Top-down Cracking Research Articles

Numerical analysis of the effects of subgrade settlement on top-down cracking in epoxy asphalt pavement

Numerical analysis of the effects of subgrade settlement on top-down cracking in epoxy asphalt pavement

Semi-analytical modelling of realistic tire-pavement contact: an analysis of pavement surface cracking damage under critical driving conditions

This paper aims to evaluate the surface cracking phenomenon on a flexible pavement subjected to diverse vehicle running conditions. Top-down cracking initiation is addressed through a continuum damage framework coupled with a semi-analytical model of tire-pavement rolling contact. The acceleration, braking and cornering scenarios were selected to represent the effect of combining normal and tangential loads. The differences between these loading cases are accurately computed by simulating the realistic contact stresses on the pavement surface through semi-analytical modelling. The computational cost of this modelling technique is reduced, allowing it to be used in industrial applications. It is assumed that tires and pavement are linear elastic multilayered half-spaces. The critical locations of the cracks are identified for each loading scenario and the cracking directions are discussed. This study emphasises the influence of driving conditions on premature pavement cracking which is not typically considered in the current pavement design guides. It is shown that a standard axle load may cause about 9 times more surface damage on a circular intersection compared to a straight-line pavement section.

Quantitative analysis of asphalt concrete’s tension-compression asymmetry effects on pavement response through 3D numerical modeling with dual viscoelastic model

Asphalt concrete (AC) exhibits noticeable tension-compression (TC) asymmetry, but it is typically considered isotropic in pavement design. This study aims to quantitatively evaluate the effect of AC’s TC asymmetry on pavement response under loading through numerical modeling. To achieve this objective, a temperature-dependent dual viscoelastic constitutive model was applied to incorporate AC’s TC asymmetry into pavement modeling. Besides, three pavement structure models, including one with thick AC layers, one with thin AC layers, and one with a Portland cement concrete (PCC) base, were developed. The responses of the three pavement structures under traffic and environmental loading conditions were simulated. Modeling results showed that AC’s TC asymmetry can significantly increase the vertical strain in AC, leading to higher stress concentration and larger deformation in AC layers. Unlike the conventional understanding that tensile strain concentrates at the bottom of AC layers, high tensile strains were observed in the top AC layers, especially for the pavement with thick AC layers or a PCC base, which may lead to top-down cracking. High tensile strains were observed on the granular subbase for the pavement with thin AC layers, which may induce bottom-up cracking. Besides, AC’s TC asymmetry also significantly increases the shear strains, especially the horizontal shear strain in AC layers, which may result in debonding and shoving distresses in AC layers. It was also noticed that the pavement response highly depends on its temperature and vehicular speed. A higher temperature or lower vehicular speed leads to more significant AC’s TC asymmetry as well as its effects on asphalt pavement’s response. The outcomes of this study are expected to help enhance the design and maintenance of more durable asphalt pavement.

Multiscale finite element analysis of layer interface effects on cracking in semi-flexible pavements at different temperatures

This paper presents comprehensive research work on the crack initiation behavior of Semi Flexible Pavements (SFP) with the help of a one-way coupled multiscale modelling approach. The study focuses on elucidating the influence of layer interface conditions on potential cracking patterns under different temperature conditions. By integrating material properties at both local (mixture) and global (pavement) scales using a local de-homogenization approach, the interlocking effect was addressed within the asphalt binder's mesoscale properties. CT-image based mesostructure was employed to reconstruct the Representative Volume Element (RVE). Cohesive Zone Model (CZM) was utilized to simulate cracking initiation within the RVEs, with simulation results validated against practical engineering inspections. Additionally, a potential macroscopic failure index was introduced for SFP. It was found that the typical macroscopic failure indexes utilized for AC pavement may not be suitable for SFP due to the higher degree of heterogeneity. Analysis showed that SFP layer's coarse aggregate and cement grout at the bottom may experience compressive stress, while asphalt binder beneath the tire load may face high tensile stresses. Regardless of the interface conditions, top-down cracking was found to be the dominating failure mode in SFP. Besides, the vulnerable area in bonded interface SFP shifts from under tire load to the adjacent area with the rise in pavement temperature, while bottom-up cracking may appear only in unbonded interface SFP under low temperature conditions. Subsequent analysis demonstrated that top-down cracking is prominent in bonded interface SFP, especially at higher temperatures, compared to unbonded interface SFP. It is expected that critical observations for SFP highlighted above will certainly help in understanding critical failure modes and, hence, designing and constructing durable SFP structures.

Study on crack propagation behavior of bridge deck asphalt pavement

Crack is a typical distress on bridge deck asphalt pavement (BDAP), which destroys the integrity and continuity of the pavement structure. However, the research on the crack propagation mechanism of BDAP is still limited. In this study, the three-point bending test was performed to investigate the propagation process of cracks in BDAP. Pre-cracks were set in the specimens with different depths (8 mm, 12 mm, 15 mm) and 4 mm widths, and two asphalt rubber hot-mix (ARHM) mixtures (ARHM-13 and ARHM-20) were selected. The critical fracture load, fracture energy, and fracture toughness were compared to investigate the crack resistance of ARHM-13 and ARHM-20 mixtures. In addition, the upper and lower layers of double-layer composite pavement specimens were fabricated with ARHM-13 and ARHM-20 mixture, respectively. The propagation process of the top-down crack (TDC) and reflection crack (RC) were investigated at different locations on the specimens. The test results show that the crack resistance of ARHM-20 mixtures is greater than that of ARHM-13 mixtures, and ARHM-20 mixtures should be used in the lower layer of BDAP to limit the propagation process of the reflection crack to the upper layer. The cracks propagated firstly from the RC and formed a through crack at the TDC in the specimens under the three-point bending loading action. The presence of TDC was found to accelerate the crack propagation of RC and exacerbate the failure of the BDAP. The crack length and deflection angle were determined by the pre-crack location. Furthermore, the decrease in temperature led to an increase in crack propagation velocity. The average propagation velocity increased from 0.03 mm/s to 0.55 mm/s as the temperature decreased from 20 ℃ to −20 ℃.

Mechanical Performance of Patched Pavements with Different Patching Shapes Based on 2D and 3D Finite Element Simulations

Patching is a common technology used in repairing asphalt-pavement potholes. Due to the differences in material properties between patched- and unpatched-asphalt mixtures, significant strain and stress concentrations could be induced; thus, further cracks and interfacial debonding distress could be caused. As a remedy, the strain and stress concentrations can be alleviated by utilizing optimum patching shapes. Therefore, this paper employed finite element methods (FEM) to deeply analyze the mechanical performance of patched-asphalt pavements embedded with different patching shapes. Three patching shapes, these being rectangular, stair, and trapezoid, were considered for use in pavement pothole repairs based on two- and three-dimensional finite element models. In the two-dimensional models, Top-Down and Bottom-Up crack propagations were simulated to assess the anti-damage performance of the patched pavements with different patching shapes. In addition, the thermal stress behaviors within patched-asphalt pavements were simulated using the two-dimensional model to analyze the performance of the patched pavements during the cooling process in construction. In addition, interface-debonding performance was simulated for the patched-asphalt pavements using three-dimensional models. In light of the simulation results, engineers are expected to better understand the mechanism within patched pavements and to improve the quality of the pavement patching.

The analysis and design of jointed plain concrete pavements with wider slabs

Despite the cost-effective nature of asphalt pavements, concrete pavements are preferred for their superior serviceability. Many agencies use Jointed Plain Concrete Pavement (JPCP) designs with a standard slab size of 3.5 × 4.5 m, focusing on transverse cracking. However, night-time Longitudinal Top-Down Cracking (LTDC) can occur in widened slabs due to tandem and tridem axles. This study employs a Finite Element (FE) approach to assess wider slabs under various loads. Longitudinal tensile stresses at critical points were found to increase with the slab width. Therefore, the study emphasizes the need for a design approach addressing transverse and longitudinal cracking. The design of the wider slabs (4.5 × 4.5 and 5.0 × 4.5 m) is demonstrated using a case study. If the longitudinal joint in a 9.0 m slab is placed at 5.0 m from the edge, the pavement could perform better than other slab sizes. However, it is necessary to design the pavement considering both longitudinal and transverse cracking.

In situ mechanical response characteristics of Autonomous Rail Rapid Transit (ART) applied to semi-flexible asphalt pavements

Autonomous Rail Rapid Transit (ART), featuring multi-axles, high tire pressure, and complete channelization, leads to severe rutting on conventional asphalt pavements. Semi-flexible pavement materials (SFP) were applied to ART corridors to mitigate rutting. Mechanical response characteristics were obtained by embedding sensors to understand the interaction between ART and SFP. Results found that the damage of corridor pavement shifted from rutting to top-down transverse cracking after adopting SFP. Nonresidual longitudinal tensile strains primarily caused top-down transverse cracking. The compressive stress at the bottom of corridor pavement caused by ART is 41%, 36%, and 58% higher than that of the BUS, respectively, under the condition of constant speed, acceleration, and deceleration. The maximum strain response caused by ART under a high-temperature environment was ten times higher than that of buses. These findings can provide data support for numerical simulations, material failures, and structural damage of ART corridors. Highlights Mechanical responses of semi-flexible pavement materials influenced by Autonomous Rail Rapid Transit (ART) were first captured using sensors. ART with high tire pressure exhibits a multi-axial cumulative effect in high-temperature conditions, resulting in pavement strains that can be up to ten times those of buses. After adopting semi-flexible pavement, the damage in ART corridors shifted from rutting to top-down transverse cracking. Nonresidual longitudinal tensile strains are the underlying cause of top-down transverse cracking.

Fatigue Cracking Behaviour and Characteristics of Flexible Pavement Subjected to Freight Coal-Truck Loading

Fatigue cracking is one of the varieties of flexible pavement distress caused by frequent traffic loads, and it is also a sign of structural collapse. Using finite element methods, numerical simulations were conducted to evaluate the strain changes that occur throughout the process of flexible pavement cracking. Several flexible pavement configurations with various thickness and different material properties of AC layer were developed, and several loading conditions in terms of the axle load, the speed, and the loading cycles of the freight truck were modelled. The numerical modelling showed that the greatest horizontal tensile strain in the 1stAC layer (surface course) is at the surface-centre of the pavement structure, which is predicted to be prone to top-down cracks. In other side, the greatest horizontal tensile strain in the 2ndAC layer (base course) is at the bottom-below of the tire tread, which is predicted to be vulnerable to bottom-up cracks. The outcomes of this study added to the knowledge gathered from previous studies, especially regarding the critical locations within the AC layer with the greatest magnitude of horizontal tensilestrain and their potency to experience either the top-down cracking or bottom-up cracking, as well as related to the effect of slowing the truck speed and increasing both the truck’s hauling load and loading cycles on the fatigue life of asphalt concrete layer. Future research needs to be done to evaluate the balance between both permanent deformation behaviour of the AC layer and to determine the optimum flexible pavement configurations.

Proposed automated contrast-enhanced microscopical method for evaluating air void structure in compacted asphalt concrete mixtures

There is no direct, less expensive, and practical method to measure the interconnectivity and parameters of air voids in asphalt mixtures other than the total air void volume calculated traditionally using bulk and maximum theoretical specific gravities. Unlike the conventional method, this paper proposes a method that is suitable for advanced applications and studies, such as for the evaluation of air void distribution and air void gradient to model and simulate long-term aging, predict top-down fatigue cracking, evaluate the effectiveness of compaction of thick lifts, and satisfy the representative volume element (RVE) requirements (a homogenous and representative specimen) for performance tests. Developing the proposed compact asphalt evaluation method included modifying the sample preparation methods and analysis from the American Society of Testing & Materials (ASTM), C457 Method C, and recently applied in the analyses of two independent studies at the Federal Highway Administration (FHWA). The first study was focused on checking the air void distribution within the small specimen for dynamic modulus and uniaxial cyclic fatigue tests using AASHTO TP 132 and TP 133, respectively. Results of air void analyses conducted on the interior and exterior sides of several slices sawn from different compacted asphalt mixtures consistently showed that the air void contents on the external sides are higher than on the interior. The second study was to evaluate whether the thicker-than-typical lift thickness to nominal maximum aggregate (NMAS) ratio was causing any top-to-bottom air void gradient in the pavement. Results showed that air void sizes and contents are consistently higher along the top ends of all the cores, and the total air void contents measured using the new method on several specimens from the field were comparable with the indirectly calculated air void percent with up to ± 0.4 percent random error. Overall, the new method is practical to apply to larger-size samples and is a tool that both agencies and contractors can use for confirming in situ void uniformity. Its application can support innovations and improve performance in asphalt pavement construction.

Pure modes I and II fracture behavior of Modified-Hot mix asphalt (HMA) under Long-Term aging condition

Top-down crack (TDC) as one of the pavement distresses, has a significant contribution to the quality of pavement service. Low-temperature top-down crack, which are subcategories of low-temperature crack (LTC) is representative of the cracks located on the pavement's surface and are directly affected by different environmental conditions such as temperature, air (oxygen), and light. Therefore, in the pavement body, this type of crack is more affected by long-term aging (LTA) than other cracks. To make sustainable mixtures, this research, it was tried to assess the long- and short-term fracture performance of hot mix asphalt (HMA) and HMA reinforced with different percentages of hospital waste pyrolysis carbon black (HWPCB) and hospital waste pyrolysis hydrocarbon (HWPHC) under mode I and II. The symmetrical specimen SCB and modified specimen SCB-2 geometries are utilized to simulate pavement crack behavior under tensile (opening) deformation and shear (sliding) deformations, respectively. For simulating the cracking behavior of semi-circular bending (SCB) samples in the laboratory with the pavement cracking behavior under the LTA process, an LTA condition, which was equivalent to a 12-year failure, was applied. Then, the long- and short-term fracture performance of the samples was examined using different fracture indices at temperatures of −15 °C. The results revealed that adding HWPCB and HWPHC to the HMA sample improved the fracture energy (GIIF and GIF) and fracture toughness (KIIC and KIC) of the HMA mixture under modes II and I (at −15 °C). Also, the improvement of the fracture stiffness and reduction of fracture brittleness of HMA specimens reinforced with HWPCB and HWPHC was concluded in long- and short-term conditions at the studied temperature (under modes II and I). From an operational point of view, the HMA mixtures reinforced with lower percentages of HWPCB and HWPHC are recommended for use in areas with an average temperature of about −15 °C and medium-heavy vehicle volumes. Also, the HMA mixtures reinforced with higher percentages of HWPCB and HWPHC are recommended for use in areas with medium temperatures and medium-heavy vehicle volumes. Moreover, the mixture containing both additives (HWPCB + HWPHC) is recommended for areas with medium temperature and high heavy vehicle volumes.

AC layer fatigue damage analysis and reflective cracking control of CRC + AC composite pavement

The current continuous reinforced concrete composite asphalt pavement (CRC + AC) design method in China does not consider the effect of the asphalt concrete (AC) layer on the longitudinal reinforcement rate of the continuous reinforced concrete (CRC) layer. To address such issues, a finite element model of CRC + AC using continuum damage mechanics theory and finite element method was established. The most unfavorable working condition and the location of the greatest damage by comparing the damage distribution under different working conditions were determined. To resolve the limitations of traditional design methods of CRC + AC composite pavement, criteria for the microcrack width of the CRC layer under different AC layer thicknesses were proposed, based on the combined effects of AC layer thickness and CRC layer microcrack width on the damage of the AC layer. The results suggest that the left lane vehicles braking and the right lane vehicles driving at a constant speed are the most unfavorable working conditions, with the greatest degree of damage found on the lane divider of AC layer. meanwhile, the microcrack width should be below 0.64 mm to mitigate the risk of Top-Down cracking and reflective cracking. Additionally, the CRC plate crack width control standards are provided for AC layer thicknesses ranging from 4 cm to 14 cm.

Thermal and structural response of a pavement solar collector prototype

Thermal and structural response of a pavement solar collector prototype

Introduction of calcium lignosulfonate to delay aging in bituminous mixtures

This study examines the merits of using calcium lignosulfonate (CLS) to mitigate negative effect of aging on bituminous mixtures. To do so, we studied how fracture energy and fracture toughness of the bituminous mixtures containing CLS change when exposed to long-term aging. Aging is implicated in premature cracking including but not limited to top-down cracks and low-temperature cracks which negatively impact road roughness, and subsequently ride quality and driver safety. Considering that latter cracks are induced by tensile and shear forces, we used semi circular bending (SCB) test to quantify fracture energy and fracture toughness of mixtures containing 5–20% CLS under both mode I and II. Each mixture was exposed to short and long term aging and tested at temperature of +15 °C and −15 °C. The study results showed that introduction of CLS increased the fracture energy and fracture toughness of the mixtures under both modes I and II. The study outcomes provides insights for advancing socioeconomics of pavements by mitigating surface cracks which in turn enhances the driver safety, ride quality and maintenance cost of pavements.

Experimental and statistical investigation on the performance of asphalt overlays reinforced with geocomposite in controlling the reflective cracks under different loadings and temperatures

One of the easiest method to repair the old pavement is to apply an overlay on them. However, the deteriorated pavement affects the overlay performance by propagating the existing cracks upwards to the overlay due to the stress and strain concentration from the loading and temperature variations. Today, using the asphalt overlays reinforced with geosynthetic interlayers is one of the most effective methods to prevent the reflective cracking. This paper investigates the effects of the temperature, bending fatigue loading frequency and geocomposite tensile strength on the asphalt overlays performance experimentally. The crack initiation and its propagation rate were analyzed by the help of image processing technique and statistically. The obtained results revealed that the temperature has the greatest effect on the reflective cracking rate, so that by increasing the temperature from 20 to 40 °C in addition to increasing the crack growth rate and changing the vertical deformation under the load, the direction of crack formation changes, and besides the reflective cracks, the top-down cracks also appear. Furthermore at the higher loading frequency more than 10 Hz, even in samples reinforced with geocomposite, increasing the temperature from 0 to 20 and 40 °C will increase the crack growth rate between 5 and 30 times. The obtained coefficients of determination (R2) and Adjusted R2 are equal to 0.9936 and 0.9907, respectively, indicating the satisfactory prediction of the model compared to the real observations.

Investigation of asphalt pavement crack propagation based on micromechanical finite element: A case study

Cracking is a prevalent issue in expressway pavements in Shanxi Province, exhibiting various types. Based on field investigations, the primary types of asphalt pavement cracks observed in Shanxi expressways can be categorized as top-down crack (TDC, surface crack) and reflection crack (bottom-top crack). These two types differ significantly in terms of cracking mechanisms, development modes, treatment methods, and impact severity. This paper aims to simulate the initiation and propagation processes of top-down cracks and reflection cracks using the finite element method, aiming to provide a basis for distinguishing between the two. In this paper, a microstructure numerical model of a three-phase asphalt concrete pavement is established. Finite element software is utilized to simulate the initiation and propagation of top-down cracks and reflection cracks on asphalt pavement, while investigating the influence of various factors on crack propagation. The findings demonstrate that top-down cracks exhibit multi-point cracking on the pavement surface, resulting in a tortuous and discontinuous development process. Conversely, reflection cracks display significant stress concentration at the crack tip, leading to propagation even under loads significantly lower than the material's tensile strength, following a single propagation path. Aggregate distribution form, preset crack length, tensile strength of ITZ, and load distribution form do not have a significant effect on the primary cracking mode. However, they do influence the crack initiation point, cracking load, and propagation path to some extent.

Mechanistic analysis of bottom-up crack in asphalt pavement using cohesive zone model

The bottom-up crack (BUC), one kind of reflective crack that initiates at the bottom of asphalt layer and propagates upwards, has become one of the major distresses of asphalt pavement. The Mode Ⅰ dominated bilinear cohesive zone model (CZM) after calibration was introduced into finite element (FE) model to simulate the BUC propagation in asphalt pavement under displacement load. The mechanism of crack propagation under different types of periodic load was analyzed based on two indexes from Mode Ⅰ dominated bilinear CZM. The FE model and corresponding periodic load were modified to limit the occurrence of top-down crack propagation. A combined method based on the developed model was adopted to predict the BUC propagation velocity at varied heights and the remaining life of pavement. The results showed that the acceleration of BUC propagation decreased with the crack tip height. Moreover, the predicted remaining life of pavement based on the proposed method was reasonable referring to the engineering design specifications.

A comparative study on the performance of field-sampled asphalt mixtures for heavy-duty pavements using laboratory testing and mechanistic-empirical simulations

The demand for durability and resilience in asphalt pavements has led to the progressive implementation of performance-enhancing technologies like bitumen modification using polymers or fibers. This is particularly important in a port environment, where roads are subjected to heavy traffic. The main objective of this study is to contribute to the current state of knowledge on the performance of asphalt mixtures, including polymers and fibers, by conducting a comprehensive laboratory investigation of eight field mixtures, followed by an evaluation of their expected performance in five test sections using the AASHTOWare Pavement ME Design software. The eight mixtures included two lean asphalt mixes to be used as a replacement for granular layers, three base mixtures, and three surface mixtures. Laboratory testing showed that the addition of a blend of 91% polypropylene and 9% glass fibers increased stiffness and resistance to moisture damage. Also, this fiber blend improved cracking resistance when used in a relatively flexible mixture. It was found that top-down cracking predictions followed the trend observed in semicircular bending tests. Conversely, the predicted rutting performance did not align with the rut depth trend in the laboratory. Furthermore, the use of SMA instead of a dense-graded surface layer appeared to increase fatigue cracking in pavement sections with granular bases unless a high-modulus base asphalt layer was used. This study was a first attempt to use advanced pavement performance predictions in Belgium. The data gathered during the future monitoring of the test sections built as part of this study will provide valuable primary data for the local calibration of pavement distress models.

A framework for predicting top-down crack initiation and growth for flexible pavements

ABSTRACT Top-down cracking (TDC) is recognized as a significant form of distress in asphalt pavements. While the NCHRP project 1-52 introduced a mechanistic-empirical (ME) predictive model for TDC, this model was found to be less accurate in certain traffic conditions—overpredicting crack initiation in sections with medium to low traffic and underpredicting in high-traffic sections. To enhance the precision of TDC predictions, a new fracture-mechanics-based framework has been developed. This improved framework employs a Hot Mix Asphalt (HMA) fracture mechanics methodology, resulting in a marked enhancement in the accuracy of predicting crack initiation times when compared to the original sub-model from NCHRP 1-52. The new framework also incorporates a novel aging model for the asphalt mixture, ensuring more precise inputs for the crack propagation model. The propagation prediction sub-model has been refined by implementing a J-integral-based Paris’ law developed in the NCHRP 1-52 project. The efficacy of this updated framework was rigorously tested on eighteen diverse pavement sections across various geographic locations, with well-documented performance history and material properties. The outcomes indicate that the predicted initiation and propagation of TDC closely align with actual field observations, demonstrating the robustness and improved reliability of the new model.

Reinforcement design optimisation for continuously reinforced concrete pavement: one-mat vs. two-mat

ABSTRACT Over the years, thicknesses of continuously reinforced concrete pavement (CRCP) increased to accommodate rising truck traffic. With a fixed percentage of longitudinal reinforcement relative to the concrete cross-sectional area, thicker slabs necessitate more reinforcement and reduced bar spacing, potentially hindering consolidation. To address this issue, two-mat steel design was implemented in Texas for pavements with thickness of 330 mm (13 in.) or larger. Performance evaluations of thick CRCPs revealed that horizontal cracking developed at the depth of reinforcement where one-mat steel was placed, while no horizontal cracking was observed where two-mat steel was used. Pavement responses with one-mat and two-mat reinforcements with different depths were analysed by three-dimensional modelling with a finite element analysis (FEA) programme for the wide range of environmental loadings. Maximum concrete vertical tensile stresses around longitudinal reinforcement at transverse crack area are a good indicator of horizontal cracking potential; those stresses were evaluated, along with concrete stresses at top of the slab, which are responsible for top-down transverse cracking. The results show that the two-mat design causes higher concrete stresses at the top of the concrete slab and lower concrete stresses around the longitudinal reinforcement, leading to increased transverse cracks and a reduction in horizontal cracking potential.