Fatigue Resistance Of Asphalt Binders Research Articles

Assessment and mechanism of antioxidant activity of phenols as asphalt antioxidants

ABSTRACT The interest in the antioxidant properties of phenolic compounds in asphalt has grown significantly. This study primarily focuses on the comprehensive assessment and elucidation of the antioxidant activity mechanisms of various phenolic compounds as asphalt antioxidants. The suitability of different antioxidant indices for evaluating the effectiveness of phenolic anti-aging agents in base and SBS modified asphalt is assessed by experimental outcomes. Through this analysis, the anti-aging mechanism of phenolic antioxidants in asphalt is unveiled. Phenolic antioxidants were observed to diminish the G* value of aged asphalt, elevate the δ values of aged asphalt binder, augment the non-recoverable creep compliance of aged asphalt binder, decrease the percent recovery of aged asphalt binder, enhance the fatigue performance of aged asphalt binder, and lower the Ic = o and Ic = c of aged asphalt binder. This indicates that phenolic antioxidants improve the aging and fatigue resistance of asphalt binders, with antioxidant activities in the following order: p-Coumaric acid < resveratrol < tea polyphenol. Moreover, incorporating phenolic antioxidants into SBS modified asphalt not only restrains asphalt oxidation but also mitigates SBS degradation.

Performance of Oil-Absorbing organogel Polystyrene-Stearyl methacrylate as a fume suppressant of asphalt binder

Hazardous fumes can be generated during the high-temperature construction of asphalt pavement. Various fume suppressants have been developed, but many may compromise the performance of asphalt binder, which shortens the service life of asphalt pavement. This study aims to investigate the performance of a novel fume suppressant, namely oil-absorbing organogel polystyrene-stearyl methacrylate (P(S-SMA)), which can reduce the construction fumes of asphalt binder while maintaining good rheological performance. The results of the Fourier Transform Infrared Spectroscopy (FT-IR), Fluorescence Microscopy (FM) and asphalt fume mass tests showed that adding P(S-SMA) can improve the aging resistance of asphalt binder and reduce the particles (≥1 μm) and volatile organic compounds (VOCs) released up to 19.6 % and 30.4 % within 1 h, respectively. The rheological test results indicated that P(S-SMA) could effectively improve the viscoelastic properties, high-temperature performance and fatigue resistance of asphalt binder due to the combination of “supporting” and “hardening” effects after adding P(S-SMA). With 5% P(S-SMA) added, elastic and viscosity properties were increased by 90.6 % and 25.3 % and fatigue life was increased by 38.9 % and 26.4 % at the strain levels of 2.5% and 5%, respectively. This study proved the feasibility of using P(S-SMA) as a novel performance-enhancing fume suppressant of asphalt binder.

Study on effect of thermal, oxidative and ultraviolet coupled aging on rheological properties of asphalt binder and their contribution rates

ABSTRACT This paper aims to investigate the effect of different environmental conditions on the aging properties of virgin asphalt binder and evaluate the magnitude of aging on asphalt binder under different environmental conditions. The effect of thermal, oxidative and ultraviolet aging on the rutting resistance, fatigue resistance and cracking resistance of virgin asphalt binder was characterised based on rheological parameters. The contribution rate of different environmental factors to the aging of asphalt binder was quantitatively analysed. Results showed that high temperature repaired cracks in the asphalt binder caused by ultraviolet aging. The single aging factor of heat, oxygen and light had little effect on the rheological properties of asphalt binder. High temperature and oxygen would accelerate the aging effect of the asphalt binder aging process. Thermal–oxidative–UV-coupled aging had a more pronounced effect on the aging of asphalt binder than thermal–oxidative aging. The fatigue resistance of asphalt binder is more sensitive to the response of aging. The contribution rates of thermal–UV aging, UV–oxidative aging and thermal–oxidative aging were all greater than the sum of the contribution rates of the two corresponding single factors. The aging of asphalt binder was mainly due to thermal–oxidative aging when the aging temperature exceeded 80°C.

Improvement in asphalt binder rutting performance and fatigue life using electrospun polyacrylonitrile (PAN) nanofibers

Recently, high aspect ratio materials like nanofibers with outstanding mechanical properties have been developed and used to improve the mechanical characteristics of construction materials. However, despite the excellent results obtained in asphalt binder modification, only a few types of polymeric nanofibers have been used for this purpose. In this sense, polyacrylonitrile has good thermal and mechanical characteristics to maintain the shape at the typical temperatures the asphalt is heated.This study evaluates the effect of electrospun polyacrylonitrile (PAN) nanofibers on the rutting resistance and fatigue parameters of asphalt binders. For this, fibers with an average diameter of 1.3 µm were prepared and randomly dispersed into neat PG 64–22 asphalt binder. Subsequently, a dynamic shear rheometer (DSR) was used to determine G*/sin δ, Jnr, R3.2, and Nf.In the range studied, Jnr3.2 showed a reduction of up to 35%, and the elastic recovery increased up to 4.5 times compared to the reference material. It was observed that the PAN nanofibers increased the fatigue resistance of asphalt binder at temperatures when the material is predominantly viscoelastic. These results show a promising new application of PAN nanofibers to improve the performance of asphalt pavements.

Biomass valorization toward sustainable asphalt pavements: Progress and prospects

To cope with the global climate crisis and assist in achieving the carbon neutrality, the use of biomass materials to fully or partially replace petroleum-based products and unrenewable resources is expected to become a widespread solution. Based on the analysis of the existing literature, this paper firstly classified biomass materials with potential application prospects in pavement engineering according to their application and summarized their respective preparation methods and characteristics. The pavement performance of asphalt mixtures with biomass materials was analyzed and summarized, and the economic and environmental benefits of bio-asphalt binder were evaluated. The analysis shows that pavement biomass materials with potential for practical application can be divided into three categories: bio-oil, bio-fiber, and bio-filler. Adding bio-oil to modify or extend the virgin asphalt binder can mostly improve the low temperature performance of asphalt binder. Adding styrene-butadienestyrene (SBS) or other preferable bio-components for composite modification will have a further improved effect. Most of the asphalt mixtures prepared by using bio-oil modified asphalt binders have improved the low temperature crack resistance and fatigue resistance of asphalt mixtures, but the high temperature stability and moisture resistance may decrease. As a rejuvenator, most bio-oils can restore the high and low temperature performance of aged asphalt and recycled asphalt mixture, and improve fatigue resistance. Adding bio-fiber could significantly improve the high temperature stability, low temperature crack resistance and moisture resistance of asphalt mixtures. Biochar as a bio-filler can slow down the asphalt aging process and some other bio-fillers can improve the high temperature stability and fatigue resistance of asphalt binders. Through calculation, it is found that the cost performance of bio-asphalt has the ability to surpass conventional asphalt and has economic benefits. The use of biomass materials for pavements not only reduces pollutants, but also reduces the dependence on petroleum-based products. It has significant environmental benefits and development potential.

Sprayed-Polyurea-Modified Asphalt: Optimal Preparation Parameters, Rheological Properties and Thermal Properties

For promoting modifying application of sprayed polyurea (SPUA) in asphalt pavement materials, the effects of sprayed polyurea materials on high-temperature and fatigue performance of asphalt binders were investigated from different aspects. First, the optimal preparation parameters of sprayed-polyurea-modified asphalt binders (SPMAs) were determined by designing an orthogonal test. Then, the high-temperature and fatigue properties of sprayed-polyurea-modified asphalt binders with different contents were characterized by rheological testing methods, including Brookfield rotary viscosity (RV) test, performance grading (PG) test, multiple stress creep recover (MSCR) test, linear amplitude sweep (LAS) test and time sweeping (TS) test. Finally, the thermal properties of the asphalt binders were analyzed by differential scanning calorimetry (DSC) test. The results showed that the optimum preparation parameters were determined by the extreme difference analysis method and analysis of variance (ANOVA) method, and the shearing time was 40 min, the shearing rate was 6000 rpm and the shearing temperature was 150 °C. Sprayed polyurea positively affected high-temperature performance of asphalt binders and could improve fatigue resistance of asphalt binders. Moreover, the Brookfield rotary viscosity test, multiple stress creep recover test and linear amplitude sweep test had high sensitivity to the performance of sprayed-polyurea-modified asphalt binder, which could help to distinguish the effect of sprayed polyurea dosing on performance of asphalt binders accurately. The differential scanning calorimetry test showed that sprayed polyurea was beneficial to high-temperature stability of asphalt binders, which explains the reason why sprayed-polyurea-modified asphalt binders have excellent high-temperature performance from a microscopic perspective.

Temperature and Aging Effects on the Rheological Properties and Performance of Geopolymer-Modified Asphalt Binder and Mixtures.

Using geopolymer as a modifier for asphalt binders and mixtures gained momentum for investigation in recent decades. Limited research investigations attempted to link the effect of temperature and traffic loading on the rheological properties and performance of geopolymer-modified asphalt binders. The primary objective of this study is to evaluate the effect of fly ash-based geopolymer (GF), styrene-butadiene-styrene (SBS), and the combination of GF with SBS on the rheological properties and performance of asphalt binders at low and intermediate temperatures. The rheological properties and performance of neat and modified asphalt binders (4%GF, 8%GF,12%GF, 2%SBS, and hybrid (2%SBS+8%GF)) were evaluated utilizing dynamic shear rheometer (DSR) and bending beam rheometer (BBR) devices. To evaluate the fatigue resistance of asphalt binders, the linear amplitude sweep (LAS) and viscoelastic continuum damage (VECD) models were applied. The dynamic or complex modulus and moisture damage resistance were measured to investigate the influence of modifiers on the performance of asphalt mixtures. The findings demonstrated that for both unaged and RTFO-aged asphalt binders, additives reduced the temperature sensitivity of both G' and G″. When the binders were exposed to long-term aging using a pressure aging vessel (PAV), it was noticed that the 8%GF binder became more susceptible to temperature changes. The 2%SBS binder had the lowest creep stiffness compared with the neat and other modifiers, while the hybrid binder exhibited the highest resistance to fatigue distress at different temperatures compared with the other binders. The modified asphalt mixes (8%GF, 2%SBS, and hybrid) achieved the maximum tensile strength (St) compared with the neat asphalt binder, with an increase of more than 80%. The St increased from 580.4 kPa to 740.4 kPa, 884.8 kPa, and 917.4 kPa by utilising the 8%GF, 2%SBS, and hybrid binders, respectively. Furthermore, the modified asphalt mixture exhibited more ability to resist cracking, attaining the highest fracture energy in dry and freeze-thaw conditions.

Differentiation of thixotropy from damage for accurately characterizing fatigue resistance of asphalt binder

Accurate characterization of the fatigue resistance of asphalt binder is of great significance to the prediction of asphalt pavement performance. Traditionally, apparent changes in viscoelastic parameters, including dynamic shear modulus and phase angle, with the number of loading cycles are used to define the fatigue performance of the asphalt binder. However, thixotropy also leads to changes in these viscoelastic parameters, and its contribution is not yet well understood. This study develops a method to quantify the effects of damage and thixotropy on the changes of viscoelastic parameters under the cyclic stress-controlled loading mode. The new method includes the four key steps: (1) determining the thixotropy influence-dominated phase; (2) establishing a thixotropy model to characterize the influence of thixotropy on the effective dynamic shear modulus; (3) calculating damage density from the apparent and effective dynamic shear moduli; and (4) characterizing thixotropy behavior based on Black space diagram. The effectiveness of the newly developed method is verified by the time sweep test, which is conducted on two types of asphalt binder under varying stress levels.with a loading frequency of 10 Hz and a test temperature of 25 °C. The results show that: (1) the change of dynamic shear modulus is resulted from the damage and thixotropy, while that of phase angle is only caused by the thixotropy; (2) thixotropy leads to the decrease of dynamic shear modulus and increase of phase angle; and its influence on viscoelastic parameters increases with the loading time and stress level increased; (3) under the influence of thixotropy, the dynamic shear modulus is linearly related to the phase angle, which is independent of the stress level applied and the damage accumulated in the asphalt binder.

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.

Characterization of Fatigue Resistance of Warm Mix Binders Using Linear Amplitude Sweep Test

Fatigue failure in asphalt pavements occur due to the accumulation of damage under repeated traffic loading. Fatigue cracks generally occur within the binder phase of the asphalt mixture. Hence the specifications for properties related to fatigue resistance of asphalt binder become an important screening tool to select binders that are not inherently susceptible to fatigue under given environmental and traffic conditions. The Current Superpave Performance Grading (PG) specifications use parameter |G*|.·sinδ of asphalt binder to assess the fatigue susceptibility of asphalt mixes. These specifications do not accurately characterize the fatigue resistance of asphalt binders because |G*|.·sinδ is determined by applying a cyclic loading in the Dynamic Shear Rheometer (DSR) at a very small strain amplitude (1%). In this study, Linear Amplitude Sweep (LAS) test was considered to characterize the fatigue resistance of asphalt binders with warm mix additives. Warm mix asphalt (WMA) is a developing technology that can allow asphalt concrete to be produced at lower temperatures. This paper presents result of a study carried out to investigate the fatigue characteristics of warm-mix asphalt binders using a linear amplitude sweep test. Three warm-mix additives; Sasobit®, Evotherm™ and Rediset® are considered. Viscosity grade (VG 30), Polymer modified binder (PMB 40) and Crumb rubber modified binder (CRMB 60) were selected as base binders for this investigation. Physical and rheological tests were carried out for the characterization of these binders. The LAS test was carried out at 25 °C in a DSR, and the fatigue parameters were calculated from stress–strain plots. Test results showed that the changing trend in fatigue life of mixes is more related to the fatigue parameter Nf from LAS test than to |G*|. sinδ values of the binders. It was also observed that most of the warm mix binders have improved fatigue resistance at 25 °C in comparison to the control binders. The effect of Rediset® additive was found to be insignificant in the case of VG 30 grade binder only.

Fatigue crack density of asphalt binders under controlled-stress rotational shear load testing

Fatigue crack is one of the most common distresses in asphalt pavement. In this study, the fatigue crack behaviors of asphalt binders were evaluated under repeated cyclic controlled-stress loadings. Fatigue crack density, defined by the initial sample radius and effective radius of the undamaged part during fatigue testing, was used as an indicator. Also, an effective radius function was developed using the torque equilibrium principle and dissipated strain energy (DSE) equilibrium principle. The data revealed that fatigue crack density of asphalt binder manifested three changing tendencies, in which the secant method was employed to partition their profiles based on concavity and convexity characteristics. Specimens made of #50, #70 unmodified asphalt, SBS modified asphalt, and #50 asphalt mastic, respectively, were tested by time sweep tests on a Dynamic Shear Rheometer (DSR) at different stress levels and rest time. The variations in fatigue crack density at the three stages, as well as the changes in fatigue crack density growth rate in the second stage, were all analyzed. The asphalt binder showed fatigue crack density profiles composed of three stages: crack initiation, steady growth, and unstable growth. Stage II had the smallest increase in fatigue crack density among the three stages but underwent more than 50% load cycles throughout the whole fatigue process. Hence, fatigue crack density growth rate (RD) could be used to evaluate the fatigue resistance of asphalt binders. A positive power-law relationship between RD and stress level was recorded since higher stress levels meant more serious damage. By contrast, RD displayed a negative power-law relationship with resting time, revealing that the rest time, that is, self-healing, effectively postponed the fatigue crack propagation rate.

Effect of Thermal and Oxidative Aging on Asphalt Binders Rheology and Chemical Composition.

Aging of asphalt binders is one of the main causes of its hardening, which negatively affects the cracking and fatigue resistance of asphalt binders. Understanding asphalt aging is crucial to improve the durability of asphalt pavements. In this regard, this study aims at understanding and differentiating the effect of temperature and oxygen uptake on the aging mechanisms of unmodified asphalt binders. For that, four laboratory aging procedures were employed. The two standardized procedures, rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), were considered to simulate the short-term and long-term aging of the asphalt binders, respectively. In addition, two thin-film aging test procedures, the nitrogen atmosphere oven aging test (NAAT) and ambient atmosphere oven aging test (OAAT) were employed to assess the effect of thermal and oxidative aging on unmodified asphalt binder properties. The NAAT procedure is based on the principle that the inert gas minimizes the oxidative aging. The rheological and chemical characterization showed that the high temperatures considered during the NAAT procedure did not change the properties of the unmodified asphalt binders. Therefore, it can be hypothesized that no significant thermal and oxidative aging was observed during NAAT aging procedure for the considered binders and that oxidative aging is the main cause for the hardening.

Investigating the Crack Initiation and Propagation of Asphalt Binder in Linear Amplitude Sweep Test

The linear amplitude sweep (LAS) test has been widely accepted for estimating the fatigue resistance of asphalt binders in the last 10 years. This paper proposes a fracture mechanics–based analytical approach for crack initiation and propagation characterization in the LAS test, aiming to more precisely explore the binder crack growth and failure mechanism. Seven unmodified neat asphalt binders and one styrene-butadiene-styrene (SBS) polymer-modified binder are selected in this study. The crack length (a), rate of cracking (da/dN), stress intensity factor (K), and energy release rate (G) are the fundamental parameters for the data interpretation approach proposed in this paper. Experimental and analysis results demonstrate that the energy-based failure definition (either from continuum damage mechanics or fracture mechanics) should be utilized to detect the material-dependent failure occurrence in LAS test. The fracture behavior of asphalt binder in the LAS test follows the two-phase crack growth (TPCG) model in terms of the crack initiation and crack propagation. The crack propagation phase further consists of stable crack growth and unstable crack growth. It is found that the fatigue performance of asphalt binder is intrinsically governed and dominated by its resistance to the crack propagation. The SBS binder in this study clearly displays slower crack propagation behavior than other neat binders. Additionally, the traditional fatigue life can also be divided into the crack initiation life and crack propagation life, which is promising to clarify the specific modification contribution to binder fatigue resistance. The two critical crack lengths of initiated crack and propagated crack for a given asphalt binder are found to be correlated to each other, indicating the potential links between the binder crack initiation and propagation behaviors.

A comparative study for fatigue characterization of asphalt binder using the linear amplitude sweep test

Currently the linear amplitude sweep (LAS) test is one of the main fatigue protocols to estimate the fatigue resistance of asphalt binder. In past 10-years, several data interpretation approaches have been developed for the LAS-based binder fatigue modeling. The objective of this paper is to compare the currently available analytical approaches for the data interpretation of LAS test and further investigate the potential links between the different LAS-based fatigue evaluations of asphalt binders. Totally 20 types of unmodified and modified asphalt binders are selected in this study, which actually cover 35 sample conditions under different aging and temperature levels. Experimental and analysis results indicate that the full fatigue performance of asphalt binder can be characterized from with the S-VECD & GR approach. The failure property in LAS test is also well correlated to the binder fatigue life simulation and thus can be utilized to more efficiently distinguish the binder fatigue resistance. Furthermore, the performance predictive accuracy of AASHTO TP101 specification method is strongly dependent on the selected failure definition. Taking the artificial failure definition of 35% reduction in |G*|·sin δ largely underestimates the binder fatigue life when compared to the S-VECD & GR approach. However, when a material-dependent failure definition of peak stress is alternatively employed in specification method, the correlation of the predictive binder fatigue life between the two analytical approaches is significantly improved and a linear relationship is additionally found between the S-VECD & GR approach and specification method. Therefore, it is recommended that when only the standard LAS test with one loading rate is available in practice, the peak stress failure definition should be used in AASHTO TP101 specification method to provide relatively accurate fatigue performance estimation of asphalt binder.

Development of a Computer Program for Calculation of the Alpha Parameter in the Linear Amplitude Sweep Test and Comparison with Rheological Parameters

Characterizing and modeling the fatigue performance of an asphalt binder is important when designing asphalt mixtures which can resist premature fatigue failure. Performance grading (PG) standards include the fatigue factor ( G*.sinδ) to evaluate the fatigue resistance of asphalt binders. This criterion seems to be inaccurate, especially when applied to modified asphalt binders. American Association of State Highway and Transportation Officials (AASHTO) TP 101 has been designed to evaluate the fatigue resistance of asphalt binders using Schapery’s work potential theory. The damage evolution rate ( α parameter) is the key element of this method and is calculated from the rheological properties of the undamaged asphalt binder using the slope of the relaxation modulus versus the time on the log-log scale. Owing to the difficulties of conducting the relaxation test, the relaxation modulus is usually obtained using conversion methods. However, AASHTO TP 101 uses a simplified indirect method to calculate α. The present study developed a computer program called RheoSUT with which to construct relaxation master curves using different methods. The relaxation master curves of 27 asphalt binders were evaluated for estimation of the value of α. The results indicated that AASHTO TP 101 yields higher values of α. The results of the sensitivity analysis show that overestimation of α will result in up to about 200% error in the estimation of the fatigue life ( Nf). It is also shown that binder aging and styrene-butadiene-styrene (SBS) modification directly affected the rheological parameters and relaxation master curves. Finally, it is recommended to use the relaxation-master curved based methods of calculation of α instead of the storage-modulus based ones.

Fatigue resistance of aged asphalt binders: An investigation of different analytical methods in linear amplitude sweep test

This paper aims to investigate the fatigue resistance of asphalt binders using different analytical methods and fatigue failure criteria with the consideration of various aging conditions. Four different performance grade (PG) binders with and without modifiers were tested by Linear Amplitude Sweep (LAS) test to characterize their fatigue behavior. The fatigue failure strain was determined using three different definitions: peak value of shear stress, peak value of phase angle and the maximum stored pseudo-strain energy. The damage characteristic curves and fatigue life were obtained by two kinds of analytical methods: dissipated energy-based method and pseudo-strain energy-based method. Statistical analysis shows that there is no distinct difference between these three criteria of fatigue failure for aged and unaged asphalt binders. However, for the modified asphalt binders at unaged condition, it is hard to observe the peak value of phase angle or stored pseudo-strain energy. The fatigue life determined by the pseudo-strain energy-based method is slightly higher than that of dissipated energy-based method across the entire loading strain range. In addition, the fatigue resistance of neat asphalt binder tested in this paper is deteriorated at high strain levels but improved at low strain levels and the critical strain level is approximate 4.5%. The effect of aging is asphalt specific and depends on the strain levels from the experimental results.

Development of failure criterion and fatigue model to characterize the fatigue resistance of asphalt binders under controlled-stress time sweep tests

The fatigue resistance of asphalt binders is of great significance to the design and maintenance of asphalt pavements. This study aims to develop a fatigue model that is independent of material types for asphalt binders subjected to controlled-stress time sweep tests. The ratio of dissipated energy change (RDEC) method and the normalized stiffness ratio (NSR) method are first evaluated with regard to this objective. It is demonstrated that both methods fail to provide a fatigue model that is independent of material types. A new failure criterion is then developed through analysis of the three phases of the dynamic shear modulus versus load cycles graph. The fatigue life is defined as the load cycle corresponding to the second inflection point on such a graph. In accordance with the plateau value concept utilized in the RDEC method, a new fatigue-related parameter is defined as the RDEC value at the fatigue life determined by the NSR method. Combine the fatigue life with the new fatigue-related parameter in the form of power function yields a new fatigue model, which is then fitted to the data points of all tested asphalt binders. It is found that all of the data points are located at or close to the best-fit line with an R2 value of 0.978. Therefore, this new fatigue model has the potential of being material type independent.

Fatigue resistance of asphalt binders and the correlation with asphalt mixture behaviour

The prediction of asphalt pavements performance in relation to the main distresses has been proposed by different researchers, by means of laboratory characterisation and field evaluation. With respect to fatigue, there are different approaches to determine what failure criterion to be considered, what testing conditions to be used and which specimens’ geometry to be produced. Tests performed in asphalt binders and mixtures have been recommended to characterise the fatigue resistance, and correlations among the several scales are proposed in order to make it more practical and more precise to predict the performance of asphalt layers. In terms of laboratory fatigue characterisation of asphalt mixtures, some of the most common tests are the four-point bending beam, diametral compression, the push-pull tests, among others. The characterisation of asphalt binders is also relevant, since fatigue is dependent on their rheological characteristics. Linear viscoelastic parameters of the binders, time sweep and amplitude sweep tests were used to rank three asphalt binders (one neat 30/45 penetration grade binder; one SBS-modified binder; and one highly modified asphalt, HiMA) in terms of fatigue behaviour. HiMA showed the highest fatigue resistance. One dense hot mix asphalt (HMA) mixture (prepared with the AC 30/45 neat binder) was characterised in terms of different fatigue test methods and correlated with binder tests, comparing the two scales approaches. The fatigue life of the asphalt mixture followed in agreement with results from the asphalt binder.

Shear properties of waste glass-asphalt mastics

This study aimed at using waste glass to improve shear properties of asphalt binders. Asphalt-glass mastics were prepared at four glass/asphalt (G/A) ratios: 0.05, 0.10, 0.20, and 0.30 by volume of asphalt. The Superpave dynamic shear rheometer (DSR) was used to measure the complex shear modulus value (∣G*∣) and phase angle (δ) for the control asphalt binder and the glass-asphalt mastics using frequency sweep tests conducted at nine loading frequencies: 10, 5.0, 3.0, 1.78, 1.0, 0.5, 0.3, 0.178, and 0.1 Hz and at a wide range of temperatures: 10, 20, 30, 40, 50, 60, and 70°C. Findings of the study showed that the waste glass filler improved ∣G*∣/cos δ (elastic part), ∣G*∣sin δ (fatigue parameter), and ∣G*∣/sin δ (rutting parameter) of the asphalt binder by decreasing δ and increasing ∣G*∣ especially at lower temperatures and high frequencies. Consequently, this enhanced the rutting and fatigue resistance of asphalt binders and improved the Superpave high temperature performance grade. It was also found that the increase in the ratio of the mix to the control asphalt binder for any of these parameters and the decrease in the phase angle ratio of the mix to the control asphalt binder were statistically significant (using 0.05 significance level) at 0.30 G/A ratio. Hence, the glass can be mixed in practice with the asphalt binder to increase its stiffness and therefore the rutting resistance and to improve the asphalt binder’s elastic part as a result of the decrease in the phase angle, which will improve the fatigue resistance.

The effect of EAF dust and waste PVC on moisture sensitivity, rutting resistance, and fatigue performance of asphalt binders and mixtures

Considering the increase in the amount of industrial waste in recent years, the reuse of recycled materials has become commonplace in various industries. In the pavement industry, such recycled materials can be used as a modifier of the asphalt mixtures. Electric arc furnace dust (EAFD) and waste polyvinyl chloride (PVC) are two industrial waste materials that are hazardous to the environment. This study aimed to investigate the effect of EAFD and PVC materials on the physical, mechanical, and chemical properties of asphalt binders and mixtures. For this purpose, chemical properties, microstructural characteristics, fatigue life, and rutting resistance of EAFD and PVC modified asphalt binders were studied using FTIR, SEM, LAS, and MSCR tests, respectively. In addition, the effect of PVC and EAFD additives on tensile strength, moisture sensitivity, and rutting performance of asphalt mixtures were evaluated. The results of the FTIR test showed that the addition of EAFD and PVC additives to asphalt binder significantly reduce the carbonyl index of neat asphalt binder and improve the moisture sensitivity and aging resistance of asphalt binders and mixtures. The results of the MSCR test indicated that EAFD and PVC additives reduce asphalt binder strain and subsequently increase rutting resistance, especially at high stress levels. Also, according to the results of the LAS test, adding PVC and EAFD powders to neat asphalt binder increase the fatigue resistance of asphalt binder against micro-crackers at low strain levels. The results of experiments on asphalt mixtures showed that EAFD and PVC additives improve tensile strength, moisture susceptibility, and rutting performance of asphalt mixtures. Overall, the results of this study illustrated that using EAFD and PVC waste materials in pavement industry, not only eliminate environmental problems caused by these materials and reduce the cost of stabilizing them, but also improve the technical performance of asphalt binders and mixtures.