Pavement Materials, Structures, and Performance

Microwave heating technology has been adopted in asphalt pavement maintenance to reduce the total cost resulting from the energy consumption. In this paper, laboratory preparation and microwave heating tests of carbonyl iron powders (CIPs)/asphalt binder were carried out. The modeling procedure, microwave heating efficiency and the properties of the CIPs/asphalt binder - such as penetration, softening point and ductility - were studied. The results show that microwave heating efficiency of CIPs/asphalt binder is enormously higher than that of ordinary asphalt binder. Adding a certain amount of CIPs can improve the asphalt binder's resistance to deformation at high temperature. All of these can put forward a theoretical basis to design asphalt mixtures suitable for use in snow and ice removal by microwave pavement maintenance vehicles.

Stone matrix asphalt (SMA) is a gap-graded asphalt mixture performing better than conventional dense-graded mixtures. It contains a high concentration of coarse aggregates (forming stone-on-stone contact between them) and high asphalt content. The coarse aggregate skeleton results in better load distribution and the high asphalt content adds durability to the mixture. Due to the high mastic (filler and asphalt) content, there is possibility of drain down during various stages in construction. SMA mix should be prepared with a suitable stabilizing additive to prevent the drain down of mastic material from the mixture. In this study, SMA mixtures are prepared in a Super pave Gyratory Compactor (SGC) with shredded waste plastics, which are mixed with aggregates prior to the addition of Viscosity Graded (VG) - 30 asphalt. Mixtures are prepared with asphalt contents of 5.0 to 7.0 per cent (by weight of aggregates) and stabilizer contents of 0, 4, 8, 12 and 16 per cent (by weight of asphalt). Volumetric and Marshall properties, tensile strength, and moisture susceptibility characteristics are determined. From the laboratory studies, it is observed that addition of waste plastics in shredded form can be used instead of stabilizers by controlling the drain down and enhancing the performance.

Lowering production temperature in warm mix asphalt technology may lead to inadequate drying of aggregates, resulting in low-quality asphalt production. Due to difficulty in direct observation of the drying and heating process and measurement of aggregate temperature inside the dryer, numerical analysis offers an alternative way to study heat transfer and aggregate temperature revolution. In this paper, coupled computational fluid dynamics (CFD) and discrete element method (DEM) are used to simulate aggregate movement and heat transfer in a simple drum. The effects of aggregate size, drum rotation speed and flights on aggregate temperature evolution and fluid temperature on the heating efficiency are studied. The results show that coupled CFD-DEM technique is an appropriate approach to study aggregate movement and temperature evolutions in the drum directly. Small particles can be heated more easily than large particles. Determination of optimal drum rotation speed needs to consider particle movement models as well as resident time in a real drum with inclined angle. High fluid temperature could reduce heating time of particles to reach the target mixing temperature. The preliminary results may provide some guidelines for operating the mixing drum efficiently and designing the drum to control quality of asphalt mixes and save energy.

A laboratory evaluation of the characteristics of palm kernel shell ash (PKSA) /cement-stabilized, reclaimed asphalt pavements (RAP) subjected to British Standard Heavy (BSH) (modified Proctor) compactive effort was carried to determine the compaction characteristics, California bearing ratio (CBR) and durability characteristics of the mixtures. Test results show that the properties of RAP improved when treated with PKSA and up to 6 % cement (C) additive. The particle size grading improved from 89.5% coarse aggregates for 100% RAP to 80-99.5% coarse aggregate with 0.5-20 % fines for the various RAP + PKSA + C mixes containing up to 6% cement. Optimum CBR values of 55 (unsoaked) and 60% (soaked in water for 24 hours) for 70% RAP + 24% PKSA + 6% Cement mix is durable with minimum water absorption characteristic and can be used as subbase and subgrade materials in road construction.

Moisture damage is one of the most important factors affecting durability of asphalt pavements. Selection of appropriate aggregates with optimum properties will help to improve the quality and durability of pavements. Recent studies showed that contact angle measurement using sessile drop instrument is an economical and convenient method for determining the surface energy of solid aggregates. However, there are few studies which compared contact angle measured on aggregate surface with varying surface roughness. Therefore, the present study is intended to compare contact angles measured on limestone which is polished with different grade Silicon carbide grits to reduce surface roughness. Contact angles were measured at selected points using probe liquids such as water, ethylene glycol and diiodomethane. In addition, measurements of surface roughness were made using three-dimensional optical profilometer. Also, using the contact angle measured, surface energy components were calculated. Energy ratio and compatibility ratio parameter of limestone with PG 64-22 were determined using the surface energy components. From present study, it was observed that surface roughness could cause variations in contact angle measurements which could be minimized by appropriate polishing of aggregate surface.

This paper presents the effects of different polishing levels on direct contact angle measurements on the surface of a granite aggregate specimen utilizing a sessile drop device. Contact angle measurements were performed on the rough surface of the specimen and also after each polishing stage using different grades of silicon carbide and aluminum oxide grits. The sessile drop tests were conducted on the same locations on the surface of the specimen after each polishing level and the behavior of the contact angles was observed. The results indicate that, as the surface roughness decreases with polishing, the standard deviation of the contact angle test results becomes smaller indicating consistency in contact angle measurements. The contact angles also decrease with increase in the smoothness of the specimen surface with polishing.

It is widely admitted that the behaviour of bituminous materials may be considered as linear for small strain and becomes nonlinear when the strain (stress) amplitude level increases. In this research, the "small" nonlinearities (when the applied strain amplitudes are lower than about 10^-4 m/m) are investigated. An improved complex modulus test campaign has been carried out for a large range of temperatures and frequencies on two types of mixtures (GB3 and GB5®). From experimental results, nonlinearity of mixes is observed - even at small strain amplitudes - for both norm and phase angle of complex modulus. Nonlinearity evolution changes follow the considered values of temperature and frequency. A key output of the study is that the Time Temperature Superposition Principle (TTSP)is valid even in the nonlinear domain. A master curve of the estimated linear viscoelastic strain limit could be plotted as a function of equivalent frequency.

The use of recycled asphalt shingle (RAS) as a partial replacement to petroleum-based virgin asphalt cement binder has received considerable attention in recent years due to economic and environmental reasons. The objective of this study was to conduct a comprehensive laboratory evaluation of dense-graded asphalt mixtures containing RAS, including stone-mastic asphalt (SMA). Dense-graded asphalt mixtures were designed to meet Super pave design criteria. A suite of laboratory tests was conducted to evaluate the low, intermediate, and high temperature performance and moisture resistance of laboratory-produced asphalt mixtures using the Thermal Stress Restrained Specimen Test (TSRST) , the Semi-Circular Bending (SCB) test, and the Hamburg Loaded-Wheel Tester (LWT). Results indicate that the draft revision of AASHTO PP53 over-estimates the actual shingle asphalt binder availability factor. In addition, asphalt mixtures containing 5% RAS performed equally to the control asphalt mixture containing no RAS at low, intermediate, and high temperatures. In addition, the utilization of RAS showed an improvement in the permanent deformation (rutting) performance by resulting in a lower rut depth as compared to the control mixture without RAS.

This study was initiated with an objective to address the rheological characteristics of the foamed Warm Mix Asphalt (WMA) modified with the newly fabricated size, Nano-sized Hydrated Lime (NHL), in comparison to Regular-sized Hydrated Lime (RHL). The NHL material was used with two particle sizes of 50and 100 nanometers (nm). The foamed WMA was produced by adding Advera. The rotational viscosity test was performed to study the effect of hydrated lime particle size on the binder's viscosity. The Dynamic Shear Rheometer (DSR) test was employed to evaluate rutting and fatigue cracking of the binders. Additionally, the Bending Beam Rheometer (BBR) test was used to evaluate the low temperature characteristics of the long-term, aged asphalt binders. The hydrated lime particle size did not show significant effect on the binder viscosity. The NHL can be used as an effective way to reduce the rutting as compared to the RHL. Although NHL-modified binders can suffer from the increased stiffness, the binders met fatigue and low temperature cracking specifications.

Flexural stiffness and fatigue life of asphalt concrete are determined by a four-point bending test using AASHTO T321 test protocol. A sample is prepared using a kneading compactor and is usually placed in the loading frame regardless of the direction of compaction. That means that the sample may be placed upside down (flipped) rather than placing the sample as it is compacted. To evaluate the flipping effect, a number of beam samples (375 mm x 63 mm x 50 mm dimension) are prepared and tested in two different ways to determine the flexural stiffnesses. First, these samples are tested in the way they are compacted. Secondly, the tests are conducted on flipped samples. Results show that the flipped samples always have greater stiffness (varies 3-26%) than the usual samples. In addition, based on field instrumentation on Interstate 40 (I-40) in New Mexico, it is revealed that thermal contraction and expansion due to daily and yearly temperature fluctuations at the bottom of asphalt concrete produce a relatively large amount of strain. Analyzing with Mechanistic-Empirical Pavement Design Guide (MEPDG), it is found that vehicle strain, daily and yearly thermal strains cause 5%, 0.01% and 95% fatigue damage at the bottom of HMA based on field measured strain and MEPDG fatigue model. Therefore, damages due to thermal expansion and contraction should be considered to determine the fatigue life of asphalt concrete.

Being a porous and composite medium, concrete's microstructure influences its strength, dimensional stability and durability. Thus, adequate characterization of hardened concrete is needed for the proper design and maintenance of concrete-based geo-infrastructure such as foundations and dams. Design and maintenance of concrete structures are generally practiced; however, concrete materials are assumed to be a homogeneous material or simply a two-phase composite (aggregate and hardened mortar). Within this context, this research aims to develop a method of modeling concrete microstructure using three-dimensional (3-D) finite element analysis and x-ray tomography, such that concrete microstructure and its influence in response to various physical loadings can be accurately represented. For this research, a MATLAB program was developed to read in a set of two-dimensional (2-D) x-ray images taken of a concrete cylinder test specimen, each in the horizontal plane, but 1 mm apart in height. The grayscale intensity value for each pixel in the images gives an indication of the density of the material at that specific point, making it possible to distinguish different material phases (such as aggregate, hydration products of cement, and voids). In this program, pixels are designated to be hydration products of cement, aggregate (fine and coarse), or void based on the grayscale intensity values. With high-resolution X-ray images, finer designations are possible. Each pixel of solid material is converted to a hexahedron finite element with appropriate coordinates for each of the eight nodes such that the elements connect and gaps between the 2-D images are closed. Each phase is then assigned with a set of unique material properties. The 3-D model is imported in ABAQUS for the finite element analysis. A variety of digital tests can be conducted using this technique, which constitutes an economical alternative to experimental tests.

This paper investigates the consolidation and shear strength of compacted red clay samples (before and after inundation) in Guangxi, China through laboratory tests. The unconfined shear strength of both undisturbed and remolded specimens in the process of reducing or adding water content was also studied. The studies show that, in moisture-density curves, the maximum dry density of the remolded specimen is greater than that of the undisturbed specimen. However, the optimum water content of the former is smaller than that of the latter. When the compacted specimens are subjected to a vertical load, the vertical deformation reaches steady state in a short time with a small value. After inundation, the increment of the vertical deformation is also very small. However, the unconfined shear strength of the red clay specimens with slightly higher water content is much better than that of those with lower water content. The test results also show that the dehydration or humidity absorption has significant effect on the shear strength of red clay, especially for the remolded specimen.

Preventing the polymer-modified asphalt from aging is of significance for the promotion of long-life asphalt pavement. This study investigated the effect of the hindered amine light stabilizer (HALS) on improving the aging resistance of asphalt modified with two types of commonly used styrene-butadiene-styrene (SBS). The HALS/SBS modified asphalt was prepared via melt blending. The thin film oven test (TFOT) and ultraviolet (UV) irradiation test were performed to simulate the thermal- and photo-oxidative aging, respectively. The rheological and aging properties of HALS/SBS modified asphalts were investigated through dynamic shear rheometer (DSR). Results indicate that the addition of HALS changes the viscoelastic behavior of SBS modified asphalt depending on the SBS copolymers and testing conditions. It was found that the HALS has significant improvement on both the thermal-oxidative and UV aging resistance for the radial SBS modified asphalt. As for the linear SBS modified asphalt, however, the HALS was found to have noticeable improvement on its UV aging resistance, but very limited improvement was observed on the thermal-oxidative aging properties.

The development of sustainable management practices for coal fly ash requires the understanding of the release of toxic elements from fly ash into the environment. Reactive mass transfer modeling implemented by AQUASIM was able to adequately describe the release and transport of magnesium and cadmium from fly ash. However, the adsorptive interactions between arsenic and carbon residues in fly ash complicated the modeling of the retardation of arsenic transport in fly ash. Selenium was another toxic element that exhibited strong retardation in the column leaching study due to adsorptive interactions. The results from this study suggest that processes, in addition to reactive mass transfer, need to be included to describe the leaching of elements exhibit strong adsorption/desorption characteristics. The modeling approaches reported in this study provide a framework for assessing the release and transport of toxic elements from fly ash during beneficial reuse.

In this paper, fractionated bio-char, a carbonaceous co-product from bio-fuel production, is utilized as an asphalt modifier. Laboratory testing was conducted to evaluate the modification effect of bio-char on asphalt cement and mixture. The bio-char used in this study was derived from switch grass and produced through a fast pyrolysis method. The binder samples, made by incorporating bio-char into one commonly used asphalt binder in the U.S., were tested for their rheological characteristics, rutting, and fatigue performance. It was found that bio-char was capable of significantly increasing the rutting resistance of the asphalt binder. The fatigue and cracking resistance was little affected by modification. The modified HMA mixture showed better resistance in rutting, moisture damage and cracking.

The residual thermal stress in asphalt due to temperature fluctuations greatly affects pavement stability and service life of pavement structures. In this paper, a coupled viscoelastic phase-field and Navier-Stokes system for the residual thermal stress in asphalt binder is developed. We simplify the asphalt binder to two compositions, resin and oil. The phase separation is modeled by the conserved Cahn-Hilliard dynamics, which is coupled with the fluid module in COMSOL commercial software. In order to capture the deforming interface, a self-adaptive mesh is employed for the finite element calculations. The numerical results show that the phase separation phenomenon has a significant influence on the residual thermal stress and leads to a non-uniform stress distribution in the system. Furthermore, stress concentration is observed at microstructure boundaries.

The Mechanistic-Empirical road design guide has been more and more used in the road design to consider the long-term performance of the road. In some road sections, there is pipe buried in the road for the sake of drainage. To investigate the effects of the shallowly-buried pipe on the permanent deformation of road surface under cyclic traffic loading, one laboratory test of an unpaved road with buried Steel-reinforced high-density polyethylene (SRHDPE) pipe under cyclic loading was conducted. In the tests, a 61-cm diameter SRHDPE pipe was buried in a compacted sand trench covered by AB-3 and sands. A Mechanistic-Empirical model was calibrated with the laboratory test data and adopted to predict the permanent deformations of the road under cyclic loading. It was found that the M-E model could simulate the road permanent deformation well under cycling loading before the road failed. Parametric study shows that pipe stiffness had considerable effects on the road deformation under cyclic traffic loading.

The ultra-thin asphalt pavement with a thin surface layer compared to traditional pavement structure appears to show distinctive premature pavement distresses such as significant cracks and rutting. The research establishes models simulating National Highway 1 in Congo (Brazzaville) by MEPDG software. Considering load level and material properties, the research analyzes the reasons for premature pavement distresses in ultra-thin asphalt pavement. By adjusting the key factors of modulus and thickness of each layer, the simulation arrives at the 95% reliability requirements of pavement structural strength such as down-top cracks and rutting. The research also predicts the performance of various pavement structures to resist high traffic growth rate, and draws conclusions about reasonable indicator trends of ultra-thin asphalt pavement.

In recent years, shakedown theory has been suggested as a more rational theoretical foundation for pavement structural design. This paper suggests a numerical approach to find shakedown load limit of layered pavements based on an investigation of residual stress field, which plays an important role in helping the structure to reach the shakedown status. A finite element model is established for pavement structures under repeated moving surface loads, where the Mohr-Coulomb yield criterion with associated plastic flow is assumed to capture the plastic behaviour of pavement materials. A criterion based on static shakedown theorem is suggested to distinguish shakedown and non-shakedown status of pavement structures subjected to different magnitudes of loads, thereby achieving a numerical shakedown limit. Comparisons between the numerical shakedown limits and theoretical shakedown limits of Wang and Yu (2013a) show good agreement. Investigation of the development of residual stresses in layered pavements also provides deep insight to the application of shakedown theory. In addition, the proposed approach can be easily extended to pavement materials following non-associated plastic flow rule.

The cohesive and adhesive bond strength of the asphalt-aggregate system, sensitive to environment temperature, will impact asphalt pavement rutting resistance. This paper used the Whihelmy plate method to test the change process of surface free energy of AH70 asphalt and SBS modified asphalt in the range of 20 to 70 Centigrade. Surface free energy of aggregates was measured by contact angle meter. The results show that the surface energy decreased as temperature increased. When the temperature exceeds the asphalt binder softening point, the adhesion bonding of asphalt-aggregate will reduce. The adhesion between asphalt and limestone or basalt is higher than that between asphalt and diabase or sandstone. By analyzing the correlation of surface energy parameters and dynamic stability of the six type asphalt mixture, a linear correspondence between the surface energy at 60 centigrade and rutting resistance is derived. This research may provide a theoretical basis for the optimization of selecting asphalt and aggregate and rutting preventive maintenance.

To solve the worldwide problem of structural analysis for port interlocking concrete block pavements, a three-dimensional, mechanistic model is developed. In particular, the layout pattern of interlocking concrete blocks and its size are carefully considered. A dual spring with uniaxial compression and lateral shearing functions is employed to simulate the interlock effects among concrete blocks. The influences of concrete block sizes, sub-grade reaction modulus and the interlock intensity on the structural responses of port interlocking concrete block pavements are discussed. The deflections and the flexural stresses on base are summarized by comparison of results based on the model hereof and obtained with a multi-layered elastic system model. The validity of the model is logically verified. The study showed that with increase of the lateral shearing stiffness of dual spring, the elections and the flexural stresses on base decrease slightly, and the size of concrete block has somewhat of an influence on the structural responses of port interlocking concrete block pavements; whereas, the effect of sub-grade reaction modulus on the structural responses is substantial. Therefore, the research can be used as a basis for design of port interlocking concrete block pavements.

In August and September of 2005, Louisiana was devastated by Hurricanes Katrina and Rita. There were approximately 2,000 miles of roadway in the Greater New Orleans area which were submerged in floodwaters for up to 5 weeks. After the hurricanes, there was great concern in the Louisiana Department of Transportation and Development (LADOTD) about the pavement structures in the flooded area due to the sustained flooding, as well as the pavement damage from the heavy debris trucking traffic. In this study, the pavement performance system (PMS) data for District 02 (most seriously influenced by hurricanes) collected before and after the hurricanes were analyzed to assess the pavement performance damage due to the sustained flooding and/or the heavy debris trucking traffic. The PMS data illustrated increased damage to highways as a result of heavy trucking or vehicle loading required to transport the vast amounts of debris following the hurricanes. In addition, the data established an escalation in deterioration occurring as subgrade components were not initially designed to sustain such vehicle loads and may have been further weakened as roadways were submerged in water for extended periods of time.

Ground Penetration Radar (GPR) is fast becoming a viable technology for pavement survey. It is a noninvasive, continuous, high-speed field test tool that has been used for evaluation of pavement conditions. Potential applications of GPR include: (1) determination of pavement layer thickness; (2) striping layer of asphalt pavement; and, (3) subsurface defects and underground objects. Currently, the Office of Materials at Mn/DOT owns a SIR 2000 data acquisition system and 4 antennae. The GPR technology has been used in the state to help local and district engineers evaluate pavement conditions, such as pavement thickness and underground objects. The Minnesota Road Research (MnROAD) test facility has been used to verify the system and it shows that the calculated pavement thickness from GPR is within 5% of traditional field test coring result. Furthermore, a research project is being conducted to use GPR time history data to obtain dielectric constant and pavement thickness together. Software based on wave propagation is developed to analyze and determine the two parameters. The results showed that this method gives reasonable results on both dielectric constant and thickness. This is an improvement over the current GPR analysis, which requires an estimate on dielectric constant to obtain pavement thickness. The paper will describe Mn/DOT's experience on GPR applications and data analysis techniques.

Pavement preservation is recognized as a means to a lower life cycle cost of a road asset; but, possibly not all surface distress data is documented and kept to further enhance a beneficial decision for the best treatment at the proper time. This paper presents a study to identify the types of treatments used in Alaska and how the treatments had performed. Forty-four road sections in Alaska that had received a pavement preservation treatment were surveyed in person along with data available from the AKDOT&PF. The PASER manual for asphalt roads was used to evaluate the distresses for the road sections. Different treatments provided varied improvement of pavement life, which is also consistent with the findings from parallel research efforts of literature and survey conducted by the research team. In addition, pavement failure modes in different regions of Alaska are different. The same pavement preservation treatments may be applied to different regions but to prevent or mitigate different failure modes. Use of some treatments (for example, chip seals) should be considered job-specifically. There is a need to create a pavement preservation database and keep good records of current and future pavement preservation projects for better evaluating and applying them.

This research project evaluates existing mechanistic models that predict permanent deformation (rutting) in asphalt mixes by comparing computer-simulated permanent deformation to that measured in a full-scale accelerated pavement test. Six pavement sections were constructed in the Civil Infrastructure Systems Laboratory (CISL) of Kansas State University with six different asphalt mixes. The sections were loaded with up to 700,000 repetitions of a 89.8 kN(22,000lb) single axle load. The transverse profiles at the pavement surface were measured periodically. For material characterization, asphalt mix samples fabricated in the laboratory were subjected to dynamic modulus (|E*|), static creep - flow time (F_t), dynamic creep - flow number (F_n), triaxial and uniaxial strength tests. The finite element software Abaqus was used to simulate and evaluate three permanent deformation prediction models: creep, elasto-visco-plastic, and Drucker-Prager. The predicted permanent deformation was then compared to permanent deformation measured in CISL for the six asphalt pavement sections. It was found that, with some improvements, creep and elasto-visco-plastic models could be used to predict permanent deformation in asphalt mixes, while the Drucker-Prager model, with hardening criteria, over-predicts permanent deformation.

Thermal stress due to a decrease in temperature is usually considered the product of modulus of Hot-Mix Asphalt (HMA), coefficient of thermal contraction (CTC) of HMA and the decrease in temperature. The effects of viscoelasticity, nonlinear temperature profile and stress history on the modulus of asphalt concrete were widely explored in the literature. However, the nonlinear behavior of CTC was neglected in all thermal stress models. This study incorporates the temperature-dependent CTC in a simplified thermal stress model and validates the results comparing with the field observations. As the first step, this study measures the dynamic modulus at low frequency and low temperature. The CTC of asphalt concrete is then determined in the laboratory at different temperatures and validates the results using the data from an instrumentation pavement section. Then, the thermal stress model has been developed using the low temperature CTC, temperature and frequency dependent stiffness and the decrease in temperature. Finally, these models are used to predict transverse crack spacing and are compared with two field observations. In addition, the critical temperature of asphalt concrete is predicted with age of pavement by intersecting tensile strength and developed tensile stress curves. Results show that the simplified viscoelastic model - without considering stress history and nonlinear temperature profile - predicts the crack spacing accurately. In addition, the critical temperature of asphalt concrete is not a constant value. It increases with the age of the pavement.

Rubblization is a process of mechanically breaking the existing concrete pavement into smaller-sized pieces using heavy-duty pavement breakers, such as Resonant Pavement Breaker (RPB) and Multiple-Head Breaker (MHB). Previous research studies indicated that bothpieces of equipment could perform well when a strong subgrade is present under the concrete layer. However, when the subgrade is relatively weak, subgrade yielding could happen during the rubblization. The use of MHB in rubblization has increased significantly over the past few years because MHB can adjust the amount of fracturing energy transferred to the pavement, which can help control the subgrade damage potential. In this study, a numerical damage model based on impact loading and fracture energy will be proposed to predict the behavior of the weak subgrade under MHB drop hammers. This model can potentially be used to calibrate the rubblization operation (speed, frequency, weight, height of hammer drop, etc.) of MHB for rubblizing concrete pavements over weak subgrades.

State and local Departments of Transportation, who have primary responsibility for the upkeep of their roadway pavement, must do so under tight budgets. At the expense of lower functioning roads (such as urban and rural collectors), these agencies tend to focus more of their maintenance and operations budget on high-volume roads - such as freeways and multilane highways - due to their importance. However, municipal officials responsible for the maintenance of collector roads are still expected to provide pavements of acceptable quality to the public, but they must do so under even tighter budgets. This paper presents a comparative analysis of the effectiveness of two pavement maintenance and rehabilitation techniques for municipal roads. One is the mill-and-overlay method, and the other is a resurfacing technique called NovaLite. The HDM-4 pavement management software was used to perform the analysis on 5^th Street in downtown Chattanooga, which is under the jurisdiction of the City of Chattanooga Public Works Department, a municipal agency. The results of the analysis indicate that NovaLite is superior to mill-and-over lay in initial cost, time and ease of construction, and extent of disruption of traffic. Even when lifecycle costs are considered, the analysis also shows that NovaLite maintains its advantages in cost and effectiveness, suggesting a way forward for cash-strapped municipalities.

An online monitoring system was recently built to acquire the inner condition and response of the runway pavement at Shanghai Pudong International Airport. Seven sections were instrumented to detect the responses of pavement when aircraft were taking off, landing, and taxiing. Sensors used in the system include strain gauges, multi-depth deflect to meters, temperature sensors, earth pressure cells, moisture sensors and three laser distance sensors for aircraft position. Most of the sensors are fiber-optic Bragg grating-based sensors, and some are electronic signal-based sensors used to improve the reliability and variety of the data. Instruments are divided into dynamic and static parts, which are aimed at measuring pavement responses caused by aircraft load and environmental influence. The instruments are all fiber optic cable connected within the airport area for radio frequency control. This paper presents: (1) the layout of sensors; (2) verification tests of the instruments; (3) process of installation; (4) method of data collection; and (5) initial responses test of pavement.

Long-term abrasion due to traveling vehicle occurring on the asphalt concrete pavement can reduce the friction which, in turn, can increase the risk of a highway accident. This work presents a predictive degradation model of skid resistance for in-service asphalt pavement surface based on laboratory polishing test results using the commercial grade asphalt polishing machine, characteristics of aggregate gradation curve, and field traffic conditions represented by average daily traffic. A nonlinear convex power function is used to form the prediction formula, within which two parameters - named "time index" and "scale index" - are assumed to have a first-order relationship with all predictors. Validation of the developed prediction models is presented by comparisons between the predicted values and field-measured values for five pavement sections from the Ohio highway system. The prediction results show a good consistency between field observations and model response values. Using the predictive model and assuming that abrasion and polishing are the controlling processes in pavement functionalities and performance, then the life prediction of an asphalt concrete pavement can be determined.

This paper investigated the failure potential in asphalt pavements under multi-axial stress states. A 3-D finite element (FE) pavement model was developed to predict the stress states in the pavement under moving tire loading. The calculated stress states were evaluated using Mohr-Coulomb criteria, respectively, for the bulk asphalt material and the interface between asphalt layers. The study results indicate that it is important to consider multi-axial stress states when considering the failure at pavement near-surface and layer interface. The failure potential at pavement near-surface varies depending on the depth and the horizontal location with respect to the tire. This indicates that "what appeared to be surface cracking" could initiate at the pavement surface or at some distance below pavement surface. At the layer interface, the maximum longitudinal shear stress was located at the tire center when the tire was approaching or leaving, while the maximum transverse shear stress was located at the tire edge. However, the longitudinal shear stress causes the greater failure potential due to the smaller confinement.

Fracture is a very complex process that involves the nucleation and growth of micro and macro voids or cracks, mechanisms of dislocations, flip bands, and propagation of micro-cracks, and the geometry of the material. However, the simplest and most common experiment measuring the mechanical response of engineering materials is the uniaxial tensile test. The moisture susceptibility of warm mix asphalt (WMA) was a major concern by some researchers. This study adopted indirect tensile test load-deformation curve to explain the moisture-induced damage of asphalt plant and laboratory compacted foaming WMA mixtures. Test results indicated that dissipated energy and the viscoelastic angle-based approach can be effectively adopted to evaluate the moisture susceptibility characteristics of WMA mixtures.

Faulting is considered as a major distress type in jointed concrete pavements. The effects of faulting have implications on the pavement, both structurally and in terms of serviceability. Faulting if not maintained in a timely manner can also lead to other distresses and impose considerable repair costs. Several factors play a role in the complex process associated with faulting. Traffic loads and layer stiffness, strength, and thicknesses are important, as well as other factors, such as the presence of water underneath the slab as it may be associated with the potential for rainfall are factors to be addressed in design. This paper presents a design process for predicting erosion-affected distress that occurs in concrete pavements using mechanistic parameters such as shear stress, erosion resistance of sublayer, and deformation. This mechanistic-empirical process also considers key climate effects in terms of the number of wet days. This process is embroidered within a computer program that analyzes a concrete pavement structurally and predicts the erosion and faulting at the slab joints. This program is capable of being calibrated with field performance or laboratory erosion data. Field data were used to validate the model's outcomes. Results show that the model fits well with the field data and can be implemented for design and maintenance management purposes.

The present study established treatment family performance models of typical asphalt resurfacing treatments at different traffic levels. Investigated treatments include HMA overlay, mill & fill, micro surfacing and slurry seal. Regression analysis showed that using an exponential model instead of a linear model did not significantly improve the R-squares. Thus, linear treatment performance models were established in order to provide a rational base for performance prediction and treatment effectiveness analysis. In addition, a strong linear relationship was identified between pavement performance deterioration rate and traffic level. The treatment effectiveness was calculated as the area between pavement deterioration curve and the lower threshold. It was found that HMA overlay had the highest effectiveness, followed by slurry seal, mill & fill and micro surfacing. The two emulsified asphalt treatments (micro surfacing and slurry seal) had higher cost-effectiveness than the two HMA treatments (HMA overlay and mill & fill).

With the advancements in image processing and 3-D technologies, the automated pavement surface condition survey technologies have gained popularity in recent years. However, there are still some issues that have hindered the full acceptance of the automated data collection technologies. This paper presents the research effort of studying the viability of fully automated assessment of pavement distress in a pavement management system (PMS)in terms of the inherent error between the manual and the automated data. Cracking distress data were collected manually and with an automated method at selected sites. The manually surveyed data were compared with the automated distress data to assess the differences.

This study evaluates the effect of freeze-thaw (F-T) cycling on the mechanical properties of cementitiously stabilized materials (CSM). Ultrasonic testing was applied to monitor the P-wave velocity (constrained modulus) change during the F-T cycling. Unconfined compression strength (UCS) test was performed at the end of F-T cycling. It was found that F-T cycling could be detrimental to CSM as the constrained modulus decreased to 7% to 96% depending on the CSMs. The residual UCS was 35% to 84% of the initial UCS at the end of the test. It was found that the greater the cement content, the stronger the anticipated durability. Clay-lime and silt-fly ash showed limited resistance to F-T cycling.

Cassava peel ash (CPA) was used to stabilize lateritic soil (LS) as highway material. The treated soil was subjected to British Standard heavy (modified Proctor) compactive effort and tested in order to determine the index properties, compaction characteristics (maximum dry density, MDD and optimum moisture content, OMC) and strength characteristics (unconfined compressive strength, UCS and California bearing ratio, CBR) of the treated soil. Test results show that the properties of lateritic soil improved when treated with CPA. The particle size grading for 100% LS show a composition of predominantly 99.6% coarse aggregates and 0.4% fines. This composition, however, improved with the addition of cassava peel ash to contain 94.3 - 99.6 % coarse aggregates and 0.4 - 5.7 % fines for the various lateritic soils - cassava peel ash mixes. The optimum mix of 70% LS + 30% CPA which gives the maximum unconfined compressive strength values of 630.59 kN/m2 (1st day-unsoaked), 577.67 kN/m2 (7th day-unsoaked) and 1009.40 kN/m2 (7th day-soaked) and California bearing ratio values of 55 % (soaked for 24 h) and 35 % (unsoaked) can be used as subbase and subgrade materials in road construction. Further works may be assessed in terms of the resilience modulus of the material.

Emulsified asphalt treated base (EATB) is a cold mixture of emulsified asphalt (emulsion) and granular material. The resilient modulus (M_R) of EATB is an essential parameter for both material evaluation and pavement design. Triaxial tests can be used to measure M_R and capture its nonlinear property affected by the stress state. However, such complicated test is not available for most routine practices. In this study, triaxial tests were conducted to measure M_R of EATB at different stress states. The effects of influencing factors, such as residual binder contents, aggregate property, dry density and temperature, on resilient property of EATB were also investigated. The nonlinear predictive models were further developed based on the modified universal soil model and all factors and interactions among them were incorporated.

It is of economic and social benefit to use the fine sand in coastal areas as subgrade filling, which can overcome the lack of construction materials in these areas. However, the engineering properties of fine sand are different with the ordinary filling materials resulting from the bad gradation and looseness of structure. In this paper, a series of laboratory tests - including the sieve analysis, compaction characteristic, CBR and modulus - was performed to assess the feasibility of filling with typical fine sands in Hainan and Shanghai. Then, the in-situ tests on construction method and quality were carried out. It is shown that, when fine sands are confined and covered by fine grain soils, sand-filling subgrade can provide sufficient stiffness and stability.

Flexible pavements are relatively thick in Hong Kong. Their thicknesses are generally designed to be at least 300 mm, generally due to high traffic volume. The design is based on the fatigue failure concept of the main structural layer (i.e. roadbase) after a prolonged number of traffic passages and, in turn, it is highly related to the stress levels being experienced in the pavement layers, including the subgrade. This paper presents the data collected on the dynamic stresses of the subgrade layer by soil pressure gauges under a major highway in Hong Kong. The results illustrate that the vertical stresses are in the range of 0.5 to 5kPa. These correspond well to the theoretical analysis results obtained by the software mePADs, by using the typical properties of the pavement layers. Subsequently, horizontal stresses at the bottom of the roadbase were also estimated. These fundamental findings provide an important yardstick for the review of design and analysis for fatigue life of flexible pavements in Hong Kong.

Base-course layers of a pavement structure usually are composed of granular materials which are typically in an unsaturated condition during their service life. Pavements during the last decade have been encouraged to be designed based on the mechanistic methods which use the resilient modulus (M_R) as a key parameter. The soil suction has a significant influence on the M_R of granular materials. In this paper, various equations proposed for predicting the M_R of unsaturated granular materials from the literature are summarized. Three equations proposed for predicting the M_R of granular materials summarized in this paper are selected to provide comparisons between the measured and predicted M_R values of three different granular materials. The strengths and limitations of the three equations are discussed. In addition, the relationship between the M_R and the soil-water characteristic curve (SWCC) is highlighted with recommendation to use it as a tool in the prediction of the M_R for granular materials.

This paper presents the behavior of subsoil under cyclic load transmitted by pavement layers. The response of subsoil to cyclic load is recorded in situ by the observation system (sensors) installed on the testing ground prepared for this purpose, being a part of the test road to the complex of warehouses in Bierun, near Katowice, in Poland. A different behavior of the homogeneous subsoil under pavement is observed for different seasons of the year, when pavement construction works as a flexible structure in summer, and as a rigid plate in winter. Albeit the observed character of subsoil response is the same regardless of the applied load and area values, This response can be divided into: ≤ zone of indirect action of the applied load; this zone extends to the depth of 1.0 m under the pavement, ≤ zone of a small strain, extending to about 2.0 m.