Fatigue Life Of Pavement Research Articles

Fatigue Life Assessment of Modified Asphalt Concrete

Fatigue life is affected by the growth and accumulation of cracks, under the action of repeated vehicular loading, aging and effect of the environment. The main objective of the study is to provide a comparative evaluation of pavement fatigue life between modified and conventional asphalt concrete under the influence of changing the percentage of asphalt content by (0.5% ±) of the optimum, changing the testing temperature and under long-term aging and moisture damage impacts. Asphalt cement with a penetration grade (40-50) and aggregate with nominal maximum size of 12.5 mm, filler and two types of additives, fly ash and silica fumes have been implemented. Slab samples were prepared using the roller compactor device, Beam specimens were obtained by cutting each slab to five beams of 400 mm x 60 mm x 50 mm size. Beams were tested using Nottingham four point bending beam device under the influence of three levels of microstrain (750, 400, 250), and different testing temperatures (5, 20, 30) ° C. Beams were also exposed to long-term aging and moisture damage impacts. At 4.4% asphalt content, the Fatigue life increased with the use of silica fumes and fly ash by (50% and 111%) and stiffness increased by (124% and 155%), respectively, as compared with conventional mix. When testing temperature increased to 30 °C, the fatigue life increased by (48%) and (78%), and the stiffness increased by (66%) and (78%), for asphalt concrete modified with silica fumes and fly ash, respectively.

Prediction of the Remaining Fatigue Life of Flexible Pavements Using Laboratory and Field Correlations

The main objective of this study was to develop comprehensive criteria to evaluate the remaining service life of existing roads as regards their field fatigue cracking characteristics using fractur ...

Use of Finite Element Analysis and Fatigue Failure Model to Estimate Costs of Pavement Damage Caused by Heavy Vehicles

The transportation of heavy loads potentially causes more damage to pavements than regular vehicle traffic. This study investigated the impact of heavy vehicles on asphalt pavement to optimize axle configurations, select routes, and estimate permit costs. Finite element analysis, validated by field measurement, was used to evaluate pavement responses under various heavy load scenarios. From the results, the remaining pavement service life was predicted with the use of pavement distress models. The permit cost for a single pass of a heavy vehicle was estimated from the reduction of pavement fatigue life and associated pavement maintenance cost. Sensitivity analyses were conducted to determine factors affecting pavement fatigue damage and permit costs. Field measurement indicated that a significant longitudinal pavement defection occurred under the heavy vehicle. The results from finite element analysis showed a significant overlapping effect between multiple axles over the depth. Pavement defection was caused mainly by the deformation within subgrade soil. Generally, pavements with high thickness and stiffness would incur less damage and lower permit cost. A pavement structure with deep bedrock would incur more damage and higher cost. Because of the temperature dependency of asphalt mixtures, the damage cost in winter was much less than that in summer, even considering the potential weak subgrade during the spring thaw. It was also found that newly constructed pavements would incur higher permit cost than relatively older pavements. To reduce potential pavement damage and the associated cost effectively, the number of dollies and axle distance should be increased to spread the load to a larger area.

Development of a test method for evaluation and quantification of healing in asphalt mixture

It is now well recognised that microdamage healing may extend the fatigue life of asphalt pavement. In this study, a test was developed to quantify the healing of asphalt mixture, both dense-graded and open-graded, using the SuperpaveTM Indirect Tensile Test testing system. The healing test consists of repeated load damage tests (resilient modulus tests) during the damage phase followed by a healing phase during which resilient modulus tests are performed on a limited basis to measure modulus recovery (healing). Appropriate load level, as percentage of tensile strength, for the damage phase was found to depend on mixture brittleness index. A decrease in resilient modulus with an increasing number of load cycles is indicative of accumulation of microdamage during the damage phase. Recovery of resilient modulus during the healing phase is indicative of damage recovery or healing. Rate of healing was found to not be constant but rather changed with time at a decreasing rate for any given mixture. Therefore, a healing rate parameter was defined to allow for comparison between mixtures. Results showed that, in general, expected trends were observed. Mixtures tested at higher temperatures healed at a faster rate than those at lower temperatures and mixtures subjected to less oxidative ageing healed at faster rates than those subjected to more oxidative ageing.

Analysis on the Fatigue Life of Asphalt Pavement under Traffic Flow Loads

To study the fatigue life of asphalt pavement under traffic loads, a 3-D finite element analysis (FEA) Visio-elastic road model was established on the layered theory with ANSYS software. The fatigue damage was calculated with the maximum horizontal tensile strain of asphalt layer bottom based on the fatigue fracture mechanics, when single axis went across. Then the fatigue life was obtained after the fatigue damage occurred in some degree by the Miners linear cumulative damage rule. The results show that it taken 3.4 years when the damage area reached 10% of wheel path area, and 4.5years when reached 45%; while the calculated result was 5.5 years by axial-load conversion method. The analysis shows that the fatigue life of asphalt pavement calculated by fatigue fracture mechanics rule has more significance in practice.

Use of Cyclic Direct Tension Tests and Digital Imaging Analysis to Evaluate Moisture Susceptibility of Warm-Mix Asphalt Concrete

This paper presents a simplified viscoelastic continuum damage material model for the evaluation of moisture susceptibility of asphalt concrete. The model is based on cyclic direct tension testing and layered viscoelastic analysis. The visual stripping inspection afforded by digital imaging analysis is also proposed as an intuitive and straightforward method for moisture susceptibility evaluation. These methods were applied to a Superpave® 19-mm hot-mix asphalt mixture and corresponding warm-mix asphalt mixtures modified by a polyethylene wax-type additive with and without an antistripping agent. The fatigue life predicted by the simplified viscoelastic continuum damage and layered viscoelastic analysis models had a strong correlation with the percentage of stripping determined from specimen surfaces that were fractured during cyclic direct tension testing of the hot-mix and warm-mix asphalt mixtures with various asphalt contents. In addition, a polyethylene wax-type additive combined with an antistripping agent was found to provide a longer fatigue life and less stripping than a pure polyethylene wax-type additive. The findings from this paper should provide guidance to agencies and material engineers in developing asphalt binder modifiers that lengthen the fatigue life of pavements and reduce moisture susceptibility.

Bending Fatigue Test and Interlayer Pavement Models for Beams of Asphalt Mixture

AbstractThe fatigue life of composite beam samples were measured by flexural fatigue test under different bonding oil contents, temperatures, and loads. The measurement was conducted to study the influence of interlayer contact on the fatigue life of asphalt pavement and to fine tune the pavement fatigue model. The results show the following: (1) The integrity and fatigue life of asphalt pavement decreases because of interlayer contact. (2) Fatigue life first increases then decreases with increasing bonding oil content. An optimum bonding oil content increases fatigue resistance to a higher level. (3) Fatigue failure more readily occurs at normal temperatures than at low temperatures. In addition, fatigue life significantly decreases when pavement is exposed to overweight vehicles. The relationship of fatigue life with bonding oil content, temperature, and load was identified and total fatigue equations were established.

Fracture Mechanics-Based Fatigue Behavior of Jointed Concrete Pavement

Concrete experiences thermal and hygral deformations at early ages due to it intrinsic properties and the environmental effects. Micro-cracking results on the top surface of pavement if deformations are restrained. These micro-cracks propagate transversely and downwards over time under traffic loadings, especially during early ages. This situation can be severe if upward curling conditions exist in pavements. Estimation of the remaining fatigue life of pavements with such cracks is of significance for scheduling prompt maintenance. Conventional fatigue models established based on uncracked beam tests are no longer applicable for such cases. It is necessary to develop a fracture mechanics-based fatigue model for pavement with cracks. This study provides a new fatigue life prediction methodology for pavement with cracks. Both model prediction and experimental test results suggest that fatigue life is significantly reduced if concrete develops a partial depth crack at early ages. These results can explain the observed premature transverse cracking failure in jointed concrete pavement. Crack growth behavior can be characterized as three stages, in which the steady stage is the most important one when prompt maintenance is needed to avoid structural failure.

Calibration and Validation of the Shell Fatigue Model Using AC10 And AC14 Dense Graded Hot Mix Asphalt Fatigue Laboratory Data

Mechanistic Empirical pavement design has been adopted by New Zealand and Australia for more than a decade ago and recently by many other countries around the world. The detailed procedures for the mechanistic empirical analysis are detailed in the Austroads and New Zealand supplement publications. Because the mechanistic empirical analysis relies on empirical performance models that are very dependent on material types and environmental conditions, the success of the design procedure depends on the use of well designed, calibrated and validated performance models. In the Austroads Mechanistic Empirical pavement design, fatigue and rutting are the two performance indicators used in the design. Austroads guidelines adopt Shell fatigue transfer function to predict the fatigue life of asphalt pavements. However, it was observed by many practitioners and confirmed by this study that Shell Transfer functions significantly overestimate the design thickness or in other words underestimate the fatigue life of the asphalt mixes. In this paper, calibration and validation of the Shell fatigue transfer function which is currently adopted in the Austroads design guidelines are demonstrated. The calibration factor based on the four points bending fatigue test results was found to be in the order of 5.7. Using the calibrated Shell model produced a 26% to 27% thinner asphalt thickness compared to the current Austroads design guidelines.

Effect of HMA ageing and potential healing on top-down cracking using HVS

It is well known that age-hardening is a major deteriorating factor for cracking in the asphalt pavement, while healing may play a beneficial role in enhancing pavement fatigue life, though healing potential of hot mix asphalt (HMA) mixture may decrease with ageing. However, there is limited direct evidence and understanding of the combined effects of these two factors on cracking performance, particularly in full-scale pavements. In this article, the effects of ageing and healing on top-down cracking performance were evaluated on the basis of three full-scale tests conducted in the Florida Department of Transportation's accelerated pavement testing (APT) facility using the heavy vehicle simulator (HVS). The test results showed that ageing and potential healing appeared to have played key roles in the cracking performance of the asphalt pavement in the APT facility. When the pavement was subjected to slight-to-moderate ageing, it may be able to maintain a relatively high level of healing which helped to effectively recover damage due to HVS loading. The extensively aged pavement might have completely lost the ability to heal, which made it more susceptible to cracking. In addition, the analysis of cracking using the enhanced HMA fracture model (HMA-FM-E) showed that the predictions of the model agreed well with the observations from the tests, which further demonstrated that the loss of healing potential with ageing must be considered to better understand cracking performance of asphalt pavements.

Development of a Damage-Based Phenomenological Fatigue Model for Asphalt Pavements

Bottom-up fatigue cracking is one of the major distresses for asphalt pavements. Accurate prediction of fatigue cracking for asphalt pavement is of paramount importance for a cost-effective pavement design. A fatigue model based on mechanistic-empirical pavement design is modified from an Asphalt Institute model. However, there are some controversies about the effectiveness of the mechanistic-empirical pavement design fatigue model. The major concern exists on the use of dynamic modulus as a key parameter and there is no damage property of asphaltic mix to predict fatigue, which is induced by damage to the material. This study developed a damage-based phenomenological fatigue model. The pavements at the Federal Highway Administration’s Accelerated Loading Facility (ALF) were used to test the effectiveness of existing models, including the mechanistic-empirical pavement design fatigue model, and validity of the damage-based fatigue model. The data used in this study included dynamic modulus, critical strain-energy density of hot-mix asphalt (HMA), tensile strain at the bottom of HMA layer, and the fatigue life of ALF pavements. It was found that the damage-based model significantly improved the accuracy of the prediction, when compared with the mechanistic-empirical pavement design fatigue model and other conventional models.

Comparative analysis of strains and durability of asphalt pavement of perpetual and standard type

This paper analyses the key strains and fatigue performance of the following types of road pavements using fatigue cracking and subgrade rutting as the evaluation criteria: conventional asphalt pavement and pavement structure with fatigue-resistant layer (as in perpetual pavement concept). Calculations were performed for two wheel speeds: 60 km/h and 5 km/h. The study included a comparison of results obtained for pavements differing in terms of material specifications and structure: reference model built of only elastic layers and two models built of viscoelastic asphalt layers and layers of aggregate cement-treated base (CTB) on soil subgrade. The determinations included strains, deformation and displacements (for which VEROAD software program was used) also the above-mentioned failure criteria determined using the Asphalt Institute equations. For predicting the fatigue life of pavement the lower asphalt layer was assumed to have the modulus value equal to the initial modulus calculated with Van der Poel equation and dynamic moduli calculated as sensitive or insensitive to the wheel speed respectively. The effect of the respective factors on the life of pavement in million standard axles (msa) was assessed, demonstrating that the calculations assuming elastic behaviour of all the pavement layers lead to overestimating the pavement life. Finally, it was found that the wheel speed had a significant effect on the strain and on the fatigue life of pavement.

Modeling Mechanical Response of a Perpetual Pavement Test Road

AbstractIn order to model perpetual pavement response, the traffic loads, pavement temperature, and mechanics responses collected from the Shandong perpetual pavement test road were used to develop axle load spectrums, temperature probability functions, and response regression models with load and temperature variables. The random sample methods of a probability distribution function were developed and the numerical simulation of parameter inputs and mechanical responses under a whole year of traffic volume and temperature cycles was realized. The results showed that the simulated mechanical response conformed to the actual response and both followed an approximate normal distribution. The response of different pavement structures was also compared. The research proves that the Monte Carlo method can help to understand the pavement mechanical response under the influence of both load and temperature. Finally, based on the simulated tensile strain distributions, the pavement fatigue life of all sections wa...

Evaluation of healing effect by rest periods on asphalt concrete slab using MMLS3 and NDE techniques

Fatigue life of asphalt concrete pavement is one of the most important factors in pavement management systems, which can be increased by healing effect. The healing effect by rest periods was evaluated by the third scale Model Mobile Loading Simulator (MMLS3) and Nondestructive Evaluation (NDE) techniques. Impact method of stress wave was optimized to accurately analyze the phase velocity and obtain effective sampling depth. In general, the phase velocities decrease as the pavement structure is degraded by the increase of wheel applications or load levels along both of the stress wave and ultra sonic measurement, while the recovery of phase velocities during rest periods is successfully evaluated by both techniques. Finally, based on the observation of phase velocities of waves, it was possible to confirm the healing effect of Asphalt Concrete (AC) by rest periods.

Multiple axle loadings

ABSTRACT The effect of multiple axle loads on the fatigue life of asphalt pavements is a key issue dealing with the effect of heavy trucks on pavement distresses. Equivalent Single Axle loads are currently calculated with simplified hypotheses. This is an important stake for the ecological transportation: increasing the load per truck results in decreasing the emission of toxic gases per ton of transported goods. To study the effect of multiple axles, real displacement signals in the pavement are needed. The LCPC's accelerated testing facility (Nantes, France) enables the measurement of real loading signals in an experimental pavement. Parameters describing the pavement strain curves were computed for this database. A factorial analysis gives four independent parameters that define an experimental plan of a campaign of fatigue tests whose aim is to identify how the fatigue life is affected by the shape parameters.

Calculation Stress Intensity Factor for Asphalt Pavement Basing on Weight Function Theory

Under the continuing action of temperature stress and load vehicle, the crack in cement stabilized aggregate base can easily reflect up into the asphalt surface layer, affecting driving condition and then affecting the fatigue life of pavement. On the basis of fracture mechanics, taking center crack loaded with uniform tensile stress as study state, methods were derived to calculate the stress intensity factor (abbreviated in the following “SIF”) of the crack at the bottom of asphalt layer using weight function theory and method of Petroski and Achenbach. Through the comparison of different SIFs under different conditions, factors affecting the SIFs such as crack length, load conditions, modulus ratio between base and surface layer and different jointed conditions were studied. To facilitate comparison, taking completely smooth and completely continuous as study boundary conditions. According to calculation results, factors mentioned above all influence the SIF values of the crack at the bottom of asphalt layer greatly, among which jointed condition between base and surface layer has the most important influence. The SIF values of the completely smooth interface is several times that of the completely continuous interface. We can take measures to improve the jointed condition between the asphalt surface layer and the cement stabilized aggregate base thus can reduce reflection crack effectively.

Research on Adaptability of Semi-rigid Material as Base Course for Long-life Asphalt Pavement

AbstractIn the light of semi-rigid material as base course for perpetual asphalt pavement, the bearing capacity and fatigue life of asphalt pavement with semi-rigid base cause and different asphalt...

Evaluation of predicted pavement fatigue life based on surface profiles and asphalt mixture types

The objective of this study is to evaluate pavement fatigue of both the 12.5 mm+PG58-22 and 12.5 mm+PG64-22 asphalt mixtures by evaluation of the pavement damage index, which is calculated based on the simulated dynamic load and the fracture parameter. The pavement damage index is the change in the pavement fatigue life between a target profile and an as-built profile. To achieve the objective, the dynamic load was simulated based on the pavement surface profile, vehicle speed, and vehicle suspension. The dynamic load increases when the surface profile is rougher, while the incensement of the dynamic load on rougher pavements is accentuated when the speed is higher. For the two asphalt mixtures, the coefficient of variance of the simulated dynamic load and the fracture parameter, which is calculated from the slope of the linear portion of the creep compliance, are used to calculate the pavement damage index. The pavement damage index increases as both the variance of the dynamic load and the confidence level increase. At lower temperatures, the value of n increases. This result indicates that, as the temperature decreases, a larger reduction in the fatigue life of the pavement is expected for the same pavement surface profiles. The 12.5 mm+PG64-22 asphalt mixture has a larger reduction in the pavement fatigue life than the 12.5 mm+PG58-22 asphalt mixture.

A Critical Discussion on Mechanistic-Empirical Fatigue Evaluation of Asphalt Pavement

Mechanistic-empirical fatigue equation is used for evaluation of fatigue life or fatigue performance of asphalt pavements. To evaluate fatigue performance, an appropriate field fatigue equation is necessary. It is experienced that the fatigue performance of an in-service pavement is significantly uncertain while using such equation. This paper attempts to identify some of the possible reasons of inadequacy involved with field fatigue equation. Certain issues have been addressed which may improve the fatigue prediction level.

Use of Small Samples to Predict Fatigue Lives of Field Cores

Fatigue cracking is one of the major distresses in asphalt pavements. Accurate prediction of fatigue life of asphalt pavements can be extremely important both during the design stage and for prediction of remaining service life of in-service pavements. Traditional fatigue life predictions based on bending beam tests can be costly and time-consuming. The uniaxial push–pull (tension–compression) tests run on cylindrical samples have been a novel alternative. However, the traditional sample size for the push–pull tests may prevent its use for thin in-service pavements. This paper presents the results of a study investigating the possibility of using smaller sample sizes for push–pull tests. The viscoelastic continuum damage (VECD) characteristics of regular and small-size samples are compared, and the difference is observed to be negligible. In addition, a practical fatigue life formulation is derived on the basis of VECD theory. Uniqueness of the derived fatigue life ( Nf) equation, differing from previously derived VECD-based Nf equations, stems from the fact that it does not force a certain form of equation to fit the damage characteristic curve. Finally, the differences in fatigue lives of different layers of the field sections at FHWA's accelerated loading facility are investigated.