Pavement Structural Capacity Research Articles

The influence of interlayer bonding conditions on the propagation laws of reflective cracks in semi-rigid base pavement based on the DEM and GPR

Reflection cracks represent the predominant internal distress in semi-rigid base asphalt pavements and often accompanied by additional secondary issues that detrimentally affect the pavement structural bearing capacity. The propagation and deterioration of reflective cracks are affected by many factors, for example the interlayer bonding conditions. It is crucial to identify the propagation and deterioration of reflective cracks to prolong the life of pavement structure. The purpose of this article is to explore the influence of interlayer bonding conditions on the propagation laws of reflective cracks. This work employs the discrete element method(DEM) to explore the propagation patterns of reflection cracks accompanied different bonding conditions between the surface layer and base layer subjected to moving load. The results of discrete element simulation reveal a three-phase progression laws when the reflective cracks expand from the base layer to the pavement surface，involving rapid propagation, stable propagation, and failure process. With the interlayer bond strength decreases, expansion of reflective crack is significantly accelerated. Meanwhile, once the critical bond strength threshold is reached, complete debonding will occur between the surface and base layers. The results are ultimately verified through the core sampling from practical engineering using three-dimensional (3D) ground penetrating radar(GPR) detection, along with the radar image recognition of reflective cracks and poor interlayer bonding. The results will serve as a foundation for researching the mechanism and treatment measures for two internal pavement distress, namely reflection cracks and poor interlayer bonding.

A Review and Comparison of FWD and Benkelman Beam in Evaluation of Pavement Structure Capacity

A Review and Comparison of FWD and Benkelman Beam in Evaluation of Pavement Structure Capacity

Assessing Remaining Service Life and Structural Performance of Substandard Airfield Pavement for Low-Volume Traffic with an Accelerated Aircraft Loading Simulator

A field evaluation to investigate the remaining service life and structural capacity of a substandard airfield pavement under accelerated aircraft traffic is reported in this paper. The pavement test section consisted of a relatively thin asphalt concrete layer with a considerably thin base course. A single-wheel aircraft simulator was used to mimic the loading conditions of two cargo aircrafts, C-17 and C-130. Two operating tire inflation pressures, namely normal tire pressure (NTP) and approximately 20% below NTP (reduced tire pressure), were investigated as a strategy to improve the pavement’s service life while maintaining the total aircraft load. The rut development was the primary pavement distress measured while the pavement structural capacity was routinely assessed with a heavyweight deflectometer and a portable lightweight deflectometer (LWD) at selected traffic intervals. PCASE software was also used to computationally predict the service life of the selected substandard airfield pavement. Overall, this nonstandard airfield pavement exhibited acceptable performance for an expedient aircraft mission with a C-17 (less than 100 passes) or a sustainment aircraft mission with a C-130 (less than 5000 passes). From this study, reducing the operating tire pressure did not influence the allowable number of passes to failure, considering the failure criterion as a rut depth of 25.4 mm. It was found that the LWD showed promise to monitor deterioration of substandard airfield pavements during aircraft operations. The PCASE results were not in full agreement with the field study and outlined the critical need of improving the current evaluation technique specifically for substandard airfield pavements.

Using Cement as Filler to Enhance Asphalt Mixes Performance in Hot Climate Regions

This paper investigates the addition of different percentages of ordinary Portland cement as a filler in conventional asphalt concrete for a range of heavy traffic. Road pavement agencies in hot areas face the daunting challenge of preserving their pavements in a fair to good condition to increase their lifespan. This challenge is due to the high occurrence of permanent pavement deformation via rutting, which is one of the major distress factors influencing pavements. This is a particularly serious issue in hot and arid countries which are closely associated with various aggravating factors. These aggravating factors include the choice of bitumen binder viscosity, the type of bitumen, the available low-quality materials, and the high environmental temperatures. Ultimately, poor performance will show within the first few years of service as permanent deformations such as rutting, shoving, and depressions. The examined properties include the resilient modulus and the resistance to rutting. Findings indicate that the resistance to rutting and the rigidity of the asphalt concrete are both substantially increased as the cement content is increased. Moreover, to meet the heavy traffic spectrum requirements, increasing the embedded cement content in the asphalt concrete improves pavement structural capacity. Finally, based on the rigidity expected for different cement levels, design curves are provided for pavement design in hot climates using low quality aggregate materials.

Light Weight Deflectometer Evaluation of Low-Volume Road Structural Deterioration under Rapidly Increased Traffic Patterns

When evaluating low-volume road (LVR) condition, there is not a tremendous emphasis on structural capacity, since deterioration is typically caused by environmental factors. However, in cases where LVRs experience rapidly increased traffic loading, structural condition becomes important. The research objective was to determine whether the light weight deflectometer (LWD) can be used as a structural evaluation tool for LVRs. This study explored three major factors that affect measurement of flexible pavement structural capacity: load-induced deterioration (e.g., rutting and cracking), soil moisture, and asphalt temperature. Four full-scale flexible pavement test items were constructed with varying base-course materials and layer thickness typical of LVR. Instrumentation was installed during construction to monitor moisture content, temperature, and ambient weather conditions. Accelerated traffic was applied with a 4-axle military truck. A total of 10,000 cumulative vehicle passes were completed. Falling weight deflectometer (FWD) and LWD testing equipment were utilized to measure pavement structural condition at selected traffic intervals. The LWD was shown applicable for LVRs experiencing accelerated traffic. The LWD is portable and is more efficient for LVRs when high rut depths are permitted. The LWD tracked trends of the FWD; therefore, the LWD, based on these experiments, can be recommended for use in lieu of FWD to assess structural condition in some LVR conditions.

Using Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) to monitor the effects of seasonal moisture variation on the structural capacity of pavements

Moisture fluctuations in pavement foundation due to environmental conditions (e.g., heavy precipitation, freeze–thaw cycles, groundwater table variation, etc.) can significantly affect pavements’ short- and long-term performance. Moisture variation in the pavement foundation is often monitored as a way to anticipate the structural capacity of pavements. Thus, the ability to monitor moisture variation through a proven non-destructive technology (NDT) such as Ground Penetrating Radar (GPR) would be beneficial for asset management by transportation agencies. This paper summarizes the Minnesota Department of Transportation’s (MnDOT) efforts at validating the use of GPR to monitor moisture in the pavement foundation through comparison with Falling-Weight Deflectometer (FWD) parameters that represent the structural condition of the pavement. The results in this paper are based on GPR, FWD and in-place moisture sensor data collected over 17 months on MnROAD instrumented test sections. The pavement test sections considered in this study included unbound aggregate bases (UAB) with virgin and recycled materials (i.e., RCA and RAP) covering a broad range of geotechnical behavior. Previous efforts established a strong correlation between GPR-based moisture measurements and sensor-based moisture measurements. This correlation is further validated by investigating the relationship between GPR-based moisture measurements and FWD-based indices for structural capacity. The observed correlation is reasonable and in good agreement with the expected correlation between volumetric moisture content (VMC) of the base layer and the structural capacity of a pavement. This agreement validates the use of GPR to monitor moisture in pavement foundation. GPR is not a replacement for FWD, but it can be used in asset management efforts in addition to FWD to assess moisture fluctuation in pavement foundation during and after extreme environmental events (e.g., flooding, freeze-thawing) to determine when and where FWD testing may be necessary.

Analiza MES i zmęczeniowa nawierzchni podatnych na podstawie modelowania rozkładu temperatury

The effect of temperature on asphalt pavement structure is of great importance due to the nature of binder used in the asphalt layers. An equivalent temperature is commonly applied to eliminate the effect of temperature dependence in calculations of mechanical properties of the asphalt and of the pavement. Equivalent temperatures, applied as constant values, are supposed to have the same effect on fatigue behavior of the pavement in the period of one year as the real varying weather conditions. The aim of the presented research was to compare the behavior of the pavement under realistic temperature data throughout a single year with the results of the traditional pavement design method. Temperature data were obtained from a previously established weather station. Binder viscosity and asphalt dynamic modulus were defined based on the temperature profile for asphalt layers divided into 19 sublayers. This subdivision was introduced to better reflect the changes in strength characteristics of the asphalt layers along the depth of the structure. Comparison with the simple calculation using the equivalent temperature method showed that the detailed model outlined in this paper can provide better prediction of the overall pavement structural capacity. The focus of this study is to apply asphalt layer discretization to reflect temperature variation and its influence on changes in strength properties of asphalt mixtures. Temperature at each sublayer was estimated using the German specification, dynamic modulus was determined using the Witczak model, and the structural analysis was performed employing the finite element method.

A model for variation with time of flexiblepavement temperature

Abstract The bituminous material performance is affected basically by the prevailing temperatures. The mechanical properties of these materials can vary significantly with the changes in the temperature magnitude. Hot mix asphalt (HMA) is a visco-elastoplastic material, so the pavement structural capacity is affected by the temperature variations. To determine the characteristics of the strength of the flexible pavement rationally, the prediction of the distribution of temperature in HMA pavement layers is a must. Heavy loadings subjected to highways and roads can cause serious deterioration to the HMA pavements. In this research, the temperature for three thicknesses of asphalt pavement structure was measured, and the air temperature to predict a model explains the relationship between the temperature and the depth of the pavement structure. The suggested model was successfully validated utilizing the data from three depths of asphalt pavement structure and the temperature on the surface of the asphalt pavement. The developed model consists of two independent variables, which are the depth within the pavement and ambient air temperature. The predicted model will be useful for the pavement designers those in need to predict the temperature of the profile of pavement to determine the engineering characteristics of field pavement.

Using Falling Weight Deflectometer (Fwd) and Ground Penetrating Radar (Gpr) to Monitor the Effects of Seasonal Moisture Variation on the Structural Capacity of Pavements

Using Falling Weight Deflectometer (Fwd) and Ground Penetrating Radar (Gpr) to Monitor the Effects of Seasonal Moisture Variation on the Structural Capacity of Pavements

Generalized Methodology to Develop Mechanistically Informed Asphalt Mixture Layer Coefficients for AASHTO 1993 Pavement Design Approach

This paper presents a generalized framework for determining mechanistically informed layer coefficients (a-values) for asphalt mixtures in the AASHTO empirical pavement design approach. The layer coefficients influence the layer thicknesses and consequently the structural capacity of pavements. Therefore, it is critical to determine reliable mechanistically informed a-values. A set of 18 commonly used asphalt mixtures in New Hampshire was selected for investigation including different types of hot mix and cold central plant recycled mixtures that are used as wearing, binder, and base course layers. Laboratory characterization was conducted using the complex modulus, semi-circular bend, and direct tension cyclic fatigue testing methods. The mixtures were evaluated using three performance index parameters: complex modulus rutting index parameter, rate-dependent cracking index parameter, and a new continuum damage parameter ([Formula: see text]). The measured field performance of wearing course mixtures in terms of International Roughness Index was used to back-calculate the in situ performance-based layer coefficients (aIRI-values). Using a normal distribution function, the results from performance testing were incorporated with the aIRI-values to develop mechanistically informed mix-specific layer coefficients. In addition, a typical layer coefficient at specific reliability levels for each mix category including hot mix wearing course, hot mix binder and base course as well as cold central plant recycled mix course are proposed for New Hampshire. The recommended a-values are 0.48 for hot mix wearing, 0.41 for hot mixed binder and base, and 0.28 for cold recycled base mixtures; these are approximately 25% higher than the currently used a-values in New Hampshire.

3D-finite element pavement structural model for using with traffic speed deflectometers

ABSTRACT The traditional practice for pavement structural capacity evaluation is mostly dependent on the falling weight deflectometer (FWD) measurements. However, this practice has several challenges due to its stationary nature. Recently, a Rolling Weight Deflectometer (RWD), capable of measuring the pavement deflections at regular traffic speeds, has been introduced into the market. This research aims to develop a finite element (FE) model simulating pavement structural response under the moving RWD loads. This model could be further utilised for accurately estimating pavement layers mechanical characteristics. The model was successfully validated utilising the RAPTOR (a commercially available RWD) data collected on the National Center for Asphalt Technology (NCAT) test track. A good correlation between the simulated and the measured values was found – yielding an average root mean square percentage error (RMSPE) of approximately 2.40% between the RAPTOR and the FE deflections.

Empirical-Markovian approach for estimating the flexible pavement structural capacity: Caltrans method as a case study

An Empirical-Markovian approach is proposed to estimate the pavement structural capacity as a function of key stochastic and design parameters. The key stochastic parameters are the initial and terminal deterioration transition probabilities typically estimated from pavement distress records. These two transition probabilities have a major impact on the pavement performance trend predicted using Markovian processes. In addition, typical pavement design factors are included as related to traffic loadings, materials properties, and climate conditions. In particular, two distinct Empirical-Markovian models are developed to estimate the pavement structural capacity in terms of relative strength indicators such as the structural number (SN) and gravel equivalent (GE). The first model can estimate the structural capacity based on the initial transition probability and relevant design parameters, while the second one deploys the terminal transition probability along with other design parameters. The recommendation is to use the higher of the two structural capacity values estimated for a particular pavement project. The sample models presented based on the California Department of Transportation (Caltrans) design method have resulted in good model fittings as demonstrated by the various deployed statistics and error analysis, thus indicating the usefulness of the proposed Empirical-Markovian approach in estimating the pavement structural capacity for rehabilitation and design purposes. The model exponents can be obtained from solving a linear system of equations using data from a small project sample or solving a multi-variable linear regression model when a large road sample is available. The latter case provided sample generalized models with statistics indicating their high significance.

Toll concessions: management strategy and deflection performance of the N3TC network in South Africa

This paper discusses the N3 Toll Concession’s approach to optimise management of the road network during the Concession Period and to achieve the end of Concession requirements. To be able to achieve this, accurate traffic and performance data is essential. On the N3, traffic is continually measured on the network, and the condition and performance in terms of rutting, roughness, surface texture and deflections is measured annually. Deflections are considered to be a good indicator of the structural capacity of pavements, and are expected to increase with time and traffic carried. This assumption underlies many available pavement design methods. This paper shows that for 22 representative sections on the N3 Toll Route, the deflections do not increase with time or traffic within the periodic maintenance periods. This leads to the conclusion that the use of deflections as an indication of remaining structural capacity for the heavy duty N3 pavements in conventional pavement design analysis is not appropriate.

Monitoring analysis of two pavement sections of highway BR-448/RS included in the Asphalt Thematic Network Project

Highways are the mode of transport used for the transportation of the majority of loads and passengers in Brazil; however, the lack of conservation of pavements has caused several economical losses to the country. Only through suitable pavement management the rehabilitation measures taken might ensure a satisfactory level of service. The present research aimed at evaluating the performance of two pavement sections of the federal highway BR-448/RS, in southern Brazil. For three years, the evolution of the pavement structural capacity and functional condition were followed in order to propose performance trends. Deflections, permanent deformations, and surface defects surveys scarcely varied and were quite low due to the thick asphalt layers used (19 cm). On the other hand, segregation of the asphalt mixture was observed when the final layer was laid. That segregation affected pavement texture, reduced tire-road friction, and caused the formation of surface water films; thus, reducing the road safety. In general, the proposed trend lines predicted quite accurately the pavement performance throughout the period evaluated and will be used in the MeDiNa software database for the creation of a new Brazilian pavement design method.

Asphalt concrete master curve using dynamic backcalculation

ABSTRACT The dynamic backcalculation of pavement layer properties, and more specifically the ability to determine the asphalt concrete master curve, using Falling Weight Deflectometer (FWD) data has caught the attention of many researchers for years. The damaged or aged master curve of existing pavement structures allows the accurate prediction of the pavement structural capacity and remaining life – a goal that cannot be achieved through laboratory testing. To address this need, the authors developed a dynamic backcalculation application that employs the ABAQUS software for forward calculation using implicit dynamic analyses, and the Newton-Raphson’s root-solving algorithm for optimisation. The capabilities of the application were demonstrated for three simulated flexible pavement structures and two asphalt concrete mixes using 40 combinations. The asphalt concrete moduli at the FWD most dominant frequencies around 17 Hz, and the variables of unbound layers converged to the exact values in few iterations for all combinations. The master curves, and mainly the maximum moduli, were reliably determined to less than 1% and 4% error for about 60% and 85% of the combinations, respectively. The potential for determining the master curve and maximum modulus was shown to be dependent on the asphalt concrete mix, asphalt concrete temperature and pavement structure.

Machine Learning for Pavement Performance Modelling in Warm Climate Regions

Accurate pavement performance modelling is an essential requirement for cost-effective pavement design and enhances pavement management decision making. Due to the complexity of the pavement structure and pavement response, dominant failure mechanisms may vary depending on the climate region: cold or warm. This study investigated the significance of pavement design factors on pavement performance in warm regions and compared them to set of factors previously identified for cold regions. An artificial neural network (ANN) supported by a forward sequential feature selection algorithm was employed to identify the most significant design factors prevailing in warm climate regions using data extracted from the Long-Term Pavement Performance database. In addition, five machine learning techniques were utilized to model the pavement performance in warm regions, namely: regression tree, support vector machine, ensembles, Gaussian process regression, and ANN. Moreover, conventional regression modelling was used for comparison assessment. The analysis revealed seven design factors that are significantly impacting asphalt pavement performance in warm regions: initial roughness, relative humidity, average wind velocity, average albedo, average emissivity, traffic volume, and pavement structural capacity. The results indicate that pavement performance in warm climate regions is dominated by different environmental factors than those found for cold climate regions. The ANN modelling technique produced the most accurate asphalt pavement performance models.

Application of Ground Penetration Radar and Light Weight Deflectometer for Pavement Quality Control and Quality Assessment

Pavement evaluation requires the frequent assessment of structural and functional condition. Earlier functional assessment of pavement were rapid and non destructive whereas structural evaluation required destructive testing. With growth in technology the light weight deflectometer (LWD) and ground penetrating radar (GPR) replaced the destructive testing in most part of the world. This paper highlights the use of LWD and GPR as non destructive testing tool in pavement evaluation. LWD and GPR test were conducted on the granular material to investigate the composite modulus of layer for their quality assessment. LWD test results were found to be significantly affected by the base plate diameter, contact between plate and surface layer, whereas drop height does not show significant difference on composite modulus. GPR technology has showed its versatility in pavement layer thickness evaluation, void and crack detection, and sub surface exploration. Ground coupled GPR has been used for subsurface exploration. At project level pavement management system, the combined use of GPR and deflection testing device has resulted in effective monitoring of pavement structural capacity. Hence LWD and GPR had showed its effectiveness for quality control and quality assurance (QC/QA) in PMS.

Effect of anisotropy and nonlinearity assumptions on the predicted surface deflections

The analysis of pavement responses such as surface deflections in flexible pavement is quite important for mechanistic pavement design and for rehabilitation design. In addition, in the mechanistic empirical design, the multilayer linear elastic and isotropic behavior is commonly used to model flexible pavements. However, it is well known that unbound granular base course and subgrade materials are nonlinear and anisotropic in nature. It is therefore important to understand the effect of the modelling assumptions on pavement responses and which modelling technique provides the closest matching to the actual field measurements. In this paper, surface deflection simulations under the effect of the FWD loading and pavement structure were modelled utilizing both isotropic and cross anisotropic analyses for 3250 pavement sections. Two types of pavement structures were investigated in this study: thin and thick surface flexible pavements. Thin surface asphalt pavements are made either of unbound granular base with surface treatment such as chip seals or thin asphalt concrete layer of 50 mm or less which is commonly used for low traffic rural roads in many parts around the world. Thick asphalt pavement is made of granular unbound base with asphalt concrete layer of greater than 100 mm and up to 240 mm thickness. The actual field measurements of pavement surface deflections using FWD were compared with both linear elastic isotopic and nonlinear cross anisotropic computer simulations results. The linear isotropic analysis was found to overestimate pavement structural capacity quite considerably for thin asphalt pavements. However, both linear isotropic and nonlinear cross anisotropic provided close matching to field results for thick asphalt pavements.

Numerical assessment of the structural contribution of porous friction courses (PFC)

Porous Friction Courses (PFC) are Hot Mix Asphalt (HMA) materials with high air void contents that are placed as thin layers on top of conventional flexible pavements to obtain safety and noise-reduction benefits. These layers are considered an additional component of the pavement and, consequently, their structural contribution is not typically considered. This paper uses Finite Element (FE) modelling to evaluate the potential contribution of PFCs with different thicknesses to the overall structural capacity of three different flexible pavements. The results show that PFC layers do contribute to the pavement structural capacity but that this contribution strongly depends on their different microstructural and geometrical characteristics.

Evaluation of the structural capacity of rigid pavements at the network level

Pavement surface deflection has been used by researchers and highway agencies to assess the structural condition of the pavement structure. None of the currently available approaches provides an acceptable evaluation method for the rigid pavement structural capacity at the network level. In this research, pavement structural ratio (PSR) and overall pavement structural index (OPSI) were derived from deflection bowls generated from finite element simulations and validated by actual field deflection data measured by falling weight deflectometer and performance data extracted from long-term pavement performance database. The PSR parameter provides structural evaluation of the rigid pavement slab and the base course above the subgrade only. Whereas, OPSI parameter provides an overall evaluation of the pavement structure and the subgrade.