Pavement Test Research Articles

Mechanistic evaluation of a monitored pavement constructed with asphalt surface treatment

Este artigo objetiva apresentar os resultados preliminares de um trecho monitorados em Goiás, incorporando análises mecanicistas de modo a contribuir com o banco de dados de materiais, tecnologias e desempenho de um pavimento asfáltico executado com Tratamento Superficial Duplo (TSD). Para isso, nesta pesquisa foram realizados ensaios laboratoriais com os materiais em termos de caracterização, comportamento mecânico e resiliente dos componentes de cada camada, verificando também o comportamento do cascalho melhorado com cimento em três teores diferentes. A seção de teste do pavimento foi monitorada durante a execução e até 6 meses após liberação do tráfego, por meio da determinação das deflexões, das macro e microtexturas, da medida da trilha de roda, da avaliação do tráfego e da identificação dos defeitos aparentes. O dimensionamento do TSD também foi avaliado. As tensões e deformações desenvolvidas ao longo das camadas foram obtidas e os módulos de campo determinados por meio de retroanálise. Os resultados mostraram ganho de desempenho mecânico com a adição de cimento no cascalho, falhas na execução, surgimento precoce de patologias, elevadas deformações nas camadas inferiores à base e superdimensionamento de emulsão no TSD.

Frequency adjustment method for in-situ seismic modulus of asphalt concrete

ABSTRACT In a mechanistic-empirical (ME) pavement design method, the modulus of asphalt concrete (AC) is essential. The in-situ AC modulus can be obtained by the surface wave method (SWM). However, the measured modulus needs to be adjusted to the design frequency values. This study aimed to propose a frequency adjustment method for the in-situ AC seismic modulus. For this purpose, coring and dynamic modulus tests, FWD (Falling Weight Deflectometer) tests, and PSPA (Portable Seismic Pavement Analyzer) tests were carried out in the accelerated pavement test (APT). The master curves generated by the dynamic modulus results correlated well with the moduli determined from the other tests. Based on this relationship, a frequency adjustment factor was developed for the seismic modulus of the undamaged AC layer. For the damaged AC layer, the proposed factor was modified by incorporating the effect of the damage. Finally, to validate the frequency adjustment factor, the measured maximum tensile strains in the APT were compared with the values determined from the adjusted seismic moduli. The results prove that the frequency adjustment factor is appropriate to obtain the design modulus from the surface wave test. The PSPA test is also recommended to obtain the in-situ AC seismic modulus.

Hilbert-Huang transformation (HHT) based texture profile analysis for continuous friction characterisation of pavements

ABSTRACT Continuous friction measurement equipment (CFME) has been demonstrated as an appropriate method to acquire friction around the critical slip ratio for the Pavement Friction Management (PFM) programme. Through a comprehensive field data collection on testing sites with different preventive maintenance (PM) treatments, this study assessed the influences of various characteristics on the CFME measurements. Field friction data were collected by a Grip Tester, one type of CFME, and the corresponding texture profiles were acquired by a high speed texture profiler. For each testing site, friction data was measured under nine operational conditions with three water film depths and three testing speeds. An adaptive signal processing technique, Hilbert-Huang Transformation (HHT), was applied to extract amplitude and instantaneous frequency of profiles as the texture parameters. Subsequently, the HHT texture parameters, along with pavement conditions and testing operational characteristics, were deployed as the influencing factors for the development of statistical friction model. The results reveal that the CFME measurements are most sensitive to the change of water film depth and pavement surface texture properties. This study is anticipated to gain a better understanding of the characteristics of CFME measurements and implement CMFE to support PFM programme effectively.

Performance Evaluation of Fiber-Reinforced, Stress Relief Asphalt Layers to Suppress Reflective Cracks

In this study, the performance of the fiber-reinforced, stress-absorbing membrane interlayer (F-SAMI) method was evaluated to suppress reflective cracks, which usually occur when the overlay method is applied for the maintenance of existing aged pavement. The F-SAMI method has an effect of suppressing the occurrence of reflective cracks by constructing a material composed of emulsified asphalt, fibers, and aggregates between the surface layer and the base layer. The mechanical performance of the F-SAMI was evaluated through both small-scale (model mobile load simulator 3, or MMLS3) and large-scale (accelerated pavement testing, or APT) pavement acceleration tests on the specimen and pavement structures, respectively, with the F-SAMI layer applied between the surface layer and the base layer. In this study, the base layer was made with an asphalt mixture or a concrete mixture, and the surface layer was made with polymer-modified stone mastic asphalt (PSMA). Evaluation was conducted by applying four types of F-SAMI layer, according to the content of asphalt and aggregate and compared with the case where general tack coating was applied. In order to induce the occurrence of reflective cracks, a notch was made in the center of the base layer. As a result of the experiment, it was shown that regardless of the mixture type of the base layer, the specimen or pavement with the F-SAMI method was much more resistant to reflective cracking than those with the tack coating. In addition, it was found that the F-SAMI method with aggregates was more resistant to reflective cracks than that without aggregates.

Evaluation of Bonded Concrete Overlay of Asphalt under Accelerated Loading

Bonded concrete overlay of asphalt (BCOA), previously known as ultra-thin whitetopping (UTW), has been widely used to repair aged asphalt concrete (AC) pavements with moderate distresses. Because of the increasing costs of roadway maintenance, Louisiana has a great interest in determining whether thin BCOA (usually 2–6 in.) is a suitable and cost-effective alternative to the current practice of roadway maintenance. The objective of the study was to evaluate the performance of BCOA pavement and to identify the influence of in-situ interface bond strength on the performance of BCOA pavements. Three full-scale BCOA test sections with thicknesses of 6 in., 4 in., and 2 in. of Portland cement concrete (PCC) over an aged asphalt pavement were tested under accelerated pavement test (APT) loading under typical pavement conditions in southern Louisiana. Each section was trafficking-loaded to a failure (i.e., all the slabs in the loading path were cracked) under alternating load magnitudes of 9 kips and 16 kips of the ATLaS dual-tire wheel load. A falling weight deflectometer (FWD) backcalculated the effective thickness, a trench-cutting investigation was undertaken, and in-situ pull-off test revealed that a good bond was established initially between the PCC and AC layer. Several non-destructive test (NDT) methods indicated that the distresses of a BCOA slab could be coupled with a possible debonding at the PCC-asphalt interface. This paper mainly focuses on the APT results and the performance of BCOA test sections with different overlay thickness.

MRAC and MPC Controllers for Load Application System of the Accelerated Testing Equipment of Pavements

For the study of pavement structures, different methodologies and devices have been used and those have been modified and modernized. The development of these routes directly impacts the social and economic development of the different regions. Through the roads, the interconnection between different points is allowed, and the resources that need to be invested for its construction are high. Trends show real-scale studies to determine real operating parameters that allow improving design processes. For this reason, test devices have been developed that simulating real operating conditions, but these machines require robust and efficient control. Adaptive and predictive controls are the most used in industrial processes, where it is necessary to reduce performance and operation costs—obtaining smooth transitions in the control signal, especially when techniques are used with follow-up to reference models. This document shows the design of the MRAC (Adaptive Reference Control Model) and MPC (Predictive Control Model) controller applied to a hydraulic loading system for real-scale pavement test equipment. The mathematical development of the plant and the controllers is presented, along with its implementation, simulation, and analysis. The main objective of this work is to verify the effectiveness of these controllers for this type of real scale system since due to the number of variables that affect these devices and the complexity of the study material.

Accelerated testing of a recycled road structure made with reclaimed asphalt pavement material

The study focuses on implementing the reclaimed asphalt pavement (RAP) recycling method on a classical road pavement, by totally replacing the base course with one made with reclaimed materials. For this purpose, four flexible pavements were constructed, instrumented and tested on an accelerated pavement testing (APT) facility, while capturing the structural condition. The contribution of each structural layer to the total rut depth and the variations of maximum strains were determined. The APT provided reasonable results that reinforce the potentially promising considerations of implementing the RAP recycling method in the perspective of the future development of the road networks.

Identification of Pavement Model Parameters in the Area of Discontinuous Surface Deformation Based on FWD Tests

Determination of the parameters of the pavement model in the linear discontinuous surface deformation (LDSD) area is presented in the article. The values are based on back calculations which involve results obtained from the elastic half-space model and the elastic—perfectly plastic model implemented in the finite element code compared with the results of the pavement deflection measured with Falling Weight Deflectometer (FWD). Based on the results of the calculations which have been matched to the results of the in situ measurements, the obtained values of the parameters of the pavement model within LDSD zone and outside it, were analysed. The results of pavement tests indicate at least a threefold increase in pavement deflections in the discontinuous deformation zone compared to deflections in the sections not affected by LDSD. The results of in situ tests and computational analysis presented in the paper allow their use in pavement reinforcement design in the area of anticipated LDSD.

Drainage Capacity and Resistance to Clogging of Porous Asphalt Concrete Based on the Water Penetration Test and Constant Head Permeability Test

Abstract Porous asphalt concrete (PAC) can decrease the risk of hydroplaning, reduce splashing and spraying, improve visibility, reduce traffic noise, and improve driving safety, but the clogging of the void affects its durable function. To investigate this, the fine aggregate was chosen as a plugging agent, and the permeability coefficients and water permeability coefficients were measured by using an asphalt mixture permeability testing device and pavement surface permeameter to simulate a multicycle drainage clogging experiment of PAC. The influence of asphalt mixture design parameters, including voids volume (VV), the nominal maximum aggregate sizes (NMASs), grading types on the drainage capacity, and resistance to clogging, was investigated. The two test results indicated that VV has a manifest influence on both drainage capacity and resistance to clogging. The NMAS has an obvious influence on resistance to clogging but no clear influence on the drainage capacity. PAC with the coarser gradation has better performance on drainage capacity and resistance to clogging. The clogging location is concentrated on the top 40 mm of the PAC-13 specimen. The fine particles with diameters of 0.15 to 2.36 mm are the key particles causing the clogging in the PAC-13 specimen. Water permeability coefficients and permeability coefficients have a very high correlation.

Accelerated Pavement Testing to Evaluate the Reinforcement Effect of Geogrids in Flexible Pavements

This study presents an accelerated pavement testing (APT) to evaluate the reinforcement effect of geogrids in flexible pavements. A full-scale conventional three-layer flexible pavement structure was constructed, and was divided into one unreinforced section and two reinforced sections with base reinforced by geogrids placed at different depth of base course. The testing program was divided into three parts: performance testing, response testing, and forensic evaluations. The performance testing recorded the development of surface permanent deformation with the number of loadings. The falling weight deflectometer (FWD) was employed to investigate deflections and moduli of flexible pavements in the response testing. The excavation of pavements was to further analyze reinforcement mechanisms. Test results demonstrated the benefits of incorporating geogrids in base course in reducing the permanent deformation and improving the modulus of base course. Compared with the unreinforced section, accumulated permanent deformations in the two reinforced sections decreased significantly, with a drop of 13%–37%, and the back-calculated moduli of the reinforced base increased by 58%–78% after APT. It was possible that sufficient permanent deformation was needed for mobilizing geogrids to constrain lateral movements of granular particles, to increase the overall structural behavior of the reinforced base course, and to improve the stress distribution on the subgrade. These interaction mechanisms were also confirmed in the pavement trench. For a pavement system consisting of a thin surface and base layer, the proper placement position of geogrids was at the base–subgrade interface for this test and loading arrangement.

Evaluation of two nano-silane-modified emulsion stabilised pavements using accelerated pavement testing

ABSTRACT Upgrading, maintenance and rehabilitation of road infrastructure is expensive, especially in view of the growing scarcity and cost of suitable road building materials. In areas with high mica content and secondary minerals such as smectite in the natural materials, stabilisation with cement is not viable. The Council for Scientific and Industrial Research of South Africa has embarked on a research programme to evaluate the performance of substandard materials improved with anionic nano-silane modified bitumen emulsions for use in base and subbase layers. This work comprises laboratory testing as well as Accelerated Pavement Testing using the Heavy Vehicle Simulator (HVS). The results of a full-scale HVS test on a light pavement as well as initial analysis on a medium traffic road are discussed. It has been shown that stabilisation of available substandard materials using an anionic nano-silane modified bitumen emulsion compared with the standard approach of importing high quality crushed aggregate can lead to savings as high as 40%–50% for equivalent performance. In addition, there was also a significant reduction in construction effort and time.

Effect of truck speed on the response of flexible pavement systems to traffic loading

ABSTRACT The road network in South Africa, particularly in urban areas, is experiencing a steady increase in traffic volumes and congestion. Speed has a significant effect on the response of flexible pavement systems to traffic loading. Truck tyre loads are more often analysed as a static load in order to simplify the computations, although in reality the pavement system is subjected to a dynamic load. This paper investigates the influence of truck speed on flexible pavement system response to moving traffic loading. A truck with standard axle loads was used to conduct runs at controlled speeds and wander over a full-scale instrumented pavement test sections on road R104 east of Pretoria. The findings of this research indicate that pavement deflections increase exponentially as the truck speeds reduce to speeds below 30 km/h. Furthermore, deflections decrease marginally as the truck speeds increase to speeds greater than 40 km/h. Different flexible pavement systems present different exponential factors that reflect differences in sensitivity of the pavement systems to changes in truck speed. It is thus essential to introduce adjustment factors to deflection measurements done at different truck speeds on different pavement systems in order to compare such deflection data.

Full-Scale Evaluation of Relatively Thin Airfield Pavements

A full-scale airfield pavement test section was constructed and trafficked by the U.S. Army Engineer Research and Development Center (ERDC) to evaluate the performance of relatively thin airfield pavement structures. The test section consisted of four test items that included three asphalt pavement thicknesses and two different aggregate base courses. The test items were subjected to simulated aircraft traffic to evaluate their response and performance to realistic aircraft loads. Rutting behavior, instrumentation response, and falling weight deflectometer response were monitored at selected traffic intervals. It was found that the performance of the airfield pavement sections were most sensitive to aggregate base course properties, where a 50% reduction in base course strength resulted in a 99% reduction in allowable passes. The data suggested that when sufficient asphalt thickness is not provided, the failure mechanism shifted from subgrade failure to base course failure, particularly at higher subgrade CBR values. In addition, the number of aircraft passes sustained was less than that predicted by current Department of Defense (DOD) methods that include assumptions of a high-quality aggregate base and a minimum asphalt concrete thickness. The results of this study were used to extend existing DOD pavement design and evaluation techniques to include the evaluation of airfield pavement sections that do not meet the current criteria for aggregate base quality and minimum asphalt concrete surface thickness. These performance data were used to develop a new base failure design curve using existing stress-based design criteria.

Asphalt fatigue endurance limit estimation and impact on perpetual pavement design

ABSTRACT The National Cooperative Highway Research Program (NCHRP) Project 9-38 developed a method for estimating asphalt fatigue endurance limit (FEL) which employs bending beam fatigue (BBF) lives. Another project, NCHRP 9-44A, used BBF test data to formulate a healing-based FEL prediction model. Both procedures were evaluated in this study by utilising data from the National Center for Asphalt Technology Pavement Test Track. The estimated FELs were used in perpetual pavement design to investigate their impact on asphalt thickness. The NCHRP 9-44A-predicted FELs increased with longer rest periods, but largely stabilised after 8 s, which agreed with the NCHRP 9-44A researchers’ conclusion that no healing occurs after a rest period of 5–10 s. Overall, the NCHRP 9-38 method yielded greater FELs. Without binder modification and/or high binder content, both methods provided similar FELs, if a rest period longer than 5 s was entered in the NCHRP 9-44A model. Generally, the NCHRP 9-44A-predicted FELs produced thicker layers. However, for conventional asphalt mixtures, both sets of FEL yielded similar thicknesses, if the NCHRP 9-44A model applied a rest period exceeding 5 s. The NCHRP 9-44A model’s predictive capability will increase if it is recalibrated with mixtures containing modified binder and/or higher binder contents.

Mechanistic Analyses and Modeling of Pavement Sections Utilizing Sustainable Aggregate Quarry By-Product Applications

This paper presents a modeling study based on finite element (FE) analysis to mechanistically evaluate flexible pavements constructed with quarry by-products (QB). Twelve pavement test sections, a control section, and 11 others incorporating QB as unbound subgrade replacement and chemically stabilized base/subbase applications were evaluated for field performance using accelerated pavement testing (APT). First, falling weight deflectometer (FWD) deflection basin parameters were calculated and compared with critical pavement responses to evaluate the structural adequacies of the QB pavement sections. The moduli of the constructed pavement layers were then backcalculated from the FWD deflections using the GT-PAVE FE analysis program with nonlinear and cross-anisotropic layer characterizations. For stabilized QB applications, the layer properties calculated from this analysis for the base/subbase layers were used to calculate critical pavement responses. The sections were compared using a response benefit parameter, defined as the ratio of maximum resilient surface deflection in a conventional pavement, as the control section, to that obtained for each section having a certain QB application in consideration. According to the results obtained from the APT sections and the mechanistic FE analyses, the measured and calculated FWD deflection basins were successfully matched with individual sensor errors not exceeding 5% for all 12 test sections. The calculated response benefits indicated significant advantages for using cement-stabilized QB applications over fly ash-stabilized QB applications and conventional flexible pavement sections. Considering the pavement structural response benefits and good performance trends observed, major cost benefits can be realized by routine use of these sustainable QB applications.

Load Deflection Profile of Concrete Block Pavement

Although worldwide concrete block pavements have been applied successfully in roads and industrial pavements since past 70 years, recently they are used in India in urban roads, footpaths, petrol pumps, parking areas, industrial hardstands and border roads. The concrete blocks form the surfacing of the pavement and are the major load spreading elements. There have been many past stories in respect of load deflection behaviour of block pavements and the outcome of which is inconsistent. This paper describes the results of experiments conducted to access the variation of block parameters, sub-base thickness and loading plate diameter on the load deflection profile of the pavement. The test pavement 3000 mm × 3000 mm was constructed on a sandy clay sub-grade to study these parameters based on plate load test. The applied load on the pavement was 51 KN, which corresponds to the half of the single axle legal limit presently enforced in India. The results thus obtained are compared to those of earlier findings, and the corresponding conclusions are drawn.

In-situ and numerical investigation on the dynamic response of unbounded granular material in permeable pavement

Permeable pavements have been widely used as an effective means to improve hydrological characteristics and the ecology of the urban environment. This study aims to investigate the response of fully permeable pavement (FPP) subjected to dynamic loading under dry and saturated conditions. A full-scale test track topped with polyurethane bound permeable material (PUPM) was built to obtain the stress response with an accelerated pavement test (APT) system. In addition, comprehensive analyses were performed based on the coupled Stress-dependent Moisture-sensitive Cross-anisotropic Elastoplastic (SMAEP) model in FEM. The APT test showed that the worst state was observed when the pavement structure was fully saturated, and that and brittle failure of the pavement surface occurred when the critical load level was achieved. The prediction of vertical stress predicted by Stress-dependent Cross-anisotropic Elastic (SAE) and SMAEP were both validated with the field data. The horizontal stress predicted by SAE gave a very high and unreasonable tensile stress prediction at the bottom of the unbounded granular base (UGB) layer when subjected to the high load level. With the consideration of moisture effect and the plastic properties of the material, the prediction made by SMAEP is effective to estimate the dynamic response of the UGB layer. Based on the sensitivity analysis, the optimized designs for FPP based on PUPM were suggested.

A Study on Performance of Roller-Compacted Concrete Pavement in Accelerated Pavement Tests

Abstract Roller-compacted concrete pavement, or RCCP, is well-known for its low cost and fast construction. Through compaction, the friction induced by aggregate interlock provides additional load carry capacity at the beginning of construction. Although its construction procedure is quite different from typical conventional concrete pavement, RCCP consists of the same basic ingredients as conventional concrete pavement. The characteristics of RCCP make it an excellent alternative for port, intermodal, street, and highway applications. Even though this pavement has been used for decades, research on and experiences in its application are still limited, particularly in Korea. In order to evaluate the performance of RCCP, two phases of an accelerated pavement test were conducted. In Phase One, the performance of RCCP at two different strengths (35.6 and 30.4 MPa) is evaluated. In Phase Two, the performance of RCCP with different thicknesses (5, 7.5, and 10 cm) is investigated. The number of load repetitions to fatigue crack occurrence in each section is compared to the estimated fatigue failure determined from the fatigue equation for RCCP. The crack development in each section is compared to the crack model for jointed plain concrete pavement. Overall, it is confirmed that RCCP has equal or better performance compared to the estimation in terms of fatigue cracking.

Development of fatigue damage model of asphalt mixtures based on small-scale accelerated pavement test

As the primary surface type for high-grade Chinese highways, the long-term performance of asphalt pavement can affect significantly transportation efficiency. It has been confirmed that fatigue cracking is one of the major failure modes for asphalt pavement, which can cause a great reduction of asphalt pavement durability. Currently, the fatigue properties of asphalt mixtures are evaluated mainly based on traditional laboratory fatigue tests, such as bending fatigue tests and indirect tensile fatigue tests. However, none of these fatigue test methods can realistically evaluate the fatigue performance of asphalt pavement under the repeated wheel load. To resolve this issue, the model mobile load simulator (MMLS3), which is a small-scale accelerated pavement test device, was utilized to evaluate the fatigue life of six kinds of asphalt mixtures. The fatigue damage variable was defined as stiffness reduction. Based on the small-scale accelerated pavement test, a stiffness reduction model for asphalt mixtures was determined. A stiffness reduction law for asphalt mixtures during the fatigue process was proposed. The stiffness evolution process could be divided into three phases, which are the adaptation phase, the quasi-stationary phase, and the failure phase. A maximum value of the rate of stiffness reduction from the quasi-stationary phase into the failure phase was proposed as the failure threshold. Besides the fatigue life obtained from the failure criteria had a good agreement with the test results. The results from this research can be used as a theoretical reference for evaluating the fatigue life of asphalt mixtures and improving the durability of asphalt pavement.

Development and application of a non-destructive pavement testing system based on linear structured light three-dimensional measurement

Automatic detection dramatically improves the efficiency and accuracy of asphalt pavement inspection. However, the existing detection systems cannot coordinate the balance between efficiency and accuracy. Three-dimensional pavement detection was proposed and developed in this article. The theoretical model of camera imaging was first established based on optical triangulation. The camera’s intrinsic and extrinsic parameters were evaluated by utilizing a checkerboard calibration target, and the camera lens distortion was also considered to ensure the accuracy of the three-dimensional measurements. The subpixel coordinates of the single-stripe center were extracted based on two-dimensional image processing technology, and then the pixel coordinates were converted into real-world elevation coordinates based on the camera imaging model. The cubic spline method and the three-dimensional data filtering method based on the pavement surface profile were applied to restore the data and remove the noise, respectively. Then the three-dimensional reconstruction was achieved based on Delaunay triangulation algorithm. We expect that this new system can significantly reduce the costs without decreasing the test accuracy, thus making large-scale engineering applications viable.