Falling Weight Deflectometer Tests Research Articles

Falling weight deflectometer dispersion curve method for pavement modulus calculation.

The falling weight deflectometer (FWD) test is a common non-destructive testing method for evaluating the structural capacity of pavements. At present, data processing of the FWD test mainly focuses on the deflection data, while paying less attention to the deflection-time history. Because a FWD is equipped with impulse loads and geophones, which allow for the generation and capture of surface wave signal propagation, it is hypothesized that Rayleigh wave dispersion theory can be applied to calculate the modulus profile along the pavement depth by analysing the dispersive properties of the deflection signal measured during FWD tests. To test this hypothesis, we develop a new methodology for the FWD test and data analysis, referred to as the FWD dispersion curve method. We first introduce the concept of the new method, followed by an illustration of the procedure and the experimental set-up. Case studies on three concrete pavement segments are then presented to evaluate the effectiveness of the FWD dispersion curve method. Modifications to the existing FWD device are further recommended for the impact loading sources and signal collection process so that the modulus of a much shallower layer, such as the concrete slab and upper asphalt layers, can be obtained. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'.

Feasibility of determining asphalt pavement condition from falling weight deflectometer test and finiteelement model updating.

Determination of pavement internal condition froma non-destructive field test is a persistent topic for its practical necessity and difficulty. It is essentially an inverse problem calibrating pavement material and structural properties from pavement responses. Considering the intrinsic complexity of asphalt pavement materials (e.g., time and temperature dependencies of asphalt mixture and stress dependency of unbound granular materials), this problem has become a typical high-dimensional optimization problem with a large and diverse set of calibrated parameters. This study investigated the feasibility of artificial intelligence-based finiteelement model updating in addressing this problem, and focused on theaccuracy as well as stability of the backcalculated results. For a comprehensive evaluation of this method, theeffects of its components such as the surrogate model representing the pavement system, theapplied pavement response, theoptimization algorithm and thebackcalculation scheme were characterized. Finally, we found thatthe sensitivity of applied pavement responses to thebackcalculated pavement condition, the number of applied pavement responses and the balance between the backcalculated pavement condition and theapplied test were of significant importance to achievingaccurate and stable backcalculation results. Corresponding modifications were recommended to be conducted in future research for improving the performance of the proposed backcalculation method. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'.

Investigation of Enzyme–Based Soil Stabilization in Field Application

The low bearing capacity of expansive soils often results in serviceability issues and premature failures of infrastructure built upon them. Various studies have demonstrated the use of different soil treatment methods using mechanical or chemical approaches to stabilize the weak ground as a precaution. Most of the reported studies are limited to either lab-based investigations or field monitoring works without the scientific connection between theory and translation. This study aims to verify the field application of a novel soil stabilization method by conducting laboratory-controlled experiments and field performance testing as verification. Enzyme–based soil stabilization was adopted for in-situ clay soil in combination with ordinary portland cement as a sustainable stabilization approach. Soil samples were collected at different regions from the field to evaluate the effectiveness and the mechanism of soil stabilization in the field by the means of replicating stabilization at the laboratory scale using identical mixing proportions of the additives. The mechanical behavior of stabilized soil was assessed through the unconfined compression strength and California bearing ratio test methods. In addition, the changes in the chemical composition of the soil due to the additives were evaluated through the X-ray diffraction testing technique and microporosity test using 2D images translated to 3D profiles from X-ray micro CT tomography. The efficacy of field stabilization was evaluated by conducting the falling weight deflectometer test in the stabilized site. Results from the study are useful to understand the efficacy of field soil stabilization and enhance the reliability of enzyme–based stabilization in practice.

Reduction of critical positive temperature gradients in jointed plain concrete pavements

ABSTRACT Temperature gradients in concrete pavements significantly affect fatigue damage accumulation, with high gradients having the potential to reduce performance under vehicle loads. While temperature profiles are non-linear throughout the depth, an equivalent linear temperature gradient (ELTG) accounts for the effect of temperature in pavement design. Critical ELTG values are difficult to predict because ELTG is affected by design parameters as well as climate conditions and varies diurnally and seasonally. To identify critical parameters which affect ELTG, a database of hourly temperature profiles was generated for a series of jointed plain concrete pavements (JPCP) throughout Pennsylvania. A stepwise regression model was developed with an R2 of 0.81 to determine maximum daily ELTG as a function of the design parameters and climate. This equation can assist engineers in making decisions on when superloads can be transported without significant damage or performing falling weight deflectometer testing will be most informative. Slab thickness, concrete albedo, and daily temperature range (DTR) were the most significant parameters that affected ELTG. A higher albedo showed an equivalent effect in reducing maximum ELTG as increasing the thickness of the slab. This finding can be used to reduce maximum gradients, which will increase the predicted service life of JPCPs.

Impact of sea level rise on asphalt pavement responses considering seasonal groundwater and moisture gradient in subgrade

Sea level rise (SLR) has been found to have a great impact on the transportation infrastructure in coastal areas. This study developed an analysis approach with numerical modeling to analyze the impact of SLR-induced groundwater rise on critical responses of coastal pavements. The numerical model employed a stress-, moisture content- and matric suction-dependent modulus model to consider the unsaturated characteristics of subgrade soil and non-linear distribution of moisture content. The model results were validated using Falling Weight Deflectometer (FWD) tests in the field. Based on the realistic moisture content collected from Long-Term Pavement Performance (LTPP) database, the critical responses of pavements were evaluated. The in-situ moisture content is non-linearly distributed along the depth, which differs from traditional assumption of monotonic distribution. The seasonal groundwater table (GWT) and subgrade soil type are two factors impacting the critical pavements responses under SLR scenarios. The pavement will be significantly impacted by SLR in the seasons with the higher GWT. The modulus of clay soil is more sensitive to moisture content than that of sandy or silty soil and thus causes the greater increase of pavement responses as sea level rises. On the other hand, the compressive stain on subgrade increases more remarkably than tensile strains at the bottom of asphalt layer under the impact of SLR.

Field Validation of Falling Weight Deflectometer Deflection-Based Critical Strain Prediction Models for Full-Depth Asphalt Pavements

Critical strains are one of the most reliable mechanistic parameters representing the structural capacity of flexible pavements. However, critical strains are currently not considered in pavement management systems (PMS) because of a lack of methodology for measuring critical strains in in-service pavements. Recently, critical strain prediction models have been developed by the Indiana Department of Transportation and Purdue University research team to estimate the critical strains of existing full-depth asphalt pavements using falling weight deflectometer (FWD) data. Even though the accuracy of these models was verified with finite element (FE) analyses, additional field validation is needed before incorporating the model results into PMS. This study focuses on validation of these previously developed critical strain prediction models using field-measured strains. Nine field sections, representing typical full-depth asphalt pavements in Indiana, were selected for study inclusion. FWD testing was conducted on the field sections and field cores were collected. Field strains were measured by a strain gauge or were determined by FE analysis using the material properties obtained from the field cores. Based on the comparative analysis, the critical strain prediction models were successfully validated with strains measured from the field. The coefficients of determination were up to 0.98 for the transverse tensile strain at the bottom of the asphalt layer and 0.93 for the vertical compressive strain at the top of the subgrade. Therefore, it is concluded that the critical strain prediction models can be used to estimate critical strains of in-service full-depth asphalt pavements for structural evaluation of PMS.

Influence of bedrock on viscoelastic responses and parametric back-calculation results for asphalt pavements and prediction of bedrock depth under FWD tests

Structural evaluation with a falling weight deflectometer (FWD) plays an essential role in the maintenance and rehabilitation of highways. Research on the influence of bedrock on the results of FWD tests and dynamic back-calculations for asphalt pavements has been a hot topic. In this study, the viscoelastic characteristics of the asphalt surface layer were described by the modified Havriliak-Negami (MHN) model rather than the layered elastic theory computing framework. The effects of bedrock on the deflection time history curves of viscoelastic asphalt pavement under the FWD test were investigated and analyzed by the spectral element method with fixed-end boundary conditions (B-SEM). The effects of bedrock on parametric back-calculation results for the viscoelastic asphalt surface layer and other elastic layers were explored by dynamic back-calculations. To exclude the impact of bedrock and improve the back-calculation accuracy, support vector regression optimized by the gravitational search algorithm (GSA-SVR) was adopted to predict bedrock depth. The viscoelastic responses and dynamic parametric back-calculation results were significantly influenced by bedrock beneath asphalt pavements, and the influence decreased (but was not eliminated) with increasing depth of bedrock. The GSA-SVR model provided excellent predictions of bedrock depth, and it can be applied for pavement performance assessment in road projects.

An alternative method for determination of compaction level for the pavement granular layers

The performance and bearing capacity of the flexible pavement structure is ensured by providing necessary foundation comprised of unbound granular material (UGM) layers and subgrade. Whin this paper the compaction level parameters and deformation modulus relations determined for UGM layers and subgrade in construction site. The experimental data were tested applied standardized and improved test methods, such as an alternative falling weight deflectometer (FWD) test method with repetitive load, the plate load tester, lightweight deflectometer, dynamic cone penetrometer, and density Proctor tests. The data were analyzed based on statistical comparison of the compaction parameters, pairwise multiple comparison of test methods, clustering procedure for setting a level of compaction evidence and variance determination. Results proved capabilities of the alternative FWD test method under repetitive load to assess the relative compactness rate and the resilient responses, and provided the regression models of the dynamic modulus of the UGM layers and subgrade.

T-shaped arrangement of geophones for rapid quantification of asymmetric behaviour of concrete slabs in central FWD tests

ABSTRACT The assessment of asymmetric slab behaviour is out of reach in standard Falling Weight Deflectometer (FWD) tests, because deflections are measured along the driving direction only. Herein, a new T-shaped arrangement of the geophones is proposed. It allows for rapid quantification of asymmetric slab behaviour in central FWD testing of concrete slabs. One geophone is positioned at the centre of impact (= centre of the slab), six along the driving direction, one right and one left of the centre. The ‘Lateral Asymmetry Index (LASIX)’ is introduced as a corresponding dimensionless deflection basin parameter. Its value increases with increasing asymmetric behaviour of the slab. The main research challenge tackled herein is to optimise the radial distance of the lateral geophones from the centre of the slab, such as to maximise the expressiveness of LASIX for the quantification of asymmetric slab behaviour. In this context, FWD tests with measurement of deflections in eight different directions are carried out, and the ‘effective asymmetry index ( A 28 )’ is introduced as another new dimensionless deflection basin parameter. It summarises the asymmetric behaviour based on deflection differences quantified for all 28 pairs of directions which can be combined out of the eight available measurement directions. The optimal radial distance of the lateral geophones from the centre of the slab is found as 1.20 m. Corresponding values of LASIX larger than 8 % refer to coefficients of directional variation of the AREA7 parameter larger than 5%. This indicates directional degradation of the pavement structure resulting from eccentric traffic loads. T-shaped FWD testing requires in situ efforts equivalent to those of standard testing, while allowing for a rapid and reliable quantification of asymmetric behaviour. It allows for the assessment of whether the standard evaluation of uniform moduli of subgrade reaction is realistic or questionable.

Modulus attenuation of semi-rigid asphalt pavement layer in accelerated pavement testing with MLS66

This research aimed to investigate the attenuation mode of the layer modulus of asphalt pavement in accelerated pavement testing (APT). A full-scale experimental section was constructed and tested using the APT facility. Two non-destructive testing (NDT) methods, named falling weight deflectometer (FWD) technique and portable seismic property analyzer (PSPA) test, were used to obtain the layer moduli of asphalt pavement during the APT test. The variation patterns of layer moduli obtained by FWD and PSPA tests were calculated and compared after the temperature was corrected to 20 ℃. It was found that the variation pattern of surface layer modulus based on field FWD measurements was consistent with the one measured from PSPA tests. That is the modulus of the surface layer increases with the APT load repetitions firstly and then decreases with the rise of the repetitions. The modulus values of the surface layer measured from PSPA tests are obviously larger than those backcalculated based on deflection basins. The ratio of the measured surface layer modulus based on the PSPA test to the backcalculated one based on the FWD test ranges between 2.06 and 2.71. The backcalculated base layer modulus always declines with the increasing loading repetitions. The attenuation patterns of the surface layer modulus and the base layer modulus in the damage stage are described as Ea=421100*N-0.6119 and Eb=128000*N-0.1096, respectively.

Laboratory and Field Testbed Evaluation of the Performance of Recycled Asphalt Mixture Using High-Penetration Asphalt

The application of recycled asphalt pavement (RAP) on a large scale is highly promoted to meet the current needs of carbon neutrality and sustainable development purposes. However, a majority of RAP mixture productions are currently relying on the restoring effects provided by the rejuvenators. Therefore, the study focuses on the feasibility of using high penetration asphalt binder (HPAB) in RAP mixture as a replacement for conventional rejuvenators. In this study, a recycled asphalt pavement mixture containing HPAB (RAP-H) was developed to resolve the cracking issue of RAP pavement in winter seasons owing to the rigid behavior of aged binders. To verify the applicability of the RAP-H mixture, the results of the quality standard test and mechanical performance test were compared with the reference RAP mixture having rejuvenator (RAP-R). Through the fatigue cracking test, by using Overlay Tester (OT) device, it was found that all specimens did not reach 93% load reduction after 1000 OT cycles, indicating a satisfied stress-bearing capacity. Additionally, the highest dynamic modulus of 27,275 MPa was found in the modified HPAB mixture, and this result is 4.4% higher than that of the reference mix. In the full-scale testbed, the long-term field applicability of the proposed approach was verified through field test construction. The measurement in practice reveals that the elastic modulus of RAP-H back-calculated from the FWD (Falling Weight Deflectometer) test is increased by more than 50% compared to RAP-R, which resulted in excellent performance characteristics of the HPAB pavement layer. In addition to the efficiency in the surface layer, an improved elastic modulus of the sub-base and subgrade layers in the HPAB section was found to be at 28.6% and 19.5%, respectively, compared to the RAP-R mix. In general, the performance of RAP-H satisfied all of the domestic and international quality and performance standards. The field test results confirmed the possibility of field application by showing performance higher than conventional recycled asphalt pavement.

Prediction of remaining service life for flexible pavement in the Southern Central States using FWD parameters

Various Departments of Transportation (DOTs) in the South-Central States and abroad have extensively used Non-Destructive Testing (NDT) surface deflection bowl data. The primary purpose of using deflection-based NDTs in network-level assessment is to identify a section of pavement in need of further investigation at the project level. The falling weight deflectometer (FWD) test is a common NDT-based test that is used by transportation agencies to assess the performance of flexible pavement.This research concentrates on simulating the deflection produced by FWD devices using 3-D Move software. Simulations based on software will decrease the need for lengthy FWD testing in the field. In the study, ninety-seven (97) pavement sections from Arkansas, Louisiana, New Mexico, Oklahoma, and Texas are used for simulation, analysis, and verification of FWD testing. The deflection values produced from software simulations were found to be strongly correlated with field test findings. In addition, the simulated deflection values were used to develop and validate various deflection bowl parameters. In this study, the normalized comprehensive deflection ratio and the normalized comprehensive area ratio are two key characteristics that were validated and produced. Eventually, load-induced impacts using these parameters are effectively analyzed in order to anticipate the remaining service life of flexible pavement structures. The prediction of the remaining service life will be an efficient tool for different DOTs and transportation agencies to initiate the rehabilitation work in time and economically.

Prediction of remaining service life for flexible pavement in the Southern Central States using FWD parameters

Various Departments of Transportation (DOTs) in the South-Central States and abroad have extensively used Non-Destructive Testing (NDT) surface deflection bowl data. The primary purpose of using deflection-based NDTs in network-level assessment is to identify a section of pavement in need of further investigation at the project level. The falling weight deflectometer (FWD) test is a common NDT-based test that is used by transportation agencies to assess the performance of flexible pavement.This research concentrates on simulating the deflection produced by FWD devices using 3-D Move software. Simulations based on software will decrease the need for lengthy FWD testing in the field. In the study, ninety-seven (97) pavement sections from Arkansas, Louisiana, New Mexico, Oklahoma, and Texas are used for simulation, analysis, and verification of FWD testing. The deflection values produced from software simulations were found to be strongly correlated with field test findings. In addition, the simulated deflection values were used to develop and validate various deflection bowl parameters. In this study, the normalized comprehensive deflection ratio and the normalized comprehensive area ratio are two key characteristics that were validated and produced. Eventually, load-induced impacts using these parameters are effectively analyzed in order to anticipate the remaining service life of flexible pavement structures. The prediction of the remaining service life will be an efficient tool for different DOTs and transportation agencies to initiate the rehabilitation work in time and economically.

Revisiting Field Performance of Cold Central-Plant Recycled Test Sections at MnROAD Low-Volume Road

In 2017 four test sections (test sections 133, 233, 135, and 235) containing a cold central-plant recycled (CCPR) layer underneath a surface treatment were constructed on the MnROAD low-volume road (LVR). Two types of CCPR mix designs were constructed: test sections 133 and 235 contained an emulsified asphalt; test sections 135 and 233 contained a foamed asphalt. Each CCPR mix design (foamed asphalt and emulsified asphalt) had two types of wearing surface layers (double chip seal and 1.5 in. HMA [hot-mix asphalt] overlay—thinlay) to create the four test sections. The rest of the pavement structure beneath the newly constructed CCPR was left in place and consistent throughout all four test sections with the remaining granular base over the existing clay subgrade. This paper presents a revisiting of the field performance of the CCPR test sections at the MnROAD LVR. To do this extensive field data was collected over approximately 3 years through visual distress surveys, and ride quality, rutting, and falling-weight deflectometer testing. Field study determined that both CCPR mix designs (foam and emulsion) performed similarly and the thinlay HMA layer outperformed the double chip seal in respect of rutting; but both surfaces are considered valid alternatives for future applications depending on the traffic volumes expected.

A new methodology to improve backcalculation of flexible pavements with stabilized foundations

Flexible pavements with stabilized foundations are often used in parts of the U.S. where subgrade and aggregate base materials are sub-optimal. Though common, there is precious little mechanistic-empirical data and few mechanistic studies featuring these pavement types. To improve the fundamental understanding and overall design and performance of flexible pavements with stabilized foundations, there is a need for full scale evaluation. To address this need, the Mississippi Department of Transportation sponsored a full-scale pavement section at the National Center for Asphalt Technology Test Track beginning in 2018. While studying many aspects of M−E analysis and design, the aim of this investigation was to overcome the challenges of backcalculating layer moduli of a flexible pavement with a stabilized foundation. Falling weight deflectometer testing was conducted three times per month on this section to characterize structural behavior over time. The backcalculation process using conventional methods yielded unrealistic results with high variability. To resolve the issue, a new backcalculation computer program (MASTIC) was developed to add additional features such as partial friction for layer interfaces which showed significant improvement over traditional full bonding conditions but did not entirely address the problem of high variability. To obtain less variable results, a new methodology was developed to examine the actual deflection basins. The “x-intercept” method filtered out deflection basins that resulted in erroneous estimation of layer moduli by examining measurements from the four outermost sensors. This study showed that integration of partial friction method and x-intercept analysis is necessary to obtain acceptable moduli of stabilized foundation sections.

Numerical analysis and conversion of dynamic and static deflection of asphalt pavement under FWD loading

During the falling weight deflectometer (FWD) evaluation, only calculating the acceptance deflection by adopting the layered elastic system theory has its limitations. In this paper, a three-dimensional finite element method was adopted to carry out the dynamic simulation analysis of typical asphalt pavement structures under FWD test. As a result, a dynamic deflection calculation model of asphalt pavement under FWD loading was established as well as the calculating method, in which a layered elastic system theory is adopted for calculations on the basis of the dynamic-static deflection ratio. Furthermore, an equivalent conversion method of asphalt pavement was proposed based on the deflection equivalent principle. Last, the applicability of the method was examined by comparing the FWD results of the pavement sections tested on-site. The method proposed in this paper to calculate the dynamic deflection of asphalt pavement is critical for the quality acceptance of asphalt pavement construction, modulus back calculation, and asphalt pavement design.

Mechanical Behaviour of Steel Slag–Rubber Mixtures: Laboratory Assessment

Slags and rubber from end-of-life tires represent a liability to the steel and tire industry, causing economic and environmental problems that are difficult to manage. Transport infrastructures can use these industrial by-products instead of extracting natural raw materials, but the adequate mechanical performance of the materials needs to be assured. This paper addresses the mechanical behaviour of slag–rubber mixtures in the laboratory with CBR, monotonic and cyclic triaxial tests. In addition, light falling weight deflectometer tests were also performed in a physical model. The results were analysed to meet technical specifications from Brazil, Portugal and Australia using railway sub-ballast layers, capping layers or road pavement layers as the base and sub-base to identify the applicability range of slag–rubber mixtures for transport infrastructures. Concerning the analysed parameters, it was demonstrated that slag–rubber mixtures can show resilient behaviour and strength adequate for the support layers of transport infrastructures provided that the rubber content is below 5% in weight and that the slag is milled to comply with the grain size distribution ranges available in the technical specifications of the cited countries.

Sustainable pavement with geocell reinforced reclaimed-asphalt-pavement (RAP) base layer

According to the Federal Highway Administration Policy, recycled material should be the highest priority in selecting pavement materials. However, the quality of the reclaimed/recycled material should meet the minimum standard to ensure long-term benefits. This study uses geocell to enhance the performance of reclaimed asphalt pavement (RAP) material. Three pavement test sections were constructed with 0.15, 0.20, and 0.30m thick geocell reinforced RAP bases (GRRBs) by replacing the existing base layer of a farm-to-market road located in the southern part of Fort Worth, Texas, USA. These test sections were monitored for a period of three years to evaluate the pavement performance in terms of rutting, cracking, and riding quality. In addition to the regular monitoring falling weight deflectometer (FWD) tests were also conducted to determine the base layer modulus. Results showed that the geocell layer reduced the permanent deformation by at least 36% compared to the unreinforced section. The application of geocell also helped control the test sections' bottom-up longitudinal cracking by providing uniform support. The FWD test revealed that the geocell enhanced the GRRB layer stiffness by 20%. The construction cost of the GRRB layer was 22.9% less than the traditional flex base layer. Replacement of flex base material with GRRB material could reduce the emission of CO2 by 37 tons for each lane-km.

Development of FWD based hybrid back-analysis technique for railway track condition assessment

Track substructure is a key component of the railway transportation system. Similar to the built environment of other surface transportation systems, track substructures are subjected to aging and deterioration. This, frequently leads to the failure and collapse of the transportation systems, resulting in the imposition of costly repairs and maintenance. At the same time, the emergence of high-speed trains and heavier axle loads, together with a need for sustainable designs, has put additional pressure on asset owners. It has been shown that frequent condition assessments of railway substructures can considerably reduce the overall annual maintenance costs. Furthermore, limited knowledge of the substructure condition leads to the employment of inefficient, time-consuming, and expensive maintenance actions. Therefore, development of time- and cost-efficient techniques to frequently monitor existing railway track substructures is vital. The falling weight deflectometer (FWD) is recognised as an effective non-destructive test used to survey ballasted railway substructures through a back-analysis process. This paper presents a novel hybrid back-analysis technique that includes an artificial neural network (ANN) and genetic algorithm (GA) to estimate the substructure layer moduli of railway tracks using FWD testing data. To this aim, firstly a dynamic finite element (FE) model was developed and validated against experimental data from the literature. This FE model then were employed to generate a reliable dataset to train the ANN. In the next step, GA was employed as an optimisation tool within the back-analysis technique/framework to optimise the layer moduli (the ANN’s input). A comparison study was performed to evaluate the performance of the developed technique. The results of this comparison revealed excellent performance and robustness of the developed technique.

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.