Pavement Test Research Articles

Accelerated Pavement Testing in Slovakia

Highway administrators, engineers, and researchers often face problems for which information already exists, either in documented form or as undocumented experience and practice. Accelerated pavement testing is one way where researchers can find answers for these problems. Full-scale accelerated pavement testing APT forms a vital link between the laboratory evaluation of materials used in pavement layers and the field behavior of these materials when combined into pavement structures. For many years APT provided pavement engineers with knowledge that improved their understanding of pavement materials and structures, as well as their behavior under typical traffic and environmental loading. It formed the basis for developing various theories about pavement behavior and supports most of the current pavement design methods.

Framework to Improve the Pavement ME Design Unbound Aggregate Rutting Model by Using Field Data

The AASHTOWare Pavement ME Design and the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures provide a methodology for analyzing response and predicting rutting performance of unbound granular pavement layers. However, this methodology has been reported to have low sensitivity to the properties of the base and subbase and the subgrade. The primary objective of this paper is to provide a framework for improving the prediction ability of the Pavement ME Design rutting model for unbound aggregate pavement layers. This goal was achieved by using accelerated testing data from full-scale pavement test sections constructed with different aggregate materials. These test sections were loaded to failure by using the accelerated transportation loading assembly at the University of Illinois. Nonlinear finite element solutions of the pavement test sections were studied so that stress-dependent modulus characterization models could be used for the anisotropic unbound aggregate base and isotropic subgrade. This approach enabled prediction of realistic stress states and accurate pavement responses. Realistic stress states and the use of a shear stress ratio concept were incorporated into the proposed framework needed to improve the rutting predictions of the Pavement ME Design damage model. Finally, a definite correlation appeared to exist between shear stress ratio values and the shift factors that were proposed for the adjustment of the model’s predicted rut depths so they would match the field-measured performance trends. The framework studied in this paper is applicable to the three-parameter Tseng–Lytton rutting model, the original version of the Pavement ME Design damage model, for the modifications needed to generate improved granular layer rut predictions throughout pavement design service life.

Advanced Modelling for Rigid Pavement Assessment Using HWD

Armed with its experience of the flexible airfield pavement testing for which an advanced dynamical method was developed and a technical guidance released in 2014, STAC took on the challenge of transposing the methodology to rigid pavements.The approach is the same as for flexible pavement: first the development of a mechanical model allowing calculating stresses and strains in the concrete slab under Heavy Weight Deflectometer (HWD) impulse loading, which can be used in a backcalculation process, and then the implementation of damage prediction laws.The developed mechanical model is based on a 3D finite element (FE) technique. It enables considering either static or dynamical impulse HWD loading, applied on the concrete slab center, slab edge, or slab corner, for an isolated slab.A thermo-mechanical model is included in the FE model and enables computing the slab deformation as a function of the thermal gradient in the slab. The resulting deformation can be used as initial geometrical input, as well as related internal stresses, for the above mechanical calculation.The numerical results have been compared with experimental data from HWD tests performed on the STAC's full-scale instrumented test facility. The latter comprises a 700 m2 rigid pavement including dowelled and non-dowelled areas. It is instrumented in the neighborhood of slab corners and middle of slab edges with sensors measuring vertical displacements on the loaded slab and the adjoining ones, and tensile strains at the bottom of the slab. An HWD survey was conducted on both dowelled and non-dowelled areas, including multi-height tests at different positions on the instrumented slabs.This paper first describes the dynamical 3D FE modeling developed, and the numerical results obtained. Then, the results of the full-scale validation are presented, which include comparison between expected surface deflections and HWD measurements, and comparison between predicted strain values and those recorded by embedded sensors.

Comparison of Uni and Bi-directional Load Induced Rutting in Flexible Pavement with Accelerated Pavement Testing Facility (APTF)

The Indian Road Network is the second largest in the world after U.S. and flexible pavement is the most sought pavement in India. In fact, majority of roads in India (more then 90%) are flexible pavement due to ease of construction and initial cost of construction. The design of flexible pavement in India mainly consider rutting and fatigue life as per Indian Road Congress (IRC:37-2001). There are many factors that affects the rutting of the flexible pavements namely speed, contact pressure, temperature, quality of construction, wandering of the vehicle and layer thickness etc. The present paper focuses on rutting itself which is governed by direction of traffic, while keeping other parameters nearly same. The effect of movement of heavy traffic in a channelized as well non channelized way on pavement resulting in rutting has been studied with the state of art equipment, Accelerated Pavement Testing Facility (APTF), by CSIR-CRRI, with the aim of finding the performance through evaluation for uni and bi-directional rutting characteristic of pavement. Rutting is the longitudinal depression in the wheel path of the pavement. It can either be instability or structural rutting. Rutting can cause hydroplaning, increase in vehicle operating cost and psychological problems while driving. The amount of rutting under unidirectional loading was compared with the bidirectional loading case with almost the same number of passes. The change in air voids were also calculated from the rutted as well as non rutted portion. The magnitude of rutting under unidirectional loading was more as compared to the one under bi-directional loading. The comparative study has clearly demonstrated that the damage to flexible pavement by rutting with unidirectional load is more critical and nearly twice as compared to the damage by bi-directional loading. This aspect stresses the need for accounting the directional movements in our pavement design guidelines and depending on whether testing uni-directional or bi-directional, a different “transfer function” or relationship to real in service loading is required.

Pavement Working Platforms Constructed with Large-Size Unconventional Aggregates

As a sustainable construction practice, recent research efforts of the Illinois Department of Transportation (DOT) have been focused on an engineered approach for developing construction specifications and performance validation of the use of large-size virgin and recycled unconventional aggregates in soft subgrade remediation. The Illinois DOT Bureau of Design and Environment has issued a special provision that specifies certain gradation bands for improved aggregate subgrade to allow enhanced use of large rocks from both primary crusher type virgin and recycled sources. Nevertheless, laboratory tests are usually inadequate for characterizing the properties and engineering behavior of large-size unconventional aggregates. Therefore, the recent field performance evaluation study using accelerated pavement testing was initiated at the University of Illinois with 12 full-scale pavement working platforms constructed with selected large-size virgin and recycled materials, including reclaimed asphalt pavement, recycled concrete aggregate, and demolition waste. For in-depth performance testing and evaluation, this paper describes test section construction and quality control sequences conducted at different phases of the study, including state-of-the-art field aggregate and pavement layer imaging techniques. The rutting performance trends of test sections were investigated in light of innovative test devices and techniques, including variable energy penetration testing, geoendoscopy, transverse ground-penetrating radar scans, as well as postfailure trenching images. Penetration of large rocks into the soft subgrade was effective in achieving a stable construction platform. Moreover, reclaimed asphalt pavement as a granular pavement layer was prone to large permanent deformations.

Laboratory and Field Evaluation of Florida Mixtures at the 2012 National Center for Asphalt Technology Pavement Test Track

The Florida Department of Transportation recently conducted a study at the National Center for Asphalt Technology Pavement test track to study cracking potential in asphalt mixtures. While cracking was the primary objective, the Florida Department of Transportation also wanted to ensure that no rutting would occur. Four mixtures were placed in test sections 100 ft in length. The four mixtures included two virgin mixtures: one used a polymer-modified binder and the other used a hybrid ground tire rubber and polymer-modified binder. The two other mixtures used combinations of polymer-modified binder with reclaimed asphalt pavement (RAP) or recycled asphalt shingles (RAS) or both. Conventional laboratory testing for rutting and cracking was performed on each mixture. In addition to the laboratory testing, field performance was assessed for rutting, cracking, and ride quality. Laboratory correlations were developed with field performance; however, because of the rapid crack propagation in the RAP–RAS test section, the correlations between 5 and 10 million equivalent single-axle loads (ESALs) changed significantly. The best correlations were developed between the resilient modulus of the mixture and cracking at 5 million ESALs and also the dissipated creep strain energy of the mixtures and cracking at 10 million ESALs. Overall, none of the mixtures experienced severe cracking in 10 million ESALs of trafficking.

Performance of Low-Volume Roads with Wearing Course of Silty Sand Modified with Rice Husk Ash and Lime

Rice husk ash (RHA) is a by-product of rice milling. Its use as soil stabilizer is a way to replace the final disposal with environmental benefit. However, RHA is not cementitious itself but when mixed with lime forms cements which improve the soil properties. A research of performance of a silty sand modified with RHA and lime as wearing course layer of low-volume roads was conducted through two full-scale test sections with different pavements built in Artigas, northern Uruguay. The alkaline reactivity of RHA is low because the husk burning is not controlled. The soil-RHA-lime mix design was conducted according to the Thompson's Method. The pavement test sections were monitored through deflection measures by Benkelman beam and observations of surface condition. The deflections decreased over time in both test sections due to the development of cementation of the study materials. After one year, the dust emission was reduced, the wet skid resistance of pavement surfaces improved and there was not rutting. The researched pavements have had a good performance under the existing traffic and environmental conditions, demonstrating that wearing course layer of silty sand modified with RHA and lime is an alternative to improve the condition of low-volume roads and to replace the final disposal of RHA, with environmental, social and economic benefits.

A Measuring Instrument for Off-road Vehicle Performance Testing

An overall description of a measuring instrument, wheel force transducer (WFT), developed for off-road vehicle performance testing is presented in the paper. For the research of off-road vehicle performance, it is important to determine the forces and torques as a response of the interaction between the wheel and the terrain. The WFT developed provides a solution of the direct measurement of the physical quantities. The WFT was designed as an automatic real-time data acquisition device with the wireless transmission technology. In the aspect of mechanical structure, only minor modifications of the wheel rim and two flanges were required for the installation of the WFT. The elastomeric of the sensor was designed with excellent mechanical strength for wheeled vehicles of weights ranging from 1.2 to 15 ton. Field tests were conducted after static calibration and dynamic calibration. The WFT was installed on the two front wheels of a 1.6-tone weight car. In preliminary field test, various vehicle maneuvers were executed for the validation of the validity, reliability and accuracy of the whole system, which was demonstrated by the test results. Six kinds of special testing pavements were selected to simulate the off-road situations. From the results, great potential of the WFT system is indicated in the application of off-road vehicle performance testing.

Design Validation through Analysis of Concrete Modular Road Behavior under Static Axial Loads

PURPOSES : The purpose of this study is to validate the design criteria of the concrete modular road system, which is a new semi-bridge-type concept road, through a comparison of numerical analysis results and actual loading test results under static axial loads. METHODS : To design the semi-bridge-type modular road, both the bridge design code and the concrete structural design code were adopted. The standard truck load (KL-510) was applied as the major traffic vehicle for the design loading condition. The dimension of the modular slab was designed in consideration of self-weight, axial load, environmental load, and combined loads, with ultimate limit state coefficients. The ANSYS APDL (2010) program was used for case studies of center and edge loading, and the analysis results were compared with the actual mock-up test results. RESULTS : A full-scale mock-up test was successfully conducted. The maximum longitudinal steel strains were measured as about 35 and 83.5 micro-strain (within elastic range) at center and edge loading locations, respectively, under a 100 kN dual-wheel loading condition by accelerating pavement tester. CONCLUSIONS : Based on the results of the comparison between the numerical analysis and the full-scale test, the maximum converted stress range at the edge location is 32~51% of the required standard flexural strength under the two times over-weight loading condition. In the case of edge loading, the maximum converted stresses from the Westergaard equation, the ANSYS APDL analysis, and the mock-up test are 1.95, 1.7, and 2.3 times of that of the center loading case, respectively. The primary reason for this difference is related to the assumption of the boundary conditions of the vertical connection between the slab module and the crossbeam module. Even though more research is required to fully define the boundary conditions, the proposed design criteria for the concrete modular road finally seems to be reasonable.

Pavement diagnosis accuracy with controlled application of artificial neural network

Results of research studies, the amount of input data available in pavement management system databases, and artificial intelligence methods serve as versatile tools, well-suited for the analysis conducted as a part of pavement management system. The key source of new and to be employed knowledge is provided. In terms of e.g. assessing thickness of bituminous pavement layers, the default solution is pavement drilling, but for the purposes of pavement management it is prohibitively expensive. This paper attempts to test the original concept of employing an empirical relationship in an algorithm verifying results produced by the artificial neural network method. The assumed multistage asphalt pavement layer thickness identification control process boils down to evaluating test results of the road section built using both, reinforced and non-reinforced pavement structure. By default, the artificial neural network training set has not included the reinforced pavement sections. Hence, it has been possible to identify “perturbations” in assumptions underlying the training set. Pavement test section points’ results are indicated in the automated manner, which, in line with implemented methods, is not generated by perturbations caused by divergence between actual pavement structure and assumptions taken for purposes of building pavement management system database, and the artificial neural network learning dataset is based on.

Impact of farm equipment loading on low-volume concrete road structural response and performance

The rapid increase in farm equipment size in the United States of America agricultural industry has raised significant concerns regarding its impact on the low-volume road infrastructure. The study described in this paper investigated the impact of heavy farm equipment (or agricultural vehicle) on the structural behaviour of rigid pavement system. A series of full-scale traffic tests were conducted at the Minnesota’s Cold Weather Pavement Testing Facility (more commonly known as MnROAD) on two existing low-volume rigid pavement sections: (1) to study the effects of agricultural vehicle and weights, traffic wander pattern, pavement structure, and environmental factors on rigid pavement responses (deflections, strains and stresses), and (2) to compare these responses with those of a standard 356 kN (80 kips) five-axle, semi-trailer truck for assessing relative rigid pavement damage caused by heavy farm equipment. Numerical analyses were also carried out for rigid pavement fatigue damage estimations by simulating field test conditions. The Finite Element Model was able to predict rigid pavement responses under complicated heavy agricultural farm equipment loading. The study findings revealed that seasonal change, traffic wander, vehicle loading/configurations, pavement thickness, slab length and modulus of subgrade support are all important factors to be considered in designing rigid pavement subjected to heavy farm equipment loading. The use of tandem or tridem axles is recommended for all farm equipment because those axles help to distribute the load and minimize rigid pavement damage.

Performance Evaluation of Carbon-Reducing Soil Pavement using Inorganic Binder

PURPOSES : This study intends to develop an inorganic soil pavement material using industrial by-products and to evaluate its applicability as a road pavement material. METHODS : In this study, a compressive strength experiment was conducted based on the NaOH solution molarity and water glass content to understand the strength properties of the soil pavement material according to the mixing ratio of alkali activator. In addition, the strength characteristic of the inorganic soil pavement material was analyzed based on the binder content. The performance of the soil pavement was evaluated by conducing an accelerated pavement test and a falling weight deflectometer (FWD) test. RESULTS : As a result of the soil pavement material test based on the mixture ratio of alkali activator, it was identified that the activator that mixed a 10 M NaOH solution to water glass in a 5:5 ratio is appropriate. As a result of the inorganic soil pavement materials test based on the binder content, the strength development increased sharply when the amount of added binder was over 300 kg; this level of binder content satisfied 28 days of 18 MPa of compression strength, which is the standard for existing soil pavement design. According to the measured results of the FWD test, the dynamic k-value did not show a significant difference before or after the accelerated pavement testing. Furthermore, the effective modulus decreased by approximately 50%, compared with the initial effective modulus for pedestrian pavement. CONCLUSIONS : Based on these results, inorganic soil pavement can be applied by changing the mixture proportions according to the use of the pavement, and can be utilized as road pavement from light load roads to access roads.

Pavement thickness and stabilised foundation layer assessment using ground-coupled GPR

Experimental results from field and laboratory investigations using a ground-coupled ground penetrating radar (GPR), dielectric measurement, magnetic imaging tomography (MIT) and dynamic cone penetrometer (DCP) tests are presented. Dielectric properties of asphalt pavement and stabilised and unstabilised pavement foundation materials were evaluated in the laboratory in frozen and unfrozen conditions. Laboratory test results showed that dielectric properties of materials back-calculated from GPR in comparison to dielectric gauge measurements are strongly correlated and repeatable. For chemically stabilised materials, curing time affected the dielectric properties of the materials. Field tests were conducted on asphalt pavement test sections with different foundation materials (stabilised and unstabilised layers), drainage conditions and layer thicknesses. GPR and MIT results were used to determine asphalt layer thicknesses and were compared with measured core thicknesses, while GPR and DCP were used to assess foundation layer profiles. Asphalt thicknesses estimated from GPR showed an average error of about 11% using the dielectric gauge values as input. The average error reduced to about 4% when calibrated with cores thicknesses. MIT results showed thicknesses that are about 9% higher than estimated using GPR. Foundation layer thicknesses could not be measured using GPR due to variations in moisture conditions between the test sections, which is partly attributed to variations in gradation and drainage characteristics of the subbase layer.

Comparison of MASW and MSOR for Surface Wave Testing of Pavements

This paper presents a computational and experimental study on seismic stiffness profiling of layered pavement systems using the multi-channel analysis of surface waves (MASW) and multi-channel simulation with one receiver (MSOR) testing procedures. Development of a new custom-programmed data acquisition system for MASW and MSOR testing using MATLAB software and National Instruments hardware are detailed. A receiver coupling method is presented, which was found to perform the best among several methods examined by the authors. The cross-correlation function is employed to statistically quantify the repeatability of impacts, which is critical for MSOR tests in which multi-channel records are simulated by performing multiple impacts over a range of incremental offsets from a single fixed receiver. Experimental dispersion data from MASW and MSOR tests performed at the same asphalt pavement site with the same testing system are compared, and MASW is found to enable measurement of dispersion data to much higher frequencies using the authors’ methods than MSOR. Inversion results from the MASW and MSOR data at the same asphalt pavement site also are compared, and it is found that MASW is able to provide measurements of the stiffness of the pavement surface layer with reduced variability.

Performance testing of asphalt pavements with recycled asphalt shingles from multiple field trials

Transportation agencies have become increasingly interested in modifying hot mix asphalt (HMA) pavements with recycled asphalt shingles (RAS), yet they share common questions about the effect of RAS on the performance of HMA. In this study, the field and laboratory performance of RAS mixes produced from seven different transportation agencies are investigated as part of Transportation Pooled Fund TPF-5(213). Field demonstration projects were conducted that evaluated multiple aspects of RAS that include RAS grind size, RAS percentage, RAS source, RAS in combination with warm mix asphalt technology, RAS as a fiber replacement for stone matrix asphalt, and RAS in combination with ground tire rubber. Field mixes from each demonstration project were sampled and tested for their permanent deformation, fatigue cracking, and low temperature cracking performance. Recovered asphalt binder from each mix was also evaluated. Pavement condition surveys were conducted for each project after completion.

Optimal design for concrete pavement situated above box culvert: experimental and numerical study

This study examined the pavement distress data obtained from the field as well as the effects of the soil cover depth, joint position and reinforced slab length on the behaviour of concrete pavement using the finite element method. An ultimate strength model with a similarity of 1/2 was designed and constructed. Finite element analysis incorporating an implicit direct numerical integration scheme was conducted to obtain an optimal design for the pavement structure above a box culvert. An accelerated pavement test was conducted for validation, in which a realistic traffic load was imposed on the pavement model constructed in the laboratory. The strain histories were measured at each section and compared with those of numerical analysis. The optimal joint position and reinforced slab length that can minimise the damage to the pavement structure above a box culvert were also determined.

Investigating the effect of aircraft impact loading on the longitudinal top-down crack propagation parameters in asphalt runway pavement using fracture mechanics

Effect of aircraft impact loading during landing time on the crack propagation parameters was investigated. Boeing 777-300 aircraft specifications were considered. In order to simulate loading condition and nonlinear unbound layers characteristics, two codes were implemented by subroutines of ABAQUS™ software. The model was validated by American national airport pavement testing facility data. The effect of aircraft vertical velocity, pavement friction coefficient, crack position, crack depth and asphalt elastic modulus was studied. Aircraft vertical velocity and asphalt elastic modulus were recognized as the most significant parameters. Increase of these parameters considerably increased the stress intensity factors and reduced fatigue life.

Permanent deformation behaviour of reinforced flexible pavements built on soft soil subgrade

This study focuses on evaluating the effectiveness of using various geogrid products to improve permanent deformation resistance in soft subgrade soils commonly encountered during roadway construction in Pennsylvania. Permanent deformation behaviours of the soft soils both with and without the inclusion of geogrids were investigated. Cyclic moving wheel loads were applied through a reduced-scale accelerated pavement testing (APT) device, a one-third-scale model mobile load simulator (MMLS3). Tests were conducted on two soil types, each modified with three different biaxial geogrids placed at the base–subgrade interface. The total permanent deformation/surface rutting of the pavement and the permanent deformation of the subgrade were measured at selected intervals of the wheel loading applications. The pavement sections were trenched upon completion of the accelerated testing to measure the deformed profiles of the cross sections from which the permanent deformations in the asphalt layer and the base layer were determined. Sections modified with geogrids were found to have similar performance with the control section in terms of the total permanent deformation. While the geogrids did not show significant effects on the asphalt layer permanent deformation, sections with geogrids consistently showed a significantly higher base layer permanent deformation as compared to the control sections. Measurements of the subgrade permanent deformation showed that two of the geogrids consistently reduced the permanent deformation of subgrade built with the two types of soft soil. The relative layer contribution to the total permanent deformation suggested a base layer failure in both sets of the accelerated tests, most likely due to the inadequate compaction of the base layer during construction. Sections modified with geogrids exhibited a significantly higher base layer contribution, along with a significantly lower subgrade contribution, to the total permanent deformation, whereas the control section showed the opposite of the layer contributions.

Adaptation and validation of stochastic limiting strain distribution and fatigue ratio concepts for perpetual pavement design

Traditional perpetual pavement thickness design is based, in part, on controlling strain levels at the bottom of the asphalt concrete layer below an endurance limit to prevent bottom-up fatigue cracking (FC). A field-based limiting strain threshold was developed from cumulative distributions of field-measured tensile strains in the 2003 and 2006 research cycles at the National Center for Asphalt Technology Pavement Test Track to understand the limiting strain necessary to control FC. Additionally, the fatigue ratio, the ratio of the nth percentile strain to the fatigue endurance limit, was developed. Both the tensile strain distributions and fatigue ratios showed a clear difference between sections that experienced bottom-up FC and those that did not. However, it is necessary to adapt these thresholds to strains predicted by perpetual pavement design tools. PerRoad, a stochastic perpetual pavement design programme, was used to predict strains for the same 2006 sections. Previously developed strain distributions and fatigue ratios were adjusted to reflect observed differences in predicted and measured strains. Cumulative distributions and fatigue ratios based on predicted strains for the 2009 research cycle validated the updated limiting strain distribution and maximum fatigue ratios for designing perpetual pavements to resist bottom-up FC.

Using accelerated pavement testing to examine traffic opening criteria for concrete pavements

The risk of cracking in a concrete pavement that is opened to traffic at early ages is related to the maximum tensile stress σI, that develops in the pavement and its relationship to the measured, age dependent, flexural strength of a beam, fr. The stress that develops in the pavement is due to several factors including traffic loading and restrained volume change caused by thermal or hygral variations. The stress that develops is also dependent on the time-dependent mechanical properties, pavement thickness, and subgrade stiffness. There is a strong incentive to open many pavements to traffic as early as possible to allow construction traffic or traffic from the traveling public to use the pavement. However, if the pavement is opened to traffic too early, cracking may occur that may compromise the service life of the pavement. The purpose of this paper is two-fold: (1) to examine the current opening strength requirements for concrete pavements (typically a flexural strength from beams, fr) and (2) to propose a criterion based on the time-dependent changes of σI/fr which accounts for pavement thickness and subgrade stiffness without adding unnecessary risk for premature cracking. An accelerated pavement testing (APT) facility was used to test concrete pavements that are opened to traffic at an early age to provide data that can be compared with an analytical model to determine the effective σI/fr based on the relevant features of the concrete pavement, the subgrade, and the traffic load. It is anticipated that this type of opening criteria can help the decision makers in two ways: (1) it can open pavement sections earlier thereby reducing construction time and (2) it may help to minimize the use of materials with overly accelerated strength gain that are suspected to be more susceptible to develop damage at early ages than materials that gain strength more slowly.