Fatigue Damage Resistance Research Articles

Investigation of LAS-based fatigue evaluation methods for high-viscosity modified asphalt binders with high-content polymers

The objective of this paper is to investigate the microstructure of high-viscosity modified asphalt binder (HVA) containing high-content polymers and its effect on fatigue performance, as well as the applicability of different analytical methods and failure criteria of linear amplitude sweep (LAS) test to HVA. In this paper, two types of HVAs with different polymer contents, a commercial HVA, a conventional polymer-modified asphalt binder, and a base asphalt binder were first prepared or selected. Fluorescence microscopy tests, time sweep tests, and LAS fatigue tests were then performed on these binders. Finally, the fatigue properties of the different binders were analyzed in depth using different analytical methods and failure criteria. The results show that the polymers in HVA crosslink with each other to form a strong cross-linking structure, and the phase inversion of the polymers renders them into a continuous phase, which significantly improves the fatigue damage resistance of the HVA; moreover, the evolutions of stress with shear strain for the fatigue process of HVAs is related to the polymer network. Besides, the two-dimensional damage characteristic curve (DCC) cannot accurately reflect the evolution of the fatigue performance of HVA, and this paper suggests the use of a three-dimensional DCC curve with strain information. Furthermore, the 35% reduction in C0 in the dissipative energy method is not a suitable failure criterion, a more accurate fatigue performance ranking can be obtained by using the yield stress as the failure criterion. Although the fatigue resistance of HVA after yield stress is theoretically considered using the pseudo-strain energy approach, HVA does not show a peak of stored pseudo-strain energy even when the strain is increased to 60% in the LAS test. Therefore, the maximum strain value (30%) in the standard LAS test is not sufficient in characterizing high-polymer HVAs because there is not enough fatigue accumulation of HVAs in this range, consequently, the maximum shear strain parameter in the LAS experiment needs to be reconsidered.

Multilayered elastic medium reinforced with interfacial thin film: A theoretical model for geogrid reinforced HIR asphalt pavement

Aiming at modeling the reinforcement behavior of geogrid reinforced HIR asphalt pavement structure accurately and efficiently, a mathematical formulation using the Generalized Kelvin Solution (GKS) based method for multi-layer three-dimensional elastic system with the consideration of elastic membrane without thickness is put forward in this thesis to simulate the geogrid reinforcement for HIR pavement. Solutions in transform and physical domain, solutions for z = 0, and specific solutions of surface displacements are determined. Four special cases including homogeneous half space with buried and surface thin film reinforcement, Boussinesq's solution, unreinforced multilayered half space are introduced to validate the solution. Moreover, the mechanical effect of geogrid on the deformation, stress state and fatigue life of the pavement structure is investigated using the proposed model and solution. The geogrid stiffness has significant effect on the vertical and radial strain. After the reinforcement, both the radial stress and hoop stress near the interface reduce to a very low level, the stress concentration is effectively alleviated. Meanwhile, geogrid reinforcement plays a positive role on enhancing the fatigue damage resistance of pavement stricture Our proposed method provides a novel way to model reinforcement mechanism of the geogrid on pavement structure, which is helpful to engineering practice.

Effect of different rejuvenation methods on the fatigue behavior of aged SBS modified asphalt

Reclaimed bituminous mixture can be used in new pavement after rejuvenation. Common rejuvenation method and reactive rejuvenation method can be used to restore the properties of aged SBS modified asphalt(ASMB). This work focused on the recovery effect of fatigue resistance for ASMB by different rejuvenation methods. The effect of common and reactive rejuvenation on the fatigue behavior of ASMB was investigated by multi-stress creep and recovery test, linear amplitude sweep test and fatigue-healing-fatigue test. The results show that, as compared with common rejuvenation method, reactive rejuvenation method is more conducive to restoring the creep recovery rate and the non-recovered creep compliance of ASMB. Linear amplitude sweep test indicates that reactive rejuvenated ASMB shows the good fatigue stress cracking resistance, the fatigue life of which at 2.5% and 5.0% strain levels is increased by 30% and 71% as compared with that of common rejuvenated binder. Meanwhile, the self-healing index of reactive rejuvenated ASMB is also enhanced by 28.7%, which indicates its better self-healing potential and fatigue damage resistance. Furthermore, the fatigue life of SMB is reduced by 77.7% after aging, while that of ASMB is extended by 93.5% after common rejuvenation, and the fatigue life of reactive rejuvenated ASMB is almost twice than that of common rejuvenated binder. It means that reducing the adverse effects of aged asphalt and reconstructing the broken SBS cross-linking structure during rejuvenation process of ASMB are all crucial for restoring its fatigue resistance.

Fatigue behaviors and damage mechanisms for Nb3Sn triple-helical structure at liquid nitrogen temperature

Nb3Sn triple-helical structure is the elementary structure in the superconducting cable of ITER magnets and undergoes prolonged fatigue loading in extreme environments leading to serious damage degradation. In this paper, the fatigue behaviors of the Nb3Sn triple-helical structure have been investigated by the strain cycling fatigue experiments at liquid nitrogen temperature. The results indicate that Nb3Sn triple-helical structures with short twist-pitches possess excellent fatigue damage resistance than that of long twist-pitches, such as longer fatigue life, slower damage degradation, and smaller energy dissipation. Meanwhile, a theoretical model of damage evolution has been established to reveal the effects of twist-pitches on fatigue properties for triple-helical structures, which is also validated by the present experimental data. Furthermore, one can see that the Nb3Sn superconducting wires in a triple-helical structure with the shorter twist-pitches have a larger elongation of helical structure and less cyclic deformation, which can be considered as the main mechanism of better fatigue damage properties for the triple-helical structures during the strain cycling processes. These findings provide a better understanding of the fatigue properties and damage mechanisms for Nb3Sn triple-helical structures in superconducting cables of ITER magnets.

Short-Term Performance Characterization and Fatigue Damage Prediction of Asphalt Mixtures Containing Polymer-Modified Binders and Recycled Plastics

This study evaluated the short-term performance properties and predicted cracking performance of asphalt mixtures containing polymer-modified asphalt (PMA) binders and recycled polyethylene (RPE). To that end, binder rheological testing, mixture performance testing, and FlexPAVE simulations were conducted. Furthermore, three PMA mixtures were selected for field evaluation on the National Center for Asphalt Technology Test Track and rapid performance testing during production. The PMA binders modified with styrene-butadiene-styrene (SBS), reactive elastomeric terpolymer (RET), and RET-compatibilized RPE had significantly improved elasticity and rutting resistance compared with the unmodified binder. The PMA binders also exhibited good storage stability with minimal separation tendency. Both polymer modification of the asphalt binder and adding RPE via the dry process improved the rutting resistance of the mixture. Although the unmodified and PMA mixtures exhibited notably different load-versus-displacement curves from the Indirect Tensile Asphalt Cracking Test (IDEAL-CT), they had similar cracking tolerance index ( CTindex) results. The Gf-versus- l75 /m75 interaction diagram allowed a more robust understanding of the IDEAL-CT results by considering mixture toughness and brittleness, and their interactions with CTindex. In all cases, polymer modification increased the stiffness and fatigue damage resistance of asphalt mixtures, while adding RPE via the dry process embrittled the mixtures, making them more susceptible to fatigue damage. The PMA mixtures had significantly better predicted cracking performance in FlexPAVE simulations than the unmodified mixture. This improvement was mainly caused by polymer modification of the asphalt binder. Finally, adding dry RPE pellets improved the rutting resistance but reduced the intermediate-temperature cracking resistance of the plant-produced PMA mixture containing an SBS-modified binder.

Grain size effects on high cycle fatigue behaviors of pure aluminum

Friction stir processing (FSP) was used to prepare coarse-grained (CG), fine-grained (FG), and ultrafine-grained (UFG) materials to investigate the grain size effects on high cycle fatigue properties. A linear relationship similar to the Hall-Petch relationship was acquired between the fatigue strength and grain size. Excellent grain boundaries stability in FSP UFG material inhibited the formation of large-scale shear bands and grain growth, which contributed to higher fatigue strength exponent and fatigue damage resistance. Compared with other UFG materials, increasing the fraction of high angle grain boundaries can significantly improve the fatigue strength.

Study of Fatigue-Damage Characteristics of Recycled Asphalt Mixture

To investigate the influence of methyl styrene block copolymers (SMC) modifier on the fatigue performance and damage evolution of recycled asphalt mixture (RAM), RAM with reclaimed asphalt pavement (RAP) ratios of 30%, 50%, and 70% and 90# asphalt mixture were used for four-point bending fatigue test. The fatigue performance and damage evolution process of RAM were analyzed using the stiffness attenuation rate and the relative change rate of dissipated energy (RDEC). Linear amplitude sweep (LAS) tests and atomic force microscopy (AFM) tests were carried out for mixed asphalt in the mixture. The results show that under the same test conditions, with the increase of RAP content, the damage development of RAM is faster, and the fatigue damage resistance is worse. Compared with 90# asphalt mixture, RAM has better fatigue resistance. The fatigue property of the mixed asphalt is better than that of the 90# asphalt. With different RAP contents, the modulus changes of RAM and mixed asphalt are almost the same on macro and micro scales, which proves that the difference of fatigue performance between 90# asphalt mixture and RAM probably is caused by asphalt. A fatigue failure criterion based on the peak dissipation energy is proposed for the LAS test, and the applicability and accuracy of the criterion were proved by grey correlation analysis. Under this criterion, the power function model is introduced to describe the development process of fatigue damage in LAS test, which has high fitting reliability.

Incorporation of the Multi-Layer Plastic Packaging in the Asphalt Binders: Physical, Thermal, Rheological, and Storage Properties Evaluation.

The amount of residual Multi-layer Plastic Packaging (MPP) in Canada has greatly increased in the last two decades, which has economic and environmental consequences. MPP is primarily made up of two or more layers of Polyethylene (PE), Polyester (PET), Nylon (NY), and Metalized Polyester (METPET). While MPP has not been used as an asphalt modifier, some of the materials commonly found in MPP, such as PE and PET, have also been successfully used as asphalt modifiers. Nevertheless, a few recent studies have demonstrated the potential for reusing MPP as an asphalt modifier to improve asphalt pavement performance. Recycling post-industrial MPP instead of using raw polymers could lead to economic and environmental benefits. However, a comprehensive study to evaluate MPP as a viable asphalt additive is lacking. The main objective of this study is to evaluate the feasibility of using MPP as an asphalt modifier via the wet method, considering the physical, thermal, rheological, and storage properties of the MPP-modified binder at different MPP concentrations (2%, 4%, and 8%) in asphalt cement (PG 58-28). MPP-modified binders were evaluated using the following instruments: Differential Scanning Calorimeter (DSC), Thermogravimetric Analysis (TGA), Superpave Dynamic Shear Rheometer (DSR), Rotational Viscosity (RV), and Environmental Scanning Electron Microscopy (ESEM). Test results indicated that the incorporation of MPP has a strong potential to improve permanent deformation resistance at high temperatures. In addition, MPP shows a moderate impact on fatigue cracking performance at intermediate temperatures. Overall, in low-temperature climates, using less than 4% of MPP additives would offer higher fatigue damage resistance along with adequate permanent deformation. In high-temperature climates, higher concentrations of additives may be preferable to resist permanent deformation. Finally, MPP is a challenge for existing recycling systems, and its incorporation into asphalt applications may develop more sustainable materials that would contribute to circular economy principles.

Fatigue damage evolution in asphalt mixture based on X-ray CT images

The fatigue damage of asphalt pavement occurs and develops under repeated vehicle loads, and its macro manifestation is the deterioration of mechanical properties and serviceability. In order to explore the internal cause of fatigue damage of asphalt mixtures, this paper proposed a method to obtain the internal section images of asphalt mixtures in different fatigue damage stages based on the X-ray CT (Computed Tomography) scanning technique and indirect tensile fatigue test. The fatigue damage evolutions in two different gradation types of AC and OGFC asphalt mixture were studied. The results show that the difference in gradation type causes different initial air void shapes, size and distribution, which result in different formation modes of the main cracks and fatigue damage resistance of asphalt mixture. The evolution of air voids during fatigue loading can be divided into three stages: compression, steady growth and rapid expansion. The macro fatigue damage presents an excellent linear relation (R-values > 0.98) with the internal structural damage.

Effect of PAN fiber with bionic layered surface structure generated in situ by Fenton reaction on performance of SBS/RP asphalt binder

• Innovative application of Fenton reaction in the modification of polyacrylonitrile fibers. • Biomimetic multi-layered structure modified polyacrylonitrile fibers. • KF-PAN/SBS/RP modified asphalt had better viscoelastic performance. • KF-PAN/SBS/RP modified asphalt had better low temperature anti-cracking performance, high temperature stability and fatigue damage resistance. • KF-PAN/SBS/RP modified asphalt had better rutting resistance and high temperature adhesion performance. In this study, a surface modified polyacrylonitrile fiber (KF-PAN) with a fish-scale whisker-like biomimetic hierarchical structure was successfully prepared via in situ competition effect of Fenton reaction. The modified fibers were used as secondary modifiers to prepare fiber-reinforced styrene–butadienestyrene (SBS) block copolymers and rubber powder (RP) modified asphalt binders (KF-PAN/SBS/RP). Energy dispersive spectroscopy, scanning electron microscopy, and atomic force microscopy analyses revealed the successful construction of bionic hierarchy on the fiber surface, and confirmed rough surface of the KF-PAN fibers. The hierarchical structure of the fiber surface acted as a buffer in the asphalt and strengthened the mutual interaction of the fiber and asphalt. Dynamic rheometer shear and strip-tensile tests showed that the KF-PAN/SBS/RP modified asphalt exhibited better viscoelasticity, rutting resistance, and tensile properties than the PAN/SBS/RP modified asphalt. The linear amplitude sweep test showed that KF-PAN/SBS/RP modified asphalt had better fatigue resistance. Thermogravimetric analysis tests indicated that the surface bionic structure of KF-PAN fibers boosted thermal stability of the fibers, which in turn enhanced the thermal stability of KF-PAN/SBS/RP modified asphalt. Fluorescence microscopy analysis showed that incorporating KF-PAN fibers improved the SBS and RP microstructure inside the asphalt, forming a good mesh structure, and alleviating the stress concentration phenomenon in SBS/RP asphalt under external traffic load.

Kinetics-based fatigue damage investigation of asphalt mixture through residual strain analysis using indirect tensile fatigue test

Fatigue damage, one of the major distresses of asphalt pavement, has been found to have a phenomenological correlation with the accumulated residual strain (RS) of the asphalt mixture tested by stress-controlled fatigue test with excessive creep. However, it remains a challenge to quantitatively model such phenomenological correlation. This study aims to address this challenge by applying the kinetics theory to the indirect tensile fatigue test (ITFT) with excessive creep data of various asphalt mixtures. First, ITFTs of asphalt mixtures under different conditions were conducted to analyze the RS response. Then, the RS kinetics model was established based on the fast-constant rate kinetics model. Finally, two of the kinetics model parameters, the RS constant rate (kc) and activation energy, were successfully applied to characterize the fatigue life (Nf) and the fatigue damage resistance of the asphalt mixture, respectively. It was found that the established RS kinetics model can accurately describe the development of the accumulated RS determined by ITFT. The kc determined by ITFT is an effective indicator for the rate of the initial damage evolving to the failure threshold. The established kc-based fatigue equation can be used to predict the Nf of the asphalt mixture tested by ITFT from kc. The RS accumulation activation energy can effectively characterize the fatigue damage resistance of the asphalt mixture tested by ITFT.

Composition Design of Waste Vegetable Oil–Based Rejuvenator Based on RSM and Performance Evaluation of Rejuvenated Asphalt

In order to develop an environment-friendly asphalt rejuvenator, waste vegetable oil (WVO) was selected as the base oil. The composition of the rejuvenator was first designed based on the response surface methodology (RSM), and 16 groups of rejuvenator samples were obtained. Then, these samples were used to regenerate aged asphalt and 16 groups of rejuvenated asphalt samples were prepared. Afterward, the viscous, conventional, rheological, and fatigue resistance properties of these rejuvenated asphalts were measured and evaluated, and the optimal composition of rejuvenator was determined. Results show that the addition of WVO-based rejuvenator can reduce the viscosity and softening point of aged asphalt, increase its penetration and ductility, and restore the physical properties and viscosity of aged asphalt to that of original asphalt. With the addition of WVO-based rejuvenator, the high-temperature performance of aged asphalt gradually declined, but the rejuvenator with optimal composition can restore its high-temperature performance to the similar level as original asphalt. The addition of WVO-based rejuvenator can evidently improve the fatigue damage resistance and low-temperature cracking resistance of aged asphalt, achieving a good regeneration effect. The fitting equation based on RSM can achieve an accurate and reliable prediction on the viscous, conventional, rheological, and fatigue damage properties of rejuvenated asphalt. According to the results of model optimization, the optimal composition of WVO-based rejuvenator is recommended as WVO:Dibutyl phthalate (DBP):antiaging agent (AA) = 90:9:1.

Effect of Freeze–Thaw cycles on the pavement performance of SBS modified and composite crumb rubber modified asphalt mixtures

The effect of freeze–thaw cycles on the pavement performance of SBS modified asphalt mixture (SBSMA) and SBS/crumb rubber composite modified asphalt mixture (CCRMA) was studied using a triaxial repeated creep test, semicircular bending fatigue test based on digital image correlation (DIC), and thermal stress restrained specimen test. The mechanical model of the residual strain (RS) of the asphalt mixtures is established, and the residual viscous flow strain (εRvf,N) and residual viscoelastic strain (εRve,N) are separated. Based on the horizontal strain (Exx) of DIC, a new mesofatigue damage variable (D) is proposed. According to the characteristic curve of D, the antifatigue damage parameter (AFDP) is established and the correlation between AFDP and fatigue life (Nf) is analyzed. Simultaneously, a calculation model of the relaxation temperature stress (σRts(T)) of the asphalt mixture at different cooling rates (v) is established based on the finite element method. Results showed that the growth rates of RS, εRvf,N, and D of both asphalt mixtures accelerate, AFDP decreases, and freeze–break temperature (TD) rises with increasing freeze–thaw cycles. However, the growth rates of RS, εRvf,N, and D of CCRMA are always slower than SBSMA, the AFDP is larger than SBSMA, TD is lower than SBSMA, εRve,N is a fixed value under specific conditions, and a good correlation exists between the AFDP and Nf. The pavement performance of the asphalt mixtures worsens after the freeze–thaw cycles, and the influence of a salt freeze–thaw cycles is greater than that of a water freeze–thaw cycles. Moreover, CCRMA has better high-temperature deformation resistance, fatigue damage resistance, and low-temperature cracking resistance than SBSMA. The conversion point temperature (TZ) increases with the acceleration of v, and the σRts(T) calculation model can accurately reflect the σRts(T) of the asphalt mixture at different v.

Effect of laboratory oxidative aging on dynamic shear rheometer measures of asphalt binder fatigue cracking resistance

Long-term aging can significantly affect the fatigue property of asphalt pavements. The influence of aging on fatigue resistance of asphalt binder has not been fully understood and unified conclusions are lacking. In this work, the effect of laboratory oxidative aging on fatigue damage resistance and linear viscoelastic (LVE) parameters of asphalt binder is studied. Tests included the temperature-frequency sweep, linear amplitude sweep (LAS) testing and time sweep from the output of dynamic shear rheometer (DSR). Different undamaged parameters (e.g., Glover-Rowe parameter (GRP), dynamic shear modulus |G*| at 64 °C, |G*|·sinδ (δ is the phase angle)) have been proposed as the indicators of aging sensitivity of the asphalt binder and are discussed. The fatigue test results are interpreted under different aging levels by using Simplified viscoelastic continuum damage (S-VECD) analysis. The trends of LVE parameters with increasing aging levels are very intuitive and show a tendency to increase in value with aging. The number of cycles to failure (Nf) shows a less intuitive trend than the LVE parameters. The existing failure criteria GR works well for the Nf prediction for highly aged materials. From the results of measured and predicted Nf from time sweep and LAS tests, fatigue damage resistance appears to increase with long-term aging at low strain levels (less than 7% strain levels in this work). When the aging level continues increasing, the fatigue resistance eventually declined in most cases evaluated. The objective of this study is to evaluate the fatigue resistance of asphalt binder under different aging levels by using various parameters and failure criteria.

Effect of maleic anhydride grafted and gamma-irradiated waste polypropylene on rheological properties of asphalt binder

ABSTRACT Waste polymers have been employed as a modifier in bitumen to improve the performance of the binders and reduce plastic pollution. Grafting of maleic anhydride (MA) is a method to increase the chemical and physical consistency between the polymer and binder. In this study, maleic anhydride grafted waste polypropylene was employed as a bitumen modifier. Gamma irradiation is applied to waste polypropylene to improve the compatibility. The effects of MA-grafted irradiated waste polypropylene (PP-γ-MA) on physical and rheological properties of bitumen were investigated through a test program. Storage stability tests signifies that the gamma irradiation could diminish the phase separation between the modifier and bitumen. The thermorheological tests showed employing PP-γ-MA improves the high temperature performance, whilst it has a slightly adverse effect on low temperature performance of bitumen. The results of multiple stress creep recovery (MSCR) test indicate that PP-γ-MA reduces the non-recoverable deformation and enhanced elastic recovery of the material, whereas the linear amplitude sweep (LAS) test result signifies PP-γ-MA improved the fatigue life of asphalt by increasing fatigue damage resistance under different strain levels. The rheological test results emphasised on the usability of PP-γ-MA as a modifier in binders.

Laboratory investigation of the effect of nano Caco3 on rutting and fatigue of stone mastic asphalt mixtures

In this research, the influence of Nano Caco3 as an additive on the mechanical characteristics of stone mastic asphalt (SMA) mixtures is investigated. For this purpose, asphalt binder 60–70 is modified with different ratios of Nano Caco3 to create the SMA samples. Indirect tensile fatigue, wheel track, and indirect tensile strength tests were conducted to evaluate fatigue, rutting, and moisture damage resistance of modified and control samples. The results revealed that by adding Nano Caco3 particles, the fatigue life of SMA mixtures is increased and their final strain is reduced. Nano Caco3 has a good potential to delay the formation and propagation of fatigue cracks in the SMA mixture. The results of the wheel track test demonstrated that Nano Caco3-modified SMA mixtures had lower rut depth than control mixtures. Also, the rutting performance of the SMA mixture was improved at high temperatures and stress levels. The results of the indirect tensile strength test showed that the addition of Nano Caco3 increased the moisture damage resistance of the SMA mixture and improved its performance when it was subjected to continuous exposure to water. It was observed that almost in all cases, modified SMA mixtures with a Nano ratio of 0.9%, exhibit the best behavior.

Martensitic transformation within nanotwins enhances fatigue damage resistance of a nanotwinned austenitic stainless steel

We investigated the low-cycle fatigue behavior of a novel nanotwinned 316L stainless steel consisting of nanotwinned austenitic grains embedded in the matrix with characteristic dislocation arrangements. We excitingly found that the α\\prime-martensitic transformation is activated traversing twin lamellae to undertake the localized deformation of nanotwinned grains at high strain amplitudes. These α\\prime-martensite nuclei are mainly originated from the intersections between “zigzag” slip bands and twin lamellae. Thanks to the effective release of stress/strain localization by the α\\prime-martensitic transformation within nanotwins, the fatigue strength and fatigue life in the low-cycle regime are simultaneously enhanced.

Achieving very high cycle fatigue performance of Au thin films for flexible electronic applications

The fatigue damage behavior of the nanocrystalline Au films on polyimide substrates was investigated. It was found that the very high-cycle fatigue damage resistance of the Au film was significantly enhanced by at least a factor of ∼2 in supported loading through adding an ultrathin Ti interlayer at the Au film/polyimide interface. Such a better fatigue damage resistance is mainly ascribed to the effective suppression of voiding at the Au film/polyimide interface through modulation of the Au/Ti interface, and thus the propensity of the cyclic strain localization and grain boundary cracking is reduced. The finding may provide a potential strategy for the design of flexible devices with ultra-long fatigue life.

In-Situ Calibrated Modeling of Residual Stresses Induced in Machining under Various Cooling and Lubricating Environments

Although many functional characteristics, such as fatigue life and damage resistance depend on residual stresses, there are currently no industrially viable ‘Digital Process Twin’ models (DPTs) capable of efficiently and quickly predicting machining-induced stresses. By leveraging advances in ultra-high-speed in-situ experimental characterization of machining and finishing processes under plane strain (orthogonal/2D) conditions, we have developed a set of physics-based semi-analytical models to predict residual stress evolution in light of the extreme gradients of stress, strain and temperature, which are unique to these thermo-mechanical processes. Initial validation trials of this novel paradigm were carried out in Ti-6Al4V and AISI 4340 alloy steel. A variety dry, cryogenically cooled and oil lubricated conditions were evaluated to determine the model’s ability to capture the tribological changes induced due to lubrication and cooling. The preliminarily calibrated and validated model exhibited an average correlation of better than 20% between the predicted stresses and experimental data, with calculation times of less than a second. Based on such fast-acting DPTs, the authors envision future capabilities in pro-active surface engineering of advanced structural components (e.g., turbine blades).

A Study on the Influence of the Chemical Nature of Fillers on Rheological and Fatigue Behavior of Bitumen Emulsion Mastic.

Cold Bitumen Emulsion (CBE) mixture technologies have been recently developed to lower pavement construction temperatures to reduce environmental costs and control gas emissions. Due to its poor early mechanical strength, active fillers (i.e., cement) have been used to obtain high early stiffness in order to have the potential for timely construction of the next layer. There is, however, a lack of understanding about the impact of active fillers on the viscoelastic behavior and fatigue damage resistance of CBE mastics. This study, therefore, aims to identify the influence of active fillers on the rheological properties and the resulting fatigue behavior of CBE mastic, supported by chemical analysis for the filler-bitumen emulsion. For this aim, bitumen emulsion was mixed separately with seven fillers/blended fillers to prepare the CBE mastics. Various experiments, including continuous pH monitoring tests (chemical reactivity of filler-bitumen emulsion), Strain Sweep (SS) tests, Temperature-Frequency Sweep (TFS) tests, Time Sweep (TS) tests, and Linear Amplitude Sweep (LAS) tests were conducted on the CBE binder and the prepared mastics. Results show that the rheological performance and the fatigue damage resistance depend not only on the filler inclusions but also on filler type and chemistry. On this basis, the rise in complex shear modulus and the decrease in the viscous component is associated with a significant enhancement in fatigue performance for specific fillers.