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Open accessJournal ArticleDOI: 10.1080/14680629.2019.1635516

Predicting crack growth in viscoelastic bitumen under a rotational shear fatigue load

04 Mar 2021-Road Materials and Pavement Design (Taylor & Francis)-Vol. 22, Iss: 3, pp 603-622
Abstract: This study develops a damage mechanics-based crack growth model to predict crack length in a typical viscoelastic material (i.e. bitumen) under a rotational shear fatigue load. This crack growth mo...

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26 results found

Open accessJournal ArticleDOI: 10.1016/J.JCLEPRO.2020.120709
Abstract: This study aims to characterise the healing properties of asphalt binders at different damage levels. The healing and the damage levels were quantified by crack length (CL) in binder samples generated by rotational shear fatigue loads in strain-controlled dynamic shear rheometer (DSR) tests. For comparison, the healing was also characterised by the commonly used material parameters including pseudo shear stiffness (S) and dissipated pseudo strain energy (DPSE). A normalized healing index was formulated using the above three parameters, respectively. A healing test of polymer-modified bitumen was designed based on DSR including a strain-controlled time sweep test plus a rest duration and followed by another strain-controlled time sweep test. The healing tests were performed at different rest start times (5min, 10min and 20min), rest durations (5s, 10s, 0.5min, 1min, 2min, 5min, 10min, 20min, and 40min), and amplitudes of the shear strain (5%, 7%, and 10%) at 20 °C and 10 Hz. Results show that the CL-based healing index is a fundamental and accurate parameter to evaluate the healing rate and healing potential of the bitumen. DPSE-based healing index is applicable only when the energy is mainly dissipated to generate cracks. Healing is underestimated when characterised using S or DPSE-based healing indices. Healing index increases due to the advance of rest duration or the decrease of the damage level, and the healing rate can be essentially modelled by Ramberg-Osgood model. Higher damage levels (introduced by higher load levels or longer loading time) can effectively decrease the binders’ healing potentials when the binders are at the relatively low damaged levels. The healing potential becomes low when the material is at severe damage state, thus will remain at that low levels even though the damage level increases.

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Topics: Dynamic shear rheometer (50%)

32 Citations

Open accessJournal ArticleDOI: 10.1016/J.CONBUILDMAT.2019.117824
Haopeng Wang1, Xueyan Liu1, Martin van de Ven1, Guoyang Lu2  +3 moreInstitutions (3)
Abstract: 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.

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Topics: Rubberized asphalt (62%), Crumb rubber (57%)

23 Citations

Open accessJournal ArticleDOI: 10.1177/0361198119899151
Yangming Gao1, Linglin Li1, Yuqing ZhangInstitutions (1)
Abstract: Fatigue resistance of bituminous binders plays a critical role in determining the fatigue performance of asphalt pavements. It is reported in the literature that, under a rotational shear fatigue l...

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Topics: Fracture mechanics (50%)

13 Citations

Open accessJournal ArticleDOI: 10.1016/J.MECHMAT.2020.103462
Hui Li1, Xue Luo2, Xue Luo1, Weizhuo Yan1  +1 moreInstitutions (3)
Abstract: The cohesive cracking within asphalt binders has a significant influence on fatigue cracking resistance of asphalt pavements. To more clearly understand the mechanism and accurately characterize the process of the cohesive cracking occurring within the asphalt binder, an energy-based mechanistic (EBM) approach is applied to determine crack length and the pseudo J-integral is adopted to calculate crack growth rate in this study. First, a critical strain level separating nonlinear viscoelasticity from damage is determined based on a statistical analysis approach, and the result indicates that 0.7% is a critical nonlinear strain level for unmodified asphalt binder. Then, the crack length of asphalt binders is derived based on a torque equilibrium equation and two energy balance equations, as well as crack length is measured and verified based on an image processing method. It is found that contact regions in cracked area of the asphalt binder are formed when performing a strain-controlled rotational shear load. The contact regions have two stages, which first increase to the peak and then decrease with the increase of loading time. Next, the crack growth rate is formulated based on the pseudo J-integral Paris’ law equation considering nonlinear viscoelasticity. A linear relationship between the crack growth rate and the function of material properties (such as shear modulus, phase angle) in double logarithmic scales is proven and experimentally verified. In addition, the Paris’ law parameters (n and A) associated with crack growth rate are determined. Results show that they are independent on strain levels and temperatures. For example, six values of n of the unmodified asphalt binder are approximately equal to 1.10 at 5%, 6%, 7% strain levels when test temperatures are 15°C and 20°C. They are inherent material properties for the asphalt binder.

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Topics: Viscoelasticity (53%), Shear modulus (51%), Asphalt (50%)

12 Citations

Open accessJournal ArticleDOI: 10.1016/J.IJFATIGUE.2020.105738
Yangming Gao1, Linglin Li1, Yuqing Zhang1Institutions (1)
Abstract: This study aims to model fatigue crack initiation in bituminous binders. An energy-based crack initiation criterion is developed for bitumen under a rotational shear fatigue load. Based on a damage mechanics analysis of fatigue cracking process, the crack initiation is defined and local energy redistribution around crack tips due to ‘factory-roof’ cracking is quantified. A quantitative energy criterion is proposed for the fatigue crack initiation in the bitumen using viscoelastic Griffith’s theory. The crack initiation criterion is validated through comparing the predicted and measured surface energy of the bitumen. The results show that bitumen fatigue cracking under the rotational shear fatigue load can be divided into two stages: the edge flow damage and the ‘factory-roof’ cracking. The crack initiation is dependent of the shear modulus and surface energy of bituminous binders, critical crack size, and loading amplitude. The energy-based crack initiation criterion along with the DSR fatigue tests can be potentially used to determine the material surface energy.

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Topics: Damage mechanics (56%), Shear modulus (50%)

11 Citations


29 results found

Open accessJournal Article
01 Jan 2001-NCHRP Report
Abstract: This report documents the results of a study on the applicability of Superpave specification (AASHTO MP1, "Standard Specification for Performance Graded Asphalt Binder") and protocols developed for asphalt cements to modified asphalt binders. A survey indicated that, although the majority of state agencies intend to increase future use of modified binders, very little is known about the binders' behavior. In addition, there are serious concerns regarding their storage stability, aging, and mixing and compaction temperatures. Using advanced rheological characterization of a selected set of binders and mixtures, it was found that the binder specification parameters in the current AASHTO MP1 are not adequate to rank the modified binders according to their contribution to mixture damage. The concepts of viscous flow and energy dissipation were explored in an effort to derive binder parameters that more effectively relate binder to mixture behavior. Suggested test protocols and specification parameters were developed to integrate the new concepts into a future specification. A direct measure of the glass transition behavior and the use of a design-cooling rate were identified as reliable estimators of the binders' role in thermal cracking. Also, a storage stability test and a particulate additive test were developed and proposed as standard tests. The concept of low shear viscosity was introduced for the determination of laboratory mixing and compaction temperatures to avoid excessive heating and to consider the shear-rate dependency of modified binders. Revisions to the binder grading system are recommended to include a three-level grading scheme. A field validation plan is proposed to test the validity of these concepts and to derive reliable specification criteria and limits.

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504 Citations

Journal ArticleDOI: 10.3141/1723-18
Abstract: Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in flexural fatigue testing because of the distinctly different application of energy during the loading history. The most widely accepted definition is a decrease in initial stiffness by 50 percent. Procedures examining energy input and dissipated energy have required different schemes for each mode in an attempt to describe similar states of damage in the mixture. A proposed method is presented for examining dissipated energy to select a consistent level of material behavior that is indicative of the damage accumulation in the mixture. This procedure shows the similarity between the constant stress and constant strain modes of testing and is shown to provide the potential for unifying the now phenomenological description of fatigue...

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231 Citations

Journal ArticleDOI: 10.3141/2207-13
Abstract: Current asphalt binder specifications lack the ability to characterize asphalt binder damage resistance to fatigue loading. Multiple accelerated testing procedures that attempt to efficiently and accurately characterize the contribution of asphalt binders to mixture fatigue are under investigation. One of these tests, which has received significant acceptance by experts and has been submitted as a draft AASHTO standard, is the linear amplitude sweep (LAS) test. This procedure uses viscoelastic continuum damage mechanics to predict binder fatigue life as a function of strain in the pavement. The LAS test uses cyclic loading with systematically increasing load amplitudes to accelerate damage and provides sufficient data for analysis in less than 30 min. Although results of the current LAS testing protocol are promising, the time and the complex numerical procedures required for the analysis have raised concern. In addition, insufficient damage accumulation was observed when the strain amplitudes proposed in...

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213 Citations

Open access
01 Jan 1993-

186 Citations

Journal ArticleDOI: 10.3141/1766-07
Abstract: The original SuperPave asphalt binder specification criterion for fatigue, G* sin δ, has received considerable criticism. Recently, a time sweep using the dynamic shear rheometer (DSR) has been proposed as an alternative test method for developing load-associated fatigue information for asphalt binders. This proposed test method is examined with respect to a phenomenon called edge fracture. Edge fracture is reported in the literature for steady state and oscillatory flow in DSR, but it has not been reported for asphalt binders. The modulus, when plotted versus number of cycles generated in a time sweep test, has the appearance typical of fatigue behavior; however, the actual response of the material depends markedly on the initial modulus of the material. The development of the modulus with repeated shearing is described with respect to flow of the asphalt binder at its circumference. The data are examined with respect to their validity as a measure of fatigue, and recommendations with respect to the use ...

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Topics: Dynamic shear rheometer (62%), Test method (50%)

172 Citations

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