Dynamic Rheological Tests Research Articles

Study on the Rheological Properties of Nano-SiO2 Composite Modified Basalt Mineral Fiber Asphalt Mortar

Abstract To investigate the impact of mineral fiber modification and dosage on the rheological properties of fiber asphalt mastic, basalt fiber surface roughness was enhanced using nano-SiO2 solution. Fiber asphalt mastic was prepared with a filler-bitumen ratio of 1.6 and fiber dosages of 0%, 1.3%, 2.6%, 3.9%, and 5.2%. The taper entry test, dynamic shear rheology test, and bending beam rheology test were employed to analyze the variations in taper entry, shear strength, complex modulus (G*), phase angle (δ), rutting factor (G*/sinδ), modulus of strength (S), and rate of change of strength (m) of the fiber asphalt mastic. The results indicate that the optimal dosage of mineral fibers in fiber asphalt mastic is 2.6%. Nano-modified basalt fibers significantly enhance the anti-shear capacity of asphalt mastic. The high-temperature stability of fiber asphalt mastic improves with increasing fiber dosage, but the improvement becomes negligible beyond a 2.6% dosage. The interfacial bonding layer formed by asphalt on the fiber surface enhances the high-temperature performance and stress dissipation at low temperatures, thereby improving low-temperature cracking resistance.

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

The severe agglomeration of Reclaimed Asphalt Pavement (RAP) particles not only leads to high gradation variability during recycling, but also impedes the miscibility between new-old binders. This phenomenon imposes significant limitations on maximizing the utilization of RAP with high content and value. This paper first realized the effective separation of asphalt milling material by the self-developed RAP refined processing equipment to obtain coarse RAP with low binder content and fine RAP with high binder content. The fine RAP with high binder content underwent a deep rejuvenation process, and the recovery efficiency of the asphalt mortar was evaluated by CT scanning test, microscope observation test, and dynamic shear rheology test. Moreover, to investigate the strength formation characteristics of recycled asphalt mixtures with high RAP content, specific tests including wheel tracking test, three-point bending test, Hamburg Wheel Tracking test, dynamic modulus test, and two-point bending fatigue test, were conducted. By using the refined processing equipment, the asphalt film on the RAP can be precisely removed, thereby addressing the issue of aged binder agglomeration. In the coarse RAP with low binder content, the binder content was reduced to 1.48 %, allowing it to be used as a direct substitute for new aggregate, whereas the binder content of fine RAP exceeded 10 %. It was found that the direct incorporation of unrefined RAP enhanced the high-temperature stability and dynamic modulus of recycled asphalt mixture, but impacted their low-temperature cracking resistance, moisture stability, and fatigue performance. After refined processing and differentiated recycling design, the agglomeration of aged binder was reduced and the miscibility of new-old binders was improved, effectively enhancing the comprehensive performance of the recycled asphalt mixture. It should be noted that the mixing homogeneity and miscibility decrease as the RAP content exceeds 75 %, resulting in the reduction of moisture stability, cracking resistance, and fatigue performance of recycled asphalt mixture.

Effects of bonding enhancers on shear stress and bonding strength of modified asphalt binders under different aging and moisture conditions

Insufficient bonding within pavement material causes widespread propagation of traffic-induced stresses, leading to accelerated damage accumulation and significant reduction in the service life of flexible pavements. This research aimed to examine the effects of using bonding enhancers, specifically Polyalkylene Glycol-based (PLG) and Alkylamines-based (ALM), on modified asphalt binders to improve the bonding characteristics. These additives were utilized at different concentration levels, i.e., 0.5 % and 1.0 %, based on the mass of asphalt binders, with the aim of enhancing the bonding performance between the materials within the asphalt mixture composite. The effectiveness of the modified asphalt binders was compared to the conventional ones through laboratory tests, which included shear-compression and pullout tests. These tests were conducted to assess the bonding performance of the modified asphalt binders by preparing different sets of sandwich samples using concrete cube substrates. A sodium carbonate solution was used as a medium to accelerate the effect of moisture damage on samples during the conditioning process. Additionally, the bonding performance of the asphalt binders was evaluated through a series of pullout and shear-compression tests under designated moisture and aging conditions. The dynamic shear rheological (DSR) test results of Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV)-aged binders incorporating bonding enhancers showed superior resistance to rutting and fatigue failure. Significant improvements in stress and shear strength were observed under moisture and aging conditions, highlighting improvements in the bonding performance of the modified asphalt binders. The incorporation of additives has positively contributed to the pavement performance, despite only a modest increase in bonding performance, tensile strength, and shear stress resistance.

Study on the Performance of Modified Qingchuan Rock/Rubber Asphalt

This paper developed a new environmentally friendly composite modified asphalt material and studied the composite modification of Qingchuan rock asphalt (QRA) and waste tire rubber powder (RP) was studied in this paper. QRA/RP composite modified asphalt was prepared by adding these two materials as modifiers into matrix asphalt and compared with matrix asphalt and QRA modified asphalt. The basic properties of asphalt before and after aging were evaluated by the rotating thin film oven test. The high-temperature performance and permanent deformation resistance at different temperatures and frequencies were analyzed by the dynamic shear rheological test. The bending creep stiffness test was used to evaluate the low-temperature performance. In addition, the microstructure and modification mechanism of composite-modified asphalt were analyzed by scanning electron microscopy and infrared spectroscopy. The results show that QRA-modified asphalt is superior to matrix asphalt in terms of mass loss, viscosity ratio, and residual penetration, while QRA/RP composite-modified asphalt is further improved on this basis, QRA/RP composite modified asphalt can effectively improve the high and low temperature performance of asphalt.. Although the addition of RP is mainly based on physical modification, it also causes weak chemical reactions and enhances the adhesion of asphalt. The interaction between Qingchuan Rock asphalt and rubber powder significantly improves the overall stability of asphalt structure.

Effect of solid content, particle size, and deflocculant on rheological properties of kaolin suspensions

In this research, two different particle sizes of kaolin were selected, and their rheological properties were characterized by steady-state and dynamic rheological tests. Stress relaxation in the flow curves was a novel finding; redefinition and interpretation of flow curves were the focus of our research. Two methods were used and compared for determining the yield stress. The results showed that suspensions with higher solid content and smaller particle size showed more compact inter-particle interactions, exerting multiple stress relaxation and a strong yield and viscoelastic characteristic. The thixotropic properties were also strongly affected by solid content and particle size, and the differences were reflected in the structural recovery capability. Finally, the effects on rheological properties by introducing deflocculant were studied; the stress relaxation disappeared gradually, and storage modulus and yield stress increased.Moreover, kaolin suspensions with smaller particle sizes required more deflocculant for adsorption and electrical neutralization, confirming that more positively charged edges were exposed after fragmentation. This study has provided an excellent approach to control and adjust the rheological properties of kaolin suspensions in industrial applications.

Analysis of viscoelastic rheological properties and storage stability of solvent cold patching asphalt

Solvent cold patching asphalt (CPA) is commonly mixed with aggregate for rapid pavement pothole repairing in cold and wet seasons, as its ordinary temperature fluidity and gradually increased viscosity. Currently, the evaluation criteria and expectations for the CPA are often related to the modified asphalt without considering the metastable viscoelastic properties of CPA required to ensure the preparation and storage effectiveness. This paper selects diesel oil, kerosene, aromatics solvent oil and isomeric hexadecane four solvents to prepare CPAs, and investigates the viscoelastic properties and storage stability of CPAs with considering the storage time, temperature and solvents incorporation proportion based on penetration test, viscosity test and dynamic shear rheological test. The experimental results show that the optimal dosage of the four diluents is 20%, among which IH-CPA has better storage stability at 30℃, and its 30d viscosity change is the smallest, which is 19.2%. Moreover, the interaction mechanism between solvent and asphalt is explored through molecular simulation model. The research outcome shows that findings from this research can contribute to a better understanding of the metastable structure of CPA, and furnish the high-performance CPA production and storage strategies.

Degradation performance and mechanism of VOCs in asphalt by alkali metal-doped La2Ce2O7-based fluorite through pyroelectric and photocatalytic synergy

Under high-temperature construction conditions, the use of asphalt can release a large amount of volatile organic compounds (VOCs), which has adverse effect on the environment and human health. Part of fluorite oxides show potential application in VOCs conversion due to their excellent photoresponse and chemical stability in addition to ferroelectricity, piezoelectricity and pyroelectricity properties. In this paper, La2Ce2O7-based fluorite was modified with alkali metal doping and its photo-thermal coupling catalytic effects on the degradation performance of VOCs in asphalt were investigated. The results show that the fluorite catalysts La1.85A0.15Ce2O7 (A=Li, Na, K, Rb, Cs) have efficient electron-hole pair separation ability. Among them, the Rb+ doped La2Ce2O7 sample not only has stronger pyroelectric effect due to increased lattice distortion and oxygen vacancies, but also has the best photogenerated charge transport property and more favorable valence band position for oxidation reaction. Under the photo-thermal synergistic effect, the catalytic degradation performance of VOCs in asphalt by Rb+ doped La2Ce2O7 catalyst can reach 82.61 % at 50 min. Additionally, dynamic shear rheological tests indicate that the addition of catalysts at this blending ratio can enhance the rutting resistance of the asphalt material. This study introduces an innovative approach to enhance the efficiency of multi-field coupled degradation processes of volatile organic compounds (VOCs) in asphalt.

Synthesis of a novel bio-based curing agent and the curing behavior of the corresponding epoxy asphalt system

Traditional epoxy asphalt is made from petroleum resources. However, petroleum-based materials may cause environmental pollution and are not renewable. In this study, a bio-based curing agent MYM was synthesized from Maleic anhydride and Myrcene. The cured epoxy EP/MYM with the weight ratio of 1:1 were prepared. When preparing the modified asphalt, carboxyl-terminated liquid nitrile butadiene rubber (CTBN) was incorporated into the EP/MYM system to obtain the EP/MYM/CTBN modified asphalt system (referred to EMC epoxy asphalt). Firstly, the chemical structure of MYM was characterized using Fourier transform infrared spectroscopy (FTIR). Secondly, the mechanical properties and thermal stability of the cured EP/MYM were investigated by tensile test and thermogravimetric analysis (TG). Thirdly, the novel EMC epoxy asphalt was prepared and its composition was optimized. The curing behavior of the EMC epoxy asphalt was investigated by differential scanning calorimetry (DSC). And the time-temperature-transition diagrams (TTT diagrams) were plotted to determine the optimal curing process. Then the surface micro-morphology of EMC epoxy asphalt was investigated by atomic force microscopy (AFM). Finally, the high-temperature viscoelastic properties of EMC epoxy asphalt were investigated using dynamic shear rheology (DSR) tests. The results showed that EP/MYM has better mechanical strength and more excellent flexibility than those of EP/MTHPA and EP/MHHPA. The weight ratio of EP:MYM:CTBN was 10:8:1.5, and the optimal amount of diluent was 8 % of the total weight of the modifier. The semi-empirical kinetic modes of curing reaction were used to plot the TTT diagram of EMC epoxy asphalt, thus determining its curing technique as 120℃/2 h+160℃/3 h. The cured EMC epoxy asphalt showed uniform alternation of light and dark areas in the AFM images, indicating good compatibility and stability. The high-temperature deformation resistance of EMC epoxy asphalt was significantly improved compared to the base asphalt. The novel epoxy asphalt system prepared in this research provides a new route for the development of echo-friendly epoxy asphalt.

Effects of Silicone Rubber on Rheological Properties and Aging Characteristics of Asphalt Binder.

Silicone rubber (SR) is a kind of polymer insulation material with excellent performance. With the service life of silicone rubber products reaching the limit, how to dispose of waste silicone rubber is an urgent problem to be solved. In this paper, silicone rubber-modified asphalt binder (SRMA) was prepared by SR and 90# base asphalt binder. The simulated short-term aging and long-term aging tests of SRMA were carried out using the thin film oven aging test (TFOT) and pressure aging vessel test (PAV). The rotary viscosity test and dynamic shear rheological test (DSR) were applied to the rheological properties of SRMA before and after aging. The degradation degree and chemical composition changes of SR were explored by the toluene insoluble matter test, Fourier transform infrared spectroscopy (FTIR), and a Fluorescence microscope (FM). The results demonstrate that SR can significantly affect the aging resistance, fatigue life, and high-temperature stability of SRMA. As the content of SR rose, the elastic component in SRMA increased, leading to a nice performance in stability at high temperatures and fatigue resistance. However, excessive content (14%wt and 16%wt) had a negative influence on the performance of SRMA. So, the optimal content was speculated to be between 12% and 14%. Furthermore, SR and asphalt binder would be aged and degraded together in the aging process, and this phenomenon was more obvious during long-term aging.

Mechanochemical preparation and performance evaluations of bitumen-used waste polypropylene modifiers

The value-added recycling of waste polypropylene (PP) as asphalt modifiers has been a popular research topic in recent years, but high blending temperatures and asphalt smoke emissions are difficult issues that have not been solved. Therefore, this study innovatively used phthalic anhydride (PA) and catalysts (NHPI or BPO) to mechanochemically turn waste PP into different reaction products as bitumen-use PP modifiers (PPM(N) & PPM(B)). To well understand the physicochemical characteristics of PPMs, thermogravimetric analysis, torque rheology, and scanning electron microscopy were adopted and analyzed. Furthermore, the penetration, softening point, viscosity, storage stability, and dynamic shear rheology (DSR) tests were also carried out to study the performance differences of their PP modified asphalt (PPMA(N) & PPMA(B)). The main results showed that the PPM(N) continues being degraded with PA, but BPO-degraded PP conversely gets chemical connections with PA. With the effects of NHPI and BPO, all PPMs can improve the deformation resistance of virgin bitumen, even at higher temperatures, but as the PA content increases, this performance will gradually deteriorate for PPMA(N) and shows a slight improvement for PPMA(B). The appropriate use of PA can decrease the mixing temperature of PPM(N) with virgin bitumen and improve the storage stability of PPMA binders, and will not significantly sacrifice the resistances of its PPMA(N) to deformation, while with the addition of PA, the mixing temperatures of PPM(B) and virgin bitumen will not be decreased as expected and the resistances of PPMA(B) to deformation remain unchanged. Overall, the proposed mechanochemical method can work out to well address the high-quality recycling and reuse issue of waste PP for its large-scale application in asphalt pavement.

Investigation of the Properties of High-Viscosity Modified Asphalt Binder under Hygrothermal Environments.

High-viscosity modified asphalt binder (HVMA) is used widely as a polymer-modified binder in porous asphalt pavement because it can improve the cohesiveness of the asphalt mixture. However, because of the high voidage in the mixture, HVMA is vulnerable to aging induced by temperature, oxygen, water, sunlight, and other climatic conditions, which degrades the performance of pavement. The properties of asphalt binder are affected adversely by the effects of hygrothermal environments in megathermal and rainy areas. Therefore, it is essential to study the aging characteristics of HVMA under the influence of hygrothermal environments to promote its application as a high-viscosity modifier. A hygrothermal cycle aging test (HCAT) was designed to simulate the aging of HVMA when rainwater was kept inside of the pavement after rainfall in megathermal areas. One kind of base bitumen and three kinds of HVMA (referred to as SBS, A, and B, respectively) were selected in this study. Short-term aging tests, hygrothermal cycling aging tests, and long-term aging tests were performed on the base bitumen and three kinds of modified asphalt binder. Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and dynamic shear rheological (DSR) tests were used to evaluate the properties of the binders on the micro and macro scales. By comparing the index variations of the four binders before and after aging, the effects of the hygrothermal environment on the properties of HVMA were studied. It was found that the effects of the hygrothermal environment expedited the decomposition of the polymer and the formation of carbonyl groups compared with the TFOT and PAV test, which TGA confirmed further. Moreover, the thermal stability of the samples was improved after HCAT. In addition, the master curves of the complex modulus showed that hygrothermal cycles made the high-temperature rutting resistance of asphalt binder increase significantly. All of the results above verified that the effect of hygrothermal cycling could accelerate the aging of HVMA and shorten its service life.

High-Temperature Characteristics of Polyphosphoric Acid-Modified Asphalt and High-Temperature Performance Prediction Analysis of Its Mixtures

To promote the application of economical and sustainable polyphosphoric acid (PPA)-modified asphalt in road engineering, styrene-butadiene block copolymer (SBS), styrene-butadiene rubber (SBR), and PPA were used to prepare PPA/SBS and PPA/SBR composite-modified asphalts, which were tested and the data analyzed. Fourier transform infrared spectroscopy (FTIR) tests and thermogravimetric analysis (TG) tests were carried out to study the modification mechanisms of the composite-modified asphalts, and the high-temperature performance of the PPA-modified asphalt and asphalt mixtures was analyzed by dynamic shear rheology (DSR) tests and wheel tracking tests. A gray correlation analysis and a back-propagation (BP) neural network were utilized to construct a prediction model of the high-temperature performance of the asphalt and asphalt mixtures. The test results indicate that PPA chemically interacts with the base asphalt and physically integrates with SBS and SBR. The PPA-modified asphalt has a higher decomposition temperature than the base asphalt, indicating superior thermal stability. As the PPA dosage increases, the G*/sinδ value of the PPA-modified asphalt also increases. In particular, when 0.6% PPA is combined with 2% SBS/SBR, it surpasses the high-temperature performance achieved with 4% SBS/SBR, suggesting that PPA may be a good alternative for polymer modifiers. In addition, the creep recovery of PPA-modified asphalt is influenced by the stress level, and as the stress increases, the R-value decreases, resulting in reduced elastic deformation. Furthermore, the BP neural network model achieved a fit of 0.991 in predicting dynamic stability, with a mean percentage of relative error (MAPE) of 6.15% between measured and predicted values. This underscores the feasibility of using BP neural networks in predictive dynamic stability models.

Carbon fibers from bitumen-derived asphaltenes: Strategies for optimizing melt spinnability and improving mechanical properties

The demand for low-cost carbon fibers with exceptional mechanical properties continues to grow across various industries. Bitumen-derived asphaltenes have emerged as a promising alternative to polyacrylonitrile (PAN), yet asphaltenes are a complex mixture of compounds, and the fundamental understanding of which asphaltenes are melt spinnable is not clearly understood. In this study, we utilized three distinct types of asphaltenes, each exhibiting notably distinct thermal softening temperatures (Ts) and aromaticity. The optimal melt processing conditions of asphaltenes were determined by dynamic rheology tests. Moreover, we introduced a novel strategy to facilitate the melt spinning of non-spinnable samples by preparing 100 % asphaltene blends with a low Ts asphaltene at different weight fractions. By this means, we achieved continuous melt spinning of precursor fibers. After careful selection of the stabilization and carbonization conditions, uniform carbon fibers were obtained from asphaltenes, which had the highest tensile strength (∼570 MPa) and modulus (∼60 GPa) values, comparable to isotropic pitch-based carbon fibers. Further post-processing of the as-spun fiber resulted in a significant increase in tensile properties, ∼1.1 GPa for strength and ∼91 GPa for modulus. Overall, this study identified spinnable asphaltene precursor characteristics and fiber post-processing methods for achieving low-cost, high-quality carbon fibers from asphaltenes.

Self-assembled lyotropic liquid crystals from natural surfactant: A study on their structural, rheological and antimicrobial behaviour

Soft self-assembled systems with smart functions have been explored over the past decades for diverse applications. However, the toxicity of synthetic surfactant based self-assembled systems and their stability always remain a point of concern. There is always a great quest to find an alternative to overcome such shortcomings of self-assembled systems. Hence, in this context, we made an effort to engineer self-assembled lyotropic liquid crystals (LLCs) using different concentrations of the medicinal plant Glycyrrhiza glabra L. in the nonaqueous polar media of glycerol, ethylene glycol and formamide. These nonaqueous solvents with considerable polarity, high cohesive energy, dipole moment and hydrogen bonding ability, not only offer the perfect environment for self-assembly, but also provide longtime stability. Nematic lyotropic ordering is obtained for studied systems at different concentrations of Glycyrrhiza glabra L./ nonaqueous solvents as confirmed via polarising optical microscopy (POM) and X-ray diffraction (XRD) analysis. Electrostatic and hydrogen bonding interactions among polar solvents and amphiphilic Glycyrrhiza glabra L. molecules could be responsible for nematic ordering. FTIR spectroscopy is employed to confirm the hydrogen bonding in LLCs. The prepared LLCs are studied through static, dynamic rheology under the shear range 1–100 s-1 to explore their fluidic behaviour and establish correlation with structural parameters. The studied LLC systems from three solvents exhibit non-Newtonian shear thinning behaviour at all concentrations. The dynamic rheology tests indicate the elastic behaviour of all LLC systems. LLCs derived from glycerol exhibit soft-solid gel-like behaviour, while weak gel-type behaviour is observed for ethylene glycol and formamide-based LLCs. Considering the medicinal value of prepared LLCs, their antibacterial activity has been checked against the gram-positive bacteria Bacillus subtilis. LLC phases show strong antibacterial activity, about 2–3 times better than that of the standard drug streptomycin used for this study.

A chemical interpretation for the post-reversion upturn in the natural rubber/accelerated sulfur system based on the viscoelastic properties and cross-link density measurements

The curing cycle of natural rubber (NR) with a conventional accelerated sulfur system (CV) generally exhibits three phases. The induction phase, the crosslinking phase, and the reversion phase. Prolonged curing of NR/CV system even at a temperature of 150 °C can show reversion. Many research reports are available in the literature with reference to the reversion behavior and the subsequent network modifications of natural rubber with accelerated sulfur. However, the literature regarding post-reversion curing behavior is scanty. This article describes the post-reversion upturn of natural rubber with a conventional accelerator sulfur system at a higher curing temperature. A network rebuilding after collapsing the initially formed network due to reversion was identified as the primary reason for the post-reversion upturn. The dynamic rheological testing capability of the Rubber Process Analyzer (RPA) was employed to characterize the network formed during curing, reversion and post-reversion phases. The cure-strain sweep data from the RPA indicated that the shear storage modulus (G′) of the broken network increased due to the post-reversion upturn. The chemical crosslink densities of the samples were also found to increase due to the upturn curing behavior. From these experimental results and the information conceived from the previous literature, two plausible mechanisms have been proposed to interpret the post-reversion upturn cure behavior.

Study of High-Temperature Rheological Properties of Emulsified Asphalt Residues

The residue of emulsified asphalt is its final state when it becomes part of an asphalt mixture. Therefore, the mechanical properties of the residue have a significant impact on the performance of emulsified asphalt mixtures. Dynamic shear rheological tests and fluorescence microscopy were conducted to explore the effects of emulsification and aging on the rheological properties and micro-morphology of emulsified asphalt residue. The results of both the temperature sweep and multiple stress creep recovery tests indicated that the emulsification of the asphalt had different effects on the rheological properties of the base asphalt and the styrene-butadiene-styrene (SBS)-modified asphalt. For the base asphalt, emulsification increases the complex shear modulus by about 5% and reduces irrecoverable creep flexibility by 30%. However, the physical grinding effect of the colloid mill during the emulsification process could destroy the internal spatial network structure of SBS, leading to a reduction in the complex shear modulus by about 5% and a 10% increase in irrecoverable creep flexibility. This phenomenon is similar to the aging of SBS-modified asphalt, which, in turn, leads to a decline in the performance of emulsified SBS-modified asphalt residues.

Friction Characteristics and Lubrication Properties of Spherical Hinge Structure of Swivel Bridge

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation.

Rheological properties of warm mixed high viscosity asphalt at high and low temperatures.

The rheological properties of asphalt can well reflect its road performance, but the rheological properties of warm mix high viscosity asphalt (HVA) are unclear. In order to study the effect of warm mixing agent on rheological properties of HVA, two kinds of warm mixing agent EC120 (EC) and Evotherm M1 (M1) were selected to prepare warm mix HVA. The rheological properties of warm mix HVA at high temperature (135~195°C), medium temperature (0~80°C) and low temperature (-6~18°C) were studied by Brinell rotary viscosity test, dynamic shear rheological test (including temperature scanning, frequency scanning, linear amplitude scanning) and bending beam rheological test. The test results show that both EC and M1 have good viscosity reduction effect on HVA at high temperature, and can effectively reduce the construction temperature. At medium temperature, M1 can effectively improve the fatigue resistance of HVA, and the fatigue life can be increased by about 30% when the dosage is 0.6%. EC can increase the rutting factor of HVA and improve its resistance to deformation, but it will reduce its fatigue performance. When the dosage is 4%, the fatigue life will be reduced by about 9%. At low temperature, M1 can reduce the creep stiffness S, increase the creep rate m, and improve the low temperature performance of HVA, while EC has the opposite effect, weakening the low temperature performance of HVA. The results are helpful to understand the rheological properties of warm mix HVA and promote its application.

Rheological Study on Blend Solutions of Non-mulberry Silk Fibroin and Gelatin Biopolymers

In current research work, we have studied the blending effect of non-mulberry silk fibroin (10% weight/volume basis) and gelatin (20% weight/volume basis) in formic acid. Several blends as SF10G0, SF2G8, SF3G7, SF5G5 and SF0G10 have been made and their rheological behaviour was investigated. The blend solutions were subjected to a steady shear rheological study in the variety of range of shear rates, namely 0.01–500 sec-1 and the viscosities of blend solutions were noticed to decrease in comparison to pure silk solution. The frequency sweep was employed in dynamic rheological tests to determine complex viscosity of these solutions from range of angular sweep 0.1–100 rad/sec. The consistent shear-thinning behaviour was noted for all the blends. The difference in numerical values of shear and complex viscosities indicated disobedience of Cox-Merz rule. Such analysis can be utilised for tailoring the properties of solution prior to processing them to create a versatile range of materials.

Study on Viscoelastic Properties of Various Fiber-Reinforced Asphalt Binders.

This study analyzed the viscoelastic properties of asphalt binders reinforced with various fibers, such as modified asphalt binder, modified asphalt binder reinforced with lignin fibers (LFs), polyester fibers (PFs), and polypropylene fibers (PPFs), using dynamic shear rheological (DSR) testing. Then, the experiment generated data on the dynamic modulus and phase angle, which described the dynamic rheological characteristics at varying temperatures. The generalized Maxwell model was employed to select the appropriate element, and the test curve was fitted into a discrete time spectrum based on the time-temperature equivalence principle (TTSP). The master curves of the relaxation modulus and creep compliance were established to predict the relaxation and creep properties of various asphalt binders. The analysis indicated that fiber-reinforced binders offer superior resistance to high temperatures and long-term deformation, while being less sensitive to temperature and having a more significant elastic characterization. The binders reinforced with PPFs and LFs exhibited superior performance in high-temperature settings and long-term durability, respectively. On the other hand, the binder reinforced with PFs displayed exceptional high-temperature elastic properties. Additionally, based on the experimental data and corresponding discussion, it appears that the 13-element GM model is more appropriate for fitting the data.