Design, Analysis, and Asphalt Material Characterization for Road and Airfield Pavements

Unmanned aerial vehicles (UAVs) are used for various applications in both military and civilian roles. The benefit of having relatively small and inexpensive surveillance available allows aerial surveillance of activities. In South Africa the use of the technology for nonmilitary purposes are growing. One of the potential benefits of drone surveillance is the application of the technology in areas where full airfield facilities may not be available. This poses the challenge to evaluate an area relatively quickly to determine whether the UAV will be able to take off and land on the available terrain. Factors such as the take-off and landing length and width requirements (geometry), aircraft load (bearing capacity) and landing strip roughness (riding quality) are important to determine to ensure that these UAV will not be damaged during operations. This paper presents guidelines for the evaluation of an area to determine whether it is suitable for use as an UAV airstrip, based on simple evaluation, incorporating geometric, bearing capacity, and riding quality measurements.

A soft ground arresting system (SGAS) is an alternative solution on airport runways where the runway safety area (RSA) does not meet international Federal Aviation Administration (FAA) standards. The length of the runway can be shortened if an SGAS is installed on both ends of the runway. This paper evaluates the options of using foamed concrete as the arresting bed material in an SGAS. Tests on the foamed concrete were conducted to see if it has the ability to withstand support vehicle loadings and fails underneath loading from an overrunning aircraft. The objective of the paper is to present the required and measured properties of foamed concrete (density, compressive strength and durability) and results of an evaluation into its possible implementation as an SGAS as an alternative to the engineered material arresting system (EMAS) on airport runways.

It is well known that the contact stresses between tires and the pavement surface are dynamic and affected by the tire type, tire inflation pressure, and tire load. It is important to expand the research and understanding to also evaluate the effect of these contact stresses inside the pavement layers. To conduct tests of varying loading conditions effectively inside different pavement structures, the option of using a geotechnical centrifuge to apply ranges of loads in the laboratory has been evaluated. Using the centrifuge allows application of scaled loads and tire dimensions, with correct application of stresses at all locations inside the pavement structure, at a relatively low cost. This paper discusses the results of an experiment where a specific scaled tire was used for load application, and the stresses on the surface and at the base / subbase interface collected for both static and centrifuge conditions. The effect of scaling on the data are evaluated and compared to full-scale results.

This paper presents a systematic framework to predict skid resistance of wet pavement with noncontact method. The grip potential of pavement is estimated according to the measured pavement texture based on theoretical simulation of the physical mechanism of hysteresis during rubber tire rim sliding on pavement. The rubber tire rim is modeled as interconnected Zener elements coupled with springs considering the frequency-temperature dependency and Payne effect. Time integration schedule was adopted to improve the computational efficiency. Such a method could be applied for the purpose of harmonization analysis of skid resistance and potential optimization of pavement surface texture.

The penetration depth of tire rubber into the road surface texture is an important parameter for skid resistance, drainage ability, and acoustical performances of road surfaces. In this paper, the 3-D texture of 31 typical road surfaces was measured optically. The penetration depth of a test rubber into these surfaces was tested on a universal test machine. The classic contact mechanics model of Persson was applied to predict the penetration depth. The result of this theory deviates significantly from that obtained in the experiment. Probable problems of the classic model were discussed, which lie in the missing consideration of horizontal friction force and the drawbacks of PSD. A new variable was introduced to adjust the model, and the predicting accuracy of the model was improved.

In hot-mix asphalt (HMA) pavements, rutting failure due to shear deformation is often more prevalent at intersections with turning and/or stop-go traffic, particularly when subjected to slow-speed heavy traffic loading and high temperatures. In this study, computational simulations using the PLAXIS software, were conducted based on a two-dimensional finite element (FE) and linear elastic analysis to investigate the effects of tire inclination (turning traffic) on the HMA pavement shear stress-strain response. An in-service Texas highway (US 59) with actual measured material and field data was utilized as a case study. Variables investigated in the modeling included HMA layer thickness, temperature, and HMA modulus, tire inclination angle, and HMA density. Overall, the analysis indicated that tire inclination and temperature, and HMA modulus have a significant effect on the location and magnitude of shear stress-strain responses within a pavement structure. At intersections with turning traffic that represents the highest tire inclination angle, the maximum shear stresses and strains occur at the pavement surface and are more critical under low HMA moduli values at high summer temperatures. While more computational modeling including 3-D visco-elastic analysis is still required, preliminary conclusions from this study suggest that intersections are more susceptible to surface shear failure and permanent deformation compared to other road sections.

One of the basic material characteristics of solids is Poisson's ratio. Its exact knowledge, including its dependence on time, allows us to model the effect of load, with given boundary conditions, on the behavior of material under consideration. Poisson's ratio, or rather the relationship between the longitudinal and transverse strain, has an important implication in engineering mechanical applications (assessment of pavement structure performance). Currently, Poisson's ratio usually is used as a constant, based on an incorrect assumption that a hot-asphalt mix (HMA) is a linear elastic material. This paper reports Poisson's ratio as a function of time determined from the relaxation and small amplitude oscillation tests on cylindrical specimens. An HMA is considered homogeneous isotropic material, and linear theory of viscoelasticity is applied for the experimental determination of the lateral contraction ratio.

The satisfactory performance of an asphalt overlay is influenced by various factors including the existing pavement condition, traffic loading, and environmental conditions such as moisture and temperature, among others. The objective of the work documented in this paper was to numerically evaluate the permanent deformation (PD) characteristics of typical asphalt overlays in hot tropical climates, like Zambia, using the default creep and elasto-visco-plastic models in the 2-D finite element (FE) tools of the ABAQUS software. These models are converted into a numerical formulation for implementation in FE analysis using user-defined material subroutines (UMAT). Supplemented with dynamic modulus and repeated load laboratory tests, input material properties, such as the layer modulus, were generated based on falling weight deflectometer (FWD) back-calculated data using iterative techniques and regression analysis to accurately account for local temperature normalization. The corresponding results showed that the application of local calibration factors on FWD deflection measurements before back-calculation computations provide reliable material characteristics input parameters for the FE analysis. Furthermore, the FE analytical PD predictions were also consistent and correlated well with the rutting results measured on laboratory scaled representative pavement structures under accelerated trafficking using the third-scale mobile load simulator (MLS3).

Previous studies have typically illustrated the three cracking mechanisms: (1) thermally induced fatigue due to a horizontal movement, (2) traffic induced fatigue due to vertical differential movement, and (3) surface initiated cracking due to the curling/warping of underlying slabs. Although these mechanisms are commonly observable for asphalt concrete overlay over both flexible and rigid pavements, the behavior and response of asphalt concrete (AC) overlay over a flexible pavement may be somewhat different from those over a rigid pavement due to their different characteristics of material and structure. Approximately 94% of 2.27 million miles of paved roads in the United States are overlaid with asphalt concrete. The mechanism of reflective cracking in AC overlays over flexible pavements has not been separately differentiated. Moreover, the bonding condition between AC overlays and flexible pavements is commonly assumed as bonded condition, although the interface condition can vary. This paper investigates the reflective cracking mechanism in an AC overlay over flexible pavements under different loading conditions by using a finite element (FE) analysis with bonded and unbonded conditions. The FE simulations also include partial top-down cracking conditions in the underlying flexible pavement. Deformed crack shapes and the highest stress concentration under traffic loading were investigated so that the initiation and propagation of reflective cracking are clearly understood.

The use of most suitable material models for the structural behavior modelling in the pavement design process is essential to find the most technical and economical solutions, taking into account the real pavement conditions, such as traffic and weather conditions. For this purpose, laboratory tests and the performance evaluation of experimental pavements during in situ tests have a special importance. This paper presents the results ofresearch based on the instrumentation and testing of some experimental pavement sections. At the same time, an extensive laboratory program was also undertaken to obtain the geometric, physical and mechanical properties of pavement materials. Bituminous mixtures were tested in indirect tensile tests. Granular materials were submitted to repeated load triaxial tests and an elastic nonlinear model was verified and calibrated to describe the resilient behavior of the pavement materials. This model was incorporated in the finite element program used in the modeling of the structural behavior of experimental pavements during the load tests. The comparison between results from field monitoring and from numerical modeling confirmed the importance of in situ performance evaluation to achieve a better understanding of the materials behavior useful for a technical and economical pavement design.

To describe the crack development of epoxy asphalt concrete (EAC) from the three-dimensional (3-D) scale perspective, a 3-D heterogeneous digital sample independent of laboratory is reconstructed. A bilinear cohesive-softening model is implemented into the discrete element method (DEM) framework to simulate the crack behavior. The corresponding micromechanical models describing the interaction of micro-scale components of the virtual specimen are assigned. The simulation results of a single-edge notched beam test are shown to compare favorably with the experimental results and accurately capture the distributions of fracture zone and stress within the model. The developed 3-D visualization modeling technique is capable of simulating the initiation and propagation of cracks during the bending fracture of EAC. ALso the 3-D user-defined microstructural DEM fracture model also has the potential ability to help understand various fracture mechanisms and shows a realistic cracking process of quasi-brittle materials such as EAC.

About 80% of the total road network in the India is categorized as rural roads carrying traffic less than 450 commercial vehicles per day. Huge network of rural roads are being built under the country's most ambitious prime minister's rural connectivity program (PMGSY) since its launch in December 2000. These roads are mostly designed as granular pavements with thin bituminous surfacing following the guidelines given in IRC:SP:20 (2002), which does not refer to any documented performance data. Collecting performance data on such type of pavements under different subgrade, climatic and traffic conditions is crucial for developing rational pavement design criteria and also for systematic maintenance management of the pavements. Moving a step in this direction, 19 rural road test sections were selected in the eastern part of the country for a long-term performance study, and this paper presents the data collected over a period of four and half years. The reported performance data will be extremely helpful for developing rational design criteria and systematic management of rural roads. Also a performance criterion has been developed (considering vertical stress over subgrade) for thin surfaced rural roads using the limited data available under this study.

Through analyzing the characteristics of asphalt pavement structure with roller compacted concrete (RCC) base, the control indexes and design framework of the structure were put forward. To simplify the stress calculation during structural design, a 3-D finite element(FE) model was established for this structure, and the critical load position (CLP) of the RCC plate was found located in the transverse cutting joints. The stress in CLP of RCC plate were calculated under different parameter combinations, and the nomographs of stress at the bottom of RCC layer with different thickness of AC layer were made according to the calculation results. The temperature stresses in CLP of RCC were calculated using FEM, and the calculation formula of thermal stress and thermal stress coefficient, Cx, were established.

Whitetopping refers to a thin Portland cement concrete (PCC) overlay on top of an existing deteriorated hot mix asphalt (HMA) pavement. When the PCC overlay slab thickness is between 5.1 and 10.2 cm, it is commonly referred to as ultra-thin whitetopping (UTW). In this study, the field performance of three in-service UTW sections, on US167, US65, and US90 in Louisiana were evaluated by means of pavement management system (PMS) data. The field performance survey results indicated that the cracking and patch distresses were few for these three UTW sections, which shows a good potential for UTW as an alternate rehabilitation technique for HMA pavement. The pavement condition was fair, good, and fair for US167, US65, and US90 after 13.5, 9.4 and 10.2 years of service, respectively, based on the Louisiana Department of Transportation and Development (LADOTD) PMS criterion for the national highway system. The fair pavement condition for US167 and US90 was mainly due to the relatively high international roughness index (IRI) and faulting values.

Transverse joints in rigid pavements are the locations where most pavement distress appears, leading to deteriorating riding quality and featuring high-maintenance costs. The state of stresses in the concrete surrounding dowel bars in dowel-jointed concrete pavements is a major factor that contributes to transverse joint distress. As such, a three-dimensional finite element model was developed for analyzing dowel-jointed concrete pavement. The effect of different pavement and joint related parameters on the load transfer characteristics of a joint has been evaluated using the finite element (FE) model. Group action of the dowel bar system has also been examined. Five loading cases were applied to replicate realistic vehicular loadings approaching and leaving the joint. The structural behavior of the pavement at the doweled joint was investigated for (1) pavement with and without voids, (2) dowel spacing variation, (3) pavement with and without lean concrete base, (4) slab thickness (5) tire pressure, and (6) single and dual wheel loads. The amount of load transfer was obtained from the shear force in the beam elements that simulate dowels. Results show that the voids underneath the joint causes an increase in the vertical displacement of the concrete slab and vertical stress at concrete/dowel bar interface, which could result in crushing of the concrete and dowel loosening. Wider dowel spacings result in increased shear forces and the size of the region containing engaged dowels does not change significantly with dowel spacing, only effecting the distribution of shear forces. Maximum principle stress (MPS) is about 6.7 times greater and steeperin the distribution pattern in the concrete pavement without lean concrete base (LCB). A thick concrete slab provides a significant benefit of higher load transfer andless curvature along the loaded side of the joint. The deformed shape explains why more dowels are engaged in the load transfer for the thicker concrete slab models. There were no significant effects on load transfer ratio with the increase applied wheel load. This phenomenon is also evident in the dowel shear force distribution. However, it will increases the demand on a few inner dowels beneath the wheel load, which may cause more damage to the joints and eventually lead to pavement failure. The study shows that the dowel bars perform effectively as a load transfer device in the concrete pavement system even under severe conditions.

The flexible function-layer is set between the cement concrete pavement slab and the semi-rigid base, which not only can lessen the influence of rain infiltration on subgrade and pavement structure but can also improve the contact condition of the slab and base so as to reduce the early cracking of cement concrete pavement slab caused by drying and temperature shrinkage. The 3-D finite element (FE) method was used to analyze the influence of the thermal stress of cement concrete pavement structure by the thickness and modulus changes of the function-layer. The results indicate that, first, under the positive and negative temperature gradient, the thermal stress of pavement structure was significantly influenced by the interlayer combination coefficient, whose increase would lead to a greater slab thermal stress. Second, the thermal stress of flexible function-layer and base decreased while the interlayer combination coefficient increased. The slab thermal stress linearly declined with the slab thickness, while the thermal stress of function-layer and base showed a nonlinear growth trend. The slab thermal stress was little affected by the thickness change of function-layer, but the higher modulus value of the function-layer, the greater thermal stress of pavement structure was observed. With the aforementioned analysis, this paper puts forward the reasonable function-layer thickness and modulus values.

Pervious concrete pavements have good drainage and noise reduction capabilities, and also have the ecological function of regulating surface temperature and humidity; they have been widely used in many countries. However, drainage capacity will be greatly decreased once the pores become clogged in permeable pavements. This study tries to reveal the mechanism of sediment clogging in the pores of the pervious pavement under surface runoff and provide bases for optimizing pervious pavement design. A series of laboratory tests have been conducted to demonstrate the effects of pavement slope, sediment size, inflow rate, and seepage outflow rate on the clogging phenomenon and sediment transport capacity of the porous pavement. Tests indicate that the mass of sediment clogged in the porous pavement generally decreases with increasing pavement slope, inflow rate, and sediment diameter, but the clogging risk increases with increasing seepage outflow rate. Greater sediment transport rate over the porous pavement is observed if the pavement slope, inflow rate, sediment diameter and seepage outflow rate is larger. The experimental results of dimensionless sediment transport rate have been compared with Meyer-Peter and Einstein empirical correlations. Most of the experimental points are concentrated near the empirical curves, whereas others scatter rather widely. This is mainly because the flow conditions are different, their empirical equations were based on experiments that have been done over a bed composed mainly of unconsolidated sand with large flow depth, whereas the present study uses fixed porous pavement and small flow depth, as our main interest is to study surface runoff in the urban area.

Although joint sawing has been widely used in concrete pavement to prevent uncontrolled cracking, optimum timing of joint sawing is critical to ensure appropriate crack control in designed joint locations. This paper presents a study of using concrete embedment strain gauges to monitor cracking at sawed joints by measuring the strain development at the joints. Five joints with the conventional sawing method were sawed to a depth of one-quarter of the pavement thickness. It was found that the strain gauges used in the study were capable of effectively monitoring the deformations at the joints. The results from the present study indicate that while cracking appeared at different ages in various joint locations, all five joints cracked within 7 days after paving, and no random uncontrolled cracking was observed. The joint crack times (or crack initiation time) measured by the strain gauges were generally consistent with the visual observations. Results and approach of the study can be used to identify potential late-stage random cracking problems in pavements construction with various sawing practices.

A pavement management system (PMS) consists of a set of defined procedures for collecting, analyzing, maintaining, and reporting pavement data to provide an aid tool in the decision-making process. Modeling of pavement performance is essential to pavement management. A transition probability matrix (TPM) can be used to model pavement deterioration with time. In the present investigation, the derivation of transition matrices was based on historic data of the International Roughness Index (IRI). Data used on this investigation was collected on a specific program called Corredores de Mantenimiento integral implemented by the Colombian National Highway Institute (INVIAS) from 2005 to 2009. Results indicate that the IRI was sensitive to short-term effects; therefore, it was possible to establish a model to accurately predict its condition for the available data.

Quality of pavement condition data is critical to the effectiveness of a pavement management system (PMS). Normally, if there is an error in the pavement condition data, it will affect the prediction of pavement conditions for future years. It may also affect the maintenance and rehabilitation treatment selection strategies and the budgeting and needs estimation at the network level. The Metropolitan Transportation Commission (MTC) of the San Francisco Bay area developed a pavement management program that now has more than 400 users in the United States. To enhance its existing data quality management plan and increase its effective use of pavement management program, MTC implemented a new quality acceptance (QA) program in 2013. This program is expected to significantly improve the quality of the PMS data. The QA program includes (1) developing a Rater Certification Program that ensures good quality data by using certified and trained technicians for the PMS, (2) hiring a third party and neutral institution to audit the various contractors' quality control plan, and (3) verifying the data collected by contractors and checking data collected against pavement deterioration models and curves in the PMS database. The methods used in the MTC's QA program should potentially benefit other agencies that are using pavement management systems.

This paper provides the engineering benefits of the pavement management system (PMS) applied on the national highways in Korea for the last 20 years. 40% of service life of the pavements was enhanced, and 75% of rehabilitation cost per unit length was reduced. Two types of distress analysis methods based on ViziRoad and image process were evaluated. ViziRoad is easy and convenient to be used for general surveys. The image process approach provided is more reliabl, but is definitely time-consuming. To overcome these limitations, the grid image process method was proposed.

As an effort toward developing a simple and practical laboratory cracking test method that can be used routinely, on a daily basis, to optimize Hot-Mix Asphalt (HMA) designs, various monotonic loading "single shot" cracking tests were comparatively evaluated in the laboratory alongside the repeated (dynamic) loading Overlay Tester (OT_R) test. These monotonic crack tests included the Indirect Tension (IDT) test, Semi-Circular Bending (SCB), Overlay Tester in a monotonic loading mode (OT_M), and Disc-Shaped Compact Tension Test (DSCTT). The research methodology entailed characterizing the cracking resistance potential of various commonly used Texas HMA mixes of known field cracking performance, with different mix-design variables. The corresponding findings indicated that while the monotonic loading tests, particularly the OT_M and IDT are much simpler, more practical and more repeatable with lower variability in the test results, the dynamic loading OT_R test, where both crack initiation and propagation phases are sufficiently accounted for, exhibited superior screening capabilities in terms of the HMA cracking resistance potential and sensitivity to mix-design variables such as the asphalt-binder content and temperature variations. Overall, the results indicated that both the IDT and OT_M could potentially serve as routine surrogate and/or supplementary crack tests to the OTR, subject to field validation.

Current practices lack a standard procedure for evaluating the performance of trackless tack. The primary purpose of this study is to develop a procedure through literature search that incorporates the combined shear and tensile stress state that an interlayer tack coat experiences in between a hot-mix asphalt overlay and an existing pavement into the crack mouth opening displacement (CMOD), a standard method to predict the fracture energy. Recent developments in facture testing and numerical simulation techniques have provided stronger links between material fracture properties and field cracking performance of asphalt pavements. Using the fracture energy as a criterion, performance of various trackless tack materials can be compared. The higher fracture energy required to crack a material, the better performance the material will have. The fracture energy methodology can be applied to characterize the performance of trackless tack with confidence.

This study determines the cross-anisotropy of field cored asphalt concrete sample in the laboratory. Two sizes of cube samples are prepared by cutting field collected core samples from an instrumented section in New Mexico, USA. One batch of cube samples are subjected to compression loading to failure through the top face and the other batch through the side face of the sample. Results show that the side face can sustain an average compressive stress of 77% of the compresses stresses of top faces. For validation, Finite Element Model (FEM) is constructed and stress-strain data from the field instrumented pavement section is used. FEM and field responses show a cross-anisotropy value of 80%, which is close to laboratory value.

The asphalt mixtures rutting resistance depends on many factors connected to mineral composition and its characteristics, volume relationships, binder content and its properties. In the research program 15 samples of different binders were tested, 5 binders in stone matrix asphalt, 5 in asphalt concrete and 5 in high modulus asphalt concrete. The used binders were pure bituminous binder and PMBs with different amount of polymer. The binders' test program contained typical, conventional tests, as well as tests dedicated to Polymer Modified Binders. Finally, the three types of asphalt mixtures were tested at rutting test according EN 12697-22 specification. From the research it was concluded that there are a few relationships between specified binder properties and asphalt mixture characteristics. Among others the Multiple Stress Creep Recovery (MSCR) test results of samples tested at temperature related to rutting test temperature and viscosity are related to the rutting properties.

Asphalt pavements in Zambia have been experiencing premature failures due to distresses such as rutting, fatigue cracking, bleeding, moisture damage, and pot-holing. Most of these failures have been attributed to poor workmanship of contractors who fail to adhere to specifications. Literature has, however, revealed that the materials used and the mix-design methods adapted also have a significant effect on the long-term performance of these asphalt pavements. To mitigate for these effects, some developed countries have developed new approaches such as Superpave and balanced mix design (BMD) methods that are performance-based, for the design of hot-mix asphalt (HMA) with the primary objective of improving the performance of asphalt pavements. By contrast, Zambia, like most developing countries, still uses the empirical Marshall Stability method that has inherent challenges in satisfactorily addressing the aforementioned pavement failures. This paper presents a theoretical review of the material types and mix-design methods currently used in Zambia to verify if premature failures of pavements can be attributed to the materials used and/or the mix-design methods adapted. Different mix-design methods and their characteristic attributes were comparatively reviewed to assess their potential applicability for use in a developing tropical countries like Zambia.

In China, the static creep modulus of hot-mix asphalt (HMA) was utilized to calculate the resilient deflection and tensile stress in asphalt pavement for structural thickness design. However, the static creep modulus does not match the stress and strain performance of HMA. In this paper, the dynamic modulus of HMA was studied by means of the modified loading time and the theoretical analysis and laboratory experiments. A field construction pavement structure, namely the connecting highway between Shiwu high-speed railway station and the Dawu County, was used to calculate the strain at the bottom of asphalt layer under the measured dynamic modulus by three-dimensional finite element(FE) software (i.e., ANSYS). According to China's specification, the dynamic modulus testing was carried out for the materials of this highway. The results of calculating and analysis indicated that the mechanical responses in asphalt pavement were different and the dynamic modulus should be used for the thickness design of the asphalt layer in China.

The use of porous mineral powders, includingwaste of the industry, is the perspective direction in the solution of a problem of receiving quality asphalt. The use of such fillers can promote increased heat resistance, crack resistance, and shift resistance of a road composite. It also saves onpreparation of asphalt mix and reduces environmental pollution. Porous fine fillers make for stronger structuring rather than denser. Micropores differ the high adsorptive potential. Therefore, the considerable part of surface-active components of bitumen are occluded. Conversely, bitumen impoverishment by easy fractions, which is caused by a selective filtration, can accelerate processes of aging of bitumen considerably. Therefore, inclusion in road construction of such raw materials causes the necessity of its comprehensive investigation. In this work, features of interaction of porous mineral materials with bitumen are described. The analysis of influence of porous mineral powder from a ceramsite dust on crack resistance of asphalt and bitumen aging in a composite is carried out. It is shown that mineral powder from expanded clay allows increased crack resistance of asphalt. However, it is necessary to control its influence on intensity of aging knitting.