively impacted the high-temperature stability of aged asphalt. The castor oil and soybean oil recycled asphalts have significantly larger relative molecular masses and have advantages in high-temperature performance. This paper reveals the impact of different bio-oils on asphalt regeneration, which contributes a theoretical basis for promoting the practical implementation of bio-oil in road projects, with obvious economic and social benefits.

Analysis of the viscosity and self-healing performance of warm-mix recycled asphalt: A method combining molecular dynamics simulations and laboratory tests

The technology of warm-mix regeneration has been frequently used in the production of asphalt pavement; however, the viscosity and self-healing properties of warm-mix recycled asphalt (WMRA) need further study. Therefore, the viscosity and self-healing properties of WMRA were analyzed by combining laboratory tests and molecular dynamics (MD) simulations. First, WMRA with different SWA and reclaimed asphalt pavement (RAP) contents were prepared in the laboratory. Then, different simulations, including viscosity simulation and self-healing simulation and Brookfield Viscosity test, were developed to analyze the performance variation rule. Experimental results showed that the Sasobit warm-mix agent (SWA) significantly reduced asphalt viscosity, and the recycled asphalt’s viscosity increased with asphalt aging deeply. In contrast, the addition of 2% SWA made the viscosity of 100% RAP similar to that of new asphalt. Considering the viscosity reduction effect, asphalt performance and economy, a 3% SWA content is recommended. Both SWA and the degree of aging can reduce the healing performance of WMRA. There is little difference between the two factors in reducing self-healing performance. In general, the study's findings serve as a useful guide for the performance analysis of WMRA.

Suitability of warm mix asphalt (WMA) technologies based on performance and energy consumption

Studying the effects of material variability on the performance of warm mix asphalt (WMA) is important to understand the benefits of reduced production temperatures. This study compares the performance of five different WMA mixtures prepared with two varying base binders and two different aggregate sources. The rutting, fatigue, and moisture sensitivity of asphalt mixtures were evaluated using cyclic compression test, indirect tensile cracking test, and modified Lottman test, respectively. Additionally, a theoretical analysis was used to compare the energy consumption during the production process. The results indicated that the performance of WMA is a function of the type of the base binder, aggregate source, and the type of WMA technology. Nonetheless, all the WMA mixtures contributed to higher energy savings in comparison to hot mix asphalt (HMA). Based on the ranking framework used in this study, the use of Rediset is recommended to achieve adequate performance and lower energy consumption.

Research on low-temperature and fatigue properties of recycled asphalt based on the stability of the micelle structure

The research is focused on the asphalt colloid system and provides a detailed analysis of why the effective recovery of low-temperature performance and fatigue performance is challenging during the regeneration of aged asphalt. This study initially examined the alterations in the stability of colloidal structures and micelle structures while rejuvenating aged asphalt. These were performed through four-component analytical tests and asphaltene-resin (A-R) adsorption experiments, respectively. Subsequently, the impact of the regeneration process on the low-temperature performance and fatigue performance of aged asphalt was assessed using bending beam rheometer (BBR) tests and linear amplitude sweep (LAS) tests, respectively. In addition, linear regression analysis was employed to determine the relationship between the stability of colloidal and micelle structures and the performance of recycled asphalt in terms of low-temperature and fatigue resistance. The results show that regeneration of aged asphalt results in 100% recovery of colloidal structural stability, while the maximum recovery of micelle structural stability is only 68.2%. The stability of the micelle structure in recycled asphalt is primarily influenced by the proportion of aged asphalt to virgin asphalt. When the mass ratio of aged asphalt to virgin asphalt is 2:8, the stability of the micelle structure can be restored to 58.1%. However, when the mass ratio is reversed to 8:2, the stability of the micelle structure can only be restored to 21.6%. The impact of the regeneration agent on the recovery of micelle structure stability is minimal. Out of all the samples that underwent regeneration, the highest level of enhancement in the stability of the micelle structure achieved by the rejuvenators was approximately 15%. Linear regression analysis showed that the low-temperature performance of recycled asphalt was significantly affected by the stability of the colloid and micelle structure. The fatigue performance of recycled asphalt was only significantly affected by the stability of the micelle structure. Therefore, enhancing the stability of the micelle structure in recycled asphalt can effectively improve its low-temperature and fatigue performance. This study provides valuable insights into the underlying factors contributing to the subpar low-temperature and fatigue performance of recycled asphalt. Moreover, it contributes to the development of more effective rejuvenators for aged asphalt recycling.

Investigation of the effects of chemical modification and oxidative aging on the properties and compatibility of rubber asphalt based on thermodynamic principles

This study is based on the principles of thermodynamics and utilizes the Hansen solubility parameter theory and molecular dynamics simulation techniques. By introducing solubility parameters and interaction parameters, modified molecular models for rubber and aged asphalt are constructed. The study systematically investigates the mechanisms underlying the effects of polyphenolic chemical modification and oxidative aging on the performance and compatibility changes of rubber asphalt. The results show that the solubility parameter (δT) of the asphalt system decreases gradually with increasing temperature. At a temperature of 160 °C, the solubility parameter difference (ΔδT) between the asphalt and rubber power (RP) is minimized, indicating the highest degree of compatibility between the two materials. After chemical modification, the solubility parameter of the RP increases, the difference in solubility parameter between the RP and asphalt decreases, and the chemical modification improves the compatibility of the two phases. Oxidative aging causes a shift in the composition ratio of asphalt towards asphaltene, leading to an increase in the solubility parameter of asphalt and a larger difference in solubility parameter between the system. As a result, the compatibility of modified asphalt decreases.

Peanut Shell Powder as a Sustainable Modifier and Its Influence on Self-Healing Properties of Asphalt.

This paper investigated, for the first time, the feasibility of using peanut shell powder, a plant waste residue, as a modifier for asphalt, particularly its self-healing ability. Modified asphalt samples were prepared using varying particle size ranges and concentrations of peanut shell powder. Various tests, including fatigue-healing-fatigue tests, high- and low-temperature rheological property tests, penetration tests for conventional performance, and atomic force microscopy scans, were conducted to investigate the effects of peanut shell powder on the self-healing performance and other properties of asphalt. The results showed that the porous structure of peanut shell powder was able to absorb light components within the asphalt and release them under load, thus improving the self-healing and fatigue resistance properties of the modified asphalt. Experimental conditions such as temperature, healing time, and fatigue damage level also influenced the self-healing performance of asphalt. Additionally, peanut shell powder could increase the dynamic viscosity and high-temperature rheological property of modified asphalt while reducing its temperature susceptibility. However, it had a negative impact on the low-temperature ductility and creep rate, which could potentially lead to premature cracking of asphalt pavement in colder regions. Increasing the content of peanut shell powder and reducing its particle size within a certain range had positive effects. When the content of peanut shell powder was 4% and the particle size range was 80-100 mesh, the overall performance of modified asphalt was satisfactory.

Improvement of pavement engineering properties with calcium carbide residue (CCR) as filler in Stone Mastic Asphalt

Characteristics of pavement material are crucial factors in improving the stability and durability of asphalt pavement due to the poor performance of traditional asphalts. Reusing industrial waste in asphalt concrete production can address these concerns, reduce environmental problems and preserve resources. There have been few studies on the effects of using industrial waste materials on Stone Mastic Asphalt (SMA) properties. This paper examines the impact of Calcium Carbide Residue (CCR) as a filler in SMA. The study evaluates control samples, those with Rock Powder (RP) and Ordinary Portland Cement (OPC) filler, and those with CCR using Marshall stability (MS) and Indirect Tensile Strength (ITSdry and ITSsat) tests. Results show positive effects of CCR and RP on asphalt sample strength. The highest MS, MQ, and TSR values were observed in samples containing CCR80 %+RP20 %. These indices increased 45 %, 35 %, and 51 %, respectively, compared to control samples. The alkaline CCR material forms strong bonds with acidic bitumen, producing asphalt more resistant by 97 % compared to control samples. SMA modified with CCR + RP was also found to be less sensitive to water damage than traditional SMA with RP or OPC filler. The rough texture of CCR may positively affect the strength and durability of asphalt mixtures against moisture damage. Using CCR as a filler in SMA can enhance pavement engineering properties, reduce production costs and environmental problems, and develop sustainable asphalt mixtures for practical application. The main novelty of this research is the use of CCR and RP combination in SMA mixtures.

Influence of crosslinking effect on chemical and rheological properties of aged liquid bio-rubber composite SBS modified asphalt

The influence of the cross-linking effect between a liquid bio-rubber (LBR), a desulphurised crumb rubber formed via pyrolysis in bio-oil, SBS, a cross-linker, and asphalt on the chemical and rheological properties of aged LBR/SBS composite modified asphalt (LBR/SBSMA) was studied. Four types of modified asphalts were prepared by adding LBR, LBR+sulphur, LBR+SBS and LBR+SBS+sulphur to simulate cross-linking. FTIR and GPC were used to obtain oxidation, aromatisation and polymer degradation indexes and molecular weight. DSR and BBR were used to acquire rheological indexes. Sulphur was the key factor in achieving cross-linking, which promoted phase morphology stability, enhanced oxidation and aromatisation resistance and restrained polymer degradation. LBR could prevent the variation of |G*| and the change of δ in high frequency after ageing. The low-temperature performance of aged LBR asphalt was satisfactory. The cross-linking effect retained superior ageing resistance despite a slight impairment of low-temperature continuous grading temperature, producing a sustainable and high-performance modified asphalt.

Mechanical performance of cup lump rubber modified asphalt mixtures incorporating polyphosphoric acid

Natural rubber (NR) producing countries face rubber production and price fluctuations. NR production's high cost and low market price have produced an extensive demand for alternative applications of NR. This paper examined the influence of cup lump rubber (CLR) and polyphosphoric acid (PPA) on the mechanical performance of asphalt mixtures. The five modified blends were selected for the hot mix asphalt (HMA) performance analysis. The results revealed that the CLR increasing content in the bitumen ultimately increases the optimum bitumen content (OBC) for the asphalt mixture. There is a significant difference in the base mixture OBC (5.19 %) compared to the cup lump rubber-modified bitumens (CLRMBs). The CLRMB6 + 0.5PPA asphalt mixture OBC was 5.32 %, which is higher among all the mixtures. The rutting findings demonstrated that the control mixture exhibited the highest strain of 1.71 %, followed by CLRMB6 with 1.43 %, CLRMB3 + 0.5PPA with 1.1 %, CLRMB9 with 0.7 %, and CLRMB6 + 0.5PPA with the lowest strain of 0.47 %. The creep stiffness modulus of all mixtures met the minimum requirement of ≥75 MPa. The results implied that the CLR and the PPA displayed incredible potential to improve the asphalt mixture's resilient modulus (MR). The CLRMB9 resilient modulus increased significantly by 22 % compared to the control mixture. The CLRMB6 + 0.5PPA has a higher MR of 5210 MPa than the other modified mixtures and the control mixture with 3521 Ma. Thus, the study's findings suggest that the CLR, in conjunction with the 0.5PPA exhibits a decisive effect on the asphalt mixture performance and could be beneficial as a sustainable material in the pavement industry.

Investigating the Effect of Experimental Factors on the Performance of Warm Mix Asphalt with Wax Additive using Application of the Taguchi Method

The objective of this study was to assess the impact of experimental factors on the volumetric properties and performance of warm mix asphalt (WMA) with RH-WMA using the Taguchi method. The gradations of the mixtures were based on AC 14, as specified by the Public Works Department of Malaysia. An L16 orthogonal array was employed to design the mixtures, considering three factors: compaction temperatures ranging from 95 to 140°C, RH-WMA contents ranging from 1% to 4%, and asphalt contents ranging from 3.5% to 6.5%. Sixteen mixtures were prepared according to the L16 array. The study focused on investigating several volumetric properties, including bulk-specific gravity, air voids, voids filled with asphalt, and voids in mineral aggregates. Additionally, the strength behavior of the samples was analyzed using the Taguchi method. The resilient modulus and performance of the mixtures were also evaluated. The results of the study indicate that a high RH-WMA content led to a slight decrease in the strength of the asphalt mixture and air voids. However, it increased the voids filled with asphalt (VFA) and resulted in softening of the asphalt mixtures.

Performance evaluation of asphalt mixture reinforced by lignin and ceramic fiber

A single-adding fiber technology only plays a role in improving one performance of asphalt mixture such as high temperature or low temperature or water damage performance. Although double-adding fiber-reinforced asphalt mixtures are expected to improve overall road performance, existing research still only focuses on the analysis of a single performance. In this study, two representative fibers including lignin fiber (LF) and ceramic fiber (CF) were selected including to investigate the role of double-adding fibers in asphalt mixtures. The effect of different fiber proportions on the overall road performance of stone matrix asphalt (SMA-13) mixtures was analyzed via wheel tracking tests, low temperature bending test, moisture susceptibility test and fatigue test, etc. The results revealed that the combined addition of LF and CF exhibited superior improvements in mechanical strength, anti-rutting performance, moisture susceptibility, and fatigue life as compared to that of using either fiber alone. Specifically, compared to that of SMA mixtures using LF, the SMA mixtures using both two fibers improved in 11% dynamic stability, 8.6 % low-temperature bending stress, 2.1 % moisture susceptibility and 20 % fatigue life, respectively. And compared to that of SMA mixtures using CF, the mixtures using both two fibers increased in 11 % low-temperature bending strain and 8 % fatigue life, while improving slightly in dynamic stability, low-temperature bending stress, and moisture susceptibility respectively. Based on the results of efficiency coefficient method, the recommended ratio of LF to CF in the asphalt mixture is 1:2, providing a more balanced and comprehensive enhancement of road performances. This study provides a theoretical reference for the engineering application of improving the road performance of asphalt mixture through composite fiber blending, which can effectively enhance the service life of asphalt pavement.

New road surface noise corrections for New Zealand

New Zealand’s transport agency has developed a close-proximity (CPX) noise trailer and primarily operates it as a road surface research tool. Early CPX survey data revealed very high longitudinal variability in the performance of porous asphalts on the highway network (±5 dB). Further study and optimization of porous asphalt mixes has resulted in high-performance low-noise surfaces that are reliably 5 dB quieter than standard NZ porous asphalt. The new surfaces and improved surface data inspired a recalibration of NZ’s implementation of the CRTN road-traffic noise model, for which a novel method based on CPX survey data and individual vehicle pass-by measurements was employed. The relationship between CPX and wayside levels was more complex than anticipated; CPX measurements did not capture all the surface attributes/interactions contributing to the wayside level (such as porosity, directivity). The methodology proved successful and a new table of surface corrections has been published, embodying the recalibration of CRTN for NZ in 2023. CRTN predictions using the new corrections have performed well when evaluated against independent road-traffic noise monitoring data from NZ highways.

Influence of Binary Blended Fillers on Long-Term Aging Effect and Rutting Performance of Warm-Mix Asphalt

Influence of Binary Blended Fillers on Long-Term Aging Effect and Rutting Performance of Warm-Mix Asphalt

A Study on the Microscopic Properties of the Oil–Stone Interfacial Phase of a Reclaimed Asphalt Mixture Based on Molecular Dynamics Simulation

In recent years, there has been a growing body of research focused on aged asphalt and recycled asphalt. Nevertheless, despite diligent endeavors, the precise micro-interaction mechanism occurring at the interface of weathered asphalt, reclaimed asphalt, and aggregates still eludes our understanding. This study leveraged molecular dynamics simulation technology to scrutinize the inherent behavior of aged asphalt and recycled asphalt at the micro-scale, elucidating the intricate interaction mechanism occurring at the interface of recycled asphalt, aged asphalt, and aggregates. The diffusion and adhesion properties of three distinct asphalt–aggregate interfaces were meticulously compared and comprehensively analyzed using advanced molecular dynamics simulation techniques. The findings revealed a substantial decline in the performance of aged asphalt, while the diffusion and adhesion properties of recycled asphalt were observed to be largely restored, reaching a remarkable level of approximately 85% in comparison to aged asphalt. The high-temperature performance, low-temperature performance, and water stability characteristics of both aged the asphalt mixture and recycled asphalt mixture were thoroughly investigated through rigorous laboratory testing of the asphalt mixtures. Based on the experimental findings, it was observed that the overall performance of the aged asphalt mixture exhibited a reduction of approximately 40%. However, through the process of regeneration, the overall performance of the asphalt mixture could be restored to approximately 90% of its non-aged counterpart.

CHARACTERIZATION OF ASPHALT MODIFICATION USING GROUND RUBBER AND REACTIVE RUBBER NR-g-MA AS COMPATIBILIZER

This study aims to improve the quality of asphalt by adding ground tyre rubber (GR) and reactive rubber (NR-g-MA) as compatibilizers of asphalt-rubber mixability. The use of GR has been widely used to improve the performance of asphalt and extend the service life of asphalt. The NR-g-MA used was the product of the copolymerization of SIR-20 rubber grafts with maleic anhydrous (MA) through a melting process in an internal mixer. Mixing of GR in asphalt was carried out in an external mixer with composition of asphalt/GR 95/5 phr at the temperature of 180oC for 90 minutes. The performance of asphalts were measured based on conventional test of penetration and softening point. The rheological properties of asphalt were measured using a Dynamic Shear Rheometer (DSR). Important parameters of the rheological properties measured are complex shear modulus (G*) and phase angle (d). Asphalt resistance to the permanent deformation (rutting) were determined on asphalt that has undergone a short-term aging process in a rolling thin film oven (RTFO) and measured at high temperatures (58-82OC). Fatigue crack resistance was tested on asphalt that has undergone a long-term aging process using the method of pressure aging vessel (PAV) and measured at low temperatures (25-31OC). Asphalt-GR mixtures' chemical, thermal and morphological properties were studied using ATR-FTIR, DSC/TGA, and SEM respectively. The results showed that adding used ground rubber (GR) decreased the penetration value by 9.93 – 18.87% and increased the softening point of asphalt from 5.57 – 11.40%. Rheological analysis showed that the addition of GR and compatibilizer NR-g-MA increase the value of complex shear modulus (G*) and decrease the phase angle (d) of the asphalt. The addition of ground rubber and reactive rubber of NR-g-MA to asphalt improve the performance of asphalt because it has rutting resistance at high temperatures as well as improves asphalt cracking resistance at low-temperature measurements. The addition of NR-g-MA reactive rubber to modified asphalt ground rubber can increase the mixability of asphalt-rubber used tires.

Development and Performance Evaluation of an Asphalt Regenerant Derived from Waste Engine Oil Residue.

This study assessed the fundamental physical properties and chemical composition of three specific waste engine oil residue (WEORs) asphalt regenerants. Through dynamic shear rheometer and rolling thin-film oven tests, the performance of aged asphalt was evaluated using three key indicators. Thin-layer chromatography investigations probed the WEOR-induced changes in the aging asphalt components, leading to the creation of two novel asphalt regenerants, WEOR-H and WEOR-G. WEOR-G was developed from WEOR-1, liquid rubber, ultraviolet absorber, light shielding agent, and antioxidant, while WEOR-H was formulated from WEOR-2, aromatic oil, and liquid rubber. The study employed differential scanning calorimetry and conventional laboratory tests to analyze the road performance attributes of Ingevity J type regenerant (J), WEOR-G, and WEOR-H. The results indicated that WEORs increase the saturate and aromatic content in asphalt and partially replenish the missing lightweight components of aged asphalt, moderately improving the three key indicators, though the regenerative effect is restricted. Achieving a full restoration of component proportions within aged asphalt to their initial levels proved unattainable, and direct application of any of the three WEORs as asphalt regenerants is impractical. WEOR-H and WEOR-G demonstrated potential in enhancing aged asphalt binder road performance, outpacing three other WEORs. At a 14% dosage, WEOR-G and WEOR-H could increase the 10 °C ductility to 23.5 and 21.4 cm, respectively, effectively counterbalancing the insufficient ability of WEOR-1 and WEOR-2 to restore the low-temperature performance of aged asphalt. Among the regenerants, WEOR-G, possessing superior regenerative effects, the lowest glass transition temperature, and optimal low-temperature deformation resistance, emerged as the most efficacious. This inquiry furnishes vital data support for future applications of WEOR-G asphalt regenerant.

Preparation and characterization of high performance coal tar pitch-based carbon fiber

High performance carbon fiber based on coal tar pitch is a new type of functional material with unique properties, such as light weight, high strength, high modulus, high thermal conductivity, high electrical conductivity and low thermal expansion coefficient. It is a new type of functional material for both military and civilian use. In order to study the preparation of high performance carbon fiber based on coal tar pitch, this article obtained high performance carbon fiber based on coal tar pitch through raw material pretreatment, spinnable asphalt modulation, asphalt melt spinning, non-melting, carbonization, graphitization and other processes, and characterized the performance of spinnable mesocase asphalt and carbon fiber. The results show that high-performance spinnable mesophase pitch can be prepared by three steps raw material refining, hydrogenation modification and thermal polymerization. The mesophase content is 95%, the softening point is 280 °C, and the 3000 m filament can be spun under melt spinning conditions of 375 °C and 0.01 MPa. After graphitization, the coal pitch-based carbon fiber has excellent mechanical properties, small structural defects and a diameter of 12 μm. The tensile strength is 3089 MPa, the elastic modulus is 689 GPa, and the thermal conductivity is 902 w/(m·K).

Study on the Performance and Mechanism of Cold-Recycled Asphalt Based on Permeable Recycling Agent.

In order to investigate the influence of recycling agent composition on the recycling effect of aged asphalt in the cold recycling process, the design and optimization of cold recycling agent composition were performed through the central composite design-response surface method combined with the dynamic shear rheometer (DSR) test and the bending beam rheometer (BBR) test. The molecular weight distribution and component changes in aged asphalt before and after the addition of a cold recycling agent were also analyzed by gel permeation chromatography (GPC) and hydrogen-flame ionization test. The results showed that the permeable cold recycling agent has a recycling effect on the aged asphalt, but its effectiveness is greatly affected by recycling agent composition. The best recycling effect was achieved when the ratio of aromatic oil and penetrant in the cold recycling agent was 61.2:38.8, respectively. In terms of the recycling agent and aromatic functional groups in the aromatic oil, the aromatics in the recycling agent are derived from the aromatic oils, and the penetrant is only fused and permeated with the aromatic oils. After the admixture of the cold recycling agent, the penetrant in the recycling agent allows the aromatic oil to enter the aged asphalt at room temperature. The light components volatilized by aging are replenished, allowing the aged asphalt to recover some of its properties.