Pavement Test Research Articles

Assessing and predicting fatigue damage of road pavement using embedded sensors and deflection measurements: a full scale test

Regular and long-term infrastructures monitoring is fundamental for asset management, as it provides information on the actual mechanical conditions and triggers maintenance actions. Several tools are currently used for this purpose, such as embedded sensing devices, deflection measurements and visual inspections. In this paper, we analyse data from a full-scale experiment performed on the accelerated pavement testing (APT) facility of the Université Gustave Eiffel (formerly Ifsttar) during the BioRepavation project. Dvnifferent monitoring data are recorded and compared: strains from asphalt strain gauges (ASGs), deflections from Benkelman beam and Falling Weigh Deflectometer (FWD) and crack development survey. Deflections measurements at the end of the fatigue test were used to inverse calculate the layer moduli of pavement. Based on this model, numerical strains are calculated and compared with sensor measurements. The analyses conducted proved that instrumentation embedded ASGs and temperature probes can be used valuably to assess pavement fatigue.

GPR Monitoring of Artificial Debonded Pavement Structures throughout Its Life Cycle during Accelerated Pavement Testing

The paper gives an overview of a ground penetrating radar (GPR) experiment to survey debonding areas within pavement structure during accelerated pavement tests (APT) conducted on the university Gustave Eiffel’s fatigue carrousel. Thirteen artificial defect sections composed of three types of defects (Tack-free, Geotextile, and Sand-based) were embedded during the construction phase between the top and the base layers. The data were collected in two stages covering the entire life cycle of the pavement structure using four GPR systems: An air-coupled ultra-wideband GPR (SF-GPR), two wideband 2D ground coupled GPRs (a SIR-4000 with a 1.5 GHz antenna and a 2.6 GHz-StructureScan from GSSI manufacturer), and a wideband 3D GPR (from 3D-radar manufacturer). The first stage of the experiments took place in 2012–2013 and lasted up to 300 K loadings. During this stage, the pavement structure presented no clear degradation. The second stage of experiments was conducted in 2019 and continued until the pavement surface demonstrated a strong degradation, which was observed at 800 K loadings. At the end of the GPR experiments, several trenches were cut at various sections to get the ground truth of the pavement structure. Finally, the GPR data are processed using the conventional amplitude ratio test to study the evolution of the echoes coming from the debonded areas.

Pavement moduli back-calculation using artificial neural network and genetic algorithms

An Artificial Neural Network (ANN)-based back-calculating program combined with a Genetic Algorithm (GA) optimization algorithm was developed for the back-calculation of flexible pavement layer moduli. Deflections measured using geophones on a model pavement structure under accelerated pavement testing (APT) with the MLS30 were utilized for back-calculating the pavement layer moduli. As theoretically expected of visco-elastic materials that are temperature dependent, the back-calculated moduli of the asphaltic layers, namely the surfacing and base, exhibited a decreasing trend with an increase in the temperature and number of APT load cycles. By contrast, the moduli of the unbound base layer and subgrade exhited insensitivity to temperature changes and did not decay significantly as a function of the APT loading. Overall, the integrated GABP algorithm (based ANN formulation) exhibited potential in satisfactorily back-calculating the pavement layer moduli form geophone measured deflections with acceptable accuracy. The splitting fatigue test results show that the fatigue life of asphalt mixture decreases with the increase of loading cycles, which can verify the feasibility of back-calcultion model.

Pavement design method in Japan with consideration of climate effect and principal stress axis rotation

Current Japanese design guide uses mechanical-empirical criteria to predict the failure loading number against fatigue cracking and rutting. However, these criteria have some limitations that the variation in moduli of base and subgrade layer due to the fluctuation in water contents, freeze–thaw history, and stress states are not considered. As well known, these factors greatly affect the soil mechanical properties like resilient modulus. Besides, present rutting failure criterion provides no indication of the behavior of rutting over time, and the effect of principal stress axis rotation on rutting development is also not captured. To overcome such limitations, this study modified the present Japanese pavement design method through the following two main aspects: (1) Replacing constant elastic modulus of base and subgrade layer to resilient modulus related to stress states and complex climate conditions, which are defined as the combination of fluctuating water content and freeze–thaw action; (2) Modifying rutting failure criterion by considering generally used MEPDG model and also the effect of principal stress axis rotation. All modifications are performed based on laboratory element test like suction-controlled freeze–thaw triaxial test, which could simulate complex climate conditions, and multi-ring shear test, which could simulate principal stress axis rotation. Besides, modified criteria are examined by comparing to long-term measured performance of test pavements built in Hokkaido, the north island of Japan. Modified Japanese pavement design method shows high applicability and accuracy on the pavement life prediction, especially for the flexible pavement in cold regions like Hokkaido.

Structural Evaluation of Flexible Pavement Constructed with Steel Slag–Fly Ash–Lime Mix in the Base Layer

The concept of utilizing industrial wastes for road construction can be materialized only by evaluating the field performance of roads constructed with these wastes. The present study encompasses the laboratory investigation of steel slag–fly ash–lime (SFL) mix substantiated by field evaluation of flexible pavement test sections constructed with SFL mix in the base layer. Based on grain size analysis and unconfined compressive strength (UCS) test, 75% steel slag+19% fly ash+6% lime mix was chosen as a potential replacement for wet mix macadam (WMM) in the base layer of flexible pavement. The UCS test results were supported by the shear strength parameters and resilient moduli of optimum SFL mix. The superior stiffness characteristics of the SFL mix obtained in laboratory investigation were validated with a detailed structural evaluation of flexible pavement test sections constructed with 150 and 250 mm thick SFL base. Stiffness-based quality control approach was adopted during the construction of test sections through light weight deflectometer (LWD). SFL base layers exhibited higher in situ stiffness when compared to that of WMM. From the structural evaluation of test sections with falling weight deflectometer (FWD), sections with SFL base layer exhibited lower peak deflections than that of conventional WMM. The back-calculated elastic modulus computed from FWD test for SFL base layers was more than five times that of WMM. Furthermore, test sections with SFL base layer showed a service life ratio up to 2.6 and a notable cost saving up to 15% compared to conventional WMM layer.

Performance of AC overlays using geogrids on PCC contraction joints

It is widely known that vertical displacements and strains occur on the joints and these cause defects on the asphalt concrete (AC) overlays on existing Portland cement concrete (PCC) pavements. Various approaches were introduced to minimize these defects. In this study, the effect of joint support formed using the geogrid material with grout mortar on the vertical displacement of PCC and the strain at the bottom of the AC layer. Produced layers were exposed to 1,186,000 Equivalent Single Axle Load (ESAL) in an APT (Accelerated Pavement Test) facility and the results were monitored. According to the obtained results, the use of AC overlay reduces vertical displacement in the PCC by 75%. When geogrid reinforced AC overlay was used, an additional reduction in displacement by 41.2% was achieved. Geogrid reinforcement reduced strain values formed at the bottom of the AC layer from 29.5% to 92.5%. The use of geogrid at joints instead of increasing the thickness of the AC layer from 50 to 80 mm resulted a more significant reduction in both strain and displacement. Besides, the usage of a geogrid interlayer instead of increasing the thickness of the AC layer also provided a significant cost reduction of 57.9% in overall cost.

Evaluation of Cost-Effective Modified Binder Thin Chip and Cape Seal Surfacings on an Anionic Nano-Modified Emulsion (NME)-Stabilised Base Layer Using Accelerated Pavement Testing (APT)

Emulsion stabilisation of base layers surfaced with chip seals often proves problematic, with chips punching into the base and early distress. This can be aggravated by the use of modified binders that restricts the evaporation of moisture from pavement layers. The introduction of new-age (nano)-modified emulsion (NME) stabilisation has the advantage that water is chemically repelled from the stabilised layer, resulting in an accelerated development of strength. A need was identified to evaluate the early-life performance of selected chip and Cape seals, together with identified modified binders on anionic NME-stabilised base layers constructed with materials traditionally classified as unsuitable, using archaic empirically derived tests. Three different chip seal surfacings with unconventional modified binders were constructed and evaluated using accelerated pavement testing (APT) with the Model Mobile Load Simulator—3rd model (MMLS3). The objectives of the experimental design and testing were to evaluate the binder performance, chip seal performance in terms of early loss of chips before chip orientation, punching of the chips into the anionic NME-stabilised base and deformation characteristics of a Cape seal that was hand-laid using an anionic NME slurry without any cement filler. It was shown that that chip seal surfacings can be used at low risk, on a base layer containing materials with fines exceeding 22%. The selection of specific modified binders can reduce risks associated with chip seal surfacings, which can impact construction limitations. The recommended use of elastomer-modified binders on newly constructed or rehabilitated layers, resulting in moisture entrapment, needs to be reconsidered.

Bender Element Field Sensor for the Measurement of Pavement Base and Subbase Stiffness Characteristics

Layer modulus values are important input parameters in mechanistic pavement design and evaluation methods. Direct measurement of the stiffness characteristics of pavement base/subbase has been a challenging task. Nondestructive testing methods that are commonly used based on surface deflection measurements not only require a backcalculation process, but also have limitations on measuring local stiffness within the layer. This paper presents the result of a recent research effort at the University of Illinois aimed to develop a new sensor for the direct measurement of the in-situ moduli of constructed unbound pavement layers. The new sensor employs bender element (BE) shear wave transducers embedded in a granular base/subbase to evaluate the layer modulus from shear wave velocity measured at any depth and any orientation. To provide appropriate protection for the BE sensor and its cable connections, a stainless-steel cable guide, a sensor protection module, and a protection cover for the sensor were designed and optimized. A laboratory calibration box containing sand-sized crushed aggregates was used in the development stage of the BE sensor design. The BE sensor results were also studied for a typical dense-graded base course aggregate commonly used in Illinois. Finally, the BE sensor was installed in a field trial in newly constructed airport pavement test sections, and its layer modulus measurements were compared with results estimated from Dynamic Cone Penetrometer testing. The new BE field sensor has proven to be a viable direct measurement technique in transportation geotechnics applications to monitor stiffness characteristics of pavement granular base/subbase layers.

Estimation of the Vehicle Speed Using Cross-Correlation Algorithms and MEMS Wireless Sensors.

Traffic information is critical for pavement design, management, and health monitoring. Numerous in-pavement sensors have been developed and installed to collect the traffic volume and loading amplitude. However, limited attention has been paid to the algorithm of vehicle speed estimation. This research focuses on the estimation of the vehicle speed based on a cross-correlation method. A novel wireless micro-electromechanical sensor (MEMS), Smartrock is used to capture the triaxial acceleration, rotation, and stress data. The cross-correlation algorithms, i.e., normalized cross-correlation (NCC) algorithm, the smoothed coherence transform (SCOT) algorithm, and the phase transform (PHAT) algorithm, are applied to estimate the loading speed of an accelerated pavement test (APT) and the traffic speed in the field. The signal-noise-ratio (SNR) and the mean relative error (MRE) are utilized to evaluate the stability and accuracy of the algorithms. The results show that both the correlated noise and independent noise have significant influence in the field data. The SCOT algorithm is recommended for speed estimation with reasonable accuracy and stability because of a large SNR value and the lowest MRE value among the algorithms. The loading speed investigated in this study was within 50 km/h and further verification is needed for higher speed estimation.

Evaluation of Reinforced Flexible Pavements by Repeated Load Testing.(Dept.C)

In a previous research , the C.B.R. Test has proved to be useful in evaluating reinforced subgrade soils [1] . When testing specimens after soaking with and without reinforcement one can come up with two values of C.B.R. for comparison . However , the need to evaluated reinforced subgrade soils in a loading conditions that are as similar as possible to fields is warranted . The purposed of this research is to investigate the life cycle improvements of pavements when they are reinforced by geotextiles and a geonet , Four pavement test groups were constructed to simulated the field conditions as possible . One group was the control sections , and the other three were reinforced with geosynthetics . Simulated traffic repeated loads were applied and the vertical deformation of tested pavement surface was measured at the edge of loading plate . It is concluded that testing relatively larger scale models by repeated loading is more realistic than C.B.R. Also , geonets perform better than geotextiles when employed as reinforcement.

Suitability of Nondestructive Testing of Asphalt Concrete for Detecting the Impact of Moisture Damage

Asphalt pavement susceptibility to moisture damage is considered as a major issue in the durability and service life of the roadway. Quick and nondestructive testing of asphalt concrete pavement are the major concern for predicting its suitability for evaluation. In the present investigation, nondestructive test has been implemented to detect the moisture damage issue of asphalt concrete mixture. Asphalt concrete specimens were prepared using Marshall method. Aggregates gradation of wearing, binder and base course was implemented for the preparation of the specimens. Specimens were tested for ultrasonic pulse velocity before and after practicing the moisture damage procedure. The variations of seismic modulus among various gradation before and after the moisture damage were considered as a criterion for moisture damage and related to tensile strength ratio TSR. It was observed that the pulse velocity decline by a range of (11 to 16) for asphalt concrete after moisture damage. It was concluded that the Seismic modulus as calculated from the ultrasonic pulse velocity test was effective in distinguishing the impact of moisture damage. The seismic modulus at optimum asphalt content decline by (34.7, 46.7, and 52.6) % after moisture damage for wearing, binder, and base course mixtures respectively. The ultrasonic pulse velocity test is recommended for assessing the susceptibility of asphalt concrete mixture to moisture damage.

Modelling the response of large-size subbase materials tested under varying moisture conditions in a heavy vehicle simulator

Pavement design methods must be able to predict the behaviour of pavement materials at increased moisture levels due to climate changes causing increased precipitation and more intense rainfall events. This paper intends to examine the influence of moisture and gradation on pavement response. An instrumented accelerated pavement test (APT) has been conducted on two thin flexible pavement structures with unbound base course and subbase materials using a heavy vehicle simulator (HVS). The two pavement structures were identical except for the gradation of the subbase material, where one had a 0/90 mm curve with a controlled fines content, and the other had an open-graded 22/90 mm curve. The APT was conducted using constant dual-wheel loading, and three different groundwater (GW) levels were induced in order to change the moisture content in the structures. The HVS was stopped regularly for carrying out response measurements from the instrumentation. The analysis is focussed on the response of the unbound aggregate layers to varying moisture levels in the pavement structure. The increased GW level causes a substantial increase in rutting. Conflicting results are found regarding the development of stresses and strains throughout the APT. Two models, linear elastic and non-linear elastic, is employed to model the responses from the pavement structures.

Permanent deformation modelling of large-size unbound pavement materials tested in a heavy vehicle simulator under different moisture conditions

ABSTRACT Climate changes alter the environmental conditions which pavement design is based on, invalidating empirical design methods. Transition to mechanistic design requires the ability to model the behaviour of pavement materials under relevant environmental conditions. An accelerated pavement test (APT) is designed to test two instrumented pavement structures under moisture conditions which are altered by raising the groundwater table (GWT). Open-graded and well-graded subbase materials are used to investigate the effect of gradation on moisture dependency. Pavement response behaviour is modelled using a non-linear elastic (NLE) approach. Accumulation of permanent deformation under different moisture conditions is calculated by two models and compared to measured surface rutting. Moisture transport through the structures differs due to the subbase gradation. Increased GWT accelerates the accumulation of permanent deformations in both structures, identified by both models. One model provides a significantly better fit to the subgrade deformations and the width of the rutting profile.

Nondestructive quality testing of concrete and asphalt concrete pavements

The technical level of the applied methods and controls has an impact on the result of construction and installation works. One of the main tasks of contractors in the process of paving is to quickly determine the parameters of asphalt pavement. The quality of the asphalt pavement device allows you to increase the service life and reduce the cost of repairing road surfaces. A number of methods and means of nondestructive quality testing of concrete and asphalt concrete pavements are considered. Some characteristics of defects of concrete and asphalt concrete pavements are given. The main attention is paid to ground-penetrating radar methods, eddy-current, radiation and acoustic, also the devices implementing these methods are considered.

Seasonal and diurnal variations of back-calculated layer moduli in flexible pavement and FWD testing guidelines

Seasonal and diurnal variations can significantly impact falling weight deflectometer (FWD) measurements and, thus, deflection-based parameters such as back-calculated layer moduli. Therefore, it is necessary to evaluate and quantify these effects. The back-calculated layer moduli data from the Long-Term Pavement Performance Seasonal Monitoring Program study were analyzed within each climatic region. The effects of seasonal and diurnal changes were quantified and related to ambient temperatures were related to the development of general measurement guidelines. The HMA layer moduli showed minimal variation during the spring and fall seasons in every climatic region and were consistently higher based on the deflections measured before noon. However, temperature correction, generally applied to the HMA layer moduli, can eliminate the temperature impacts of the FWD measurements. Because the unbound layer moduli are back-calculated from the single measured deflection basins on the surface, temperature and moisture conditions at the time of measurements can affect the material properties. The base and subgrade moduli showed minimal variation within the temperature ranges of the spring and fall seasons. Therefore, such temperature within each climatic region may result in layer moduli values closest to their representative in-field conditions. In addition, the unbound layer showed no effect of time within a day, suggesting that FWD testing can be conducted at any time during the day. Based on the results, the preferred temperature ranges for FWD measurements are 55–70 °F and 65–75 °F in the freeze and non-freeze regions, respectively. FWD measurements can be conducted at any time during the day. The preferred seasons for testing are spring and fall in all climatic regions.

Accelerated testing of super lightweight UHPC waffle deck under heavy vehicle simulator

A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (CFRP) or high strength steel (HSS) reinforcement. The proposed system lends itself to accelerated bridge construction, rapid deck replacement in bridges with load restrictions, and bridge widening applications without the need to replace girders. Performance and failure modes of the proposed deck were initially assessed through extensive lab experiments and finite element analysis, which together confirmed that the proposed deck panel meets the AASHTO LRFD requirements. The proposed deck system is not susceptible to punching shear of its thin slab and fails in a rather ductile manner. To evaluate its long-term performance, the system was further tested under the dynamic impact of wheel load at the Accelerated Pavement Testing (APT) facility of the Florida Department of Transportation using a Heavy Vehicle Simulator (HVS).

Effects of irregular loading patterns on fatigue life measured in indirect tensile fatigue test: a traffic-based study

Loading patterns used in pavement tests are responsible for modeling the traffic loads applied on the road. This paper suggests a framework to aggregate hourly distribution of daily traffic into 3-h loading blocks, keeping fixed the loading times across all blocks but allowing the rest periods to differ block to block. Difference in rest times among loading blocks is a consequence of different headways between heavy vehicles, better reflecting the influence of asphalt self-healing than when fixed rests are used. Field-specific loading patterns are generated by combining the loading blocks, providing irregular shapes compared to the classical loading pattern commonly used in labs. Traffic data of Tehran-Karaj freeway was obtained and analyzed to generate 3 irregular loading patterns representing the traffic conditions of 3 days with different temperatures. Indirect tensile (IDT) fatigue test was performed at the temperature of each experimental day using the classical loading pattern as well as the irregular one corresponding to that temperature. Moreover, for each temperature, the fatigue test was performed at 3 different stress levels predetermined by an Indirect tensile strength (ITS) test. Results show that by applying the irregular loading patterns instead of the classical one, the measured fatigue lives of specimens increase ranging from 19 to 29%. It should be further underlined that the average value of rest periods is constant under both loading conditions, and irregularity caused these improvements. Moreover, the larger percentages of fatigue life improvements are attributed to the tests with lower stress levels as they underwent more irregular loading patterns than the tests with higher stress level.

Recursive pseudo fatigue cracking damage model for asphalt pavements

ABSTRACT Mechanistic-empirical (M-E) fatigue models for asphalt concrete (AC) pavements often ignore damage induced-changes in the AC, although laboratory testing and field studies show that AC modulus deteriorates as the extent and severity of cracking accumulates. This study developed a pseudo fatigue cracking damage model that incorporated damage-induced changes in AC modulus and AC fatigue endurance limit (FEL) for a more realistic fatigue analysis. The model, based on layered elastic theory, implements incremental-recursive damage accumulation, and its goal is to further minimise empiricism in M-E fatigue modelling. Bending beam fatigue (BBF) test data from 20 AC mixtures constructed at the National Center for Asphalt Technology Pavement Test Track during several research cycles were used to formulate the model. The functional form of the model was identified through iteration and showed high potential in simulating BBF damage curve. The model inputs are AC modulus, FEL and applied strain level. In applying the model, a trial pavement cross-section is simulated in WESLEA, a layered elastic analysis programme, to generate a fatigue damage curve, where AC modulus degrades versus load applications. Suggestions for implementing the model in pavement design procedures are discussed. Field validation is recommended before the model is used for pavement design.

FEATURES OF CONDUCTING FIELD RESEARCH AT THE OBJECTS OF THE ROAD NETWORK AND LABORATORY STUDIES OF ROAD SURFACE SAMPLES DURING THE FORENSIC CONSTRUCTION AND TECHNICAL EXAMINATION AND FORENSIC EXAMINATION OF MATERIALS, SUBSTANCES AND PRODUCTS

According to the requirements of regulatory documentation, there are a large number of indicators measured for asphalt concrete. Modern expert practice shows that the forensic examination of asphalt concrete although relies on the research methods specified in GOST (National Standards of Ukraine), but requires its optimization. Carrying out field research at the objects of the road network, regulates the methodology, sequence and rules for measuring and taking samples of the road surface for laboratory tests. The main stages of research at the objects of the road network: I. Preparation for field research. II. Identification of the object on the ground. III. Inspection of the object of study in order to establish the characteristics and boundaries of the work. IV. Fixation (photo-video shooting, topography) of the performed works. V. Carrying out measurements of the volume of completed construction work. VI. Sampling. VII. Recording the results of research. VIII. Conducting laboratory tests. In turn, laboratory tests have the following main stages: I. Photo of packaging, photo of samples (center marks or cuttings). II. Numbering (marking) of research objects. III. Measuring the thickness of the center marks layers. IV. Mechanical separation of center marks or cuttings into layers. V. Washing objects and drying it to constant weight. VI. Determination of the average density of asphalt concrete. VII. Determination of water saturation. VIII. Making a pooled sample. IX. Determining the amount of astringent. X. Determination of the grain composition of the mineral part of the mixture. XI. Determination of the actual density of the mixture by pycnometric method (for RMACM). XII. Determination of residual porosity (for RMACM). XIII. Reshaping of samples (for HACM). XIV. Determination of the average density of reshaped samples. XV. Determination of water saturation of reshaped samples. XVI. Determination of compaction coefficient. XVII. Determination of compressive strength. The expert practice of the authors in this article made it possible to transform the stages of forensic examination of asphalt pavements so that the effectiveness of such examination has increased. The proposed methodology, sequence and rules of field research on the objects of the road network in terms of sampling of pavement and subsequent laboratory tests of these samples, enable experts to provide a qualitative and objective conclusion.

Mechanical response of hydronic asphalt pavement under temperature–vehicle coupled load: A finite element simulation and accelerated pavement testing study

Hydronic asphalt pavement (HAP) is an environmentally friendly functional pavement. It has an energy-harvesting function and can emit energy to melt snow in winter. However, the mechanical response characteristics, especially under vehicle-temperature coupled load, and long-term performance of HAP systems remain under-investigated. Motivated by this absence of research, the mechanical response of HAP under vehicle–temperature coupled loading was analyzed using the finite element method. Results indicated that concrete between adjacent pipes bears large tensile stress. Mechanical damage, therefore, is likely to occur in those areas. The effects of parameters, like pipe spacing, embedded depth, inlet fluid temperature, and air temperature, on mechanical response were also studied to determine a more optimized pavement structure. The study conclusions can provide a theoretical basis for universal application and standardized design method of HAP. Furthermore, in-situ testing sections of the aforementioned optimized HAP structure were constructed and their rutting performance was evaluated using the one-third-scale model mobile load simulator (MMLS3) to verify whether its long-term performance can meet the requirements for road durability. Results indicated that the average rutting depth of the HAP structure after 400,000 consecutive loadings was less than 1 mm, which is significantly less than that of the control section without pipes. The pipes in HAP not only enable the conventional pavement to harvest energy and melt snow but also can enhance the rutting resistance performance of the pavement to a certain extent.