Search

O novo Método de Dimensionamento Nacional (MeDiNa) emprega a abordagem mecanística-empírica para o dimensionamento dos pavimentos asfálticos. O presente artigo contribui com a aplicação do Método MeDiNa na avaliação estrutural da Estrada Rio do Morro, pavimentada recentemente e inventariada com a medição de bacias deflectométricas através do FWD e viga Benkelman para 110 pontos de teste. Para tanto, foi realizado um comparativo entre as medidas de deflexão e os módulos de elasticidade retroanalisados com o software BackMeDiNa a partir dos dados obtidos com os dois equipamentos. Na sequência foi empregado o software MeDiNa e os módulos anteriormente retroanalisados para a previsão da vida de fadiga do pavimento. Os resultados demonstraram a maior dispersão entre os resultados obtidos com deflexões da viga Benkelman e a eficiência do BackMeDiNa no processo da retroanálise a partir dos dados e considerações de cálculo da pesquisa.

Frequent flooding and wet weather events are the challenges for managing road infrastructure. In this study, falling weight deflectometer (FWD) equipment is employed to investigate the effect of moisture consequence of January 2011 flood at Queensland, Australia on a flooded road. The impacts of the flood on the structural strength were obtained for the whole section as well as different layers individually. These two sets of data provide a clear picture of the road condition as sound, severe or warning before and after the maintenance of the road. Furthermore, the moisture content of the spotted road at field condition providing the structural stiffness was obtained with a correlation of FWD data. These analysis and investigations play an essential role in optimizing the maintenance method for the roads suffering from the flood. [ABSTRACT FROM AUTHOR]

Remaining life is an important indicator of pavement residual effective service time and is directly related to maintenance decision-making with limited funds. This paper proposes a fast and non-destructive model to predict the remaining life of rigid PCC (Portland cement concrete) pavement, with or without asphalt overlay. Firstly, a model was constructed according to the current Chinese design specifications for concrete pavement integrating an inverse design concept. Secondly, the prediction model was applied to three typical pavement sections with 1430, 1250 and 1000 slabs, respectively. Ground penetrating radar (GPR) was utilized to determine the geometric parameters in the predictive model and the physical state of the pavement. A falling weight detector (FWD) was utilized for determination of the mechanical parameters. A more reasonable equivalent elastic modulus of foundation was back-calculated instead of using the limited model in the design specification. Thirdly, the remaining life was predicted based on the current mechanical and geometric parameters. The distributions of the remaining life of the three pavement sections was statistically analyzed. Finally, a decision-making system to inform maintenance strategy was proposed based on the remaining life and the technical condition of each slab. The results showed that the relationship between the remaining life and the mechanical parameters, geometric parameters and the physical state of the pavement was highly consistent with engineering experience. The success rate of the prediction model was as high as 96%. The proposed fast and non-destructive prediction model showed good engineering applicability and feasibility. The decision-making system was shown to be feasible in terms of economic benefits.

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Foamed bitumen stabilised (FBS) pavement is becoming more widely used around the world, yet comprehension of its properties within a pavement configuration is not well understood. The performance of FBS pavements in New Zealand using falling weight deflectometer (FWD) data has been reviewed to enable rationalisation of modelling techniques. FWD derived parameters and models for FBS are compared to international guidelines, as well as currently recommended design parameters and models in use internationally. Interpretation of FWD derived data strongly indicates that moduli of FBS (and cement treated) layers are primarily dependent on the stiffness of supporting layers (subbase and subgrade). Consequently, alternative models which quantify characteristic FBS moduli based on supporting layer stiffness and standard central deflection have been determined. An assessment of FWD recorded surface temperatures (at the time of testing) versus FBS moduli indicates that in-service pavements constructed in accordance with New Zealand customary practices exhibit significant temperature sensitivity (as would be expected owing to the inclusion of bitumen in the FBS layer). Subsequently, appropriate correction factors for standardising moduli to a reference temperature have been evaluated. [ABSTRACT FROM AUTHOR]

Numerous ways to use recycled asphalt (RA) in the road base course will provide both environmental and economic benefits, allowing to recycle and utilise this initially waste material in road or pavement reconstruction projects. However, the properties and parameters of RA necessary for the application of reclaimed asphalt pavement (RAP) in a new pavement structure in most cases are not detectable in the design stage, which complicates design and construction process. The purpose of this paper is to study possibilities for evaluating the performance and parameters of RA, as well as to review the possibilities, methods and applications for RA testing. Data for this case study were obtained from recently completed road structures in the form of FWD measurements, together with lab explored parameters of drilled pavement cores. Based on that data, the relationships between the main pavement structural parameters, such as modulus on the surface of the pavement, compressive strength of RA core segment, thickness of bound layers and back calculated modulus were examined. On the way to exploring different analytical approaches, two approximation models were developed and compared, using the obtained data: by directly approximating the obtained data and after processing them with artificial neural network (ANN). [ABSTRACT FROM AUTHOR]

The diffusion of smart infrastructures for smart cities provides new opportunities for the improvement of both road infrastructure monitoring and maintenance management. Often pavement management is based on the periodic assessment of the elastic modulus of the bound layers (i.e., asphalt concrete layers) by means of traditional systems, such as Ground Penetrating Radar (GPR) and Falling Weight Deflectometer (FWD). Even if these methods are reliable, well-known, and widespread, they are quite complex, expensive, and are not able to provide updated information about the evolving structural health condition of the road pavement. Hence, more advanced, effective, and economical monitoring systems can be used to solve the problems mentioned above. Consequently, the main objective of the study presented in this paper is to present and apply an innovative solution that can be used to make smarter the road pavement monitoring. In more detail, an innovative Non-Destructive Test (NDT)-based sensing unit was used to gather the vibro-acoustic signatures of road pavements with different deterioration levels (e.g. with and without fatigue cracks) of an urban road. Meaningful features were extracted from the aforementioned acoustic signature and the correlation with the elastic modulus defined using GPR and FWD data was investigated. Results show that some of the features have a good correlation with the elastic moduli of the road section under investigation. Consequently, the innovative solution could be used to evaluate the variability of elastic modulus of the asphalt concrete layers, and to monitor with continuity the deterioration of road pavements under the traffic loads. [ABSTRACT FROM AUTHOR]

Potential benefits in applying polypropylene fiber to stabilize expansive soils and cement treated bases is already been reported in previous studies. So a critical need exists to incorporate the use of fiber into the Texas Department of Transportation's (TxDOT's) Guidelines for Modification and Stabilization of Soils and Base for Use in Pavement Structures. The present paper discusses the results collected from the first experiment al test section on FM897 in the TxDOT Paris District. Three 500-ft (152.4m) test sections were constructed with 2 percent cement on FM897 in February 2020 in the north bound lane loaded truck direction which includes a new sandstone base, full depth reclamation (FDR), and control. However, only the new sandstone base and FDR sections were built with fiber. In this project, two types of fibers were used--(a) fibrillated fiber Fibermesh300, and (b) macro-synthetic fiber Enduro 600.The surface and base layers from the new sandstone base section were removed and used for the edge widening area of the FDR and control sections. Based on the laboratory tests, the optimum fiber contents were found to be 0.6 percent and 0.4 percent for a new sandstone base and FDR, respectively. The laboratory Unconfine Compression Strength (UCS) results showed significant improvements (>112.36 percent) when fibers were added to the sandstone base. To have better control, fiber and cement were manually distributed, following the US Army Corps of Engineers' recommendations. Because of unexpected construction equipment failure that caused compaction delays of approximately 5 hours, cement was in contact with moisture for approximately 5 hours before compaction. UCS results showed an approximate 55 percent reduction when there was a 5-hour delay from the time water was introduced (resulting in the start of the hydration process) until the time of compaction. It indicated that there are detrimental effects on UCS i f there is delay on compaction. There were significant reductions on the normalized W1 deflections at 5 months after construction. In particular, the FDR and new sandstone base sections (with fiber) experienced over 52 percent reduction as compared to 1 week after construction FWD data. Furthermore, the averaged W1 deflections were lower than before construction for both FDR and new sandstone base sections (with fiber). This indicates that there were rapid increases in structural capacity and significant strength developed in the fiber sections between 1 week and 5 months. Further research is needed to explain the mechanism and phenomena. [ABSTRACT FROM AUTHOR]

In this study, laboratory and field constructed Jointed Plain Concrete Pavements (JPCP) were evaluated with Fibre Reinforced Polymer (FRP) dowels and compared with JPCP consisting of steel dowels. Laboratory evaluations on representative concrete JPCP sections with FRP and steel dowels consisted of static and fatigue testing followed by analytical modelling. Laboratory testing of JPCP with FRP and steel dowels focused on joint deflection and dowel strain data collection for determining Load Transfer Efficiency (LTE) and joint Relative Deflections (RD) under static and 5 million cycles of fatigue load corresponding to a 45 kN (10 kip) wheel load of HS-25 truck. The static data showed low relative deflections for concrete sections with smaller dowel diameter of 25 mm and spacing of 150 mm than the currently used 38 mm diameter dowels with 300 mm spacing. Analytical calculations were carried out to show the effect of applied loads on the bending and shear deflections, and bearing stresses. After laboratory evaluations, new field construction and rehabilitation of JPCP was carried out using FRP and steel dowels. Some of the field evaluations consisted of static, dynamic, and falling weight deflectometer (FWD) tests. After 5 and 13 years of field service, FWD tests showed that the LTE of joints with FRP dowels were around 90% and met the applicable performance requirements. [ABSTRACT FROM AUTHOR]

Cakung-Cilincing Jakarta National Road Section has very rapid traffic load for rigid pavement. The purpose of this study are determining overlay thickness and choosing suitable method for implementation. AASHTO 1993 and AUSTROADS 2011 method are used in this study and using on Falling Weight Deflectometer (FWD) data. This study shows that value of Concrete Elasticity Modulus less than 3 million, then this rigid pavement is severely damaged. Based on AASHTO 1993 Method analysis, it needs 11 cm for flexible overlay and 12 cm for rigid overlay on lane 1 with 59% remaining life and lane 2 with 53% remaining life. AUSTROADS 2011 Methods use only FWD data and for overlay thickness determination is use new pavement analysis. Analysis using AUSTROADS 2011 Methods shows that flexible overlay requirement is 24 cm and rigid overlay requirement is 18.50 cm. Comparation between these two methods shows that AASHTO 1993 Method Analysis produce less overlay thickness than AUSTROADS 2011 Methods.

The falling weight deflectometer (FWD) is a widely used nondestructive test (NDT) device in pavement infrastructure. A FWD test measures the surface deflections subjected to an applied impact loading and the modulus of pavement layers can be determined by back-calculating the measured deflections. However, the modulus of asphalt layers is significantly influenced by temperature; hence, the temperature correction must be considered in back-calculation to evaluate the moduli of asphalt layers at a reference temperature. In addition, the in situ temperature at various pavement depths is difficult to measure. A model for evaluating the temperature at various depths must be established to estimate the in situ temperature of asphalt layers. This study collected the temperature data from a FWD test site to establish a temperature-evaluation model for various depths. The cored specimens from the test site were obtained to conduct dynamic modulus tests for asphalt layers. The FWD tests were applied at the FWD test site and the back-calculation was performed with temperature correction using the frequency-temperature superposition principle. The back-calculated moduli of asphalt layers were compared with the master curve of dynamic modulus to verify the application of the frequency-temperature superposition principle for FWD back-calculation. The results show that the proposed temperature-evaluation model can effectively evaluate the temperature at various depths of pavement. Moreover, the frequency-temperature superposition principle can be effectively employed to conduct temperature correction for FWD back-calculation. [ABSTRACT FROM AUTHOR]

Copyright of Roads & Bridges / Drogi i Mosty is the property of Road & Bridge Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 than100 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. [ABSTRACT FROM AUTHOR]

Pavement deflection has been used widely as a nondestructive technique to evaluate the structural capacity of pavements at both network and project levels. Current devices include Falling Weight Deflectometer (FWD) and the Deflectograph, which can record the deflection bo wl shape. Utilizing these devices, a load is applied on the pavement surface and deflections at several lateral locations are recorded. Various transpo rtation agencies use several evaluation methods to evaluate the integrity of the pavement layers. Most of these up-to-date developed indices are exclusively based on either central deflections or one deflection point along FWD deflection bowl. However, no standardized method is available that utilizes the full FWD deflection bowl. This study aims to introduce new comprehensive pavement layer deflection and deflection bowl area parameters that are based on the entire FWD deflection bowl rather than one single deflection point and to relate the developed parameters to the field measured distress data. Required data for the study were extracted from the Long-Term Pavement Performance (LTPP) database. Thirty-five different pavement sections in the State of Texas were utilized in the study. Four comprehensive deflection parameters w ere developed. In addition, a scale was developed that may be utilized for the overall pavement structural condition evaluation. The developed parameters as well as the scal e were found to be well correlated to field performance of considered pavement sections. The newly developed parameters can als o be easily implemented in pavement management databases (PMS) that would help state department of transportation (DOTs) in making more informed decisio ns about the most suitable maintenance strategy. [ABSTRACT FROM AUTHOR]

Highlights • Backcalculate asphalt pavement layer moduli using ANN-GA program. • The relatively greater reduction of modulus was at high frequencies for asphalt concrete. • The slight modulus degradation was observed in granular base layer and subgrade. • The deterioration trend of asphalt concrete modulus was consistent with field fatigue cracking. Abstract This study aims to assess asphalt pavement condition in terms of backcalculated moduli of asphalt concrete (AC) and unbound material layers. An integrated Artificial Neural Network – Genetic Algorithm (ANN-GA) program was developed to backcalculate layer moduli using pavement surface deflection measured under falling weight deflectometer (FWD) test. Three pavement sections with FWD testing conducted at different time periods were used in the analysis. As damage developed in AC layer over years, the master curve of AC dynamic moduli showed the similar sigmoidal shapes but the modulus decreases as compared to the undamaged AC. The relatively greater variation of modulus degradation was observed for dynamic modulus in the high frequency range. On the other hand, the nonlinearity parameters obtained from backcalculation can be used to characterize modulus distribution at different depths in granular base layer and subgrade. The slight modulus degradation was observed in granular base layer and subgrade. The deterioration trend of AC modulus was found consistent with fatigue cracking measured at pavement surface based on field distress survey results. The study results indicate that FWD testing with advanced analysis can be successfully used to evaluate in situ pavement condition from structural point of view. [ABSTRACT FROM AUTHOR]

This paper presents the results from a test program to characterise resilient modulus (M R ) of subgrade soils for different geographic regions in South Carolina. For this study, Shelby tube samples of subgrade soils were collected from existing pavements in different regions: SC-93 in Pickens county (Upstate Area), US-521 in Georgetown county (Coastal Plain), and US-321 in Orangeburg county (Coastal Plain, near the fall line). Resilient modulus model parameters were obtained using both the bulk stress model and the generalised constitutive resilient modulus model. Statistical analysis was performed to develop M R estimation models for undisturbed soils using soils index properties. A correlation between laboratory measured M R with the modulus from Falling Weight Deflectometer tests was also developed. Finally, the effects of M R on subgrade rutting were studied using MEPDG. Results showed that the developed models offer higher reliability than the universal Long-Term Pavement Performance models in estimating the resilient modulus of undisturbed soils and predicting subgrade rutting for South Carolina. [ABSTRACT FROM AUTHOR]

In the Mechanistic–Empirical Pavement Design Guide (MEPDG), dynamic modulus of asphalt mixes is used as one of the input parameters in pavement analysis and design. For in-service pavements, MEPDG method uses a combination of some field and laboratory tests for structural evaluation of asphalt layers in rehabilitation projects. In this study, ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in provinces of Khuzestan and Kerman in the south of Iran. These provinces are known as hot climate areas and have severe climatic conditions. At each site, Falling Weight Deflectometer (FWD) testing was conducted and core samples were taken. These samples were extracted and mix volumetric properties and binder characteristics were determined. Results of these tests were used as input parameters in Witczak dynamic modulus prediction model for determination of MEPDG undamaged dynamic modulus master curves. Finally, the damaged (in-situ) dynamic modulus master curves were developed upon modifying the undamaged master curves with the damage factors determined from back calculation analysis of FWD data. It was found that with the above mechanistic-empirical procedure, it would be possible to successfully evaluate in-service asphalt layers located in severe climatic areas.

Reclaimed asphalt pavement (RAP) is a type of material that already suffers long-term aging in the field, so its aging characteristics become prominent since they are closely related to premature distresses and longevity of recycled pavements. While most of investigations of RAP mixtures are carried out in the laboratory, this study focuses on in situ aging of asphalt pavements with RAP overlays. A kinetics-based aging modeling approach is proposed to analyze and quantify long-term field aging of RAP overlays using the Falling Weight Deflectometer (FWD) data and climate data. The kinetics-based approach contains a modulus aging model with kinetic parameters (e.g. aging activation energy) for asphalt mixtures. Eight asphalt overlays are selected with different mixtures (RAP and virgin), thickness (50 mm and 125 mm), and surface preparation (milling and no milling). An asphalt pavement with an overlay has a composite aging process since the aging speeds of different asphalt layers are different. Thus an approach to separate the FWD modulus is developed in order to obtain the actual aging behaviors and properties of the overlay. By applying the kinetics-based modeling to the separated FWD moduli, the aging activation energies of both the overlays and old asphalt layers are determined. It is found that the RAP overlay has the highest aging activation energies and slowest aging rates among the RAP overlay, virgin overlay, and old asphalt layer for the selected pavements. It also reveals through the aging activation energy that the thick overlays age slower than thin ones, and the overlays on milled pavements age slower than those placed without milling. The findings in terms of the aging activation energy can be used to explain the difference in the field performance of overlay pavement sections. [ABSTRACT FROM AUTHOR]

This paper examines the effect of integrating insulation layers on pavement strength using falling weight deflectometer testing data conducted on an instrumented test road in Edmonton, Alberta, Canada. The insulated sections of this road consisted of a -metre-thick bottom ash layer and two polystyrene layers at thicknesses of 5 and 10 cm, while the adjacent conventional section functioned as the control section (CS). For the purpose of strength comparison, the effective modulus and structural number of insulated sections were compared to a conventional CS in a non-freeze-thaw season. The durations of pavement freezing, recovering and fully recovered (non-freeze-thaw) periods were established by monitoring the moisture variations in different pavement layers. The results indicated that using insulation layers generally reduces pavement strength, and this reduction is more pronounced in the insulated section with thicker polystyrene. [ABSTRACT FROM AUTHOR]

The falling weight deflectometer (FWD) is a widely used nondestructive test (NDT) device in pavement infrastructure. A FWD test measures the surface deflections subjected to an applied impact loading and the modulus of pavement layers can be determined by back-calculating the measured deflections. However, the modulus of asphalt layers is significantly influenced by temperature; hence, the temperature correction must be considered in back-calculation to evaluate the moduli of asphalt layers at a reference temperature. In addition, the in situ temperature at various pavement depths is difficult to measure. A model for evaluating the temperature at various depths must be established to estimate the in situ temperature of asphalt layers. This study collected the temperature data from a FWD test site to establish a temperature-evaluation model for various depths. The cored specimens from the test site were obtained to conduct dynamic modulus tests for asphalt layers. The FWD tests were applied at the FWD test site and the back-calculation was performed with temperature correction using the frequency-temperature superposition principle. The back-calculated moduli of asphalt layers were compared with the master curve of dynamic modulus to verify the application of the frequency-temperature superposition principle for FWD back-calculation. The results show that the proposed temperature-evaluation model can effectively evaluate the temperature at various depths of pavement. Moreover, the frequency-temperature superposition principle can be effectively employed to conduct temperature correction for FWD back-calculation.

A Mechanistic-Empirical (M-E) design based pavement quality or performance prediction methodology incorporating nondestructive test such as Ground Penetrating Radar (GPR) and Falling Weight Deflectometer (FWD) tests is demonstrated in this study. To facilitate, three pavement sites, namely, US285, US54, and I-40 in New Mexico are selected for nondestructive tests such as GPR and FWD. It is observed that the GPR predicted AC layer thickness is more consistent than base layer thickness. The FWD test was also conducted on the same locations, and like GPR, backcalculated layer moduli also shows varying level of inconsistency in different pavement sections. Based on the GPR and FWD tests, each of these three sites is divided into two major areas: one with the mean and the other with the minimum layer thicknesses and modulus. Layer thicknesses as well as moduli are incorporated to the AASHTOWare-ME software to determine load related distresses such as bottom-up crack and rut. Based on the amount of bottom-up cracks, the US54 pavement section is predicted to fail during 15th year of its service life, and the time of failure can be very early in the area with minimum layer thickness and modulus. Based on the rut prediction, pavement sections in US54 and I-40 is predicted to fail early. Finally, this methodology is recommended to implement to perform pavement quality assessment incorporating GPR and FWD tests in both project and network levels. [ABSTRACT FROM AUTHOR]

This paper presents the results of the application of two non-destructive tests (NDT): Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) to assess the bearing capacity of a flexible pavement. The main motivation of this research was the evaluation of the use of this two methodologies, over time-consuming, unsafe and costly traditional destructive methods, as a support for the decisions regarding pavement maintenance with concerns to its structural condition. The structural models were established based on the deflections from the FWD and using the design thickness and GPR measured thickness. The layers elastic moduli were estimated through back-calculation. The influence of having continuous accurate data on layer thickness was evaluated for a case study of a rehabilitated flexible highway pavement, in which surface cracking occurred only one year after reinforcement. The results show that the variability of the layers thicknesses was high and therefore the main focus was on the sensitivity of the estimated elastic moduli to the layers thicknesses. It was concluded that the thickness of the bound layers had a high influence on the estimated bituminous layers moduli and consequently on the pavement response models. Even though the results obtained are specific to this case study this research reinforced the importance of using GPR for continuous assessment of layer thickness together with load tests performed by FWD for an accurate structural evaluation of existing pavements. This paper is of interest for COST Action TU1208 Civil Engineering Applications of Ground Penetrating Radar. [ABSTRACT FROM AUTHOR]

The subgrade provides support to the pavement system and assures an effective distribution of traffic loads in depth. Therefore, a failure in the subgrade will have consequences on the entire pavement behaviour. This work presents an integrated approach for the analysis of the road subgrade condition by combining different Non-Destructive Testing (NDT) techniques. Different Ground Penetrating Radar (GPR) systems, both antennas configuration and frequencies, were tested in order to achieve the best methodology for subgrade cracking detection. Additionally, NDT load tests were performed with two deflectometers, Falling Weight Deflectometer (FWD) and Light Weight Deflectometer (LWD), aiming to determine the elastic modulus of the subgrade and consequently detect damaged areas. The tests were conducted at a real scale test section built to simulate pavement foundation layers consisting of clay soil subgrade, frequently used in African countries. The main tests performed are presented and analysed in this paper. Troubleshooting’s are referred mainly related with GPR wave propagation on clayey materials, due to high absorption. Recommendations are made regarding the use of GPR antennas as air-coupled antennas lead to a better identification of pavement layer interfaces while ground-coupled antennas were preferable to detect anomalous areas, namely cracking and debonding. The results showed good agreement between both NDT methods (GPR and load tests) in the identification of the anomalous areas and were validated with some in-situ cores extracted. [ABSTRACT FROM AUTHOR]

Evaluation and characterization of pavements that incorporate sustainable technologies and materials such as warm mix asphalt (WMA) and Reclaimed Asphalt Pavements (RAP) becomes especially important for their future applicability. Artificial neural networks (ANN) have been recently used to forward-calculate pavement layer moduli from falling weight deflectometer (FWD) test results. A full bond layer interface condition is commonly assumed to perform pavement layer moduli calculations; however, this condition is not guaranteed to happen in the field. The objective of this study was to develop ANN models capable of predicting pavement layer moduli rapidly and reliably for full bond and full slip layer interface conditions. ANN models were used to estimate the moduli of the National Center for Asphalt Technology (NCAT) Test Track structural sustainable sections for the full bond (FB) condition and the full slip (FS) condition. The results indicated that WMA sections had lower moduli at all tested temperatures compared to a control section (7-10% lower), likely due to the reduced binder aging experienced by these sections. RAP sections had higher moduli (16-43% higher) and were less susceptible to changes in temperature due to the presence of stiffer aged binder. Overall, backcalculated layer moduli using the conventional iterative approach had the highest error, followed by a significant decrease in error by ANN predicted moduli under full bond condition. However, the consideration of the ANN with full slip condition yielded the best results (lowest error). [ABSTRACT FROM AUTHOR]

The process of pavement maintenance and rehabilitation starts by collecting the data which will form the base for evaluation of pavement functional and structural condition. Collection of data can be performed by destructive and non-destructive testing. Usually preferred are the non-destructive methods, that do not damage the pavement, and the process of pavement evaluation is objective and repeatable. Non-destructive testing methods are becoming more and more popular, especially for assessing the structural condition of the pavement. Non-destructive testing by a Falling Weight Deflectometer (FWD) and the analysis of so collected data by the process of backcalculations is today the usual tool for assessing pavement bearing capacity. One of the basic input parameters for analysis of the data collected by FWD is pavement layers thickness.

This study evaluates airfield pavements’ functional- and structural-condition to determine the most economical maintenance method. As a part of the analysis, Pavement Condition Index (PCI) for several runways, taxiways, and aprons has been determined by MicroPAVER. Structural evaluation of airport pavements has been performed by Falling Weight Deflectometer (FWD) test. Evaluation of Layer Moduli and Overlay Design (ELMOD) also determines the required overlay thickness based on the E-values, i.e. FWD data analysis. Damage analysis determines the time of repeated overlay application. In addition, functional parameters have been included to determine the time of functional maintenance. Maintenance and rehabilitation alternatives have been selected to develop different program strategies. Life Cycle Cost Analysis (LCCA) has been performed to determine the maintenance cost. Structural condition based maintenance cost is compared to functional condition based maintenance cost. Comparison shows that structural condition based approach yields cheaper maintenance strategies than functional condition based maintenance approach.

This summary of the author’s PhD thesis supervised by Prof Dr Alfredas Laurinavičius and defended on 21 December 2011 at the Vilnius Gediminas Technical University. The thesis is written in Lithuanian and is available from the author upon request. Chapter 1 covers the analysis of the literatute. There is the review of research works carried out in Europe and other countries of the world for determining structural strength of road pavements by calculation methods during their design and gives a wide description of the main methods used in Lithuania. Chapter 2 gives the analysis of the effect of different factors on the road pavement strength, studies a damaging impact of the axle loads of moving vehicles on road pavement, also the dependency of strength and condition of road pavement on the changes in the ambient temperature and seasonal precipitation. Chapter 3 analyses the stages of experimental research, selection of a test section for experimental research, methodology for investigating pavement structure parameters and the equipment used, gives the analysis of research data obtained by the author. Chapter 4 describes statistical analysis and assessment of research results obtained on the subgrade and the lower pavement layers. Reduction coefficients are suggested to be used betwen the static and dynamic measuring methods.

Current research studies relationship between Falling Weight Deflectometer (FWD) deflection basin parameters and road pavement structural condition indicators, such as fatigue cracking and permanent deformations induced by low bearing capacity of pavement, and pavement equivalent E modulus (Eeq). The primary aim of the research was to develop limit values for deflection basin parameters: surface curvature index (SCI), base damage index (BDI) and base curvature index (BCI). Analyses of data derived from the Estonian Road Databank disproved the hypothesis of relationship between deflection basin parameters and pavement defects or rutting. Deflection basin parameters and back-calculated Eeq were found to be in good correlation. Strong relationships were found between upper layers indicators (SCI and BDI) and Eeq. Relationship between subgrade indicator BCI and Eeq, found in the research, was not very strong. Based on the aforementioned relationships, and the required min equivalent modulus of particular pavement, the equations to determine the limit values of deflection basin parameters for different types of pavements were developed. As the statistical analyses of such extensive database have been done for the first time in Estonia, the determined limit values have to be evaluated in practice and, if needed, corrected.

Road asset managers need to utilize reliable indicators for the structural condition and remaining service life at the network level to make rational decisions of the required funding and the optimum strategies for maintenance and rehabilitation. The surface deflection bowls and pavement critical responses were generated by computer simulations for a total of 2880 flexible pavement sections. The normalized area was computed from the deflection bowl data and it was found to be very well correlated with the compressive strain at the top of the subgrade. While the pavement surface curvature and area under pavement profile were highly correlated with the tensile strain at the bottom of the asphalt concrete layer. Thus, these parameters were used to evaluate the remaining service life in rutting and fatigue. Field data showed an excellent match between the trends obtained from the field and computer simulated data. [ABSTRACT FROM AUTHOR]

Pavement surface deflection has been used by several highway agencies to assess the structural condition of the pavement structure. Falling weight deflectometer, deflectograph and other devices are commonly used to measure the deflected shape of the pavement surface under loading. Several parameters have been derived from the measured deflection bowl to evaluate pavement structural condition; however, there is no universally agreed parameter that can reliably rank the structural condition of the highway network. In addition, each pavement type deflects differently under traffic loads. Therefore, it is not possible to have one single scale to evaluate and rank pavement structural capacity for all different types. In this research paper, four different scales were developed to evaluate structural capacity of different flexible pavement structures. The area ratio, deflection ratio and their normalised values were derived from the deflection bowls of both field measured deflections and computer simulated data. [ABSTRACT FROM AUTHOR]

Voids under a concrete slab are common in composite pavement because of difficulties in controlling grouting treatment. To evaluate grouting treatment for composite pavement accurately and then to optimize the grouting scheme, the modulus of subgrade reaction (the k-value) was proposed as the evaluation criteria of grouting treatment. Based on deflection basin data acquired by a falling weight deflectometer (FWD) on a test road, k-values under slabs were backcalculated and various treatment schemes were compared by statistical methods. Results show that grouting treatment makes the average support strength in the first and second lanes of test road increase by 11.21 % and 13.16 %, respectively. Grouting under the center of a slab has a negative effect on pavement strength. Hence, a four-hole grouting scheme is recommended instead of the five-hole grouting scheme. Besides, pavement grouting can also significantly strengthen the support under adjacent slabs that are not treated directly. [ABSTRACT FROM AUTHOR]

Falling Weight Deflectometer (FWD) produces pavement responses using a falling mass drop. This study investigated the features involved in the finite element modeling of FWD tests to help in the calibration of backcalculation. Falling mass, model size, subgrade damping, and boundary conditions were studied to reveal the significances of these factors on pavement responses. By modeling the falling mass in finite element models, this study has justified the idea that field-measured time history of impact force can be used as an alternative to falling mass. It is also concluded that subgrade damping, self-weight of slab, and boundary conditions are significant in modeling and interpretation of FWD finite element analysis. Finite element model with at least six times radius of relative stiffness is required to simulate dynamic responses of a continuously reinforced concrete slab. [ABSTRACT FROM AUTHOR]