Reflective Crack Propagation Research Articles

Research on the propagation mechanisms and meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement by Fiber Bragg Grating sensing technology

This study evaluated the propagation mechanisms and dynamic meso-mechanical responses of reflective cracking on the asphalt overlays on concrete airfield pavement based on flexible Fiber Bragg Grating (FBG) sensors. The encapsulated FBG sensors were efficiently calibrated, possessing outstanding capability for the measurement of transverse expansion of lateral reflective cracking propagation. Virtual three-point bending test model was proposed and validated by macroscopic indoor experiments. The DEM model facilitated quantifying the proliferation of reflective cracks, unraveling the trajectory from micro-crack inception to visible macroscopic manifestation. Results indicated that the emergence and elongation of the composite structure experienced three phases: the initiation and accumulation of microcracks, the extension of reflective cracking, and the ultimate penetration. The DEM simulation and FBG sensors were recommended to establish a mutually reinforcing mechanism for nuanced validation of reflective crack formation on the composite structures of asphalt overlays on concrete airfield pavement.

Comparative evaluation of mitigation methods for traffic-induced reflective cracking in airport composite pavement

Composite pavement provides an effective and quick solution to restore structural and functional capacity of airfield pavement. However, discontinuities of concrete slabs cause initiation and propagation of reflective cracking in asphalt overlay. This study aims to evaluate and compare the effectiveness of mitigation methods for traffic-induced reflective cracking in airport composite pavements. Finite element (FE) models were developed and validated to predict pavement responses under heavy weight deflectometer (HWD) and aircraft tire loading. The load transfer efficiency (LTE) of existing rigid pavement were evaluated under common deterioration scenarios like base erosion and concrete damage. The crack potential was indicated by pseudo J-integral considering stress intensity factors (SIFs) of different fracture modes. The results show that thicker asphalt overlay, stress absorbing interlayer, and increase of LTE can help mitigate reflective cracking. Increasing 51-mm overlay (from 76 mm to 127 mm) and applying 25-mm interlayer show the similar reduction in reflective cracking fracture potential by about 35% at early crack stage. However, applying interlayer has more benefit on cost effectiveness and pavement elevation control. On the other hand, dowel bar retrofit and base treatment can improve LTE and thus reduce the crack potential at early crack stage of 76-mm overlay by 40% on doweled pavement and 60% on un-doweled pavement, respectively.

Full-Scale Evaluation of Geosynthetic-Reinforced Hot Mix Asphalt

This study aims to evaluate the potential of using geosynthetics to reinforce flexible pavements and improve their resistance to reflective cracking. To achieve the goals, three full-scale test strips (control, geogrid, and geotextile) were constructed at Rowan University, each being 30 ft long by 15 ft wide. The pavement structure of each test strip included two hot mix asphalt (HMA) layers with a total thickness of 3.0 in., and five intentional cracks (with widths of 0.2 in.) were introduced to the first HMA layer. After sealing the cracks and applying the tack coat layer, the geosynthetic interlayer was added, and the top HMA layer was constructed. Asphalt strain gauges and thermocouples were embedded in each section to measure critical strains. All sections were also loaded using a heavy vehicle simulator (HVS) with dual-tire configurations while the temperature around the test strips was maintained at 50°F. In addition, each test strip’s deflection and rutting were measured before and after HVS loading using a heavy weight deflectometer and a laser profiler, respectively. The HVS loading results found that the geogrid-reinforced test strip had a better strain response than the geotextile-reinforced layer, and the geotextile-reinforced layer showed slightly higher bonding (lower delamination). It is noted that the results of this study are in line with a former laboratory study with respect to crack reflection and delamination. Rut profiler data recorded a 25% reduction in rut depth for reinforced sections compared to the control. Moreover, the geosynthetic interlayer was able to mitigate reflective cracking propagation. Both interlayers improved fatigue performance.

Peridynamics for Fracture Analysis of Reflective Cracks in Semi-Rigid Base Asphalt Pavement

Reflective cracking is one of the major forms of deterioration in semi-rigid base asphalt pavements. It is, therefore, very important to have a correct understanding of the internal crack propagation mechanism of asphalt pavement to propose the most effective remedial solution(s), which corresponds to that mode of failure. In this study, two-dimensional asphalt pavement layered models are first established by modifying the peridynamics theory. Then, the influence of asphalt overlay thickness and load form on reflective crack propagation is explored. On this basis, the influence of friction between the tire and road surface on reflective crack propagation is analyzed. The results show that increasing the thickness of the asphalt overlay can inhibit reflective crack propagation, and the friction force accelerates reflective crack propagation when the direction of friction is the same as that of reflective crack propagation; otherwise, it inhibits reflective crack propagation. Additionally, the most unfavorable load position is the asymmetrical load when the vehicle is far from the reflective crack.

Mechanistic–Empirical Analysis of Pavement Performance Considering Dynamic Axle Load Spectra Due to Longitudinal Unevenness

Pavement distresses are induced by mechanistic responses in pavement structure subjected to dynamic loads of moving vehicles. Pavement surface evenness deteriorates as pavement distresses propagate, which results in dynamic axle loads and faster pavement deterioration. It is vital to consider the dynamic axle load spectra to predict pavement deterioration using traffic-monitoring data. This study aimed to evaluate the effect of dynamic loads and overweight traffic on asphalt pavement overlay performance using mechanistic–empirical (M–E) pavement analysis. The relationship between dynamic load coefficients (DLCs), axle loads, and international roughness index (IRI) was obtained for accurate quantification of dynamic axle loads. Then the dynamic axle load spectra were derived by shifting the static axle load spectra in weigh-in-motion (WIM) data, given the DLC value. AASHTOWare Pavement ME software was used to analyze pavement performance with static and dynamic axle load spectra, and the impact of overweight traffic on asphalt pavement overlay performance. The impact of dynamic loads on reflective fatigue cracking was distinguished at an early stage of the service period and eliminated after the 10-year analysis period, when the propagation of reflective cracking reached a specific level. On the other hand, the consideration of dynamic axle loads increased the impact of overweight truck traffic on pavement distresses, and pavement structures of major highways tend to be more sensitive to overweight traffic because of greater DLC excitement at higher operational speeds.

Analysis of Temperature Variation and Thermally-Induced Reflective Cracking Potential in Composite Pavements

Reflective cracking is the major distress in composite pavement and can accelerate the deterioration of the whole structure. This paper analyzes the potential for reflective cracking in composite pavements because of thermal cycles. A heat transfer model was first developed to predict cyclic temperature variations with climatic inputs (solar radiation, wind velocity, air temperature, and humidity). Mechanical models were then employed to analyze thermally-induced reflective cracking potential using fracture mechanics parameters. Both models were validated through field measurement of temperature profile and crack propagation. The temperature profile in composite pavement can be predicted accurately from climate data and typical thermal material properties. Because of the temperature variation and gradient in composite pavement, concrete slabs undergo joint opening and curling deformation and stress concentration occurs at the bottom of the overlay. The loading cycles for initiation and propagation of reflective cracking were predicted by empirical equation and Paris’ law. Increasing overlay thickness can extend the pavement service life, but care is needed as different thicknesses offer varying efficiency. Thicker asphalt overlay mitigates reflective crack potential, especially at the crack initiation phase.

Mieszanki mineralno-asfaltowe z lepiszczami upłynnionymi dodatkiem oleju roślinnego do zastosowań jako elastyczne warstwy przeciwspękaniowe

The paper presents the results of research and analyses of the technical characteristics of asphalt mixtures with bituminous binders modified using SBS copolymers with the addition of bio-fluxing agents. The analysed asphalt mixtures have been subjected to water resistance ITSR tests, stiffness modulus IT-CY, and 4PB-PR tests as well as fatigue life test through 4PB-PR test. Basing on the obtained results of tests it has been stated that asphalt mixtures using elastomeric binder with the addition of bio-fluxing agents are characterized by a much greater fatigue life and water resistance in comparison to asphalt mixtures using industrially manufactured binders. Such material solutions can be effectively used as anti-crack layers preventing the propagation of reflective or fatigue cracking to the top layers of road surfaces or their strengthening. Another significant aspect of the conducted research and analyses is the fact that the addition of bio-fluxing agents allows to lower temperatures not only during production of asphalt mixtures but also during incorporation them into road surfaces, what on the other hand is very profitable.

Influence of tack coat on reflective cracking propagation in semi-rigid base asphalt pavement

Asphalt tack coat, which is usually used to ensure a bond between asphalt pavement layers, has a significant effect on mechanics response in asphalt pavement during traffic loading and temperature loading. In this paper, the tack coat is applied between asphalt overlay and semi-rigid base to investigate its influence on reflective crack in asphalt pavement. Cohesive zone model (CZM) in contact property is employed to simulate tack coat. Moreover, extended finite element method (XFEM) is utilized to analyze the reflective cracking propagation. In addition, the combined loads of temperature and moving traffic are applied on the asphalt pavement. The mechanical response, crack temperature and reflective cracking propagation are investigated in semi-rigid base asphalt pavement. Results indicate that maximal tensile stress at crack tip increases with the increase of tack coat modulus while crack propagates. However, the maximal tensile stress at pavement surface decreases with the increase of tack coat modulus while crack propagates. A decrease in tack coat modulus results in a gradual increase in temperature differences of crack initiation and crack completion. Hence, decrease of tack coat modulus between asphalt overlay and semi-rigid base can improve resistance of reflective crack in asphalt pavement.

Reflective cracking from thermal loading in asphalt–concrete composite pavements

Composite pavements made from a hot-mix asphalt layer over a Portland cement concrete slab typically suffer from reflective cracking. Due to repetitive slab joint movements, concentrated stresses occur under the asphalt layer and propagate towards the surface. Recently, top-down reflective cracking has been observed in the field on pavements with no traffic. Previous studies have indicated that asphalt ageing may be the main cause of this problem. However, top-down reflection cracks may occur when upward curling of the concrete slab base creates a concentrated stress on top of the asphalt. Other design parameters such as thickness, stiffness or joint spacing may also influence this cracking behaviour. In the study reported in this paper, reflective crack propagation under thermal loading was investigated to identify potential factors that cause top-down reflection cracks. The results showed that top-down reflection cracks appeared only in composite pavements where the slab base had a low elastic modulus.

Investigation of Thermal Reflective Cracking in Asphalt Pavement Using XFEM Coupled with DFLUX Subroutine and FILM Subroutine

Reflective cracking of asphalt concrete overlays is one of the major distresses in semi-rigid base asphalt pavement, which results in other destroy. Numerous numerical methods are performed to evaluate the fracture mechanism of reflective cracking. However, a very limited amount of the method has been performed to simulate the initiation and propagation of cracking. Extended finite element method (XFEM) is particularly suitable to simulate cracking propagation, which extends arbitrarily. In this paper, the model of semi-rigid base asphalt pavement structure is built and thermal reflective cracking mechanism is studied using XFEM coupled with DFLUX subroutine and FILM subroutine. What’s more, in order to better understand the influences of interface between overlay and upper base on the reflective cracking, cohesive element with different modulus is used to simulate the tack coat. A series of simulations with different initial cracking lengths and interface conditions between overlay and upper base are conducted to work on the reflective cracking mechanism. The results presented in this paper provide a new method to study the propagation of thermal reflective cracking in semi-rigid base asphalt pavement. The temperature field in pavement is easily obtained using DFLUX subroutine and FILM subroutine. What’s more, the conclusion indicates that initial cracking length and interface condition are the critical factors to the initiation and propagation of thermal reflective cracking.

Investigation the influences of geotextile on reducing the thermal reflective cracking using XFEM

A 3D extended finite element model (XFEM) was constructed to investigate the thermal reflective cracking propagation and anti-cracking characteristic of geotextile. Influence factors of tensile modulus and placement location of geotextile were analysed. A temperature cycling test in the material test system was utilised in this work to validate the XFEM. Thermal simulations were performed considering the influences of solar radiation, air convection and air radiation. It has been found that crack initiated and propagated as temperature declining in earlier cycle, and crack length being fixed because of no more severe temperature variation based on maximum principal stress criterion. Geotextile with high tensile modulus had a significant influence on reducing the crack propagation compared with low tensile modulus geotextile or unreinforced situation. Geotextile placing at the bottom of asphalt surface had the best crack resistance influence, and geotextile placed at one-fourth depth from asphalt course bottom was more efficient than placed at other locations in terms of anti-crack propagation.

Use of Natural Geotextiles to Retard Reflection Cracking in Highway Pavements

AbstractReflective cracking is a major phenomenon leading to premature failure of fresh asphalt overlays. Application of a geosynthetic interlayer system to retard reflective crack propagation is a...

Evaluation of geocomposite-reinforced bituminous pavements with Amirkabir University Shear Field Test

Though geosynthetics materials have been proved effective in delaying reflective cracks, they cause a reduction in shear bonding between asphalt layers, reducing their efficiency and introducing new distresses to overlay. While several devices have been developed for measuring the shear bonding between the overlay and the old asphalt pavement, they are not able to apply normal load or are limited in normal load application and cannot be used for thick overlays over geosynthetic. In this work, a new method and apparatus is developed in order to measure the shear bonding between asphalt layers without the aforementioned limitations. This apparatus, named Amirkabir University Shear Field Test, is also capable of measuring the interlayer tensile strength. The obtained results showed acceptable repeatability and good alignment with the results reported in previous studies. Thus, the device was subsequently employed in evaluation of geocomposite-strengthened specimen. The most influential factors on shear bonding were evaluated based on a full factorial design. The results revealed that temperature is the most influential factor on shear bonding between asphalt layers, followed by the tack coat application rate and the geocomposite mesh size. In addition, in order to determine the influence of interlayer shear bonding on reflective crack propagation, the initiation and propagation of reflective crack in specimens with different shear bonding were evaluated. Based on the gathered data, a power law equation relationship between the number of loading cycles and shear bonding was derived for each crack initiation and propagation phase.

Evaluation of shear bonding and reflective crack propagation in a geocomposite reinforced overlay

Geocomposites can be employed with an asphalt overlay to improve the service life of pavements and reduce reflective cracks. However, similar to other geosynthetic solutions, geocomposites can cause de-bonding between asphalt layers, thus reducing pavement longevity. This research focuses on factors that influence the initiation and propagation of shear bonding and reflective cracks in an asphalt overlay. Laboratory double-shear and pull-out tests are conducted, and the shear bonding and pull-out strength of geocomposites in asphalt specimens are calculated. The performance of each specimen in terms of reflective crack initiation and propagation are investigated. A power law model that relates crack propagation to the number of loadings is developed and verified. Observations of geocomposite sliding on the asphalt layer reveal that this phenomenon contributes less than 40% to the overall shear bonding. Analyses reveal that the number of required loading cycles to initiate reflective cracking and crack propagation varies exponentially with the shear bonding between the overlay and the existing layer. Therefore, overlay longevity declines rapidly with decreasing shear bond strength. The exponential relationship is valid irrespective of whether or not the normal load is applied on the interlayer surface. Moreover, the results indicate that temperature is the parameter with most influence on the shear bonding between the layers and the initiation and propagation of reflective cracks, while the tack-coat application rate and geocomposite grid size are less critical. Finally, this study reveals that the decrease in shear bonding between layers both increases the stress relief ability in the interlayer zone and decreases the reinforcement capacity of geocomposite grids. Increased shear bonding between the overlay and existing pavement increases the resistance to reflective cracking.

Cracking and interlayer bonding performance of reinforced asphalt pavements

Reinforcement of asphalt pavements has become a valuable constructive method for preventing reflective cracking and prolonging service life of roads. Although the overall advantages of these reinforcements seem beyond doubt, there is still lack of information about the actual benefit of different systems on the prolongation of the road’s lifespan. Further, it is not clear how they affect the bonding between layers along the pavement’s lifetime. This paper investigates the effect of three types of reinforcement systems on the performance of two layered asphalt pavements, mainly considering: (1) Reflective crack propagation. (2) Shear bonding strength. To that end, model and real pavements were constructed in the laboratory and the field using selected reinforcement systems. Designs with various mesh opening sizes and different bond coatings were considered. Afterwards, the pavements were loaded with a down-scaled (MMLS3) and a full-scale (MLS10) traffic load simulator and their performance was compared to pavements without any type of reinforcement. These devices simulate the effect of traffic-similar loading in a compressed period of time. During the loading phase, the crack formation and propagation was monitored through visual inspections and indirectly by measuring the deformation of the pavements with sensors. The interlayer bonding strength was evaluated by coring the pavements and testing the specimens with a Layer Parallel Direct Shear apparatus. Results showed that two reinforcement systems were generally successful in delaying reflective crack propagation. Only one of the systems presented at least similar or even worse performance than the same pavement without reinforcement. On the other hand, it was found that the bonding properties depend on the reinforcement system type, but that in most cases interlayer bond strength was according to the standard requirements.

Influence of Cracks on the Lifetime of Semi-Rigid Pavements

Abstract This paper focuses on a better understanding of the process of reflective cracking propagation through the pavement structure. A series of finite element numerical simulations were conducted to investigate the initial stress and strain states in typical semi-rigid pavements with and without reflective cracks under traffic loading. It was assumed that reflective-cracks propagate from the base layer to the pavement surface. The influence of selected parameters, such as the load position, overlay thickness, and subgrade quality on stress and strain concentrations was investigated. The behaviour of the pavement structure under repeated traffic loading was analyzed in terms of ground compaction. The original theoretical model proposed by Prof. Andrzej Sawicki was used to predict the deformation of a pavement subgrade subjected to traffic loading. The damaging effect of cracks appearing in the pavement structure was investigated. It was found that even a single crack in the pavement structure may significantly reduce the pavement lifetime.

Reflective Crack Propagation and Control in Asphalt Pavement Widening

Abstract To investigate the reflective crack-propagation behavior and provide control techniques for asphalt pavements widening, the finite-element models were built to simulate the widened asphalt pavement with a latent joint. The developed finite-element model considered the influence factors, including the loading modes (i.e., the symmetrical and unsymmetrical loading modes), the thickness and modulus of the asphalt concrete surface, the modulus of the new and existing stabilized bases, and the sheet stiffness of the reinforced geosynthetic. The finite-element simulation results show that increasing the thickness or reducing the modulus of the asphalt concrete surface effectively delays the propagation speed of the reflective cracks. The cracking potential reaches the minimum when the new and existing bases have a uniform modulus. Additionally, geosynthetic reinforcement across the joints significantly reduces the stress concentration around the crack tip and slows down the propagation of the reflective cracks. These benefits become greater when increasing the sheet stiffness of the geosynthetic. Finally, an experimental study was conducted to investigate the influence of the types of the asphalt overlay and the geosynthetic reinforcement on the reflective crack-propagation behavior. The experimental results indicate that the geosynthetic-reinforced structure with a lower modulus of the asphalt concrete surface significantly increases the fatigue life of widened pavements, and the polypropylene geotextile performs better than the glass-fiber grid in terms of the extension of the fatigue life.

Statistical-experimental study of geosynthetics performance on reflection cracking phenomenon

In this paper, the performance of geogrid and geotextile in asphalt overlay to delay the rate of reflective crack propagation has been studied based on the Response Surface Methodology (RSM). It was tried to investigate the effect of temperature, crack width, type of geosynthetics (polypropylene nonwoven and glass grid) and interactions between these parameters on the reflective crack propagation. In accordance with the obtained results of RSM, some equations were presented to predict with high accuracy the service life (Nf), vertical crack growth rate and initial strain using quadratic polynomial regression model. In addition, a new relationship between Nf and initial strain and temperature was assembled. Based on the obtained results it was identified that the glass grid has the best effect on improving the overlay performance.

Assessment of Composite Pavement Performance by Survival Analysis

The main objective of this paper is to identify the most appropriate rehabilitation method for composite pavements and to evaluate the influence of different factors for the reflective crack development in composite pavement by survival analysis. Four composite pavement rehabilitation methods are evaluated: mill and fill, overlay, heater scarification, and rubblization. Survival analysis is used to evaluate the four methods using three pavement performance indicators: reflective cracking, international roughness index (IRI), and pavement condition index (PCI). Rubblization can significantly retard reflective cracking development compared with the other three methods. No significant difference for PCI is seen in the survival analysis for the four rehabilitation methods. Heater scarification shows the lowest survival probability for both reflective cracking and IRI, whereas overlay results in the poorest overall pavement condition based on PCI. Parametric survival models are employed to further analyze the factors influencing reflective cracking for the four composite pavement rehabilitation methods. Traffic level is found to not be a significant factor for reflective cracking development. An increase in overlay thickness can significantly delay the propagation of reflective cracking for all treatment methods (not including rubblization). Soil types in rubblization pavement sites are assessed, and no close relationship is found between rubblized pavement performance and subgrade soil condition.

Full-scale test of thermally induced reflective cracking in airport pavements

While a reflective cracking propagation rate of 25 mm per year is well accepted by airport pavement engineers, the mechanism of reflective cracking under field conditions has not been fully investigated. A recently completed project sponsored by the Federal Aviation Administration (FAA) led to the development of the Temperature Effect Simulation System (TESS). After an in-depth evaluation of the TESS, full-scale tests to mechanically simulate thermally induced reflective cracking were conducted. A large simulation matrix was first developed to select promising joint opening and displacement rates using three-dimensional viscoelastic-based finite element analyses. A test pavement was then built, instrumented, and tested at the FAA National Airport Pavement Test Facility (NAPTF). This paper describes the successful full-scale test, crack monitoring under accelerated loading, and the data analysis used to evaluate the crack development. Main research conclusions included: (1) “25 mm per year” was quite conservative for thermally induced reflective cracking; (2) Once bottom-up reflection cracks reached a critical length, the crack evolution became very aggressive. For that reason, it is hypothetical to sandwich a strain-relieving hot mix asphalt interlayer between the Portland cement concrete slabs and the new overlay to minimise overlay stresses and to tolerate horizontal movements at the joint. Furthermore, significant insights into the mechanisms and mitigation of thermally induced reflective cracking were obtained and presented. Findings from this study are of immediate assistance to airports supporting light to medium weight aircraft and experiencing significant temperature cycling.