Rheometer Test Research Articles

Probing Tissue Viscoelasticity With STL Ultrasound Shearwave Spectroscopy Using Cole-Cole Diagrams.

Viscoelasticity is mapped by dispersion in shearwave elastography. Incomplete spectral information of shearwaves is therefore used to estimate mechanical stiffness. We propose capturing the "full-waveform-information" of the shear wave spectra to better resolve complex shear modulus μ* (ω). Approach is validated on phantom models, animal tissues, and feasibility demonstrated on human post-delivery placenta. We captured robust estimates of μ* in ex-vivo livers subjected to water bath ablation, glutaraldehyde exposure and in the placenta. Complex modulus at 200 Hz is more reflective of tissue stiffness than cross-correlation estimate. Bias increased in phantoms with higher gelatin (G) (0.65: 6% G) and oil (O) (0.58: 6% G and 40% O) concentration, compared to elastic phantoms with low stiffness (0.33: 3% G). Actual tissues also reported higher bias in cross-correlation estimate (rabbit liver: 0.61, porcine liver: 2.20, and human placenta: 0.63). Stiffness is sensitive to ablation temperature, where the overall modulus changed from 3.02 KPa at 16 °C to 2.75 KPa at 56 °C in water bath. With exposure to Glutaraldehyde, the overall modulus increased from 2.37 to 9.03 KPa. Reconstruction errors in the loss modulus decreased by 68% with the power law compared to a Maxwell model in porcine livers with Cole-Cole inverse fitting. Omitting Shear wave attenuation leads to bias. Reconstruction of rheological response with a model is sensitive to its architecture and also the framework. We use "full spectral information" in ultrasound shear wave elastography to better map μ*(ω) changes in viscoelastic tissues.

Thiol‐ene click chemistry for constructing transition layer to enhance the interface interaction between polyacrylonitrile fiber and styrene‐butadiene‐styrene modified asphalt

AbstractBased on the high chemical stability and excellent end‐group functionalization capability of polyhedral oligomeric silsesquioxane (POSS), this study utilized thiol‐functionalized POSS (POSS‐SH) in a click chemistry reaction with styrene‐butadiene‐styrene triblock copolymer (SBS). The objective was to design a functional group forming a chemical bond with the polymer matrix, resulting in the preparation of thiol‐functionalized polyacrylonitrile (PAN) fibers chemically cross‐linked with POSS‐SH/PAN/SBS hybrid material. This hybrid material not only enhanced the compatibility between the components but also facilitated a connection between the fiber and SBS, thereby improving the mechanical properties of the modified asphalt. Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), and atomic force microscopy analyses confirmed the successful modification of POSS‐SH/PAN fibers. FESEM analysis of the modified asphalt verified that POSS‐SH/PAN fibers contributed to strengthening the interfacial performance between the fiber and asphalt. Cone penetration and dynamic shear rheometer tests indicated that, compared to SBS‐modified asphalt, PAN/SBS and POSS‐SH/PAN/SBS‐modified asphalt exhibited enhanced shear strength, deformation resistance, and viscoelastic properties. Additionally, at 46°C, the storage modulus (G′) of 1.5% POSS‐SH/PAN/SBS‐modified asphalt increased by 11% compared to 1.5% PAN/SBS asphalt, with increases of 13.75% and 10.8% in loss modulus (G″) and complex modulus (G*), respectively.

Effect of Rapeseed Imidazoline Addition on the Properties of Lab-Aged 35/50 Pen Grade Bitumen

For the successful reuse of old asphalt as reclaimed asphalt pavement (RAP) added to new bituminous mixtures, it is necessary to improve some of its properties. This can be attained, for example, by adding an appropriate rejuvenator. The aim of this study was to evaluate the properties of lab-aged 35/50 pen grade bitumen rejuvenated with the addition of two varieties of rapeseed imidazoline. Dynamic shear rheometer (DSR) and ductilometer tests were further conducted to evaluate the properties of bituminous binders at the intermediate operating temperature of road pavements. The obtained results demonstrated a beneficial effect of rapeseed imidazoline on the properties of the tested pen grade bitumen after ageing when added at a rate of 6% or more. This effect was the most pronounced in the case of the fatigue cracking critical temperature (FCCT), where a lower value was obtained for the aged and rejuvenated 35/50 bitumen than for the same bitumen before ageing. The tensile curves developed from the results of the tensile force tests using the ductilometer confirmed the previous conclusions from the measurements using the DSR. However, the original plastic behaviour of the aged pen grade bitumen was restored only through the addition of rapeseed imidazoline at a rate of 8%.

Performance evaluation of asphalt binders incorporating surface-modified diatomite and bio-oil: A value-added utilization of natural resource

To study the effect of surface-modified diatomite (SMD) on bio-asphalt performance, the asphalt binders incorporating SMD and bio-oil (SMDB) was prepared with different dosages. The high-temperature characteristics of SMDB were assessed by consistency test, viscosity test, and dynamic shear rheometer (DSR). Meanwhile, the low-temperature characteristics of SMDB were evaluated by bending beam rheometer (BBR) and ductility test. The compatibility of SMDB was assessed by a storage stability test and a Fluorescence microscope (FM). The adhesion and chemical composition of SMDB were analyzed using the sessile drop method and Fourier transform infrared (FTIR) spectroscopy, respectively. Finally, the moisture stability and high-temperature properties of the SMDB mixture were studied using the tensile strength ratio (TSR) test and wheel track test, respectively. The preliminary results of this work show that the addition of SMD increases the viscosity, softening point, fatigue index, and rutting factor of asphalt and reduces the penetration. It is found that SMD improves the anti-aging performance, adhesion performance, and high-temperature stability of SMDB. Although SMD has a negative effect on the low-temperature properties and fatigue resistance of asphalt, the characteristics of SMDB at low temperatures are still superior to those of virgin asphalt. SMD at low content had little effect on the fatigue resistance of the bio-asphalt. Moreover, it is found that SMD is better than the original diatomite in enhancing bio-asphalt properties more significantly. In addition, the blending among SMD, asphalt matrix, and bio-oil is the physical modification, and the mixture has excellent storage stability. Finally, the mixture property testing results indicate that SMD improves the rutting and moisture resistance of the SMDB mixture.

Evolution of Rheological and Microscopic Properties of Asphalt Binders under Fuel Corrosion

Vehicle fuel leaks can adversely affect the performance of asphalt pavements. To study the mechanisms of fuel corrosion damage in asphalt, four asphalt binders were selected in this study, and the evolution of their rheological and microscopic properties was investigated. Fuel corrosion caused continuous mass loss in asphalt binders. Base asphalt lost more than 50% of its mass after 24 h of fuel corrosion, while modified asphalts had better resistance. According to dynamic shear rheometer tests and multiple stress creep recovery tests, modifiers improved the high-temperature rheological properties of these asphalt binders. As the degree of fuel corrosion deepened, the indexes characterizing the high-temperature performance deteriorated. Rubber-modified asphalt showed the best resistance to high-temperature deformation, while the performance of LDPE-modified asphalt was more stable. In contrast, fuel corrosion improved the resistance of asphalt binders to low-temperature cracking to some extent: the creep strength (S) decreased as the creep rate (m) increased, and the resistance of SBS-modified asphalt to low-temperature cracking was optimal, with a 36% decrease in S-value after 24 h of fuel corrosion. Fourier transform infrared spectroscopy tests showed that diesel corrosion was a process of this physical dissolution, with no change in the chemical functional groups. Meanwhile, by using fluorescence images and analyzing the four-component test results, we found that fuel corrosion disrupted the stabilized structure formed by the modifiers, and the heavy components in the asphalt binders were converted into light components. This study reveals the evolution of the rheological and microscopic properties of asphalt under fuel corrosion, which can provide a reference for the optimization of fuel corrosion resistance in asphalt pavement.

Enhancing Asphalt Performance and Its Long-Term Sustainability with Nano Calcium Carbonate and Nano Hydrated Lime

Nanomaterials enhance the performance of both asphalt binders and asphalt mixtures. They also improve asphalt durability, which reduces resource consumption and environmental impact in the long term associated with the production and transportation of asphalt materials. Thus, this paper studies the effectiveness of Nano Calcium Carbonate (Nano CaCO3) and Nano Hydrated Lime (NHL) as modifiers and examines their impact on ranges from 0% to 10% through comprehensive laboratory tests. Softening point, penetration, storage stability, viscosity, and mass loss due to short-term aging using the Rolling Thin Film Oven Test (RTFO) were performed on asphalt binders. Results indicated a significant improvement in binder stiffness, particularly at 4% Nano CaCO3 and 6% NHL content by weight. Dynamic Shear Rheometer (DSR) tests further revealed substantial improvements in rutting resistance, with NHL exhibiting superior high-temperature stability and a notable increase in the rutting factor. Marshall stability tests on asphalt concrete (AC) mixtures showed a 22.3% increase in stability with 6% NHL by weight, surpassing the 20.2% improvement observed with Nano CaCO3 and indicating enhanced load-bearing capacity. The resilient modulus of the mixtures consistently increased with the addition of NHL, suggesting improved durability in rutting. Moisture susceptibility tests revealed that NHL significantly enhances moisture resistance, exceeding the 80% TSR benchmark at just 2% content by weight and reaching an impressive 94.6% at 10% content by weight. In contrast, Nano CaCO3 demonstrated a more gradual improvement, achieving an 88.2% TSR at 10% content. Furthermore, permanent deformation analysis indicated a 68.64% improvement in rutting resistance with 10% NHL content by weight, exceeding Nano CaCO3’s improvement rate. Optimal fatigue resistance was achieved at 4% for Nano CaCO3 and 6% for NHL by weight, with respective CT index improvements of 30% and 35.4%, showing NHL’s consistent benefits across various nanomaterial contents. Overall, the study suggests that both Nano CaCO3 and NHL positively impact asphalt performance, with NHL offering more pronounced benefits across a range of properties. These findings provide valuable insights for pavement engineers and underscore NHL’s potential as an effective additive in asphalt mixture design. Real-world applications and validations are essential for a comprehensive understanding of these nanomaterials in practical pavement engineering scenarios.

Rheological performance evaluation of activated carbon powder modified asphalt based on TOPSIS method

In this study activated carbon powder (ACP) was incorporated into asphalt to substitute a portion of the conventional filler (mineral powder, MP). The dynamic modulus at elevated temperatures, temperature-dependent viscosity sensitivity, low-temperature creep, and the interaction between asphalt and ACP were examined through dynamic shear rheometer testing, viscosity testing, and bending beam rheometer testing. Moreover, statistical methodologies such as the entropy weight method (EWM) and the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) were employed to optimize the proportion of ACP by evaluating the comprehensive rheological behavior of asphalt mastic (including high temperature performance, low temperature performance, flowability, and asphalt-ACP interaction). The findings demonstrate that ACP can enhance the resistance of asphalt mastic to high-temperature deformation to a certain degree. The ratio of creep rate to stiffness (m/S) decreases with the addition of ACP, indicating that ACP may exacerbate the occurrence of low-temperature thermal cracking in asphalt mastic. The interaction ability of asphalt mastic is significantly enhanced when a portion of the filler is replaced with ACP. The loss factor shows significant impact on the comprehensive evaluation. According to TOPSIS analysis, asphalt mastic with a blending proportion of 40% ACP and 60% MP performs better in terms of comprehensive rheological properties.

Emulsions containing allantoin and D-panthenol as attractive moisturizing agents

Dry skin is the common problem affecting people which triggers many unpleasant symptoms such as roughness, peeling, burning, itching and greater sensitivity to injury and external conditions. One method to assess the water loss of skin is transepidermal water loss (TEWL) measurement. Various active substances, for instance allantoin and D-panthenol, can be used to overcome the symptoms of the dry skin. In this study, emulsions containing allantoin and D-panthenol as moisturizing agents and various oils (liquid paraffin, Cannabis sativa, Baobab and Coconut oil) were developed. The prepared emulsions were characterized by: visual and microscopic appearance and pH values. Stability analysis was conducted by centrifuge test and sensory test using sensory sensation was evaluated. Rheological experiments were performed using a rheometer, while mechanical and adhesion tests by texture analyzer. TEWL values were measured using a tewameter, after application of the emulsions to the responders skin. TEWL study noticed that regular permanent use of moisturizing emulsions with allantoin and D-panthenol limited the water loss. In conclusion, it can be stated that emulsions containing allantoin and D-panthenol as active agents and Coconut oil as oily ingredient are attractive formulations with moisturizing effect and good application features.

The Slump Flow of Cementitious Pastes: Simulation vs. Experiments.

Understanding the transient properties of cementitious pastes is crucial for construction materials engineering. Computational modeling, particularly through Computational Fluid Dynamics (CFD), offers a promising avenue to enhance our understanding of these properties. However, there are several numerical uncertainties that affect the accuracy of the simulations using CFD. This study focuses on evaluating the accuracy of CFD simulations in replicating slump flow tests for cementitious pastes by determining the impact of the numerical setup on the simulation accuracy and evaluates the transient, viscosity-dependent flows for different viscous pastes. Rheological input parameters were sourced from rheometric tests and Herschel-Bulkley regression of flow curves. We assessed spatial and temporal convergence and compared two regularization methods for the rheological model. Our findings reveal that temporal and spatial refinements significantly affected the final test results. Adjustments in simulation setups effectively reduced computational errors to less than four percent compared to experimental outcomes. The Papanastasiou regularization was found to be more accurate than the bi-viscosity model. Employing a slice geometry, rather than a full three-dimensional cone mesh, led to accurate results with decreased computational costs. The analysis of transient flow properties revealed the effect of the paste viscosity on the time- and shear-dependent flow progress. The study provides an enhanced understanding of transient flow patterns in cementitious pastes and presents a refined CFD model for simulating slump flow tests. These advancements contribute to improving the accuracy and efficiency of computational analyses in the field of cement and concrete flow, offering a benchmark for prospective analysis of transient flow cases.

Shear strength parameters for porous asphalt mixtures: From macro to meso

The shear strength of asphalt mixtures significantly influences the rut resistance of flexible pavements. Existing methods predominantly address macroscopic aspects, failing to unveil the underlying mechanisms. Moreover, experimental determination of shear strength parameters is time-consuming, but there is a lack of simple prediction methods. This study explores correlations between macroscopic parameters (friction angle and cohesion) and key mesoscopic shear-related factors in Porous Asphalt Mixtures (PAMs) using multiscale triaxial compressive tests, dynamic shear rheometer tests, and sessile drop tests. The research reveals that PAM is influenced not only by aggregate interlock but also by stiff mastic, resulting in a reduced friction angle at a lower temperature. Regression analyses establish a prediction formula for PAMs, incorporating the friction angle of the aggregate skeleton and the complex modulus of the mastic. A correlation function, inspired by Griffith's fracture theory, was also proposed to link PAM's cohesion with the complex modulus and the work of cohesion of mastic, and the friction angle of PAMs. Predictions for PAM's friction angle and cohesion align well with macro-level experimental results, with all the coefficients of determination of over 0.94. These findings enhance the understanding of asphalt mixture shear strength formation and enable shear-resistance optimisation from meso-level.

Influence of rejuvenator components on rheological properties of recycled bitumen in the full temperature range

Recovering aged bitumen from reclaimed asphalt pavement (RAP) is crucial for the evolution of pavement recycling. This study delves deeply into the effects of rejuvenator components on the rheological properties of rejuvenated bitumen across a wide temperature range. The investigation utilized the rolling thin film oven test (RTFOT) and the pressure aging vessel (PAV) test to simulate the short-term and long-term aging of the bitumen binder, respectively. Four distinct rejuvenators were then applied to recover the bitumen at varied aging levels. Detailed chemical analyses, encompassing the four-fraction (SARA) method and Fourier transform infrared spectroscopy (FTIR), were employed to identify the chemical compositions and key functional groups of both the rejuvenators and the rejuvenated bitumen. The rheological behavior of rejuvenated bitumen was assessed through a comprehensive series of tests, including conventional, temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. A Pearson correlation analysis highlighted a significant positive association between specific rejuvenator components, notably asphaltene (As), saturate (S), and aromatic (Ar), and the high-temperature performance of the rejuvenated bitumen. The findings of this research offer insights into the formulation of rejuvenators, potentially enhancing the performance of rejuvenated asphalt pavements and facilitating sustainable infrastructure advancements.

Investigation of distributed recycling of polylactic acid over multiple generations via the granule-based material extrusion process

Plastic production has experienced exponential growth in recent decades, resulting in a significant increase in plastic waste worldwide due to its durability and non-biodegradable nature. With the rapid development and worldwide utilization of material extrusion (ME) 3D printers, the generation of 3D printed thermoplastic waste has also increased rapidly. However, ME 3D printers themselves can offer a promising solution for implementing a novel, practical, and cost-effective approach to distributed recycling of 3D printed waste. While previous studies have predominantly focused on validating and evaluating the distributed recycling using the filament-based material extrusion (FME) method, research on distributed recycling over multiple cycles (more than two) using the granule-based material extrusion (GME) method is limited. This can be attributed to the fact that the GME process is relatively immature compared to the more established FME method, and recent studies on the GME method have mainly focused on the viability, optimization of processing parameters, and mechanical performance of GME printed specimens. To address this research gap, this study aimed to comprehensively investigate the GME-based distributed recycling of PLA waste over multiple recycling generations using a multi-scale characterization framework, including tensile tests, hardness tests, mass measurements, optical microscopy, scanning electron microscopy (SEM), color measurements, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and rheometer tests. The results of this study demonstrated consistent decreases in the tensile strength, melting temperature, and rheological properties of the recycled PLA samples with the increase of recycling cycles. These changes were consistent with the gradual decrease in the average molecular weights of the PLA samples. Notably, the recycling process was terminated after the third recycling cycle due to the distinct color exhibited by the third recycling printed specimens compared to the initially printed PLA specimens, as indicated by chromaticity measurements.

Experimental study on the effect of Coumarone resin on the performance of SBS-modified asphalt.

An inexpensive and high-performing solid Coumarone resin was added to Styrene-butadiene-styrene (SBS) copolymer-modified asphalt to enhance its storage stability and road performance. To assess the effect of Coumarone resin dosage on the SBS-modified asphalt, a series of laboratory tests were conducted. The composite modified asphalt's segregation test was used to evaluate its storage stability, Dynamic Shear Rheometer (DSR) and Multiple Stress Creep Recovery (MSCR) tests were employed to investigate its high-temperature performance and permanent deformation resistance, and the Bending Beam Rheology (BBR) test was utilized to measure its low-temperature performance. Fluorescence microscopy was used to observe the composite modified asphalt's microstructure, and Fourier Transform Infrared Spectroscopy (FTIR) was conducted to study the changes in chemical structure during the modification process. The results showed that Coumarone resin can improve the compatibility of SBS and asphalt, improve the high-temperature performance and deformation resistance of SBS-modified asphalt, and adding an appropriate amount of Coumarone resin can help enhance the low-temperature cracking resistance of modified asphalt. The optimal dosage of Coumarone resin recommended for SBS-modified asphalt performance enhancement is 2% under the test conditions, as determined by comparing the test results of samples with various dosages.

A novel numerical analysis method for predicting non-Newtonian lubricant (grease) distribution in ball bearings

Grease is a visco-elastic fluid and the most common lubricant for rolling bearings. During the churning phase (initial phase) of bearing operation, most of the grease is collected at various locations in the bearing, e.g. by the seal, at the bottom cage bar, in the cage pockets, which are then called grease reservoirs. These are formed based on bearing operating conditions, grease type, bearing geometry, bearing type. The grease reservoirs supply lubricant to the bearing contacts via bleeding: during operation the oil bleeds out of the reservoirs and lubricates the contacts. Since the distribution of grease is crucial to the bearing lubrication, the design of bearing components e.g., the cage, shall aim at an optimal grease reservoir creation during the churning phase. It is difficult to observe the effect of component design on the grease distribution through real life experiments, so CFD simulations with MPS (Moving Particle Semi-implicit) method are performed here. Flow Simulations with MPS method can help determine the factors influencing the grease distribution inside the bearing after churning, with the final aim of enhancing lubrication. For the current simulations, a CAE software based on MPS, namely Particleworks, was used. Grease consists of a base oil, a thickener, and additives. Since it is a non-Newtonian fluid, it has a nonlinear relation shear stress vs shear rate. It is a visco-elastic material, so it does not flow in the absence of a threshold force. For current simulations, the grease rheology has been modelled using the Herschel-Bulkley model. The model was fitted on in-house rheometer test data and was reduced to a single cage-ball segment. All critical kinematic properties were preserved, that is the speeds of both the inner ring and ball surfaces and the oscillation of the ball position within the pocket as it travels through the loaded and unloaded zones of the bearing. The location and the duration of grease injections resulted in different grease distributions in the model. For demonstration purposes, this document only focuses on the results obtained injecting a grease layer on the inner ring surface in front of the contact. This realistically predicted grease reservoirs to be located at the cage bottom, on the top of cage and in the cage pockets. Sensitivity study on particle size, time step, surface tension and the parametric variation of the bearing speed were also performed. This is an important milestone, as we are able for the first time to virtually simulate the onset of grease reservoirs at locations corresponding to evidence from real bearing operations. The distribution of grease observed at the cage pockets is very important for oil film replenishment. This outcome gives us confidence that the MPS method can be used to support the design of bearing components contributing to enhanced lubrication.

Effect of Filler to Bitumen Weight Ratio on Low-temperature Cracking Performance of Asphalt Mixture

The effect of mineral filler weight ratio on the low-temperature performance of hot asphalt mixtures with continuous gradation has been a subject of significant interest in the field of pavement engineering. This study focused on testing mastic, which is a bitumen mixture with mineral filler passing through a No. 200 sieve, using various tests, such as the bending beam rheometer test (BBR), direct tensile (DT) test, Infrared spectroscopy test (FTIR), X-ray diffraction (XRD) test, and semi-circular bending (SCB) test. Different weight ratios of mineral filler to useful bitumen ranging from 0.4 to 1.6 were investigated for PG 70-16 bitumen. According to the SHRP-A-407 standard, the weight ratio of mineral filler to useful bitumen plays a crucial role in determining the low-temperature performance of asphalt mixtures. The research findings confirm this fact, indicating that the weight ratio of mineral filler to bitumen plays a crucial role in determining the low-temperature performance of asphalt mixtures. As the filler-to-bitumen ratio increased, the stiffness of the bituminous mastic increased, leading to reduced fracture strain and decreased low-temperature cracking life. The optimal filler-to-bitumen ratio was recommended to be a maximum of 0.8 to balance performance and control low-temperature behavior. The results of this study underscore the importance of considering the rheological properties of bitumen mastic in addition to bitumen and asphalt mix when evaluating lowtemperature performance. Keywords: Asphalt mixing, Filler-to-bitumen ratio, Cracking performance, Lowtemperature, cracking.

Investigation of The Effect of Micronized Ethylene-Propylene-Diene Monomer (EDPM) Powder Wastes on Physical and Mechanical Properties in EPDM Mixtures

In this study, micronized-ethylene-propylene-diene monomer powders (m-EPDM) by the physical crushing method were added to EPDM rubber, and their effects on physical and mechanical properties were examined. Micronized EPDM powders were added at rates of 10-20-30%. EPDM rubber was pulped with micronized EPDM powder using a 1.5-liter laboratory type mini banbury. The obtained paste was vulcanized in the press at 180 °C for 20 min., and test plates were acquired. Rheological and fluidity properties of EPDM rubber with m-EPDM powder added were examined by pre-press rheometer (Moving Die Rheometer_MDR) and Mooney viscosity tests. Tensile and permanent deformation tests were performed to determine mechanical properties density, Shore A hardness tests were performed to determine physical properties and dispersion analysis was performed to distribute the additives in EPDM rubber. As a result of the study, minimum torque (ML) values increased while maximum torque (MH) values decreased depending on the amount of m-EPDM. Mooney viscosity of EPDM/30m-EPDM rubber increased by 40.9%. It was observed that cure rate index (CRI) did not change depending on the amount of m-EPDM. With the addition of 30% m-EPDM, breaking strength decreased by 39.2%, and elongation at break was reduced by 9.87%.

Biomass waste to produce bio oil as rejuvenator for asphalt based on pyrolysis technology

ABSTRACT The objective of the current study is to research the suitability of using two bio-oils produced from corncob and birch bark as two bio-rejuvenators to regenerate aged asphalt binders. To this end, the pyrolysis characteristics of corncob and birch bark were analysed using a thermogravimetric analyzer. The chemical characteristics of the bio-rejuvenators were then evaluated via an elemental analyzer and the Gas Chromatograph Mass Spectrometer (GC-MS) test. The results revealed the presence of a great quantity of lightly weighted compounds in bio-oils. Pen70 asphalt was used as control asphalt binders. The Rotational Viscometer (RV) test result showed that bio-rejuvenators could help reduce the viscosity of aged asphalt binders. In addition, the Dynamic Shear Rheometer (DSR) experiments revealed that bio-rejuvenators could reduce the complex shear modulus, decrease percent strain recovery, increase non-recoverable creep compliance and restore the fatigue performance of the aged asphalt. The Bending Beam Rheometer (BBR) tests indicated that the cracking performance of the bio-rejuvenated asphalt was also improved compared with the aged asphalt. The Fourier transform infrared spectra demonstrated that the bio-rejuvenators helped reduce the aged asphalt's carbonyl and sulfoxide indexes. In addition, the Gel Permeation Chromatography (GPC) test indicated that bio-rejuvenators reduced the polydispersity and molecular weight of the aged asphalt.

The Statistical Analysis on Physical and Rheological Properties of the Bitumen Modified with CR+SBS+Sasobit

In this study, crumb rubber (CR), styrene-butadiene-styrene (SBS) and warm mix additive (Sasobit) modified bitumen binders were statistically investigated. The data set consisting of 32 binders modified by pure, CR, SBS, Sasobit and CR+SBS+Sasobit was studied. While additive ratios were defined as independent variables, results obtained from softening point, viscosity, dynamic shear rheometer and bending beam rheometer experiments were defined as dependent variables. Experiment results were analyzed individually and collectively using response surface methodology and pearson correlation methods. When the experiments were evaluated individually, very important relationships were found between additives rates and all experimental results. Actual values and estimated values obtained as a result of statistical analysis overlapped. It was determined that there were strong relationships between all experimental results when the pearson correlation between the experimental results was examined. Optimization was made according to the test results where the viscosity of 3000 cP (suitable workability), softening point and dynamic shear rheometer test results were maximum (superior high temperature performance) and the test result of bending beam rheometer was minimum (superior low temperature performance). According to this, CR, SBS and Sasobit rates were determined as 5.6%, 4% and 1%, respectively.

Revealing time-dependent behavior of asphalt binder at low-temperature by crystallization kinetics

To gain deeper insights into the influence of thermal history on wax crystallization and thermoreversible aging for enhanced asphalt pavement durability, this study employed the extended bending beam rheometer (ExBBR) test and modulated differential scanning calorimetry (MDSC) analysis. These techniques were utilized to analyze the crystallization kinetics of diverse asphalt binders under both isothermal and non-isothermal conditions. The ExBBR test results demonstrated that the cold-temperature performance of asphalt binders experiences continuous degradation with an increasing grade loss during conditioning. The Avrami isothermal crystallization kinetic theory proved to be an accurate descriptor of the thermoreversible aging tendency in asphalt binders. MDSC test findings revealed that distinct cooling rates exert an influence solely on specific asphalt varieties, with discrepancies in thermal signals arising from diverse oil sources. The Ozawa exponent, determined through the endothermic background area selected from the baseline, serves as a reliable guide for assessing the degree of thermoreversible aging in different asphalt binders. Crucially, the appearance of crystallizable fractions in asphalt binders with varying thermal histories can be effectively modeled using both isothermal Avrami and non-isothermal Ozawa theoretical frameworks. To conclude, the study undertook the separation of four components of asphalt, analyzing the microstructural evolution of these components under identical test conditions. The contribution of each component to the asphalt crystallization process is comprehensively expounded through considerations of glass transition temperatures, as well as endothermic and exothermic peaks associated with distinct components.

Experimental study on the influence of asphaltenes with small dosage on the rheological and gelation behavior of waxy mixtures

Asphaltene, the heaviest and most polar non-hydrocarbon component in crude oil, may interact with waxes and affect the flow and gelation behavior of waxy oils. To further study the effect of asphaltene on the flow and gelation behavior of waxy oils, five wax-containing simulated oils with small dosage asphaltene content were prepared. Through pour point and rheometer test, it is found that asphaltenes can improve the low-temperature rheology of waxy oil. There is no critical turning point above which the low-temperature flowability improved. With an increase in asphaltene content from 0 wt% to 0.1 wt%, notable changes were observed in the properties of the waxy oil. The pour point, which measures the temperature at which the oil becomes too viscous to flow freely, exhibited a decrease from 25 ℃ to 13 ℃. Similarly, the gelation temperature, indicating the temperature at which the oil starts forming a gel-like consistency, also decreased from 29.0 ℃ to 27.1 ℃. These modifications can be attributed to the presence of asphaltene in the oil sample. This outcome can be attributed to the interference caused by the presence of asphaltenes, which disrupts the gel network structure of the waxy oil and consequently hinders its gelation process. Simultaneously, within the low asphaltene content range, an increase in asphaltene content resulted in a considerable decrease in the viscosity of the waxy oil at 10 °C, reducing it from 531.5 mPa s to 14 mPa s.