Binder Fatigue Research Articles

Modeling Influence of Aging and Rejuvenation Mechanisms on the Recycled Asphalt Pavement (RAP) Binder Fatigue Life through the Linear Amplitude Sweep Test

Modeling Influence of Aging and Rejuvenation Mechanisms on the Recycled Asphalt Pavement (RAP) Binder Fatigue Life through the Linear Amplitude Sweep Test

Proposal for a New Method for Evaluating Polymer-Modified Bitumen Fatigue and Self-Restoration Performances Considering the Whole Damage Characteristic Curve

Fatigue performance and self-repairing activity of asphalt binders are two properties that highly influence the fatigue cracking response of asphalt pavement. There are still numerous gaps in knowledge to fill linked with these two characteristics. For instance, current parameters fail to accommodate these two bitumen phenomena fully. This study aims to propose a new procedure to address this issue utilizing the linear amplitude sweep (LAS) test, LAS with rest period (RP) (LASH) test, and simplified viscoelastic continuum damage (S-VECD) model. This research work used four different types of asphalt binders: neat asphalt (NA), self-healing thermoplastic polyurethane (STPU)-modified bitumen (STPB), self-healing poly (dimethyl siloxane) crosslinked with urea bond (IPA1w)-modified bitumen (IPAB), and styrene–butadiene–styrene (SBS)-modified bitumen (SBSB). Before the testing process, all the materials were subjected to short-term and long-term aging. The new procedure showed a superior capacity to analyze and accommodate all bitumen fatigue performances and self-repairing activities compared to the current method. Another finding proved that asphalt binders with a higher self-restoration behavior failed to show a better fatigue performance. Moreover, the higher fatigue performance increments produced by STPU and IPA1w in NA concerning the control bitumen were 123.7% and 143.7%, respectively. Those values were obtained with 1.0% STPU and 0.5% IPA1w in NA. A breakthrough finding demonstrated that asphalt binder fatigue response is augmented when the RP was applied at a higher damage intensity (S) value. STPB and IPAB reached their highest increments of fatigue response, containing 1.0% of STPU and 0.5% of IPA1w, respectively. Those augmentations were 207.54% and 232.64%, respectively.

Evaluating and correlating asphalt binder and mixture fatigue properties considering aging conditions

Asphalt fatigue cracking is a critical distress type for flexible pavement. This study utilized the state of practice binder and mixture cracking tests and parameters to investigate how asphalt binders’ and mixtures’ fatigue performance vary between the different mix designs and evaluate their changes with aging. The potential relationships between the measured binder properties and mixture performance were also explored. Five asphalt mixtures with disparate mix designs were evaluated and three different aging conditioning levels were conducted. The binder tests include the traditional time and frequency sweep and linear amplitude sweep test, while the mixture evaluations include the semi-circular bending and cyclic fatigue test. The results indicate that the different fatigue parameters from the tests can evaluate and rank the mixes differently. The correlation analysis using the Spearman correlation coefficient shows that the mixture cracking parameters that are more predominant by asphalt mixture’s flexibility/brittleness show strong correlations (Spearman coefficient larger than 0.8) with binder cracking indices. The LAS fatigue life-related parameters generally do not correlate well with mixture fatigue indices (Spearman coefficient smaller than 0.6). Furthermore, a prediction model to estimate asphalt mixture’s fatigue performance was developed based on linear regression and Artificial Neural Network (ANN) approach, which only requires the mix design info. and binder fatigue property as the inputs, significantly reducing the time and eliminating the effort in preparing and testing the asphalt mixture specimen for mixture fatigue performance measurement.

Assessment of the effectiveness of binder fatigue, rheology and chemistry parameters in evaluating cracking resistance in high RAP mixtures modified with recycling agents

The utilization of Reclaimed Asphalt Pavement (RAP) in pavement construction has gained prominence as a sustainable approach to reduce material costs and environmental effect. However, a significant challenge associated with increased RAP incorporation lies in the potential fracture distress caused by the aged binder. The purpose of this study is to assess the cracking performance of asphalt mixtures incorporating three levels of recycled materials (30% RAP, 50% RAP, and 30% RAP along with 5% Reclaimed Asphalt Shingles (RAS)). Three softening oils were employed to improve the cracking performances at two aging levels. Performance evaluations, including cracking performance assessments at intermediate and low temperatures, were carried out and compared with control mixtures. The findings of this study reveal that the incorporation of softening oils, as investigated herein, offers a viable means of producing asphalt mixtures featuring high RAP content while preserving performance comparable to that of a virgin mix. From a binder perspective, the Glover–Rowe (G–R) parameter and fatigue life at 10% strain level emerge as robust indicators for evaluating cracking resistance under conditions pertaining to intermediate and low temperatures.

Phenomenological modeling of aging and rejuvenation on asphalt binder fatigue characteristics

Recycling agents (RAs) have been explored as additives to enhance the properties of recycled asphalt binders. Despite extensive research on RAs, a critical knowledge gap exists regarding their impact on fatigue cracking of asphalt binders, especially considering the aging processes. This study aims to comprehensively investigate the effects of recycling agents on the fatigue properties of asphalt binders, with a specific focus on the influence of aging and rejuvenation. The current Linear Amplitude Sweep (LAS) test analysis procedure is utilized to assess the fatigue properties, and the efficacy of existing LAS test-based indices is evaluated. Furthermore, a novel index based on the simplified viscoelastic continuum damage (S-VECD) theory framework is proposed to monitor changes in fatigue properties with aging and rejuvenation. A total of 26 recycled binder blends are studied and the results demonstrate that the proposed index consistently tracks the effects of aging and rejuvenation in recycled binder blends containing recycling agents. Additionally, cross-scale assessments are conducted by correlating the proposed index with mixture performance, specifically the Indirect Tensile-Cracking Test parameter (CTindex). The findings indicate that the proposed index exhibits a correlation with the CTindex after 1-day Long Term Aging testing and effectively captures the aging sensitivity across different scales.

Enhancing accuracy of predictive fatigue life model in rejuvenated RAP binders through LAS test and complex modulus test at multiple temperatures

The linear amplitude sweep (LAS) test is widely accepted as a valuable tool for assessing binder fatigue. However, due to the binder's viscoelastic nature, the fatigue life varies with temperature, leading to a challenge in determining the LAS testing temperature. This research primarily addressed inaccurate assumptions of a linear relationship between the logarithms of the storage modulus (logG′(ω)) and angular frequency (log (ω)), as well as intermediate testing temperature. Then, by performing the LAS test at four different temperatures on rejuvenated RAP binders, a method for determining the rejuvenated RAP binder's fatigue behavior was introduced. The results demonstrated that LAS parameters, including A and B, correlated linearly at various temperatures with the rejuvenated RAP binder's complex modulus (|G*|) calculated at corresponding temperatures. Therefore, a fatigue life model, considering strain level and temperature effects, was developed using a power function of |G*|. It was found that the residual analysis exhibited a lack of fit, indicating that the linear model was inadequate throughout the whole range of experimental frequencies at multiple temperatures. Moreover, the newly introduced model predicted fatigue life more accurately at various temperatures utilizing the maximum stress failure criterion and the 35% damage level. This model will allow the LAS procedure to be used in a wider range of temperatures and strain levels for which rejuvenated RAP binders are used in the flexible pavement.

Linear viscoelastic properties and fatigue S-VECD based evaluation of polymer-modified asphalt mixtures

Direct tensile fatigue tests associated with the simplified continuous damage viscoelastic model (S-VECD) have proven to be an effective tool for evaluating fatigue in asphalt materials. Thus, this study evaluated the fatigue damage of asphalt mixtures modified by the addition of polymer based on the results of the direct tensile fatigue test using the S-VECD model. Three asphalt mixtures were produced: a control asphalt binder with 50/70 penetration, a polymer-modified styrene-butadiene-styrene (SBS) asphalt binder, and a mixture produced with a modified asphalt binder (composed of 98.38% control + 1.26% Ethylene Methyl Acrylate and Glycidyl Methacrylate (EMA-GMA) + 0.21% High-Density Polyethylene (HDPE) + 0.15% Polyphosphoric Acid (PPA116%)). The binders were evaluated for physical and rheological properties, and fatigue using the Linear Amplitude Sweep (LAS) test, applying the S-VECD model. Asphalt mixtures were evaluated for stiffness using tensile strength, resilient modulus and flow number tests. The viscoelastic linear behaviour (LVE) was characterized based on the dynamic modulus test and the fatigue performance was evaluated from the uniaxial direct traction test with the application of the S-VECD viscoelastic damage model. The results of the LAS test indicated that the modified binder presented the best fatigue performance, being classified according to the binder fatigue factor (FFB) as excellent. Mixtures with binders modified by polymers showed the highest values in mechanical performance tests. As for the LVE behaviour, the mixture with the modified binder showed the expected behaviour, with higher dynamic modulus values at high temperatures (low reduced frequencies), and the lowest modulus values at lower temperatures (high reduced frequencies). In addition, for the entire spectrum of frequencies and temperatures, the modified mixture presented the lowest values of phase angle, indicating more elastic and less viscous behaviour. From the direct tensile test, based on the GR failure criterion, the modified mixture showed better fatigue performance, with a higher value of the Fatigue Factor of the Mixture (FFM). Based on the DR failure criterion, from the Sapp damage capacity, mixtures with polymers were classified with the best performances concerning fatigue. Therefore, the use of polymer-modified binders promoted asphalt mixtures with better fatigue damage performance.

Applicability of Standard Rheological Evaluation Methods for High Content SBS Polymer Modified Asphalts

High content SBS polymer modified asphalt (HCPMA) can serve as pavements under heavy traffic and a wide range of temperatures. However, the applicability and validity of standard rheological evaluation methods to characterize HCPMA are still unclear. In this study, the influence of SBS content on the conventional properties and rheological behavior of HCPMA was analyzed. A higher content of SBS can improve the performance grade of the asphalt binder to PG100-34. The slope of the Jnr-σ linear curves from the MSCR under various stress levels decreases when the SBS content increases. The slope of the Jnr-σ linear curves can replace Jnrdiff as an indicator of stress sensitivity. A higher content of SBS can also decrease the flexural creep stiffness and increase the creep rate of the binders. The binder fatigue resistance parameter increases and the binder yields at higher strain, with increasing SBS content. These results show that a higher content of SBS can further improve the resistance to rutting, thermal cracking, and fatigue. Current standard rheological methods should be modified when evaluating HCPMA. The results also show that conventional tests are not valid for evaluating the performance of HCPMA.

Performance Assessment of Self-Healing Polymer-Modified Bitumens by Evaluating the Suitability of Current Failure Definition, Failure Criterion, and Fatigue-Restoration Criteria

Fatigue cracking is a common form of flexible pavement distress, which generally starts and spreads through bitumen. To address this issue, self-healing elastomer (SHE) modified bitumens were elaborated to assess whether these novel materials can overcome the neat asphalt (NA) fatigue performance and whether the current failure definition, failure criterion, and fatigue-restoration criteria can fit their performance. All bitumens were subjected to short-term and long-term aging. Linear amplitude sweep (LAS) test, LAS with rest period (LASH), and simplified viscoelastic-continuum-damage (S-VECD) model were utilized to appraise the behavior of the mentioned bitumens. The results showed that maximum stored pseudo-strain energy (PSE) and tau (τ) × N (number of loading cycles) failure definitions exhibited high efficiency to accommodate the fatigue life of NA and SHE-modified bitumens. Both failure criteria identified that SHE-modified bitumen (containing 1% of SHE) showed the highest increment of fatigue performance (67.1%) concerning NA. The failure criterion based on total released PSE, in terms of the area under the released PSE curve, was the only failure concept with high efficiency (R2 up to 0.999) to predict asphalt binder fatigue life. As well, the current framework to evaluate bitumen self-restoration failed to fully accommodate asphalt binder behavior, because bitumen with higher restoration could not exhibit greater fatigue performance. Consequently, a new procedure to assess this property including fatigue behavior was proposed, showing consistent results, and confirming that SHE-modified bitumen (containing 1% of SHE) exhibited the highest increment of fatigue performance (154.02%) after application of the rest period. Hence, the optimum SHE content in NA was 1%. Furthermore, it was found that a greater number of loading cycles to failure (Nf) did not ensure better fatigue performance and stored PSE influenced the bitumen fatigue behavior.

Toward to a viscoelastic fatigue and fracture model for asphalt binder under cyclic loading

This paper presents a viscoelastic fatigue and fracture (VEFF) modeling and its preliminary application to asphalt binder under cyclic loading. Both traditional time sweep (TS) fatigue test and linear amplitude sweep (LAS) test are performed. The failure definition is unified from the peak of fracture energy. The binder fatigue performance is dominated by its resistance to crack propagation. A mechanistic criterion paradigm is established to be independent of the strain ramping rate in LAS and strain amplitude in TS tests. The proposed model is verified by various binders, demonstrating the reasonable use of the LAS as an accelerated fatigue protocol.

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.

Correlation of asphalt binder linear viscoelasticity (LVE) parameters and the ranking consistency related to fatigue cracking resistance

Fatigue cracking is a common distress in asphalt pavements. Different cracking parameters obtained from asphalt binder testing have been proposed to measure cracking resistance. In this work, binder tests were conducted on both polymer-modified and unmodified binders, spanning a wide range of binder grades and sources. Linear viscoelastic parameters (i.e., stiffness- or relaxation-based) and binder fatigue damaged-based parameters were both assessed. Test methods included the dynamic shear rheometer (DSR) consisted of temperature-frequency sweep and linear amplitude sweep (LAS) testing, bending beam rheometer (BBR). Parameters selected in this work include |G*|·sinδ (G* is the dynamic shear modulus, δ is the phase angle), Glover-Rowe parameter (GRP), R-value, ΔTc, and number of cycles to failure (Nf) from viscoelastic continuum damage (VECD) analysis. Some calculations, thresholds and fatigue testing temperatures of these parameters are based on the recommendations of the National Cooperative Highway Research Program (NCHRP) Project 9–59. The purpose of this work is to compare different binder parameters that have been proposed as indicators of cracking resistance. The potential changes of intermediate temperature definition are also evaluated. The results show that generally the different stiffness-based binder parameters from the DSR correlate well with each other. A correlation is observed between binder GRP and LAS damage parameters from VECD analysis.

Performance evaluation of asphalt binders modified with pyrolytic chars and WMA additive

Pyrolysis is a prominent waste-to-energy conversion process that allows for energy recovery and the creation of fuels from discarded/scrap tires and waste plastics. Tire and plastic pyrolytic chars (TPC and PPC) are solid fine carbonaceous materials released as by-products during the pyrolysis process. The application of TPC and PPC as asphalt binder modifier can yield beneficial effects on the rheological properties; however, mix preparation with TPC and PPC modified asphalt binders may require more energy due to their increased stiffness/viscosity. The introduction of warm mix asphalt (WMA) technology can help lower down the high production temperatures of the char-modified binders. This paper investigates the influence of a WMA additive on the production temperatures and dynamic mechanical properties of pyrolytic char modified binders. The production temperatures for binders were determined based on different rheological methods. Master curves were plotted from frequency sweep data. The rutting performance of the binders was determined through multiple stress creep and recovery (MSCR) tests. The MSCR data was also modelled using Burgers four-element model. Linear amplitude sweep (LAS) tests were used to evaluate the binder fatigue resistance. The incorporation of WMA additive effectively reduced the production temperatures of char-modified binders. The resistance to rutting and fatigue cracking was also enhanced after the addition of the WMA additive. Overall, the findings indicate that pyrolytic char-WMA composite modified asphalt binders have a good potential for use in road pavements.

Evaluation of fatigue and rutting properties of asphalt binder and mastic modified by synthesized polyurethane

Fatigue and rutting phenomena are major distresses in asphalt pavements. Asphalt mixture properties are highly dependent upon the asphalt binder and the mastic behavior. The purpose of this study was to investigate the behavior of the asphalt binder and the mastic, modified by the synthesized polyurethane, at high and intermediate temperatures. The filler/asphalt binder ratio (by weight) was 1.0. The dynamic shear rheometer (DSR) was used to measure fatigue ( G ∗sin δ ) and rutting ( G ∗/sin δ ) parameters. In this study, the multiple stress creep and recovery (MSCR) test was also utilized to calculate the rutting potential of the asphalt binder and the mastic. Parameters of the non-recoverable compliance ( J nr ) and the percentage recovery (%) were evaluated at high temperatures. The obtained results indicated that the synthesized polyurethane improved the rutting and fatigue properties. There was a significant correlation between the asphalt binder and the mastic in terms of the complex modulus ( R 2 = 0.9958), rutting ( R 2 = 0.9944), and the non-recoverable compliance ( R 2 = 0.9707). For the fatigue parameter ( R 2 = 0.9852), the complex modulus ( R 2 = 0.9855), and the phase angle ( R 2 = 0.8262), significant relationships were observed between the asphalt binder and mastic samples at intermediate temperatures. Overall, the chemical reaction between the filler and the asphalt binder could be effective in different behaviors of the mastic and asphalt binder. There was a 112%–164% increase in the G ∗sin δ parameter for mastics, compared to that of the asphalt binder. The complex modulus was 6 times higher by adding the filler content. • Synthesized polyurethane was used to modify asphalt binders and mastic. • There was a high convergence between mastic and asphalt binder fatigue and rutting. • The filler changes the behavior of asphalt binder. • There was no convergence between phase angle and recovery at high temperature. • Synthesized polyurethane improved asphalt binder performance.

Restriction of RAP% in HMA Based on Aggregate Gradation and Binder Properties

The use of recycled asphalt pavement (RAP) in pavement construction reduces the project cost and helps in conserving the naturally occurring aggregates. To incorporate RAP in hot mix asphalt, it is vital to know the amount and quality of the reclaimed binder. Three new asphalt binders were selected for this investigation. RAP material from one source was blended in different proportions with VG-10 and VG-30. Penetration, softening point, G */sin δ, G * sin δ and binder fatigue life Nf (from Linear Amplitude Sweep test) values of different blends were compared. The milled RAP aggregate gradation varied from source to source due to factors such as the gradation of the mix used in the existing layer, milling method and processing of RAP material. This variability controls the use of higher proportions of RAP in new mixes. To investigate the effect of RAP gradation on the proportion of RAP that can be used in the new mix, RAP sources with different gradation (three dense and two gap gradations) were selected. The proportion of RAP that can be used for preparing mixes with these gradations varied significantly with the source of RAP, and the target gradation. In most cases, it was found that allowable RAP percentages are smaller for the gap gradations compared to those permitted for dense gradations. The proportion of RAP in a mix can be increased by selecting an appropriate gradation for a RAP source or by using a suitable RAP source for a given gradation.

Evaluating the Rheological Properties and ageing Resistance of Waste PET-Modified Bitumen Binder

Reusing waste plastic can significantly contribute to saving the environment from further pollution and the economy from extra expenses. Waste plastics have a vital role in the current asphalt applications. Trial sections of roads made with waste plastic modified asphalt during 2019 in Australia, highlighted the significant importance of laboratory assessments; however, they are yet to be conducted. This study investigates the impact of using local waste Polyethylene Terephthalate (PET) plastic in bitumen binder class C320, which is a common bitumen type used for local road surfacing in Australia. The evaluation of numerous contents of waste PET modified bitumen is carried out before and after ageing conditions. Dynamic Shear Rheometer (DSR), Rolling Thin Film Oven (RTFOT) and Pressure ageing Vessel (PAV) tests were utilised to examine the rutting, fatigue, and ageing of bitumen binder. The results displayed that the use of waste plastics results in enhanced rutting and ageing resistances. Based on DSR results, bitumen samples modified with waste PET display improved performance in terms of rising the complex shear modulus and reducing the bitumen’s susceptibility to deformation at high temperatures. Furthermore, 8% of waste PET increases the fatigue cracking resistance as it shows a low fatigue factor. Further rutting and fatigue tests on asphalt mixtures samples are recommended to better understand the mechanical properties of waste PET plastic on modified C320 asphalt mixtures.

Modelling asphalt binder fatigue at multiple temperatures using complex modulus and the LAS test

ABSTRACT The linear amplitude sweep (LAS) test is useful for evaluating the fatigue of asphalt binders. In this paper, the combined effects of strain and temperatures are investigated, and a method for estimating binder fatigue behaviour is introduced at different temperatures from limited measurements. LAS tests were conducted on several different PG-grade binders at four different temperatures. The results show that LAS parameters A and B at different temperatures maintain a linear relationship with the binder complex modulus (G*) measured at corresponding temperatures. Therefore, a fatigue life model, accounting for strain level and temperature, is proposed using a power function of the binder G*, which can account for temperature effects. To verify the model, its parameters are fitted using test data at two temperatures were used to predict the fatigue life at additional temperatures. This study findings offer a simpler and reliable method to predict the values of fatigue life at new temperatures using both 35% damage level and maximum stress failure criteria that are recommended in AASHTO TP101-12 and AASHTO TP101-14, respectively. The new prediction method will allow a wider use of the LAS procedure regarding the effects of temperature and strain level for which binders are subjected to the pavement.

Microcapsule synthesis and evaluation on fatigue and healing of microcapsule-based asphalt by the entropy and TOPSIS method

ABSTRACT Encapsulation is a promising approach to enhance the self-healing ability of asphalt materials. In this study, microcapsules encapsulated waste engine oil was synthesised to improve the self-healing ability of asphalt. The factors affecting the synthesis of microcapsules, especially emulsification and core shell ratio, were investigated through a micro-observation. Dynamic mechanical properties of microcapsule-based asphalts were analysed. Fatigue and healing properties of asphalt binder were evaluated using the entropy and TOPSIS method. Results showed that a combination of sodium dodecyl sulphate and Span-60 showed better emulsification and the optimised dosage of emulsifier was 1.5 wt%. Increasing emulsifying speed, or decreasing core shell ratio, improved encapsulation efficiency. Addition of microcapsules decreased the asphalt stiffness at low frequency and the fatigue resistance of microcapsule-based asphalt went through relatively large decay when microcapsule addition exceeded 4 wt%. Three healing indexes increased with the addition of microcapsules. By entropy weight and the Technique for Order Preference by Similarity to an Ideal Solution analysis, healing index relating to fatigue life shows a larger entropy weight than others and asphalt with 2 wt% microcapsules perform better with respect to fatigue and healing properties.

Comparison and correlation of asphalt binder and mixture cracking parameters incorporating the aging effect

Cracking is one of the primary distresses in asphalt pavements, and aging can significantly affect the cracking properties of asphalt material. The primary objective of this study is to investigate comparisons and correlations between binder and mixture cracking property parameters subjected to different aging conditions, and further evaluate how these relationships would change with aging. Nine plant produced mixtures are conditioned following various conditioning protocols, and the corresponding binders are extracted and recovered from those mixtures. Mixture properties are measured from Complex Modulus (E*), Direct Tension Cyclic Fatigue (DTCF), Semi Circular Bending (SCB) and Disk-shaped Compact Tension (DCT) tests. Binder tests include Complex Shear Modulus (G*) and the Linear Amplitude Sweep (LAS) test. The binder and mixture parameters measured include thermo-rheological parameters, fatigue indices and fracture parameters. Different statistical analysis methods including the Pearson, Kendall and Hoeffding’s D analysis, and frequency curves are used to investigate the comparisons and correlations between the parameters. The results from this study indicate that while considering all the aging conditions, binder parameters evaluated generally correlate well with each other. Mixture parameters also show good correlations with the exception of the fatigue parameters. Mixture rheological and fracture parameters generally show moderate to strong correlations with all the binder parameters, while mixture fatigue parameters only show strong correlations with binder fatigue parameters. Further looking into these relationships with respect to the individual aging condition, the correlations between parameters typically are improved with increase of aging levels. In addition, the distributions of these performance parameters with aging show a close trend with change of asphalt chemical composition over time, indicating the fundamental relationship between asphalt chemistry and its engineering performance. The overall good correlations between binder and mixture parameters reinforce the concept that binders play a significant role in the cracking properties of asphalt mixtures.

Investigating the Cracking Resistance of Asphalt Binder in the UAE using Styrene-Butadiene-Styrene Polymer

This research work focuses on investigating the fatigue and thermal cracking resistance of asphalt binder with different percentages of styrene-butadiene-styrene (SBS) utilizing rheological testing methods. The laboratory experimental program includes the Dynamic Shear Rheometer (DSR) test at intermediate temperature for fatigue cracking and Bending Beam Rheometer (BBR) at low temperature to assess thermal cracking. The polymer-modified asphalt binders were prepared using four different SBS contents of 2.5, 4.2, 4.8, and 6.1% by asphalt binder weight. The test results were then used to compare the performance of four different SBS modified binders and the control asphalt binder without SBS. The findings showed that the addition of the SBS to asphalt binder improved the fatigue resistance as it was noted that the fatigue parameter (G*.sin δ) was decreasing as the temperature decreases. The BBR results also showed that the addition of SBS enhanced the low-temperature performance by lowing the creep stiffness and increasing the m-values compared to the control asphalt binder. The best performance against fatigue cracking and thermal cracking was obtained using 6.1% SBS.