Linear Amplitude Research Articles

A comparison of physics-informed data-driven modeling architectures for ship motion predictions

How to select the optimal formulations for building blended physics-machine learning models for ship motions is not currently clear. This work compares and contrasts two approaches to this problem: (1) A black-box deep learning approach based on a new neural network architecture that can better handle varying wave conditions, and (2) a clear-box model based on updates to linear response amplitude operators via a Gaussian process regression. Both models are trained and evaluated on a dataset consisting of more than 15,000 30-minute-long motion observation windows from two research vessels at sea in the Atlantic and Pacific oceans. Three different hindcast weather services are used, including two models from the EU’s Copernicus system and NOAA’s WAVEWATCH III. The evaluation shows that a tradeoff exists between the formulations, with the black-box formulation offering higher accuracy and the cost of less transparency. The weather hindcast used has a small impact on the results, and the ability of both models to generalize predictions between near-sister ships is also encouraging for the practical application of these techniques.

Enhancement of rheological performance and compatibility of tire rubber-modified asphalt binder with the addition of graphene

Rubber segregation and workability are issues associated with tire rubber powder (TRP) modified asphalt binder, restricting its widespread application. Meanwhile, graphene nanoparticles have gained considerable interest in asphalt modification due to their outstanding properties. This work has explored the influence of graphene incorporation on the compatibility and rheological behavior of TRP-modified asphalt binder. Firstly, TRP-modified asphalt and two kinds of TRP/graphene composite-modified asphalt were prepared. Then, the rheological characteristics of the asphalts were investigated using the frequency sweep, temperature sweep, multiple stress creep and recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. The compatibility and microstructure of the different modified asphalt binders were evaluated using the cigar tube test and scanning electron microscopy. Results showed that adding graphene to the TRP-modified asphalt resulted in a notable improvement in rutting performance, as evidenced by the increase in rutting parameter (G*/sinδ) and % recovery (R) and a decrease in non-recoverable creep compliance (Jnr). The graphene addition also enhanced the anti-aging performance of TRP-modified asphalt. The results obtained from the LAS test, including the damage-characteristic curves and the number of cycles to fatigue failure, suggested that the fatigue performance of the TRP/graphene composite-modified asphalt was higher compared to the TRP-modified asphalt. Similarly, the BBR test results with 12% TRP and 0.5% graphene demonstrated that the composite-modified asphalt was more resistant to low-temperature cracking. Finally, the incorporation of graphene can potentially reduce the degree of phase separation in TRP-modified asphalt binder and improve its compatibility.

Study of fatigue performance of fiber reinforced high-viscosity asphalt mastic based on rheology

Open-graded asphalt mixture pavement, with its functional benefits of drainage and noise reduction, holds promising engineering application potential. The high-viscosity asphalt mastic significantly influences the performance of this open-graded asphalt mixture. In this study, the fatigue performance of fiber reinforced high-viscosity asphalt mastic was investigated based on rheology. Shear rheometer was used to perform temperature sweep tests, time sweep tests, and linear amplitude sweep tests on the fiber reinforced high-viscosity asphalt mastic. The influences of filler/binder ratio, filler properties, fiber type, and content on the fatigue performance of the mastic were analyzed. Time sweep test data was used to establish a prediction equation for temperature-stress fatigue life of the mastic. The interconnectivity and differences between various fatigue life indicators were studied based on phenomenology and energy dissipation theory. The fatigue characteristics and damage mechanism of the mastic were investigated using a viscoelastic damage model, and the fatigue lives at different strain levels were observed. The research results indicate that fatigue damage of high-viscosity asphalt mastic mainly occurs at low temperatures. An increase in filler/binder ratio at the same temperature reduces the anti-fatigue performance of the mastic. Compared with dust, mineral powder has a larger specific surface area and better fatigue resistance performance. The established temperature-stress equation can accurately predict the fatigue life of mastic under different temperatures and stresses. The fatigue indicators Np20 and Nfm, based on energy dissipation theory, show a favorable linear relation with the fatigue indicator Nf50 based on phenomenology, and these three indicators are consistent in evaluating the fatigue performance and life of the mastic. Np20 and Nfm are found to be more applicable for evaluating the fatigue performance of fiber reinforced high-viscosity asphalt mastic. The fatigue life of the mastic decreases with increasing strain levels, and high-viscosity asphalt mastic containing basalt fiber shows better adaptability to complex traffic conditions.

Effect of styrene–butadiene–styrene triblock copolymer structure on the rheological properties of high content SBS polymer modified asphalts

Styrene-butadiene-styrene triblock copolymer (SBS) is a thermoplastic elastomer synthesized through the anionic polymerization. The effects of SBS structure including diblock content, molecular weight and styrene content on the properties of high content SBS polymer modified asphalts (HCPMA) with 8wt% were studied. The structure of SBS was characterized by the Size Exclusion Chromatography. The rheological properties of HCPMA were analyzed by performance grading, linear amplitude sweep and zero shear viscosity. The results show that the increasing diblock content decreases the melt viscosity, and improves the workability and the thermal-cracking resistance of HCPMA. However, it reduces the high-temperature performance and fatigue resistance. Higher molecular weight of SBS improves the high-temperature properties and fatigue resistance of HCPMA, but worsens the workability and hot-storage stability. Asphalts modified by SBS with a higher styrene content show better workability and high-temperature properties, while a higher butadiene content in SBS shows better hot-storage stability and thermal-cracking resistance of HCPMA. When the styrene content of SBS is 30%, the binder represents the best fatigue resistance. The results also show that rheological tests characterize HCPMA more precisely than the conventional methods.

Upcycling waste phosphogypsum as an alternative filler for asphalt pavement

Mineral fillers are an essential component of asphalt concrete. Significant amounts of mineral fillers are used in constructing asphalt pavement. However, mineral fillers are an important non-renewable natural resource which needs to be preserved. In addition, the production of mineral fillers also consumes much energy and affects environment negatively. This study set out to explore the feasibility of upcycling waste phosphogypsum as an alternative filler for asphalt concrete. The phosphogypsum was first pretreated at 60, 160, and 800 °C, and the crystalline phase of phosphogypsum was evaluated by X-ray diffraction (XRD). Phosphogypsum with three crystalline phases and limestone powder were then mixed with base asphalt binders to prepare asphalt mastic at the filler-asphalt ratio of 1:1 at 150 °C. The chemical structural changes and thermal stability features of phosphogypsum asphalt mastic were analyzed using Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG). The viscoelasticity, high-temperature performance, and fatigue characteristics of different asphalt mastics were measured by frequency sweep, multiple stress creep and recovery (MSCR), and linear amplitude sweep (LAS), respectively. The results indicate that phosphogypsum had different crystalline phases after pretreatment at different temperatures. The addition of phosphogypsum as fillers in asphalt is mainly a physical hardening effect. The 600 °C residual mass ratio of asphalt mastic prepared from phosphogypsum pretreated at 60, 160, and 800 °C was 53.9%, 56.2%, and 58.6%. As the temperature increased, the different crystallized water states in phosphogypsum were decomposed. The replacement of mineral powder with phosphogypsum can improve the high-temperature properties of asphalt mastic and the percent recovery (R), while the nonrecoverable creep compliance (Jnr) was reduced. At the extremely high-temperature of 70 °C, the improvement of the high-temperature performance of phosphogypsum asphalt mastic is more evident than that of 46 °C. Furthermore, the addition of phosphogypsum also reduced the fatigue life of asphalt mastic. This study is expected to paving the road for the upcycling of waste phosphogypsum as an alternative filler in asphalt pavement.

Rheological, Mechanical, Microscopic, and Chemical Characterization of Asphalt Binders at Extended Aging Levels

This study aims to connect asphalt binder mechanical properties to their dynamic microscopic morphology and chemical indices to provide a more thorough and fundamental picture of aging and cracking phenomena. Unmodified and modified asphalt binders were aged to five levels for a comprehensive representation of the asphalt binder service life. Rheological indices used covered linear viscoelastic cracking indicators and nonlinear parameters including fatigue life obtained by the linear amplitude sweep test. A recently validated asphalt binder cracking test, the poker chip test, was used to provide new insight into the mechanical performance of asphalt binders as they stretch into the nonlinear regime and experience cavitation damage. Rheological and mechanical properties were compared to static surface topography from atomic force microscopy (AFM) and time-sensitive asphalt binder microstructure based on electron beam loading using an environmental scanning electron microscope (ESEM). Results indicated that the parameters based on linear viscoelastic analysis and fatigue life derived from the linear amplitude sweep (LAS) test are not adequate to delineate the evolution of asphalt binder behavior with aging among different asphalt binders, due to poor ranking based on known phenomena. However, it was confirmed that the poker chip test was sensitive to longer aging cycles and could capture the total degradation of the asphalt binder’s ductility for both modified and unmodified asphalt binders. The consistency between ESEM and AFM was ensured by observing static surface structures; however, quantification of the fibril formation in ESEM images was the most critical morphological observation when it came poker chip results, because both sharing similar deformation mechanisms. Chemical characterization using Fourier transform infrared spectroscopy was also able to capture asphalt binder aging well, and could be best related to the strength of the asphalt binder. Overall, it was established that the surface microstructure has some relationship to mechanical properties, but not a definitive one, and that using ESEM as an energy absorption indicator was most similar to the comprehensive results from mechanical and chemical testing.

Extreme Wave Loading on a Vertical Circular Cylinder

Extreme wave loading on a marine structure, consisting of a quasi-static and a dynamically slamming component, often drives the design of such a structure. Their accurate predictions remain challenging tasks. This paper examines the slamming contribution to the force–time histories from a series of experiments in which the crest of a wave is forced to hit a truncated cylinder suspended from above. A range of inundation levels, representing the breaker heights, are considered. The work also provides insights into nonlinear load characteristics on a vertical truncated cylinder. A simple analytical model based on the Newtonian momentum analysis is extended to describe the scaling of the horizontal peak force with the inundation level, i.e., the relationship between the wave slamming loads and the breaker height. More specially, it is found that the peak horizontal impact force is proportional to the inundation level and the square of the linear wave amplitude. In addition, the horizontal and the vertical impact forces on a truncated cylinder are found to increase with the increasing inundation level, while the effect from the wave steepness is relatively small. Furthermore, the higher-order wave components driving nonlinear (quasi-static) loading on a structure are separated by applying a phase-based separation method assuming a Stokes-like approximation. The separation method is found to work well even for long shallow-water waves that have strong nonlinearities. The results suggested that the relative contribution from the fundamental linear wave and higher-order wave components decreases and increases with the increasing nonlinearity of long waves, respectively, characterized by the Ursell number. Finally, this increase in the higher-order wave components is found to be saturated at large Ursell numbers.

Particle-reinforced elastomer model to analyse viscoelastic properties of flake-shaped electrolyte iron particle-based magnetorheological elastomer

This paper uses parallel-plate-plate rheometry to focus on the magnetic field-dependent nonlinear viscoelastic behaviour of flake-shaped electrolyte iron powder-based magnetorheological elastomer (MRE). MRE was prepared using liquid silicon rubber as a base, a curing agent and electrolyte iron particles as fillers. Three MRE samples having 60%, 40%, and 0% filler weight fractions were prepared. The curing was carried out at 300 K. The thickness of the sample was 1.00 ± 0.04 mm. Scanning electron microscopy results showed uniform dispersal of particles within a matrix. The swelling measurement technique was used to confirm the enhanced reinforced properties of elastomer by calculating the cross-link density. The magnetic volume fraction evaluated from magnetisation measurements yields values of 18.7% for MRE-60 and 8.7% for MRE-40. Both moduli’s field-induced linear and nonlinear amplitude dependence were analysed using the modified particle-reinforced elastomer model. The result indicates that filler particles adsorbed on polymer chains were essential in determining the reinforcing properties of MRE. The improved cross-link density and particle morphology were responsible for the enhanced field-induced magnetorheological effect (277%). This value is nearly three times greater than that observed in spherical particles-based MRE.

Fluid identification by nonlinear frequency‐dependent amplitude variation with offset inversion based on scattering theory

AbstractPre‐stack seismic amplitude variation with offset inversion is a crucial technique in seismic exploration, employed to estimate reservoir elastic parameters and thus reservoir fluid properties. However, traditional amplitude variation with offset inversion methods are based on elastic theory and linear approximation, neglecting the inelasticity of medium and nonlinear theory. To overcome this limitation, a quadratic scattering coefficient equation of the viscoelastic fluid factor is derived, which provides the basis for the equation for amplitude variation with offset inversion. Traditional amplitude variation with offset inversion methods typically neglect seismic dispersion and attenuation, failing to account for the influence of the seismic wave velocity attenuation and frequency variation. Quality factors of P‐ and S‐waves represent the degree of attenuation of seismic waves. To comprehensively address the effects of seismic wave dispersion and attenuation, a novel method called pre‐stack seismic nonlinear frequency‐dependent amplitude variation with offset inversion has been developed. This method builds upon the new quadratic scattering coefficient and is utilized for reservoir fluid prediction. The reliability and stability of the method are verified through synthetic and filed data examples. Further analysis reveals that the method is more reasonable and accurate compared to the traditional linear amplitude variation with offset inversion method. The results demonstrate that the proposed pre‐stack seismic nonlinear frequency‐dependent amplitude variation with offset inversion method can effectively identify reservoir fluids, providing a novel solution for reservoir fluid identification.

Microwave Sensitivity Enhanced Asphalt Mastic with Magnetite Powder and Its Performance after Microwave Heating

Microwave heating technology is a promising method for asphalt pavement maintenance and de-icing; however, it requires the material to have a good microwave-absorbing ability and can also result in asphalt aging. It is therefore important to develop microwave-sensitive materials used for asphalt pavement maintenance and study the effects of microwave heating on asphalt aging. This study evaluates the electromagnetic characteristics of limestone powder and magnetite powder and explores the influence of microwave heating on the high-temperature rheological and fatigue properties of microwave sensitivity enhanced asphalt mastic with magnetite powder. A vector network analyzer was used to measure the electromagnetic characteristics of limestone powder and magnetite powder. The magnetite filler asphalt mastics were prepared and subjected to microwave heating for 1 h, 2 h, 3 h, and 4 h. Temperature sweep tests, frequency sweep tests, and linear amplitude sweep (LAS) tests were conducted for magnetite filler asphalt mastics before and after microwave heating. LAS experimental results were analyzed based on viscoelastic continuum damage (VECD) theory. The results show that magnetite powders have better electric field energy storage ability, higher dielectric loss and magnetic loss, and better microwave heating efficiency. The complex shear modulus (G*) and rutting factor (G* × (sin δ)−1) rapidly decrease with the increase in temperature, indicating that the mastics’ ability to resist deformation decreases sharply. The longer the microwave heating time for magnetite filler asphalt mastics, the faster the high-temperature rheological properties decreased as the temperature rose. The fatigue life of magnetite filler asphalt mastics significantly decreases with the increase in strain and microwave heating time. It is suggested to add anti-aging agents into asphalt materials to reduce the aging effect in the process of microwave heating. This study provides a reference for the application of microwave heating technology in asphalt pavement maintenance.

Effects of waterborne epoxy resin on the fatigue performance of bitumen emulsion

Bitumen emulsion faces the major concern of low mechanical strength, especially at high service temperatures. To improve the mechanical performance of bitumen emulsion, waterborne epoxy resin was used as a modifier in this study. The effects of waterborne epoxy resin on the fatigue performance of bitumen emulsion were evaluated in this study using both the stress-controlled time sweep test and linear amplitude (LAS) test. The dissipated energy concept and viscoelastic continuum damage (VECD) theory were adopted to analyze the fatigue testing data obtained from the time sweep test and LAS test, respectively. It is found that the fatigue life of the emulsion residues increased with the incorporation of waterborne epoxy resin from the time sweep test conducted at the stress levels from 300 kPa to 500 kPa. On the other hand, the LAS test indicated that the trend of the predicted fatigue life of the emulsion residues was strain dependent.

Characteristics of Waste Oil-rejuvenated RAP Bitumen: An Experimental Study

In recent years, Reclaimed Asphalt Pavement (RAP) has become very popular in pavement construction due to its benefits to the economy and the environment. The present study investigates the feasibility of employing Waste Cooking Oil (WCO) and Waste Engine Oil (WEO) as rejuvenators blended with reusable asphalt binder through physical and rheological properties at high and intermediate temperatures. Examined conventional properties of WCO-and WEO-modified bitumen include softening point, penetration, ductility and viscosity. In addition to these rheological properties, they also include Amplitude Sweep, Frequency Sweep, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS) and High-temperature Performance Grading (HTPG) tests carried out by Dynamic Shear Rheometer (DSR). The experimental outcomes revealed that both WCO and WEO could reduce deformation resistance and improve stiffness, workability and viscous behavior of aged bitumen. Moreover, the addition of waste oils improves the fatigue lives of rejuvenated bitumen and enhance fatigue cracking resistance, but at the cost of rutting resistance. Overall, WCO performs better in restoring stiff binder properties than WEO as per rheological testing. KEYWORDS: Dynamic shear rheometer (DSR), Reclaimed asphalt pavement (RAP), Rejuvenators, Waste cooking oil (WCO), Waste engine oil (WEO).

Characterization of Asphalt Mixtures with Addition of Drill-Well Gravel

One of the by-products of the oil industry that is disposed of in nature as waste is oil well gravel. When improperly disposed of, it pollutes the soil, deteriorates the urban landscape, and constitutes an environmental liability if it is destined for landfills without prior treatment. As a way of reusing gravel from oil wells, this research proposed using gravel as a filler in hot asphalt mixtures. This study evaluated hot asphalt mixtures dosed with 2% filler by the Superpave methodology. The 2% filler was partially replaced by the oil well gravel (1% gravel and 1% lime) and totally (2% gravel), compared to the use of 2% lime as a commonly used filler in traditional blends. Rheological tests such as rotational viscosity, performance grade (PG), creep and recovery under multiple stresses (MSCR), and linear sweep amplitude of strain (LAS) were carried out in order to investigate the effects on asphalt mastic when incorporating oil well gravel in the contents proposed. The asphalt mixtures were evaluated through mechanical tests: tensile strength, modulus of resilience, dynamic modulus, flow number, and modified Lottman. The rheological evaluation could prove the gain in viscosity and stiffness of the asphalt binder, showing less susceptibility to thermal variation and, consequently, an increase in the resistance to permanent deformation. It was also found that the incorporation of the gravel residue caused a reduction in the resistance to damage and shorter fatigue life to the binder at the highest deformation amplitudes. The use of gravel from oil wells did not cause a significant change in the mechanical performance of the asphalt mixtures at the tested contents, presenting itself as a sustainable option for use mainly in regions with low rainfall, such as the Northeast region of Brazil.

The Application of Bio-Emulsion from Soybean Oil Partially Epoxidized as a Maintenance Technique for Flexible Pavements

Abstract An increase in the use of biomaterials has been noted in recent years because of several impacts caused by human activities, especially for engineering and paving industry benefits. Several renewable resources, such as a nonfood source of soybean oil, have been successfully tested on modification of asphalt binders. However, their impact on the pavement life cycle is still unknown. Thereby, the objective of this research was to investigate soybean oil as a new, green supply for the maintenance of flexible pavements. The experimental plan consisted of the construction of field test sections through the application of sub-epoxidized soybean oil (SESO) over a flexible pavement surface. Rates of 0.1 and 0.3 L/m2 were chosen, and the main tests intended for study were functional procedures including the British pendulum and sand patch tests on the pavement surface, which were complemented with the indirect tensile strength test for mechanical analysis. The change in the chemical composition of the recovered binder was analyzed by thin layer chromatography and Fourier-transform infrared spectroscopy. The rheological properties were analyzed by frequency sweep, linear amplitude sweep, and multiple stress creep and recovery, and the tests were carried out with a dynamic shear rheometer. The effects of the SESO bio-emulsion demonstrated a rejuvenating activity on the properties of the aged binder, with mechanical and rheological improvements for both analyzed rates. A further investigation is indicated to evaluate the influence of time on the modification studied in this work. Such testing could ensure the use of SESO bio-emulsion as an environmentally friendly alternative for the maintenance of flexible pavements.

Performance Improvement of Asphalt Mastics Using Bamboo Fiber Reinforcement

Integrating fibers into asphalt mixtures improves their crack resistance and permanent deformation. Previous studies have found the effect of various fibers on asphalt mixtures, but bamboo fibers were not included. In addition to providing strength and toughness, bamboo fiber’s recycled nature saves resources and protects the environment. This study investigates the reinforcement effect by different particle sizes and contents of bamboo fiber on asphalt mastic. Three sizes (100 mesh, 200 mesh, and 400 mesh) and three contents (3%, 6%, and 9%) of bamboo fibers were selected to modify the asphalt mastic. The frequency sweep (FS), linear amplitude sweep (LAS), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) test were used to evaluate the linear viscoelastic properties, fatigue performance, rutting resistance, and cracking resistance of fiber-modified asphalt mastics, respectively. Results demonstrate that bamboo fibers have excellent stiffness-reinforced characteristics, increase the elasticity of the asphalt, and enhance the high-temperature stability and low-temperature crack resistance of the asphalt mastic but adversely affect the fatigue properties of the asphalt mastic. In addition, asphalt mastics exhibited the same crack initiation stage and different crack expansion behavior, and the fiber incorporation prevented further crack propagation. Burgers model was used to represent the rheological behaviors of the asphalt mastic with bamboo fiber, and the model parameters are estimated. Furthermore, the Burgers model results indicated that the fiber addition reduced the proportion of elastic compliance and viscous compliance but increased the proportion of delayed elastic compliance of the asphalt mastic. Finally, the statistical model obtained based on the statistical approach can appropriately fit the values of rheological parameters with different fiber contents and lengths. The optimal design solution is 200 mesh with 9% content.

Effect of Long-Term Aging on Fatigue and Thermal Cracking Performance of Polyphosphoric Acid and Styrene-Butadiene-Styrene-Modified Bio-Blend Bitumen.

Polyphosphoric acid (PPA) and styrene-butadiene-styrene (SBS) were adopted to produce PPA-SBS-modified bio-blend bitumen, which achieved excellent mechanical performance. However, its long-range performance, such as the fatigue and thermal cracking behavior under long-term thermal oxidation, is not well understood. Therefore, a pressure aging vessel (PAV) system was applied to simulate the aging behavior of the bitumen under the action of thermal oxidation. Then, a linear amplitude sweep (LAS) test combined with a viscoelastic continuum damage (VECD) model was applied to investigate the fatigue properties of the bitumen. Moreover, a bending beam rheometer (BBR) test was conducted to evaluate the thermal cracking resistance of the bitumen before and after PAV aging. Meanwhile, an atomic force microscope (AFM) was applied to observe the microscopic topography. The results show that the original compound-modified bitumen can bear more fatigue damage than that of the control bitumen at the failure point, and it also has excellent fatigue resistance at 2.5%, 5%, 7.5%, and 10% applied strain. Moreover, the VECD model can accurately predict the fatigue life of the bitumen under different applied strains. The variation ratio of stiffness modulus for the compound-modified bitumen is below that of the control bitumen after PAV aging, so it shows a better anti-aging performance. Finally, the AFM test shows that PPA and bio-bitumen decrease the heterogeneity of the bitumen, reducing the difference between phases.

Use of Random Forest to Predict Intermediate Temperature SCB Jc Parameter of Long-Term Aged Asphalt Mixtures

With the growing use of reclaimed asphalt pavement (RAP), recycled asphalt shingles (RAS), and other innovative additives in asphalt mixtures, there are concerns about the accuracy of Superpave volumetric-based mixture design. Performance tests in mix design procedures are needed to ensure desirable pavement performance. The Louisiana Department of Transportation and Development (LADOTD) has adopted the semi-circular bend (SCB) critical strain energy release rate parameter, Jc, to evaluate the cracking resistance of asphalt mixtures. To address practical shortcomings, this study aims to develop a predictive model to estimate SCB Jc at intermediate temperature of long-term aged (LTA) asphalt specimens from volumetric properties of plant-produced asphalt mixtures, and rheological and chemical properties of unaged asphalt binder by using a machine-learning model, random forest. Asphalt mixture SCB test and asphalt binder rheological and chemical properties tests were conducted. Stepwise correlation analysis was used to determine the most influential variables to SCB Jc. Random forest model was optimized using grid search with hyperparameter combinations. Results show that the developed random forest model was able to predict the SCB Jc fracture parameter of asphalt mixtures and a good agreement was observed between predicted and measured SCB Jc values. Variable importance scores based on mean decrease in impurity (MDI) showed that the Δ Tc had the most influence on SCB Jc prediction accuracy, and other inputs such as coarse aggregate type, LTA days, Fourier transform infrared spectroscopy test carbonyl index, and linear amplitude sweep test ALas also had significant effects on SCB Jc.

Rheological analyses of binders modified with triple combinations of Crumb-Rubber, Sasobit and Styrene-Butadiene-Styrene

The development of polymer-modified asphalt (PMA) has been a widely used technique by many researchers. Moreover, further modification of PMA binders has generated interest due to possible improvements in performance and cost. In this regard, Sasobit wax has been an alternative to reduce costs in Crumb-Rubber (CR) and Styrene-Butadiene-Styrene Copolymer (SBS) binders. However, there is little detail on the rheological behaviour of CR-SBS-Sasobit triple-modified samples for failure and damage resistance properties. Therefore, this study shows various properties of binders with triple modification of CR-SBS-Sasobit at different dosages. For this purpose, the development of single, double and triple modifications has been proposed to be tested by Multiple Stress Creep Recovery (MSCR) for permanent deformation. In the case of radial cracking and thermal cracking, it is evaluated by linear amplitude sweep test (LAS) and binder creep energy test (BYET). The results indicate that a CR-SBS combination in single or double addition achieves good thermal stability and behaviour. However, a higher elasticity is achieved in the case of a triple modification with CR-SBS-Sasobit. Specifically, Sasobit achieves 67% and 28% reduction in the cumulative deformation of MSCR for a variation of 40–80 °C, respectively. Concerning fatigue life (Nf), it is shown that CR-SBS modifications do not always acquire higher Nf than single modifications. However, adding Sasobit in triple modifications increases these values, generating bitumen with higher strength. It is also shown that adding Sasobit is a viable modifier in yield, even increasing the yield energy (Er) for samples with equal CR-SBS and reducing the percentage of SBS in the sample.

Insight into the critical evaluation indicators for fatigue performance recovery of rejuvenated bitumen under different rejuvenation conditions

This study aims to propose critical fatigue indicators for evaluating the restoration effectiveness of various rejuvenators on the fatigue performance of aged bitumen. The influence factors of rejuvenator type/dosage and aging degree of bitumen are involved, and different fatigue parameters from linear viscoelastic (LVE), linear amplitude sweep (LAS), and time sweep (TS) tests are analysed. The results reveal that bio-oil exhibits the greatest rejuvenation efficiency in improving fatigue life of aged bitumen, followed by engine-oil and naphthenic-oil rejuvenators, while aromatic-oil shows the lowest effect. Moreover, the rejuvenation percentages on fatigue parameters of rejuvenated bitumen enhance significantly with increased rejuvenator dosage but weaken as the aging level deepens. The fatigue failure temperature (FFT) from the LVE test, fatigue life (Nf5), peak strain (ɛsr), elastic modulus (E) from the LAS test, and crack width (C500) from the TS test are recommended as critical indicators for fatigue performance evaluation of rejuvenated binders. Further, the crack width greatly correlates with other essential indicators and can be predicted using correlation equations without conducting the time-consuming time sweep test. The difference in these critical fatigue parameters of various rejuvenator-aged bitumen blends provides the macroscale basis for future nanoscale mechanism exploration and superior rejuvenator development.

Evaluation of Thermal and Rheological Properties of Phase Change Material-Incorporated Asphalt Mastic with Porous Fillers

Incorporating phase change material (PCM) into paving materials can regulate the pavement temperature, improve the pavement durability, and mitigate the heat-island effects. In this research, porous fillers were used as the PCM carrier, and the thermal and rheological behaviors of the asphalt mastic with the PCM were evaluated. Two different carrier materials (diatomite and expanded perlite) and four types of PCMs were used in the study. The candidate filler, PCM, and proper blending ratios were determined based on the results of scanning electron microscope image analysis, the filter paper test, and the temperature sweep test. The thermal and rheological behaviors of the mastics with PCMs were further evaluated with different filler replacement ratios. Thermal analysis through a differential scanning calorimetry test, thermal conductivity and volumetric heat capacity test, and real-time temperature performance test were performed on the asphalt mastics. Rheological tests, including the complex shear modulus test, the bending beam rheometer test, and the linear amplitude sweep test, were also conducted. The modified mastics were found to have high heat capacity with the latent heat storage ability. The rheological analyses showed that with the addition of polyethylene glycol, while the low-temperature performance of the asphalt mastics was improved, the performance at intermediate and high temperatures was not adversely affected by the PCM.