Fatigue Performance Of Binders Research Articles

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.

Modelling effects of aging on asphalt binder fatigue using complex modulus and the LAS test

The linear amplitude sweep (LAS) test is considered a useful tool for evaluating fatigue of asphalt binders. It has been confirmed that a good correlation exists between fatigue performance of binders and mixtures in a few studies. While the change in binder fatigue with load or strain level is well studied and modeled, the effects of oxidative aging remain difficult to explain or to model in a simple format. In this paper, the combined effects of strain and aging are investigated and a method for estimating binder fatigue behavior after different aging durations from limited measurements is introduced. LAS tests were conducted on eight binders at three different aging periods in the PAV. It is found that binder fatigue damage parameters C1 and C2 have a good linear relationship with aging level when using the dissipated pseudo-strain energy approach. The results also show that LAS parameters A and B at different aging duration maintain a linear relationship with the binder complex modulus (G*) measured at corresponding aging conditions. Therefore, a new fatigue life (Nf) model accounting for strain level and aging effect is proposed using a power function of the binder G*. To verify the model, its parameters are fitted using test data at first two aging conditions and used to extrapolate and predict the fatigue life at extended aging conditions. This study findings offer a simpler and reliable method to predicted values of fatigue life at new aging condition using both 35% damage level and maximum stress failure criteria that are recommended in AASHTO TP101-12 and AASHTO TP101-14, respectively. The new model will allow use of the LAS procedure to a wider range of aging and strain level conditions for which binders could be subjected to in the pavement.

Fatigue tests and damage analyses in modified binders and gap-graded asphalt mixtures with Reacted and Activated Rubber – RAR

Several types of modifiers are currently studied, and among them, polymers and ground scrap tyre rubber stand out. The Reacted and Activated Rubber (RAR) is a new type of asphalt rubber that improves the engineering properties of the binder and mixtures. This research studied the rheological behaviour and fatigue performance of binders and gap-graded mixtures with RAR in quantities of 25% and 30%. The rheological characterisation tests were based on the Linear Viscoelasticity Theory and the principle of time-temperature superposition, which made it possible to elaborate the master curves. The fatigue performance was evaluated based on Continuum Damage Theory (CDT), getting the C-D curves and, in classic approach, getting the traditional Whöler curves. The tests on the binders were performed using the Dynamic Shear Rheometer (DSR) and asphalt mixtures tested in the Four-Point Bending (4PB) beam equipment. Modifications in AC 50/70 by RAR resulted in increased in PG, in softening point, rotational viscosity and density, and it reduced the penetration. Lower susceptibility to the frequency and temperature conditions of AB-R30 resulted in high fatigue life due to less sensitivity to the damage parameter. Comparison between the 4PB tests results of RAR produced mixtures tested at 20°C (MAB-R-25 and MAB-R30-1) and a field blend (MAB-RJ-122), expressed that the RAR modified mixtures exhibited superior fatigue life to the field blend, obtaining the MAB-R30-1 mix the highest performance. Tests with different temperatures for the same composition (MAB-R30-1, MAB-R30-2 and MAB-R30-3) and the same temperature for different compositions (MAB-R25 e MAB-R30-1) showed α parameter (CDT approach, C-D curves) with the similar behaviour of the parameter k2 (traditional approach, Whöler curves). Analysing the results, considering the research conditions (base binder, temperatures, tests, and methodologies performed) binder and mixture modifications using 30% RAR, proved to be more satisfactory.

Fatigue performance of long-term aged crumb rubber modified bitumen containing warm-mix additives

Recently warm mix asphalt (WMA) technologies have been introduced to rubberized asphalt mixtures to decrease the required construction temperatures and to alleviate the hazardous gas emissions. Rubberized asphalt pavements combining with WMA have the potential to improve the long-term pavement performance. This study aims to investigate the fatigue performance of crumb rubber modified bitumen (CRMB) containing warm-mix additives using different characterization methods. The effects of crumb rubber modifier (CRM) content (5%, 10%, 15% and 22% by weight of base bitumen) and warm-mix additives on the binder fatigue performance were investigated. Various laboratory tests, including frequency sweep tests, time sweep (TS) tests and linear amplitude sweep (LAS) tests, were conducted on the long-term aged binders to obtain indicators of fatigue performance. Results show that there is a good correlation between the measured fatigue life determined by TS tests using the dissipated energy concept and the predicted fatigue life determined by LAS tests using the simplified viscoelastic continuum damage (S-VECD) theory. However, the traditional Superpave fatigue parameter and the G-R parameter cannot characterize accurate enough the fatigue performance of modified binders. CRMB binders exhibit superior fatigue performance compared to the neat bitumen. The effects of warm-mix additives on the fatigue performance are different for neat bitumen compared to CRMB binder. Based on the findings in this study, rubberized asphalt mixture combining with WMA additives is expected to have a promising long-term fatigue performance.

Asphalt-rubber interaction and performance evaluation of rubberised asphalt binders containing non-foaming warm-mix additives

Warm mix asphalt (WMA) technology has been increasingly utilised in rubberised asphalt pavements to reduce the production and compaction temperatures and the incidental fumes and odours. This study aims to investigate the high, intermediate and low-temperature performance of crumb rubber modified asphalt binders containing WMA additives. The asphalt-rubber interactions under various mixing combinations of temperature and time were investigated through both microscopic and mechanical methods to obtain the optimum mixing procedure. The effects of WMA additives (wax-based and chemical-based products) on the binder performance were investigated by multiple stress creep and recovery (MSCR) test, linear amplitude sweep (LAS) test and low-temperature frequency sweep test. Results show that rubberised asphalt binders significantly improve the binder performance of base asphalt at different temperature ranges. The effects of WMA additives on binder performance varied with base asphalt and rubberised asphalt binder. In addition, the nonrecoverable compliance difference was found not suitable to characterise the stress sensitivity of rubberised binders and the difference in the nonrecoverable compliance for an incremental change in applied stress was proved to be a more accurate alternative. For the cyclic LAS test, the failure energy was found to have a strong correlation with the predicted fatigue life using simplified viscoelastic continuum damage analysis and therefore can be considered as a simple indicator for binder fatigue performance ranking. Relaxation modulus and rate derived from low-temperature frequency sweep tests produced comparable results for ranking the low-temperature performance of different binders. It is feasible and promising to use a unified DSR test methodology to characterise the binder performance covering the whole service temperature range.

Physico-chemo-rheological characterization of neat and polymer-modified asphalt binders

The physico-chemo-rheological properties of asphalt binder are critical for the long-term performance of asphalt pavement infrastructures. The objectives of this study are to characterize the physico-rheological properties of unmodified neat and polymer-modified asphalt binders with newly developed rheological performance tests, and further investigate the binder chemical properties as well as the possible performance relationship from macroscale to microscale perspective. Three neat asphalt binders and two styrene–butadiene–styrene (SBS) modified asphalt binders are selected in this study. The physical properties of asphalt binder include traditional penetration, softening point and ductility. The saturates, aromatics, resins and asphaltenes (SARA) fractionation test, gel permeation chromatography (GPC) and fourier transform infrared spectroscopy (FTIR) tests are respectively conducted to quantify the chemical composition, molecular weight distribution and structure properties of asphalt binders. The rheological rutting and fatigue resistance are evaluated through the multiple stress creep recovery (MSCR), linear amplitude sweep (LAS) and DSR-based elastic recovery (DSR-ER) tests. Experimental results indicate that the physical properties are only effective to distinguish the rheological performance of neat asphalt binders. The lower aromatics contents improve the binder rutting resistance and an unified relationship between aromatic contents and binder rutting performance is obtained for both neat and modified binders. In addition, increasing the amount of small asphalt molecules decrease the resistance to permanent deformation respectively for neat and modified binders. However, the small asphalt molecule is favorable for improving the binder fatigue performance. The large molecular size (LMS) parameter from GPC test is demonstrated a unified correlation to the fatigue life of both neat and modified binders.

Evaluating the Effect of High RAP Content on Asphalt Mixtures and Binders Fatigue Behavior

Abstract One of the main concerns with the application of reclaimed asphalt pavement (RAP) in the asphalt concrete pavement is fatigue cracking due to the stiffness increase with the addition of aged and stiff RAP binder. The purpose of this study is to evaluate fatigue performance of asphalt binder and mixtures with different RAP percentages (0, 15, 25, 35 and 40 %). Among these, 35 and 40 % RAP mixes are considered as high RAP content. This study describes the results of laboratory fatigue response of asphalt mixtures and extracted binders containing RAP to define the effect of RAP on the fatigue performance. To achieve this objective, mixes and binders were tested using the beam fatigue test and the time-sweep test, respectively. Test results were analyzed using two different fatigue approaches, reduction in stiffness and dissipated energy criteria. Results showed that a higher initial stiffness and initial dissipated energy initiate the fatigue failure faster. Since both binders and mixes show an increase in the stiffness and energy consumed per loading cycle with the addition of RAP, resulting mixes containing higher RAP have a very short fatigue life. Also, the fatigue endurance limit decreases drastically with the addition of RAP in the mix. The results comparing two different RAP sources showed that the RAP source has more prominent effect on the mix fatigue performance than the binder fatigue performance. Finally, the traditional fatigue life prediction model is modified to incorporate the effect of RAP in the fatigue equation. The modified regression model predicted reasonable fatigue life of the mixture with a coefficient of determination (R2) close to 1. The measured and predicted fatigue life results were found close to each other for both mix and binder containing RAP.

Introducing a new specimen shape to assess the fatigue performance of asphalt mastic by dynamic shear rheometer testing

Early failure of asphalt pavements is a common issue all around the world. Damages are caused by various reasons like insufficient binder or aggregate quality, an inadequate mix design or improper handling in the production/construction process. The effects of binder, aggregates and mix design have been widely studied and state-of-the-art testing methods are available for both, hot-mix asphalt (HMA) and for each component. An important part in HMA belongs to the asphalt mastic, where no standardized method is available to allow a quality control. Asphalt mastic is the mix of bitumen with aggregates smaller than 63 (125) µm and covers the coarse aggregates as the actual binding component in the mix. This research aims at developing a testing method for asphalt mastic based on fatigue tests. The dynamic shear rheometer (DSR) was found as a suitable device for this purpose. The DSR fatigue test consists of the 8 mm parallel-plate geometry widely used for binder performance grading with a sample height of 3 mm. Instead of a cylindrical specimen shape, a hyperboloid of one sheet is applied. This shape predetermines the point of failure and prevents adhesion/interface failures between the mastic specimen and the upper or lower DSR stainless steel plate. The specimens are prepared directly in the DSR employing a silicone mould to ensure an exact specimen shape. This test can be applied to all DSR devices without costly changes or additional equipment as long as sufficient cooling capacity and torque can be provided from the DSR. This fatigue test makes it possible to assess the fatigue performance of binders and mastic samples.

Identifying fatigue failure in asphalt binder time sweep tests

Identification of fatigue failure of asphalt binder in time sweep test results remains a question crucial to asphalt binder fatigue performance evaluation and prediction. This paper presents a comparison of different analysis approaches for defining the occurrence of fatigue failure during time sweep fatigue tests conducted in both control-displacement and control-stress loading modes. The candidate failure definitions evaluated include the traditional 50% reduction in stiffness parameter (S0.5), dissipated energy indicators including the dissipated energy ratio (DER) and the ratio of dissipated energy change (RDEC), as well as two phenomenological parameters corresponding to the peak in S×N and peak in phase angle. Both phenomenological parameters and dissipated energy based indicators were found to be effective in defining fatigue failure. Statistical analysis results further indicate that maximum S×N, maximum phase angle and RDEC approach provide equivalent fatigue life results, however, peak in S×N is strongly recommended for detecting fatigue failure of asphalt binder in time sweep tests because it is easy to calculate and well defined.

Effect of load control mode on the fatigue performance of asphalt binder

Fatigue cracking is one of the major distresses found in asphalt pavements. The ability of asphalt binder to resist the accumulation of fatigue damage can have a profound effect on the service life of asphalt pavements. However, different from other materials, the fatigue characteristics of asphalt binder depend heavily on the load control mode. That is the fatigue characteristics of asphalt binder under controlled-stress mode differ from those under controlled-strain mode. This discrepancy affects the analysis results of asphalt binder fatigue performance. Therefore, this study is aimed at analyzing the effects of the load control mode on the fatigue performance of asphalt binder through a comparison of the fatigue characteristics under two different load control modes. The effect range of the load control mode was confirmed, and the method to differentiate the region affected by load control modes from the region not affected by load control modes was put forward. The relationship between the fatigue performances of asphalt binder under different control modes was analysed. Based on the results, it is concluded that the fatigue process can be divided into two regions using the curve of normalized dynamic modulus versus normalized phase angle. And, if the controlled stress and the controlled strain are equivalent levels, the fatigue characteristics of asphalt binder are independent of load control modes in the first region. The accumulated dissipated energy at the division point of the two regions is independent of both control modes and load levels, and serves as the effect threshold of the load control mode. Besides, the curve of accumulated dissipated energy versus number of cycles under controlled-stress mode is symmetrical to that curve under controlled-strain mode.

Implications of warm-mix asphalt on long-term oxidative ageing and fatigue performance of asphalt binders and mixtures

The use of warm mix asphalt (WMA) has been increasing in recent years due to its ability to reduce the production temperatures of asphalt concrete. The long-term implications of reduced production temperatures and, hence, reduced short-term ageing on long-term performance remain largely unknown. This study evaluates the effect of age hardening in WMA binders and mixtures compared with hot mix asphalt (HMA) binders and mixtures with respect to fatigue damage. Two WMA technologies are considered: foaming by water injection and Evotherm modification. For this study, the asphalt mixtures were subjected to laboratory conditioning in a forced air convection oven to simulate long-term field ageing according to AASHTO R30. The asphalt mixtures and extracted binders were subjected to linear viscoelastic and fatigue characterisation following ageing. Because oxidative ageing occurs within the asphalt binder phase of asphalt concrete, this paper focuses on the relative performance of WMA and HMA binders at various ageing levels and compares this binder performance to the respective mixture performance. Cyclic direct tension tests were used to measure the fatigue resistance of the asphalt mixtures, and the linear amplitude sweep (LAS) test was used to measure the fatigue resistance of the binders. Simplified viscoelastic continuum damage (S-VECD) analysis was performed to interpret the fatigue test results and predict the fatigue performance of the binders and mixtures using a pavement structural model. The results demonstrate that after substantial long-term ageing, differences between the fatigue performance of WMA and HMA become insignificant. The results also demonstrate good agreement between the binder and mixture results, indicating that the LAS test coupled with S-VECD analysis is able to capture the binder's contribution to mixture fatigue.

Relationship between Binder and Mixture Damage Resistance at Intermediate and Low Temperatures

The importance of binder performance in mixture response to accelerated fatigue loading and thermal cracking was investigated. Binder fatigue performance was measured by means of the linear amplitude sweep test, and fatigue properties of the mixtures were investigated by performing a strain sweep test. The low-temperature properties of the binders were investigated by measuring the glass transition temperature and fracture properties with the single-edge notched beam (SENB) test. The mixtures' fracture properties were investigated by using the FENIX test. The experimental matrix for this study included unmodified and modified binders and limestone aggregates. A good correlation between binder and mixture fracture energy was observed at low temperatures. This good correlation indicates the importance of the fracture response of the binder to the overall low-temperature cracking performance of the mixture. Experimental results suggest that a significant part of the variation of the fracture energy of the mixture can be explained by the binder fracture properties. Good correlations were also obtained for the displacement at maximum load in the SENB and FENIX tests. Similar accelerated fatigue responses for binders and mixtures were observed when the stresses and strains were normalized. Significant reduction in stress occurred at about the same normalized strain in the binder and mixture. The mixture had remaining strength after reaching peak stress, probably as a result of the aggregate structure.