Pavement Test Research Articles

Determination of an Optimum Backcalculation Cross Section for Unconventional Pavement Profiles

The validity of backcalculation results partly depends on the pavement cross section used in the procedure. However, the development of a backcalculation cross section is challenging, particularly for an unconventional pavement (subgrade stiffer than base). The unconventional stiffness profile poses challenges to backcalculation, including compensating layer effects. This study presents a systematic investigation to determine an optimum backcalculation cross section for seven unconventional pavements at the National Center for Asphalt Technology pavement test track. Apart from the unconventional stiffness profile, the granular materials had different stress sensitivities: the subgrade was stress independent, whereas the aggregate base material exhibited some stress sensitivity. Falling weight deflectometer testing provided 2,268 deflections for backcalculation, which was executed with Evercalc 5.0, and 126 deflection tests on embedded gauges for forward calculation, which was accomplished with WESLEA 3.0. Nine candidate cross sections were evaluated. The study converged on a three-layer backcalculation cross section that provided an overall good deflection basin fit, a balanced match between measured and predicted stresses, and reasonable moduli. A key lesson is that the as-built cross section of an unconventional pavement may not necessarily yield valid backcalculated moduli, although there may be a good deflection basin fit. A working knowledge of the pavement materials is useful for developing an optimum backcalculation cross section, which should be validated through field instrumentation when available.

Pavement testing by integrated geophysical methods: Feasibility, resolution and diagnostic potential

This work is focused on the assessment of the diagnostic potential of several geophysical methods when applied to the investigation of a rigid airport pavement. The potential and limit of each technique are evaluated as well as the added value deriving from their integration. Firstly, we reconstruct a high-resolution image of the pavement by a large electromagnetic and georadar screening. An advanced processing of georadar data, implemented through the picking of the arrival times of reflections for each profile, provides a quantitative estimation of the deviation between the design and the as-built thickness of layers. Additionally, electrical tomography has been applied to unequivocally identify the anomalous zones, where higher values of resistivity would be associated to porous zones that are prone to degradation and failure. The seismic tomographic survey had the additional purpose to recover the mechanical properties of the pavement in terms of both P- and S-waves and consequently of elastic constants (Poisson's ratio), whose values were consistent with those recovered in literature. The anomalies detected by each technique are consistent in their indications and they can be correlated to failure phenomena occurring at layer interfaces within the pavement structure or to unexpected variations of the layer thicknesses. The cost-effective geophysical campaign has validated the four-layered system deduced from the original design and has been used to reconstruct a high-resolution map of the pavement in order to discriminate fractures, crack-prone areas or areas where the as-built differs from the original design.

Life Cycle Extension of a Pavement Structure

The pavement structure, namely pavement surfacing must meet the criteria required to provide operational service during the whole life cycle of the pavement. Surfacing design composed of layer strengths and proposed materials is defined by design method which calculates the stress state during long-term transport and environmental conditions. The designed surfacing life cycle is defined in respect to traffic load acting on the pavement and road class for a period of about 20 years. Given the practical aspects of road administration, pavement reconstruction is usually due only at the end of the life cycle, when the original materials are replaced by new materials and the layer strength is re-evaluated. Since the overall life cycle of the whole pavement is significantly longer than that of the surfacing, it is necessary to consider possibilities to extend the life cycle of the surfacing either through various technologies, i.e. reinforcement, overlays or recycling. Timing of execution of such action plays a paramount role, and it has impacts on future financial flows of road administrator as well as economic aspects of transportation for the whole society. This paper describes analytical calculations and experimental measurements of surfacing materials, as well as accelerated pavement testing process needed for ascertainment of operational performance of a pavement construction during its life cycle. Finally, a case study encompassing the whole method is presented.

Empirical Models for Permanent Deformation of Subgrade Soils from the Data Collected at the Pavement Subgrade Performance Study

AbstractA national pooled-fund study supported by 19 states, the Federal Highway Administration, and the U.S. Army Corps of Engineers was conducted at the Cold Regions Research and Engineering Laboratory (CRREL) of the U.S. Army Corps of Engineers in Hanover, New Hampshire. The study, titled the Pavement Subgrade Performance Study (PSPS), aimed to develop failure criteria and prediction models for permanent deformation in the subgrade soil that incorporate the effects of soil type and moisture content. Full-scale pavement structures were built with the same crushed stone base and asphalt concrete surface layers on top of five subgrade soils. The soils were placed and compacted at three in situ moisture contents: the optimum and two other contents above the optimum. The pavements were subjected to full-scale accelerated pavement testing. An extensive volume of response and performance data was collected in the study. This paper presents the development of empirical models for permanent deformation of subgr...

A Preliminary Study for Assessing the Risk of Road Collapse Using Accelerated Pavement Testing

A Preliminary Study for Assessing the Risk of Road Collapse Using Accelerated Pavement Testing

Numerical simulation tool for paving block structures assessed by means of full-scale accelerated pavement tests

ABSTRACTBlock pavements are an attractive alternative to asphalt and concrete pavements, especially in communal areas. Architects and urban planners would like to take advantage of various shapes, colours and textures of paving blocks in order to achieve a higher quality of urban space if the performance of block pavements could be better predicted to avoid large horizontal displacements of chipped stone corners and rutting. Unfortunately, the computational performance prediction of paving block structures is more complex than that for flexible pavements with homogeneous surface layers of asphalt concrete. The influence of the large number of vertical joints between paving blocks on the overall mechanical performance has not been considered sufficiently within computational tools yet. The proposed numerical simulation tool is able to take into account the complex mechanical behaviour of sand-filled joints as well as the non-linear mechanical behaviour of the underlying base courses. Joints are modelled using a Mohr–Coulomb-type friction model with the normal stresses non-linearly related with joint opening. Three different experimental set-ups were developed for the identification of the model parameters. The base behaviour was modelled using the Drucker–Prager cap model. The paper shows that the proposed tool predicts reasonable deformations and stresses in block pavements. The results of the simulations were compared with measured stresses from the full-scale accelerated pavement testing and a good agreement was observed.

The performance of a trial gravel road under accelerated pavement testing

Abstract This study presents the performance of a trial gravel road subjected to HVS (Heavy Vehicle Simulator) trafficking in a compressed time period. The road structure was constructed with 150 mm-thick aggregate base course, and 125 mm-thick sub-base course. The test road responses, such as surface deformation and rutting were recorded using laser profile measurement instrument while the unbound layers’ dynamic deflections and strains data were periodically recorded at different depths during the execution of the test by means of an array of micro strain gauges. The test road was also instrumented with Water Content Reflectometers to record the changes in moisture contents in the road layers caused by the raising of the water table level under HVS trafficking. A total number of 85,000 HVS passes were applied to the trial gravel road structure under near-optimum as well as partially submerged subgrade moisture conditions. The test results emphasize the fact that the partial soaking of the subgrade soil by raising the groundwater table level caused a serious damage to the tested gravel road, as further detailed in this paper.

Rutting prediction in airport pavement granular base/subbase: A stress history based approach

Abstract Test data from full-scale aircraft gear loading conducted at the National Airport Pavement Test Facility (NAPTF) by the US Federal Aviation Administration (FAA) were analyzed to investigate the effects of wander (offset loads) and channelized traffic loadings on the deformation behavior of unbound aggregate layers in asphalt pavement test sections. Insights were drawn on the complex rebound (recovered) and residual (unrecovered) deformation trends of granular materials due to passing of each of the 6-wheel Boeing 777 (B777) and the 4-wheel Boeing 747 (B747) gears for various combinations of loading (stress history effects), wander positions, and wander sequences. Measured field layer deformations and the accumulation rates could only be achieved when the magnitudes and variations of stress states in the granular layers, number of load applications, gear load wander patterns, previous loading stress history effects, trafficking speed or loading rate effects, and finally, principal stress rotation effects due to moving wheel loads were properly accounted for. Accordingly, measured transverse profiles and multi-depth deflectometer data were used to create individual pass residual deformation transverse profiles. The created transverse profiles were then combined with stress history effects to predict the residual transverse profiles for the test sections with P209/P154 granular base/subbase layers. The proposed method emphasizes the use of the previous load location and stress history of the pavement element to develop the residual deformation in that element. Calculation of the residual deformation in each element across the pavement surface results in the development of the complete permanent deformation transverse profile. This technique can be applied to estimate the transverse rutting profile of the pavement after trafficking based on any combination of applied wander and traffic direction.

Surface texture and friction characteristics of diamond-ground concrete and asphalt pavements

Abstract Recently, diamond grinding has gained increasing attention as pavement preservation treatment to restore desired surface characteristics, particularly friction. Compared to other pavement preservation treatments such as surface overlays and high friction surface treatments, diamond grinding may cost less, save construction time, or require minimum maintenance. Diamond grinding produces longitudinal, continuous, and line-type texture that contains corrugations with evenly spaced ridges. The improved surface texture will immediately enhance pavement surface friction and reduce the possibility of hydroplaning in rainy weather. However, little information has been documented on the texture characteristics and long-term friction performance of diamond-ground pavements. A field evaluation was conducted to examine the surface texture and friction characteristics in diamond-ground concrete and asphalt pavements by the authors. Five pavement test sections, including two diamond-ground concrete pavements, one diamond-ground concrete bridge deck, one diamond-ground asphalt pavement, and one transversely tined concrete pavement, were selected for evaluation. Laser scanner testing was performed to capture both macro and microtexture profiles. Locked wheel testing was performed to measure the friction numbers. The test results were examined and compared so as to evaluate two performances, after construction and long-term friction performance of diamond-ground pavements. It was found that longitudinal diamond grinding can provide durable, satisfactory surface friction performance for both concrete and asphalt pavements.

Using Accelerated Pavement Testing to Evaluate Reclaimed Asphalt Pavement Materials for Pavement Unbound Granular Layers

AbstractUnbound aggregate layers are commonly used as subgrade replacement and subbase over weak subgrade soils. With the recent focus on sustainable construction practices, ever-increasing transportation cost, and scarcity of natural resources, nontraditional and locally available recycled materials have become viable for the construction of unpaved and low volume roads. To this end, a research study was recently undertaken at the Illinois Center for Transportation to evaluate the engineering applications and field performances of reclaimed asphalt pavement (RAP) materials used in pavement unbound base/subbase and foundation layers. Twelve different full-scale test sections were constructed for the field performance investigations with accelerated pavement testing. Construction quality control was achieved through in-place density and modulus measurements using field testing. Periodic rut measurements were carried out on pavement surfaces throughout the accelerated loading process. Observed rutting trend...

Evaluation of pavement materials containing RAP aggregates and hydraulic binder for heavy traffic pavement

Treatment with hydraulic binder is one of the techniques for recycling of reclaimed asphalt pavement (RAP) recovered from road deconstruction. The combined presence of hydraulic binder and bituminous binder (from the RAP) in the mix makes it a composite material, on which the feedback from real road networks is still limited today and which has not yet been considered in the French rational pavement design method (RPDM). The addition of steel fibres in the composite mix allows minimising crack width, solution adopted by the steel fibre-reinforced roller-compacted concrete (FRCC™) technique. FRCC™ mixes with different fibres and RAP contents are compared with another RAP-based material treated with hydraulic binder, ERTALH®. The study discussed in this paper is part of the French National Research Agency project “Recyroute” which aims to evaluate the use of these composite materials in the base layer of heavy traffic roads. Mechanical properties of these composites were investigated by an extensive laboratory test programme. Performance of full-scale pavements was also evaluated throughout an accelerated pavement test (APT). This paper presents the main features and results of the laboratory test programme and the APT experiment as well, leading to propose design parameters of these innovative pavement structures, according to the French RPDM.

SHM and evaluation of a continuous reinforced concrete pavement

To assess the long-term behavior of a new concept of a continuous reinforced concrete pavement (CRCP), an SHM system was designed using 27 strain, 2 acceleration and 5 temperature FBG optical sensors, all embedded in concrete. The main objective was to monitor the performance of the reinforcement steel and concrete, considering vibrations and strains due to live loads and thermal effects. The test pavement was built on one of the most important highways in Mexico with nearly 50,000 vehicles per day, where 40 % are heavy vehicles. The CRCP has been evaluated under controlled and operational live loads, and dynamic responses have been correlated to temperature changes and thermal gradients. After almost 3 years of regular monitoring, it has been found that the FBG sensor system has been able to evaluate the structural evolution of the pavement. At present, structural changes have been identified due to mayor cracking as a result of combined thermal stresses, pavement deformations and dynamic loads. Stress changes and distributions have been measured, and although the pavement did not achieve the expected useful life; monitoring data has become a very useful data base to understand the pavement behavior and to redesign an operational cost-effective pavement. As for the CRCP performance, results show that the proposed design is not adequate for high loads and high traffic conditions. Pavement redesign must consider the use of more steel reinforcement to control cracking and should also take into account temperature gradients and the base–pavement interaction.

THE INFLUENCE OF PAVEMENT–VEHICLE INTERACTION ON HIGHWAY FUEL CONSUMPTION BY FIELD MEASUREMENT

Field experiments are performed in which Fuel Consumptions (FCs) are measured by operating passenger car over thirteen one-mile roadway sections at two highway speeds in Florida. The sections are composed of 6 flexible pavement sections and seven rigid pavement sections with varied pavement surface conditions and testing temperature. The first objective is to capture the fuel differences between flexible pavement and rigid pavement considering the effect of pavement roughness and pavement temperature. By ANalysis of COVAriance (ANCOVA), results show less fuel is consumed on rigid pavement opposed to flexible pavement by 2.25% at 93 km/h and 2.22% at 112 km/h. Fuel differences are found statistically significant at 95% Confidence Level (C.L.). Fuel savings on rigid pavement exhibits good agreement with authors’ Phase I direct comparison field study. Furthermore, fuel data from flexible pavement is applied to calibrate the Highway Development and Management IV (HDM-4) FC model in order to detect and quantify the impact of pavement deflection on FC. Calibrated models are evaluated and validated with experiment data. By results, the deflection-indhuced fuel effect is disclosed by the positive deflection adjustment coefficient generated from the calibration. It is also found that an increase of 0.1mm in pavement deflection at 25 °C (pavement temperature) would increase the FC by 1.53% at 93 km/h and 1.46% at 112 km/h. Results demonstrate good agreement with other findings.

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

Rice husk ash (RHA) is a by-product of rice milling. Its use as soil stabilizer is a way to replace the final disposal with environmental benefit. However, RHA is not cementitious itself but when mixed with lime forms cements which improve the soil properties. A research of performance of a silty sandy soil modified with RHA and lime as wearing course layer of low-volume roads was conducted through two full-scale test sections with different pavements built in Artigas, northern Uruguay. The alkaline reactivity of RHA is low because the husk burning is not controlled. The soil-RHA-lime mix design was conducted according to the Thompson’s Method. The pavement test sections were monitored through deflection measures by Benkelman beam and observations of surface condition. The deflections decreased over time in both test sections due to the development of cementation of the study materials. After one year, the dust emission was reduced, the wet skid resistance of pavement surfaces improved and there was not rutting. The researched pavements have had a good performance under the existing traffic and environmental conditions, demonstrating that wearing course layer of silty sand modified with RHA and lime is an alternative to improve the condition of low-volume roads and to replace the final disposal of RHA, with environmental, social and economic benefits. DOI: http://dx.doi.org/10.4995/CIT2016.2016.3451

Mechanical response of flexible pavements enhanced with geogrid-reinforced asphalt overlays

The use of geosynthetic reinforcements placed underneath asphalt overlays, which has been typically used to minimise problems associated with reflective cracking, is evaluated in this study as an approach to improve pavement structural capacity. Whereas geosynthetics have been used to increase the pavement structural performance when used to reinforce the base aggregate, as reported in numerous laboratory and evaluations experiments, such improvement has not been evaluated for the case of geosynthetics within asphalt layers. Accordingly, this paper presents the results of large model tests involving both reinforced and unreinforced hot mix asphalt overlays. Cyclic wheel loads were applied using an accelerated pavement test facility that was specifically developed for this research. A number of pavement sections were constructed using a polyvinyl alcohol geogrid as reinforcement inclusions. The results show a considerable increase in pavements structural performance, as quantified by reduction of strains in the asphalt concrete layers, in the vertical stresses within the pavement layers and in the resilient displacements at the wearing surface. The use of geogrid reinforcements was also found to lead to reduce rutting and permanent lateral movements in the surface layer. Overall, the use of geogrids within asphalt overlays was found to act as a reinforcement element that provide enhanced structural capacity to flexible pavements.

Estimating fatigue endurance limits of flexible airfield pavements

In perpetual pavements, damage from bottom-up cracking can be limited to the top surface lift through using a very thick surface layer or a binder-rich intermediate layer. This can be attained by maintaining tensile strains at the bottom of the hot-mix asphalt (HMA) layer below a certain value known as the fatigue endurance limit (FEL). This paper presents a method for estimating a strain-based FEL for flexible airfield pavements. The proposed method is based on the concept that a 50% reduction in HMA layer modulus would indicate initiation of fatigue cracking. Falling weight deflectometer (FWD) testing results, collected from National Airport Pavement Test Facility (NAPTF) flexible pavement sections, were analyzed to determine at which loading pass each section had a 50% reduction in HMA layer modulus (Nf50). NAPTF tensile strain data were also used to determine the tensile strain at Nf50 for each pavement section by averaging the peak tensile strains. The proposed approach was validated by comparing its results to those obtained using a common FEL estimation model known as the rate of dissipated energy change (RDEC) model. To further verify the results of the proposed approach, peak tensile strain was plotted vs. number of loading cycles for all sensors. Using these plots, the peak tensile strain at which the variability in the strain gauge data increased was used as an estimate of a possible FEL. The Nf50 tensile strains estimated using the proposed method were comparable to the values determined from RDEC and variability approaches.

Nonlinear, statistical models of tire-pavement noise

Tire-pavement noise is the result of a complex system of noise generation mechanisms and is affected by several different pavement and atmospheric parameters. Accurately predicting tire-pavement noise from given a set of parameters has proven difficult for researchers. The purpose of this research was to explore a wealth of pavement, atmospheric and noise data taken at the MnROAD pavement test facility and to develop a model to predict tire-pavement noise on asphalt pavements. Using a series of sub-models, variables significant to noise generation were identified. Finally, two variations of a model of noise generation were developed, each capable of predicting one-third octave band on-board sound intensity (OBSI) spectra. The model was developed using a hybrid statistical-experimental approach and was able to predict overall OBSI levels to within 1.5 dB for 80-90% of the pavements tested.

Application of 2D elastic Rayleigh waveform inversion to ultrasonic laboratory and field data

ABSTRACTIn addition to geophysical applications from the near surface to a global scale, seismic full‐waveform inversion can be applied to ultrasonic data on the centimetre and decimetre scales for nondestructive testing of pavements, facades, plaster, sculptures, and load‐bearing structures such as pillars or core samples from boreholes, which can consist of geo‐materials and non‐geomaterials. Classical non‐destructive testing approaches are based on the inversion of body‐wave travel times to deduce P‐wave velocity models. In contrast, surface waves (especially Rayleigh waves) are well suited to quantify surficial alterations of material properties, e.g., due to weathering. Furthermore, ultrasonic measurements of test samples with known material parameters close the gap between synthetic tests or analytical solutions and field data applications to estimate the accuracy of seismic modelling and inversion codes. Due to the scale invariance of the problem, the full‐waveform‐inversion approaches developed on the ultrasonic scale are also applicable to larger scale geophysical problems. In this paper, we demonstrate the potential of two‐dimensional Rayleigh waveform inversion on the ultrasonic scale using two data examples acquired with a single‐fold, low‐coverage acquisition geometry. For a simple homogeneous Plexiglas block in a controlled laboratory environment, we discuss the accuracy of visco‐elastic Rayleigh wave modelling, as well as the sensitivity of two‐dimensional elastic full‐waveform inversion with respect to small data residuals. While the inversion is restricted to the recovery of the S‐wave velocity model, a passive visco‐elastic modelling approach with a homogeneous average ‐model is required in order to describe amplitude loss and dispersion of the Rayleigh wave. The applicability of this approach under field conditions is illustrated for an ultrasonic data example from the weathered sandstone facade of the Porta Nigra in Trier (Germany). In addition to a random medium resolution analysis of the full‐waveform‐inversion result, we particularly emphasise the importance of lateral model smoothing to mitigate small‐scale inversion artefacts and to avoid erroneous interpretations. The estimated two‐dimensional S‐wave velocity anomalies correlate well with prominent surficial weathering effects in the upper about 3 cm.

Accelerated pavement testing of thin RCC over soil cement pavements

Three full-scale roller compacted concrete (RCC) pavement sections built over a soil cement base were tested under accelerated pavement testing (APT). The RCC thicknesses varied from 102mm (4in.) to 152mm (6in.) and to 203mm (8in.), respectively. A bi-directional loading device with a dual-tire load assembly was used for this experiment. Each test section was instrumented with multiple pressure cells and strain gages. The objective was to evaluate the structural performance and load carrying capacity of thin RCC-surfaced pavements under accelerated loading. The APT results generally indicated that all three RCC pavement sections tested in this study possessed very high load carrying capacity; an estimated pavement life in terms of equivalent single axle load (ESAL) for the thinnest RCC section (i.e., RCC thickness of 102mm) evaluated was approximately 19.2 million. It was observed that a fatigue failure would be the primary pavement distress type for a thin RCC pavement under trafficking. Specifically, the development of fatigue cracking was found to originate from a longitudinal crack at the edge or in the center of a tire print, then extended and propagated, and eventually merged with cracks of other directions. Instrumentation results were used to characterize the fatigue damage under different load magnitudes. Finally, based on the APT performance of this experiment, two fatigue models for predicting the fatigue life of thin RCC pavements were developed.

Development of the fracture-based flexibility index for asphalt concrete cracking potential using modified semi-circle bending test parameters

Asphalt concrete (AC) pavement sustainability can be achieved by enhancing mixture durability, improving construction practices, optimizing pavement design, and maximizing the use of recycled resources to reduce life-cycle investments. Recycled materials are commonly used to improve sustainability of AC pavement as they replace natural resources and reduce initial construction costs and greenhouse gases during the material production phase. However, net savings, in terms of environmental and economic impact, can only be realized if the performance targeted by the initial design is achieved. The use of RAP and RAS may result in a significant reduction in the demand for virgin, quarried aggregates and, more importantly, asphalt binder. However, replacing virgin materials in AC mixtures with aged, stiffer binders poses numerous technical challenges in terms of mixture volumetrics and thermal (low temperature) and flexural fatigue cracking resistance. This paper introduces a practical fracture test method to screen AC mixtures’ cracking resistance using the semi-circular bending test geometry. The selection procedure of the test method is presented along with the development of a flexibility index (FI) derived from the load-displacement curves. A discussion about the effect of viscoelasticity on fracture process is provided. The results indicate positive correlation between SCB test results and other independent fatigue tests. The proposed FI reflects positive correlation with the crack velocity, indicating brittleness of the materials, obtained from the same SCB experiments. The paper also provides a validation of the proposed IL-SCB test method results, including fracture energy and flexibility index (FI), using the number of cycles to fatigue cracking failure obtained from an accelerated pavement test sections.