Top-down Cracking Research Articles

Evaluation of top-down cracking potential for asphalt pavements with 4.75 mm nominal maximum aggregate size mixture layer using full-scale field tests and finite element analysis

This study primarily focused on evaluating top-down cracking resistance for pavement structures with 4.75 mm nominal maximum aggregate size asphalt mixtures (i.e. SP-4.75) that will help determine more effective application of these mixes for layered flexible pavement system. Crack evaluation and pavement surface response measurements were conducted using full-scale field test sections. In addition, a three-dimensional (3-D) viscoelastic finite-element (FE) pavement model was developed to further validate the results of field tests using analytical solution. The results indicated that the pavement structure with SP-4.75 mixture at the top becomes more prone to top-down cracking when a thin layer with unmodified asphalt binder is applied. It was found that both layer thickness and binder type are key parameters to control top-down cracking potential. Also, the comparative observations between analytical and experimental results confirm that the FE model developed was able to provide accurate, reliable, and realistic prediction for change in pavement surface strain responses due to different conditions of SP-4.75 layer application. It was concluded that adequate thickness and binder type should be considered for proper application of SP-4.75 mixture as a surface course of layered flexible pavement system to effectively resist top-down cracking.

Numerical Modeling and Artificial Neural Network for Predicting J-Integral of Top-Down Cracking in Asphalt Pavement

Top-down cracking (TDC) is recognized as one of the major distress modes in asphalt pavements. This study aimed to determine the fracture parameter J-integral of TDC, which is a critical input to predict the crack growth rate and fatigue life of pavements for this type of distress. Previous research studies demonstrated that TDC is affected by various factors, including the complex state of high tensile or shear stresses induced by the loading at the edge of or within the tire and material properties such as the modulus gradient in the asphalt layer, moduli of the base and subgrade layers, and pavement structures. In this study, the finite element model (FEM) was adopted to simulate the propagation of TDC by considering combinations of these essential factors and to calculate the J-integral for 194,400 cases. It was shown that the modulus gradient plays an important role in determining the J-integral, and the J-integral is not uniformly distributed within the pavement depth. On the basis of the database generated from the FEM, six backpropagation artificial neural network (ANN) models—including one input layer, two hidden layers, and one output layer—were developed by using the same input variables and output variable as those for the FEM. The R2 value for each ANN model was greater than .99, which indicates the goodness of fit. After the parameters of each ANN model have been determined, the J-integral can be predicted for any combination of the design parameters without reconstruction of the FEM.

Moving Toward Asphalt Binder and Mixture Protocols to Minimize Fatigue Cracking on Asphalt Airfields

The Port Authority of New York and New Jersey (PANYNJ) owns and operates two of the most heavily used airports in the United States. Newark Liberty International Airport (Newark) in New Jersey and John F. Kennedy International Airport (JFK) in New York handle approximately 1 million arrivals and departures each year. Although their runways witness an extreme amount of loading, the primary distress observed on them is top-down fatigue cracking with little to no rutting. Recently, the PANYNJ observed premature top-down fatigue cracking at two runways at Newark. After an evaluation of several runways at JFK and Newark, it was discovered that asphalt mixtures of similar design were resulting in varying levels of fatigue cracking performance. For a better understanding of the fatigue cracking performance of asphalt mixtures placed on airport runways in the New York and New Jersey area, a forensic study was conducted on field cores recovered from five runways maintained by PANYNJ. Asphalt binder was recovered and tested from the field cores at different depths from the pavement surface. The test results of the study showed that the Δ Tcr parameter, measured with the critical low-temperature results from a bending beam rheometer, could be used within a purchase specification to help mitigate the potential receipt of asphalt binders prone to accelerated aging and cracking. Meanwhile, the overlay tester and the semicircular bending flexibility index were found to be capable of potential implementation as quality control tests to ensure that asphalt mixtures produced for asphalt airfields in the New York and New Jersey area were not susceptible to top-down fatigue cracking.

Long-Term Field Aging of Warm-Mix and Hot-Mix Asphalt Binders

Limited field studies have considered the aging of warm-mix asphalt (WMA) binders, especially from the perspective of long-term aging. This paper quantifies the long-term (10 to 82 months) field aging properties of WMA binders and the control hot-mix asphalt (HMA) binders and identifies the key factors associated with long-term field aging of asphalt. Asphalt binders from 23 field projects consisting of 65 HMA and WMA pavements were recovered, and high-temperature performance grade (PG) was tested. The effects of climate, month of aging, WMA technologies, and original binder high-temperature PG on field asphalt aging were analyzed. A prediction model that included multiple parameters was developed and validated. Results indicated that Evotherm WMA binder had a lower high-temperature PG than HMA binder shortly after construction, but this difference reduced with time. No statistical difference of field aging between HMA and WMA binders was observed. The climate effect on asphalt field aging was apparent within dry areas or freeze areas, whereas the aging difference between dry and freeze areas was inconclusive and requires further research. Other conclusions were that ( a) the field asphalt aging affects more of top-down longitudinal wheelpath crack than transverse crack, ( b) foaming WMA binder ages slowest of all binders considered, ( c) PG 64-XX and PG 70-XX binders aged more than PG 58-XX and PG 76-XX binders, and ( d) the prediction model had good agreement with test results and was well validated. The identified factors that affected field asphalt aging were overlay thickness, in-place air voids, effective binder content, complex shear modulus, and solar radiation.

Predictive quality of the pavement ME design program for field performance of warm mix asphalt pavements

High quality predictive program provides an alternative to assess the long-term performance of asphalt pavements if well-evaluated based on field performance. The asphalt pavement performance models embedded in the Pavement ME Design program were developed based on hot mix asphalt (HMA) pavements, and the predictive quality varies depending on specific conditions. The applicability of the Pavement ME Design program as well as the embedded performance models to warm mix asphalt (WMA) pavements is even unclear. In addition, the ability of the Pavement ME Design program in differentiating HMA and WMA performance, if any, has not been evaluated. Therefore, the objectives of this study are to determine the predictive quality of the Pavement ME Design program for the field performance of WMA pavements, and further to evaluate the capability of Pavement ME Design program in detecting performance difference between HMA and WMA pavements if there is any. A total of 43 asphalt pavements (both HMA and WMA) from 16 projects were evaluated based on their field measured and predicted performance, in terms of rutting, transverse cracking and top-down longitudinal cracking. Results indicate that (1) The Pavement ME Design program can predict the field rut depth well for HMA and WMA pavements, in terms of both numerical values and rankings. However, the software in general over-estimates the field rut depth; (2) The Pavement ME Design program cannot predict field transverse cracking or field longitudinal cracking correctly irrespective of pavement type; (3) The results suggest that the effect of moisture should be considered in the Pavement ME cracking models for both HMA and WMA pavements, and (4) Overall, the predictive quality of the Pavement ME Design program for HMA and WMA is similar, either in good or poor prediction results. The WMA technology does not fundamentally alter the behavior of asphalt materials in pavement application. We suggest treating WMA similarly as HMA while applying the Pavement ME Design program for performance prediction. However, the corresponding WMA material properties should be used as input values.

Effect of horizontal loading on RCC-base composite pavement performance at heavy duty area

RCC-base composite pavement is reported as an economical and strong structural alternative to carry heavy traffic in heavy duty area such as port or container terminal. This pavement system has ability to eliminate the critical tensile strain that induces the bottom-up fatigue cracking of asphalt surface course. Other issues such as top-down cracking in asphalt surface and interfacial bonding failure may also influence and reduce the life and functionality of the pavement. In multi-layer pavement system, horizontal loading created by tire-pavement friction during brake or acceleration of vehicle is found to be an essential effect that induces top-down cracking in asphalt surface and interlayer debonding. In heavy duty area, handling vehicles frequently stop or accelerate on pavement, thus effect of horizontal loading on top-down cracking and AC/RCC interfacial bonding behavior in RCC-base composite pavement system should be numerically investigated. In this study, horizontal strain on the top of asphalt surface and AC/RCC interfacial shear stress are computed in FEM to evaluate top-down cracking and bonding behavior, respectively. This study shows that top-down cracking and bonding failure in composite pavement system may occur since horizontal loading is applied. Also, temperature may have a significant effect on top-down cracking of asphalt surface.

Effects of truck traffic on top-down fatigue cracking performance of flexible pavements using a new mechanics-based analysis framework

The mechanics-based analysis framework predicts top-down fatigue cracking initiation time in asphalt concrete pavements by utilising fracture mechanics and mixture morphology-based property. To reduce the level of complexity involved, traffic data were characterised and incorporated into the framework using the equivalent single axle load (ESAL) approach. There is a concern that this kind of simplistic traffic characterisation might result in erroneous performance predictions and pavement structural designs. This paper integrates axle load spectra and other traffic characterisation parameters into the mechanics-based analysis framework and studies the impact these traffic characterisation parameters have on predicted fatigue cracking performance. The traffic characterisation inputs studied are traffic growth rate, axle load spectra, lateral wheel wander and volume adjustment factors. For this purpose, a traffic integration approach which incorporates Monte Carlo simulation and representative traffic characterisation inputs was developed. The significance of these traffic characterisation parameters was established by evaluating a number of field pavement sections. It is evident from the results that all the traffic characterisation parameters except truck wheel wander have been observed to have significant influence on predicted top-down fatigue cracking performance.

Field performance of top-down fatigue cracking for warm mix asphalt pavements

ABSTRACTAs a result of repeated rehabilitation efforts over the past few decades, often asphalt pavements have become deep-strength pavements. Consequently, top-down cracking has become a primary distress type. In particular, the top-down cracking performance of warm mix asphalt (WMA) pavements, i.e. how does it compare with similar hot mix asphalt (HMA) pavements is largely unclear mainly due to the lack of field performance data. This paper presents an effort of monitoring the top-down cracking performance of 28 pavement projects including WMA pavements and their corresponding HMA control pavements with service lives ranging between 4 and 10 years. These pavements cover different climate zones, WMA technologies, service years, pavement structures and traffic volume levels. Two rounds of distress surveys were conducted at a two-year interval, and the material (asphalt binder and mixture) properties of the pavements were determined using field cores. The top-down cracking performance of the HMA and WMA pavements was compared based on the first and second round distress surveys. It was found that the HMA and WMA pavement in general exhibited comparable performance. The significant determinants (material properties) for top-down cracking were determined, which were vertical failure deformation of mixes measured at 20 °C from indirect tension test.

Effects of loading, geometry and material properties on fracture parameters of a pavement containing top-down and bottom-up cracks

In this paper, the fracture parameters of top-down and bottom-up cracks initiated in a multi-layer asphalt pavement is computed numerically. Using extensive two-dimensional finite element analyses, the effect of thickness and stiffness of concrete layer and base layers, length and number of cracks, and vehicle position relative to the crack plane was investigated on fracture parameters of both top-down and bottom-up cracks. It was shown that the position of front and rear wheels have great influence on the values of stress intensity factors (KI and KII) and T-stress, such that magnitude and sign of these three parameters may change significantly by moving the vehicle from the far distances towards the crack and then passing the wheels from it. The critical condition of fracture parameters is occurred where any of front and rear wheels were very close to the crack. The change in fracture parameters is more pronounced for thinner and stiffer values of overlay. In general, top-down crack is more vulnerable to propagate, since the corresponding values of KI, KII and T are significantly higher than the values of bottom-up crack. The value of KII component was not generally sensitive to the change in thickness and stiffness of pavements layers.

The Detection of Vertical Cracks in Asphalt Using Seismic Surface Wave Methods

Assessment of the location and of the extension of cracking in road surfaces is important for determining the potential level of deterioration in the road overall and the infrastructure buried beneath it. Damage in a pavement structure is usually initiated in the tarmac layers, making the Rayleigh wave ideally suited for the detection of shallow surface defects. This paper presents an investigation of two surface wave methods to detect and locate top-down cracks in asphalt layers. The aim of the study is to compare the results from the well- established Multichannel Analysis of Surface Waves (MASW) and the more recent Multiple Impact of Surface Waves (MISW) in the presence of a discontinuity and to suggest the best surface wave technique for evaluating the presence and the extension of vertical cracks in roads. The study is conducted through numerical simulations alongside experimental investigations and it considers the cases for which the cracking is internal and external to the deployment of sensors. MISW is found to enhance the visibility of the reflected waves in the frequency wavenumber (f-k) spectrum, helping with the detection of the discontinuity. In some cases, by looking at the f-k spectrum obtained with MISW it is possible to extract information regarding the location and the depth of the cracking.

Analytical method for evaluating top-down cracking in pavements

Top-down cracking is a type of cracking that significantly impacts traffic safety and comfort and reduces a pavement's service life. Here, a cement concrete pavement containing a top-down crack is investigated under traffic load using a theoretical analysis method. In order to simplify the problem, the cement concrete pavement is modelled as an elastic plate on a Winkler foundation. Fourier transform methods and a dislocation density function are used to determine the stress intensity factors of a crack tip. A parametric study is conducted to isolate the effects of crack length, pavement stiffness and distance between the crack and the edge of a vehicle wheel. The results of the study show that crack length and load position significantly affect the stress intensity factors. However, stress intensity factors are less affected by the elastic modulus of the pavement material.

A statistical based framework for predicting field cracking performance of asphalt pavements: Application to top-down cracking prediction

Most existing cracking performance models of asphalt pavements, such as top-down cracking models, are mechanistic or mechanistic-empirical based. These models usually focus on a specific type of cracking mechanism. The prediction quality of these models can also vary when field cracking conditions are complicated and clear identification of the distress type is difficult. Literature suggests that a statistical based method can account for variability and a large number of influencing factors, and could be a promising alternative. This paper aims to introduce a statistical based framework for performance prediction using top-down cracking as an example. Such a framework can be modified and implemented by local agencies for a variety of cracking distresses based on specific needs and requirements.Detailed steps of the statistical framework are presented through the development of top-down cracking models. Results indicate that the framework works effectively by integrating pavement performance concepts with several statistical methods including Partial Least Squares (PLS) Regression, Binary Logistic Regression, and Leave one out cross validation (LOOCV). Using the developed statistical based framework, critical factors that may affect the initiation and propagation of top-down cracking are identified, and their sensitivities to the field top-down cracking are further discussed.

Evaluation of structural benefits of prime coat application for flexible pavements using Accelerated Pavement Testing (APT)

This study was mainly focused on evaluating the structural benefits of a prime coat application that may positively affect pavement performance based on the pavement response measurements using Accelerated Pavement Testing (APT). Two full-scale field test sections were built using different interlayer conditions between Asphalt Concrete (AC) and base layer including prime coat and no treatment for evaluation. Strain gauges and pressure cells were instrumented for each test section to conduct pavement response measurements. Results indicate that the application of prime coat was able to significantly reduce stress and strain responses at critical locations of pavement structure by providing a structural bond between layers that result in enhanced pavement performance compared to pavement with no treatment. In addition, based on the results of relative performance estimated, it was found that pavement structures with prime coat application potentially lead to improved performance including fatigue cracking, top-down cracking and subgrade rutting compared to pavements with no treatment and pavement damage seems to be accelerated for pavement system without prime coat application. Also, the full-scale field tests conducted using APT were determined to be capable of effectively capturing the structural effect of prime coat application on change in pavement critical responses for enhanced performance of asphalt pavements with more realistic and reliable results.

A novel test specimen for investigating the mixed mode I+III fracture toughness of hot mix asphalt composites – Experimental and theoretical study

Asphalt concrete pavements containing top-down cracks can be subjected to combined opening-out of plane sliding (i.e. mixed mode I/III) deformations due to traffic loads. However, lack of a suitable laboratory test specimen for fracture toughness testing of asphalt composites under mixed mode I/III, is one of the main shortcomings of this field. Hence, a new and simple test configuration is proposed in this research for determining mixed mode I/III fracture toughness of these composite materials. The specimen which is called the Edge Notched Disc Bend (ENDB), is a disc containing an edge crack created through one side of specimen along the diameter and is loaded by a three-point bend fixture. It was demonstrated that the complete range of mode mixity from pure mode I to pure mode III can be achieved by this specimen simply by changing the crack inclination angle relative to the loading support direction. The practical ability of the suggested ENDB specimen, was then examined for obtaining the mixed mode I/III fracture toughness of a typical hot mix asphalt (HMA) composite for different mode mixities including pure modes I and III. Corresponding values of KIc and KIIIc were determined for each mode mixity and it is shown that the obtained results are in quite well agreement with the predictions of a mixed mode I/III fracture theory. Consequently, the ENDB specimen can be used as a favorite candidate specimen for mixed mode fracture toughness study of asphalt concrete materials.

열분해 카본블랙 사용량에 따른 밀입도 아스팔트 혼합물 성능 평가

본 폐타이어로부터 추출한 열분해 카본블랙(PCB)을 13mm 표층용 밀입도 아스팔트 혼합물 공용성능을 평가하였다. 최적배합설계를 시행하였고, 최적아스팔트 함량은 5.8%을 이용하였다. 아스팔트 혼합물의 탄성계수 평가를 위해 자유단 공진주 시험하였다. PCB 사용량이 증가하면, 측정된 탄성계수는 감소하였다. 다만, 감쇄비 변화는 미미한 것으로 나타났다.평가시험은 간접인장강도시험, 소성변형시험 및 포장설계법을 이용한 전산해석을 이용하였다. PCB 사용시 수침 전과 후의 강도감소율이 평균 10% 이하로 나타났다. 소성변형의 경우 PCB 10% 이상 사용시 오히려 소성변형이 크게 발생하였다. 포장 설계법 전산해석으로부터, PCB 5% 사용시 Top-Down 및 Bottom-Up 균열 저항성이 증가하였고, 소성변형 저감 효과가 크게 나타났다. 열분해 카본블랙 10% 및 15% 사용시 소성변형은 적게 나타났지만, 내구성은 크게 저하되는 것으로 나타났다. 전체적으로 PCB 5%를 이용한 표층용 아스팔트 혼합물의 공용성이 가장 우수한 것으로 나타났다. Using the pyrolyzed carbon black (PCB) from waste tires, the performance of 13 mm dense-graded hot mix asphalt was evaluated. The Marshall mix design was carried out and the measured optimal asphalt content was 5.8%. The impact resonant test was conducted to obtain the elastic modulus and damping ratio of the hot mix asphalt. The elastic modulus of HMA increased with increasing amount of PCB. On the other hand, there was no significant change in the damping ratio. The Marshall mix design, indirect tensile test, permanent deformation test, and program analysis were carried out. The strength ratio of the PCB modified asphalt mixtures was within 10%. More 10% of PCB was not good for the permanent deformation of hot mix asphalt. From the pavement design program, the use of 5% PCB in hot mix asphalt showed a decrease in the top-down crack, bottom-up crack, and permanent deformation. Judging from the limited test and analysis, the use of 5% PCB is good for enhancing the pavement performance.

Tire–Pavement Contact Stress With 3D Finite-Element Model—Part 2: All-Steel Tire on Heavy Vehicles

Abstract Heavy vehicles increase on highways in China year by year. Heavy loads are among the most important factors causing pavement distresses. The distribution of contact stresses between tires and pavement surface greatly influences the initiation and propagation of pavement distresses, especially for the top-down cracking. Therefore, to accurately and precisely describe pavement responses, the distribution of contact stresses should be first investigated thoroughly. This study focuses on simulating the contact stresses between all-steel tires on heavy vehicles and the pavement surface. A 3D finite-element model was proposed and used to simulate the distribution of contact stresses in different conditions of tires, including standstill, free rolling, accelerating rolling, and decelerating rolling conditions. This model was validated by previous study of the authors. There were three loading levels used in this study, including 20 kN, 40 kN, and 60 kN. In the standstill condition, the maximum pressures on pavement surface were simulated as 1.2 MPa, 1.2 MPa, and 2.4 MPa in 20 kN, 40 kN, and 60 kN loading levels, respectively, which were much higher than 0.7 MPa, the standard contact pressure in pavement design specification in China. An interesting phenomenon was observed that when the load passed a certain value, the width of contact area kept constant, whereas the length of contact area was prolonged. And the length of the contact area prolonged linearly with the increase of load. Based on this phenomenon, the Hertz contact theory was applied to simplify the traditional 3D finite-element model. In the simplified model, the complicated 3D all-steel tire was simplified to an equivalent medium. The 3D finite-element model and the simplified model were compared with the analytic method. This indicates that the simplified model can simulate the contact stress of all-steel tires closely to the analytic results (no more than 10 % difference) and greatly improves the calculation efficiency.

3D modelling of tyre-pavement contact pressure

Pavement design assumes uniform contact loading because of bottom-up traditional cracking (far from loading), but nowadays more and more surface damage (top-down cracking and rut) due to new technology in pavement and tyre design is observed. Then, a more realistic tyre–pavement contact modelling has to be considered. In order to go towards more realistic tyre–pavement contact, finite element method consumes a lot of calculation time; so in this article, we propose a semi-analytical model developed for the calculation of ball bearings. The contact is considered as a Hertzian contact, and the surface of the road is flat and that the tyre is smooth. Calculation of contact pressure is compared and validated with experimental data using a device called Stress-In-Motion, which allows contact pressure measurement. Different parameters are assumed in the modelling such as tyre pressure, axle loading and tyre shape. We have now a successful tool to analyse the tyre–pavement contact, more accurate and realistic and especially faster than those used at the moment.

Mechanics-based top-down fatigue cracking initiation prediction framework for asphalt pavements

In this paper, a new mechanics-based top-down fatigue cracking analysis framework is presented for asphalt pavements. A new mixture morphology-based set of material sub-models is presented for characterising key mixture properties and their change over time. Predicting the load induced top-down fatigue crack initiation (CI) time by utilising comprehensive mixture properties creates the possibility of optimising the mixture morphology while taking into account its subsequent effect on long-term pavement performance. The new framework was calibrated and subsequently validated against a number of field pavement sections with varying traffic levels that are representative for current practices and which have a wide range in material properties. The framework accounts the change in key mixture properties due to ageing and mixture-healing effect on damage accumulation while determining the overall effect of design inputs on cracking performance. Model calibration and validation were achieved based on the healing potential of the asphalt mixture. It was found out that the CI predictions for all the sections are in general agreement with the observed performance in the field, thus giving credibility for the framework.

Determination of Surface Viscoelastic Response of Asphalt Pavement

AbstractAsphalt concrete exhibits rate- and time-dependent behavior, and therefore viscoelastic response analysis is necessary to model the pavement structure behavior and explain the distress mechanisms. The newly developed Mechanistic–Empirical Pavement Design Guide emphasizes the importance of accurate determination of response at the pavement surface to efficiently model the top-down cracking and implement the sublayering scheme. However, it is shown in this study that the integrand of the Laplace-transformed step-response function at the pavement surface exhibits complicated oscillating behavior and slow convergence, making it difficult to achieve accurate viscoelastic solutions. This study proposes a procedure to effectively solve this problem. The proposed procedure uses the Lucas algorithm to reduce the complex oscillations to regular oscillations by separating the integrand into high- and low-frequency components and then uses integration, summation, and extrapolation methods to accelerate the co...

An experimental design-based evaluation of sensitivities of MEPDG prediction: investigating main and interaction effects

The mechanistic–empirical pavement design guide (MEPDG) uses mechanistic–empirical models by analysing the impacts of traffic, climate, materials and pavement structure to predict performances of pavement. The MEPDG software uses a three-level hierarchical input to predict performance in terms of terminal International Roughness Index, permanent deformation, total cracking (reflective and alligator), asphalt concrete (AC) thermal fracture, AC bottom-up fatigue cracking and AC top-down fatigue cracking. However, these inputs with different levels of accuracy may have significant impact on performance prediction. This study focuses on the sensitivity of the inputs of MEPDG distresses to identify the effect of the accuracy level of inputs based on experimental design. A local sensitivity analysis is carried out to identify the main effect of inputs considering them as independent variables. Interaction effects are also analysed based on random combination of the inputs. Sensitive input variables and their combinations are evaluated through a multiple regression analysis for respective distresses.