Fatigue Properties Of Asphalt Mixtures Research Articles

Normalized fatigue properties of asphalt mixture at various temperatures

This study normalized the mixture's fatigue behavior at various temperatures, and the strength and fatigue tests of the mixture were conducted. The stress state of the asphalt mixture includes direct tensile, uniaxial compression, and indirect tensile. The Desai yield surface and fatigue path were proposed. And a normalized fatigue characteristics model of the mixture was established. The following conclusions were obtained. With the increases in the loading rate, the strength of the asphalt mixture increased. As the temperature increases, the strength of the mixture is reduced. At various temperatures and rates, the strength forms a closed curved surface. The Desai strength yield surface was established, which forms a closed curved surface. When the loading rate and temperature are below a certain critical line, the asphalt mixture will not undergo strength damage. At a fixed stress state, the fatigue damage path of the mixture was determined. The stress ratio was determined considering the influence of the loading rate. In this way, a normalized model can be described to express the asphalt mixture fatigue properties at various temperatures and stress levels. For the asphalt mixture in an indirect tensile state, the normalized fatigue equation parameter is 4.09. This model is more suitable for reflecting the viscous-elastic behavior of the mixtures than the fatigue equation determined by the notional stress ratio.

Investigation of the fatigue life relationship among different geometry combinations of the 3-point bending cylinder (3PBC) fatigue test for asphalt concrete

ABSTRACT Laboratory testing is widely used to characterise fatigue properties of asphalt mixtures for the design of asphalt pavements. The recently introduced Three-Point Bending Cylinder (3PBC) test has proven to be an advantageous laboratory testing alternative. However, the standard sample size for the 3PBC test may hamper its use for testing as-built thin lifts of asphalt pavement. In this study, the potential to alter the sample size for 3PBC test was investigated. Various numerical techniques were explored to relate the fatigue performance in terms of the number of cycles to failure (Nf) among varying specimen diameters. In addition to Nf of the tested 3PBC sample diameter Nf (Di), strain level; 3PBC test sample diameter Di; and dynamic modulus |E*|; were selected as input variables to correlate with the Nf for the reference geometry Nf(D.R.). Initially, multi-linear regression (MLR) analysis was applied to inspect if any cogent relation could be achieved among the Nf values for different 3PBC sample diameters. In addition, multigene genetic programming (MGGP) and artificial neural network (ANN) analyses were performed to check if a better fit could be achieved. Both these techniques, however, revealed similar statistical results to the MLR model, with the ANN model achieving higher statistics.

Study on the high and low temperature performance of nano alumina modified asphalt mixture

To improve the high and low temperature performance of asphalt mixture, nano alumina was used as additive in this study. Firstly, the high temperature characteristics of asphalt mixture with different content of nano alumina were studied by rutting test and dynamic creep test. Secondly, the fatigue properties of modified asphalt mixture at different temperature were tested by indirect tensile fatigue test. Finally, the low temperature bending test and indirect tensile test were used to evaluate the low temperature performance. The results show that nano alumina can improve the high temperature and fatigue properties of asphalt mixture to some extent, while the low temperature performance decreases slightly.

Research on strength and fatigue properties of asphalt mixture with different gradation curves

The gradation design has an essential influence on the mechanical properties of asphalt mixture. Strength and fatigue are two critical mechanical properties of asphalt pavement structure. The purpose of this paper is to reveal the strength and fatigue properties of asphalt mixture with four gradation curves within the range of AC-16, namely Types A, B, C, and D. Strength and fatigue tests were conducted under indirect tensile, direct tensile, and unconfined compressive loading modes. The strength of asphalt mixture with various gradation curves shows a power function relationship with the loading rate. The fatigue performance of asphalt mixture with different gradation curves was first analyzed based on the conventional S-N fatigue model. Then, the unified fatigue models under three different loading modes were established based on the fatigue stress strength ratio, which reduced the difference of S-N fatigue equation parameters. Furthermore, the unified fatigue equations achieved the unity of strength failure and primary fatigue failure. The analysis results indicate that the mixture with Type D gradation curve realizes the highest strength and most extended fatigue life. This research contributes to the gradation design of asphalt mixture. And the unified fatigue equation provides a reference for the durability design of pavement.

Investigation on Fatigue Performance of Diatomite/Basalt Fiber Composite Modified Asphalt Mixture.

The fatigue resistance of asphalt mixture is an important indicator to evaluate the durability of asphalt pavement. In order to improve the fatigue properties of asphalt mixture, diatomite and environmental basalt fiber were added. Four types of asphalt mixtures, ordinary asphalt mixture (AM), diatomite modified asphalt mixture (DAM), basalt fiber modified asphalt mixture (BFAM) and diatomite/basalt fiber composite modified asphalt mixture (DBFAM), were chosen, whose optimum asphalt–aggregate ratio, optimum content of diatomite and optimum content of basalt fiber could be determined by Marshall test and response surface methodology (RSM). The multi-functional pneumatic servo Cooper test machine was carried out by a four-point bending fatigue test. Through the comparative analysis of flexural-tensile stiffness modulus (S), initial stiffness modulus(S0), residual stiffness modulus ratio, lag angle (ϕ) and cumulative dissipation energy (ECD), the fatigue resistance of asphalt mixture can be effectively improved by adding diatomite and basalt fiber. Grey correlation analysis was also used to analyze the degree of correlation between the fatigue life and the influencing factors such as VV, VMA, VFA, OAC, S, and ECD. The analysis results indicate that ECD has the greatest impact on the fatigue life of the asphalt mixture.

Development of fatigue damage model of asphalt mixtures based on small-scale accelerated pavement test

As the primary surface type for high-grade Chinese highways, the long-term performance of asphalt pavement can affect significantly transportation efficiency. It has been confirmed that fatigue cracking is one of the major failure modes for asphalt pavement, which can cause a great reduction of asphalt pavement durability. Currently, the fatigue properties of asphalt mixtures are evaluated mainly based on traditional laboratory fatigue tests, such as bending fatigue tests and indirect tensile fatigue tests. However, none of these fatigue test methods can realistically evaluate the fatigue performance of asphalt pavement under the repeated wheel load. To resolve this issue, the model mobile load simulator (MMLS3), which is a small-scale accelerated pavement test device, was utilized to evaluate the fatigue life of six kinds of asphalt mixtures. The fatigue damage variable was defined as stiffness reduction. Based on the small-scale accelerated pavement test, a stiffness reduction model for asphalt mixtures was determined. A stiffness reduction law for asphalt mixtures during the fatigue process was proposed. The stiffness evolution process could be divided into three phases, which are the adaptation phase, the quasi-stationary phase, and the failure phase. A maximum value of the rate of stiffness reduction from the quasi-stationary phase into the failure phase was proposed as the failure threshold. Besides the fatigue life obtained from the failure criteria had a good agreement with the test results. The results from this research can be used as a theoretical reference for evaluating the fatigue life of asphalt mixtures and improving the durability of asphalt pavement.

Microstructural analysis of the effects of compaction on fatigue properties of asphalt mixtures

ABSTRACT In the current approaches to structural analysis for asphalt pavements, the entire pavement material is usually treated to identical material, which disregards the distinct heterogeneity of asphalt mixture. Asphalt mixture is actually a multi-phase heterogeneous material that is composed of air voids, aggregate and asphalt binder. In this study, asphalt specimens were drilled from a test track and the indirect tensile fatigue test was conducted to study the fatigue properties. Digital Image Processing (DIP) was used to investigate the microstructural changes of the asphalt specimens based on X-ray Computed Tomography (X-ray CT) images. The aggregate orientation and number of aggregate contact points were determined. The distribution of the air-voids content and shape index of air voids before and after the fatigue tests were comprehensively discussed. According to the results, the microscopic analysis can effectively predict the evolutions of the internal structures of asphalt mixtures during fatigue damage. The heterogeneity due to different degrees of compaction significantly affects the fatigue properties of the asphalt mixtures. This study not only provides support for the further research on the relationship between the microstructural characteristics and mechanical damages of asphalt mixture but also provides implications for conducting the structural mechanical analysis of asphalt pavement.

Low Temperature Crack Resistance and Fatigue Properties of Asphalt Mixture with Pre-buried Heat Conduction Tube

In order to study the effect of geothermal heat transfer tube on the asphalt pavement performance, a heat transfer tube with a diameter of 8 mm was used, which was placed in an AC-16 hot mix asphalt mixture and crushed into a ruthenium plate test piece, using MTS-810 hydraulic servo test. The system evaluates the low temperature crack resistance and fatigue performance, and compares the performance with the asphalt mixture test piece without the heat conduction tube. The results show that after the heat transfer tube is buried, the failure strain of the asphalt mixture is reduced by 40.9%, and the repeated load of the three-point bending fatigue test is reduced by 53.9%. The low temperature crack resistance and fatigue performance are both larger. The degree is reduced.

An improved method of characterizing fracture resistance of asphalt mixtures using modified Paris’ law: Part II—Establishment of index for fracture resistance

The modified Paris’ law has been employed to characterize the fracture resistance of asphalt mixtures. However, the correlation between the coefficients of the modified Paris’ law has lacked theoretical justification. This study formulated the coefficients of the original Paris’ law in terms of the stress intensity factor for a long crack whose failure zones were much smaller than the crack size. These formulations were then utilized to derive the formulas of the coefficients of the modified Paris’ law in terms of the pseudo J-integral for the multitude of short cracks in a viscoelastic material such as an asphalt mixture. A theoretical model was developed between the two coefficients of the modified Paris’ law. This theoretical relation provided solid theoretical support to the empirical relation reported in the literature that was identified through regression analysis based on the results of hundreds of tests. The experimental data in this study further justified the theoretical relation.An index for fracture resistance of asphalt mixtures was established through rigorous theoretical derivation and experimental justification. The established index for fracture resistance serves as an excellent indicator of fatigue properties of asphalt mixtures. This index can be utilized in mix designs for comparing different mixtures, in field core evaluations for quantifying the fracture resistance of in-service asphalt pavements, in multiscale analyses of asphalt mixtures for linking mechanical properties at a macro level to interface adhesion at a micro level, and in other potential applications.

Fatigue Properties of Rubber Modified SMA Asphalt Mixture

To evaluate fatigue propertiesof rubber modified SMA asphaltmixture, based on optimizing the preparation process of rubber asphalt, the splitting fatigue testsof three kinds of asphalt mixture is carried out including ordinary asphalt, modified asphalt with rubber powder and SBS modified asphalt. And the freezing and thawing conditions were considered in the tests. The results show that rubber powder can improve the fatigue properties of SMA asphalt mixture, but the modified effect of rubber powder is not as good as SBS modifier, the fatigue properties of asphalt mixture are deteriorated by freeze-thaw conditions, the deterioration degree of rubber modified asphalt mixture is less than SBS modified asphalt mixture, but rubber modified asphalt mixture has better freeze-thaw durability.

Investigation of the fatigue properties of asphalt mixture designed using vertical vibration method

In this work, the flexural tensile fatigue behaviours of AC-20 asphalt mixtures were studied using beams, which were designed by the vertical vibration method (VVTM) and Marshall method. Then an analysis of variance (ANOVA) was used to examine the differences in fatigue lives, and the Weibull distribution was used to analyze the fatigue lives and establish the fatigue equations of the mixtures. Subsequently, the fatigue lives were compared and analyzed under the same stress level and repeated load force. The results showed that the test accuracy of specimens produced using the vertical vibration compaction method (VVCM) exceeds 92%. Compared to the Marshall design, the asphalt mixture fabricated with the VVTM design improved crack resistance and rutting resistance by at least 40% and 30%, respectively. The ratio of the slopes (the values of the regression coefficient b) of fatigue equations of asphalt mixtures designed by the VVTM to that of Marshall method ranges from 0.883 to 0.965, and the ratio of the intercepts (the values of the regression coefficient a) ranges from 1.278 to 1.284. The results also showed that compared to the Marshall design, asphalt mixtures fabricated with VVTM design exhibited improved fatigue lives by at least 61% (at a stress level of 0.45) and 356% (with a repeated load force of 0.378 kN).

Evaluation of the healing potential of asphalt mixtures based on a modified semi-circular bending test

Since the semi-circular bending (SCB) test has been widely used to evaluate the fatigue properties of asphalt mixtures, it has been modified in this paper by adding a certain length of rest period in each cyclic loading sequence to evaluate the healing potential of different asphalt mixtures. The digital image correlation (DIC) method was utilized to characterize the tensile strain at the bottom of specimens during the healing-based cyclic SCB test. The influence of notch depth of the specimen (0 mm, 15 mm and 25 mm) and the length of the rest period (0 s, 0.4 s, 0.8 s and 1.2 s) on the fatigue and healing behaviour were carefully evaluated. The fatigue life (Nf), total dissipated energy (Gsum), secant modulus (Ms), average deformation growth rate (Dr) and average tensile strain (εr) during the cyclic load with or without rest period were analysed. Test results show that the inserted notch reduces the fatigue life and deformation of specimens, while can hardly change the load-sensitivity and secant modulus of the specimen. Most performance recovery happens within the rest period of 0.8 s. So it is better to conduct the healing-based cyclic test with non-notched SCB specimen and 0.8 s rest period. Additionally, it is found that asphalt mixtures with modified binder present both better fatigue and healing properties than asphalt mixtures with neat asphalt, while the stone matrix asphalt mixture presents similar fatigue property but much better healing potential than one dense graded mixture with the same binder.

Characteristics of Moduli Decay for the Asphalt Mixture under Different Loading Conditions

In order to explore the moduli decay patterns of asphalt mixtures under different loading conditions, the nonlinear fatigue damage model was implemented in order to simulate the moduli decay patterns. Then, the direct tensile, indirect tensile, and uniaxial compression fatigue tests were employed under four kinds of stress levels with four parallel tests. The specimens of AC-13C Styrene-butadiene-styrene (SBS) modified mixtures were manufactured. Based on the test results, the decay patterns of the moduli during fatigue tests under different stress states were revealed, and the parameters of the damage model under different test conditions were obtained. By changing the values of the model parameters under a certain loading condition, fatigue curves were obtained. Then, the fatigue properties of asphalt mixtures under different stress states could be compared and analyzed directly. The result indicated that the evolution curves of fatigue damage for the direct tensile test, the indirect tensile test, and the uniaxial compression test all experienced three stages, which indicates that the fatigue damage characteristic of asphalt mixtures is non-linear. The decay patterns of the direct tensile moduli and the tensile moduli measured by the indirect tensile test are similar. The decay patterns of the uniaxial compression and the compression moduli measured by indirect tensile test are similar. The decay patterns of tensile and compressive moduli are obviously different. At the same cycle ratio state, the position of the decay curve for the compression moduli is higher than that of the tensile moduli. It indicates that the tensile failure is the main reason of the fatigue damage for asphalt mixture. The new analysis method of fatigue damage was proposed, which provides a possibility to compare the fatigue results that were obtained from different loading conditions and different specimen sizes.

Viscoelastic Fatigue Damage Properties of Asphalt Mixture with Different Aging Degrees

In order to reveal the effects of aging on fatigue damage evolution pattern of asphalt mixture, and to reveal the fatigue damage patterns of asphalt pavement during its service life more accurately, the viscoelastic fatigue damage model for the aged asphalt mixtures was proposed based on the Burgers viscoelastic model. The dissipation energy was taken as the damage variable, and the direct tension fatigue tests for asphalt mixture in five different aging degrees were conducted. The viscoelastic parameters of the aged asphalt mixtures were obtained.The calculationmethod of the cumulative fatigue damage was proposed, which considers the aging effects. Moreover, the critical fatigue damage degree and fatigue life calculation equations were derived by employing the fatigue damage model, which were calculated and compared. The calculation errors range from 3% to 18%, which was within an acceptable error range of 30%. The research results show that the aging has a prominent impact on fatigue properties of asphalt mixtures, which could be illustrated by the change of the parameters of the viscoelastic fatigue damage model for the aged asphalt mixtures. The prediction precision of fatigue life is acceptable for using the proposed viscoelastic fatigue damage model.

State of the art review on mix design and mechanical properties of warm mix asphalt

Warm mix asphalt (WMA) is a high-speed emerging technology of producing asphalt mixture at lower temperature with equivalent performance of hot mix asphalt (HMA). It offers benefits such as energy savings, compaction aid for stiffer mixes, reduces emission, and reduces asphalt binder aging during production. This paper is an overview of mix design concept, mix design properties and mechanical properties (moisture-induced damage, rutting resistance and fatigue life) of WMA and same was compared with the properties of control HMA mixtures. Review indicates that mix design concept of WMA is similar to that of control HMA and possesses better mix design properties. Regarding mechanical properties, WMA mixtures were found more prone to moisture-induced damage, rutting and fatigue than control HMA mixtures due to lower production temperature but similar or better resistance were noticed with the use of modified and higher grade binders, addition of anti-stripping agents (ASA) and hydrated lime (HL), use of open graded mix and inclusion of recycled asphalt pavement (RAP). Further, the effect of nominal maximum aggregate size (NMAS) and design gyration (Ndesign) on mix design, NMAS and aggregate type and its water absorption on moisture-induced damage, NMAS, wheel load, test temperature, air voids, and binder grade on rutting, and NMAS, air voids, and stress or strain levels on fatigue properties of asphalt mixtures were analysed. Results indicated that NMAS had the significant effect on moisture-induced damage, rutting resistance and fatigue life of WMA mixtures. WMA mixtures made with aggregates of higher water absorption values were more prone to moisture-induced damage and even fail to meet minimum (tensile strength ratio) TSR requirements. Results also indicated that WMA mixtures made with modified and higher grade binder grade were high rut resistant. WMA mixtures tested at high stress or strain levels shows higher fatigue damage compared to WMA mixtures tested at lower stress or strain levels.

Normalization of fatigue characteristics for asphalt mixtures under different stress states

The fatigue test methods under different test conditions have strong impact on the test results, which obstructs a precise evaluation of fatigue characteristic for asphalt mixtures. Different test conditions means different stress states. Fatigue characteristic of a material is an objective attribute, and it should not vary with test methods and conditions. In order to accurately and objectively evaluate the fatigue properties of asphalt mixtures, a normalization model of fatigue characteristics for asphalt mixtures under different stress states was established based on the yield criterion in 3 dimensional stress states and the patterns of variation between the strength and the loading rate. The compressive, tensile and indirect tensile strength and fatigue tests were carried out respectively in different loading rates. The yield surface of strength for asphalt mixture was put forward based on the strength tests results and the yield criterion. Then, the normalization model of fatigue characteristics for asphalt mixtures under different stress states was established based on the yield criterion in 3 dimensional stress states. The results show that the differences of the fatigue tests results of asphalt mixtures under different test condition are large. It is difficult to evaluate the fatigue performance in different stress states of asphalt mixtures by using the conventional S-N fatigue equation. However, these differences can be reduced or even eliminated by using the normalization model, which considered the influence of the stress state and the strength corresponding to the fatigue loading frequency and stress level. The unified expression of fatigue characteristics under different test conditions for asphalt mixtures was realized. The fatigue behavior of asphalt mixture under different stress conditions can be objectively evaluated by using the normalized model.

Sweep test protocol for fatigue evaluation of asphalt mixtures

This paper presents a laboratory test protocol for evaluating fatigue properties of asphalt mixtures through sweep tests at multiple amplitudes and frequencies. Conventional fatigue evaluation of asphalt mixtures typically relies on a limited number of single fatigue tests, and each test is performed at constant test temperature. Moreover, in order to reduce laboratory effort to a minimum, testing is quite often limited to a single test temperature, which means that the dependency of asphalt fatigue on temperature is ignored. Such test procedure is in best accordance with the European Standards. However, so-derived results may provoke misleading conclusions, as exemplarily shown in this study. In order to solve this shortcoming, a sweep test protocol for fatigue evaluation of asphalt mixtures at different temperatures is proposed. Frequency–amplitude sweeps are used for complex modulus evaluation and fatigue evaluation, but without significantly extending the laboratory effort compared to conventional fatigue testing. This sweep test protocol is applicable for fatigue evaluation of any asphalt mixture.

Evaluating the effect of laboratory aging on fatigue behavior of asphalt mixtures containing hydrated lime

Hydrated lime (HL) is typically used as an additive to enhance the anti-stripping resistance of asphalt mixtures. As a result, this particular feature of hydrated lime has received the greatest share of academic attention, and its other long-term effects such as the resulting resistance against fatigue cracks have been relatively neglected. In the present study, effects of different quantities of HL (by weight of aggregate) on the fatigue properties of asphalt mixtures was investigated by four-point bending fatigue testing of unaged and aged specimens. Laboratory long-term aging procedure was carried out in accordance with AASHTO PP2 (120 h of treatment at 85 °C). Fatigue tests were conducted in strain-controlled mode with a sinusoidal load applied with frequency of 10 Hz (without rest) at 20 °C. Fatigue life was analyzed with the stiffness reduction and dissipated energy methods. Test results showed that fatigue life of asphalt mixtures is sensitive to their HL content. Addition of 1%, 1.5% and 2% of hydrated lime to mix design was found to improve the fatigue life of unaged asphalt specimens. For the aged specimens, adding of 1% and 1.5% HL increased the fatigue life by, respectively, 25% and 50%, but use of 2% HL led to 40% reduction in this property. For all asphalt mixtures, the best improvement in the fatigue life was achieved by mixes containing 1.5 of hydrated lime.

A study on fatigue damage of asphalt mixture under different compaction using 3D-microstructural characteristics

The aim of this paper is investigating the microstructural characteristics of asphalt mixture under different compaction powers. In order to achieve this aim, a test track was built to provide asphalt mixture specimens and X-ray computed tomography (XCT) device was used to scan the internal structure. The aggregate particles and air-voids were extracted using Digital Image Processing (DIP), so the relationship between compaction and air-voids was determined at first, and then, the effect of aggregate particles on the morphology of air-voids can be evaluated, finally, fatigue properties of asphalt mixture with different air-void ratio were measured by indirect tensile fatigue test as well. The research results release the distribution of microstructures in asphalt pavement. 3D fractal dimension is an effective indicator to quantize the complexity of aggregate particles and air-voids; suffering the same compaction power, aggregates cause different constitutions of air-voids in asphalt mixture; investigation in this paper can present the essential relationship between microstructures and fatigue properties.

Fatigue Evaluation of Recycled Asphalt Mixture Based on Energy-Controlled Mode

The fatigue properties of asphalt mixtures are important inputs for mechanistic-empirical pavement design. To understand the fatigue properties of asphalt mixtures better and to predict the fatigue life of asphalt mixtures more precisely, the energy-controlled test mode was introduced. Based on the implementation theory, the laboratory practice for the energy-controlled mode was realized using a four-point-bending fatigue test with multiple-step loading. In this mode, the fatigue performance of typical AC-20 asphalt specimens with various reclaimed asphalt pavement (RAP) contents was tested and evaluated. Results show that the variation regulation of the dissipated energy and accumulative energy is compatible with the loading control principle, which proves the feasibility of the method. In addition, the fatigue life of the asphalt mixture in the energy-controlled mode was between that for the stress-controlled and strain-controlled modes. The specimen with a higher RAP content has a longer fatigue life and better fatigue performance.