bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Rubber and Asphalt Binders by Depolymerization and Devulcanization of Scrap Tires in Asphalt
Authors: Zanzotto Ludo , Kennepohl Gerhard J.
Published: August 2018

Scrap tires in three forms—crumb rubber 60 minus mesh, crumb rubber 20 minus mesh, and buffed rubber—were subjected to depolymerization and devulcanization by applying heat, high shear, and a combination of both. Different reaction temperatures and times of reaction were applied. The reaction products were submitted to the testing of rheological properties by measurement of creep and recovery, viscosity, and some conventional tests. The amount of unreacted rubber and tendency to separation during the hot storage were also tested. Selected materials were evaluated according to SHRP specification and by the gel permeation chromatography. The results from the SHRP testing indicate that these materials are less temperature sensitive than conventional asphalts prepared from the same crude oil as the base asphalt. These materials were prepared in larger quantities and are being tested for their performance in paving mixes.
Use of Scrap Tire Chips in Asphaltic Membrane
Authors: Mahboub Kamyar C. , Massie Phillip R.
Published: August 2018

Findings of a study involving the use of scrap tire chips in an asphaltic membrane are reported. The research project was designed with two objectives in mind: investigate the effectiveness of an asphaltic membrane on top of a subgrade for maintaining moisture equilibrium in subgrade and study the potential use of scrap tire chips in asphaltic membranes. The effectiveness of the membrane as a moisture barrier needs to be evaluated over a long period of time. However, the method proved to be a cost-effective way of recycling waste tires in pavements. It is hoped that this study will contribute to various efforts in the area of cost-effective and sound use of waste materials in construction.
Feasibility of Crumb Rubber Use for Asphalt Pavement Construction
Authors: Madapati Raghu Ram , Lee K. Wayne , Manning Francis J. , Franco Colin A.
Published: August 2018

There are two processes of adding crumb rubber modifier (CRM) to hot mix asphalt (HMA), that is, the wet process and the dry process; and different technologies are available for each process. On the basis of the results of the binder study and producer's practices, HMA specimens were prepared using two selected AR binders with Producer R and A CRMs for Rhode Island (RI) dense-graded and dense-graded friction course (DGFC) mixtures, respectively. Aggregates procured from four local asphalt contractors were used. In addition, gap-graded HMA specimens were prepared with 3 percent CRM and control AC-20 binder with two typical local aggregates using the dry process. Marshall mix design was performed on all mixtures to determine optimum binder content and Marshall properties. Mechanical properties were evaluated for the mixtures with and without CRM. Superpave Level I mix design was also performed for dense-graded, DGFC, and gap-graded mixtures with aggregates procured from Contractor C. Finally, the performance of pavements with and without CRM was predicted using the computer program VESYS. Results of this study indicated that the use of CRM is feasible for RI dense-graded and DGFC mixtures utilizing the wet process.
Effects of Some Aggregate and Filler Characteristics on Behavior and Durability of Asphalt Paving Mixtures
Authors: Ishai Ilan , Craus Joseph
Published: August 2018

A summary of some of the findings obtained during a series of research projects aimed to select, define, and evaluate the significant aggregate and filler properties and relate them to the behavior of bituminous concrete is presented. A concept and test method suggested for an objective quantitative evaluation of the geometric irregularity of aggregate particles (shape, angularity, and surface texture combined) in a wide range of particle sizes are discussed. The aggregate parameters were found to be significantly correlated to the physical properties and mechanical behavior of the bituminous mixtures composed of the aggregates tested. Research work and findings related to a special evaluation of important physicochemical properties of the filler and their significant effect on the immediate properties and the long-term durability behavior of bituminous paving mixtures are summarized.
Aggregate Polishing Resistance Pre-Evaluation
Authors: Crouch L. K. , Shirley Greg , Head Gary , Goodwin William A.
Published: August 2018

Current methods of pre-evaluation of aggregates for bituminous surface courses such as the British Pendulum and British Polishing Wheel and chemical or mineralogical methods are only able to identify clearly aggregates with a high probability of performing well. There is little agreement among researchers as to what engineering properties will provide adequate frictional resistance at various average daily traffic (ADT) levels. The lack of agreement has led to conservative polish-resistance specifications and subsequently higher pavement costs. The Tennessee Textural Retention Method (TTRM) uses single size aggregate (6.35 to 9.52 mm), the Los Angeles Abrasion device, and a modified version of the AASHTO TP 33 device to evaluate particle shape and texture throughout simulated aging. In this evaluation, using 25 Tennessee aggregates, the TTRM was used to characterize aggregate polish-resistance performance at various ADT levels by comparing the results obtained on other aggregates with the results from field proven performers. The TTRM ranked all Tennessee proven performing siliceous limestones and gravels in the appropriate ADT category for which they are currently approved. In addition, new promising aggregate sources were revealed. The test method had a coefficient of variation for aggregate ratings of less than 3 percent for a nine-sample repeatability test. In addition, the maximum coefficient of variation of voids tests at any given aging revolution for an individual aggregate never exceeded 2 percent. The method may be helpful in pairing aggregate polish-resistance performance with pavement need based on ADT.
Quantitative Analysis of Aggregate Based on Hough Transform
Authors: Wilson James D. , Klotz Larry D.
Published: August 2018

Deformations in asphalt pavements continue to create problems for pavement agencies. One factor that has been identified as contributing to the potential of asphalt concrete to deform is the angularity of particles in the asphalt and aggregate mix. A new video-based method of measuring angularity based on the properties of the Hough transform, a powerful mathematical tool commonly used to detect long straight lines in video images, is presented. The method detects and measures the length of any straight edge in a two-dimensional image of a particle that is then used to quantify the particle angularity. The technique resolved three different test patterns independent of size and angle of rotation. Seven sands were analyzed with the method. The results were consistent with the known qualities of the sands. Although still limited as an engineering application, shape analysis of aggregate by video imaging has the potential to provide insight into the mechanisms of pavement deformation and may provide a basis for specifications or guidelines for the use of manufactured and natural sands in asphalt concrete.
Stability of Elasto-Damper–Coupled Wheelset for High-Speed Rail Vehicles
Authors: Lieh Junghsen , Yin Jie
Published: August 2018

A symmetric wheelset with an elasto-damper coupling between the wheels is used to investigate the effect of coupling and primary stiffness and damping on the vehicle critical speed. Different suspension parameters are considered. Stability boundaries for various conditions are presented. The dynamic model of the elasto-damper–coupled wheelset is validated using published results. Both coupler and primary suspensions can dramatically affect the vehicle stability, and optimal parameters can be used to improve the vehicle performance over that of the conventional system.
Green Design in Rail Industry—Threat or Possibility?
Authors: Signal Maria
Published: August 2018

In recent years, demands from society and market awareness concerning environmental impact of technical systems and products have increased. The laws and regulations were studied, the technology in the field of green design in the United States was explored, and the findings were compared with European practices. The focus was on the transportation industry. A structured environmental work method within the rail industry can lead to increased market acceptance and increased market shares. The marking of materials and use of less dubious materials will lead to lower fees when scrapping in the future. The following benefits are reasonably short-term and hence easier to see. The use of fewer materials and standardization of those used reduce costs. Low-energy vehicles lead to lower operating costs. Easily disassembled components are beneficial when scrapping and assembling and for the customer's maintenance and repair. Environmental concerns are already being addressed in other transportation modes, such as the automobile and bus industry. Trains are already an environmentally friendly mode of transportation and the rail industry should take advantage of this. To maintain the environmental lead that trains have over other transportation modes and to stay ahead of future requirements it is recommended that the rail industry further develop green design techniques.
Ultra-Thin, Fiber-Reinforced Concrete Overlays for Urban Intersections
Authors: Speakman Jim , Scott Harris N.
Published: August 2018

An industry partnership involving state and local highway officials; ready mix concrete producers; and fiber, admixture, and cement suppliers paved the way for extensive testing of a new concrete technology in Tennessee. Known as ultra-thin whitetopping (UTW), this experimental repair procedure involves placing a layer 50 to 75 mm (2 to 3 in.) thick of high-strength concrete over milled asphalt. Crucial to a long life for the thin concrete is a high synthetic fiber content, normally 1.4 kg/m3 (3 lbs/yd3) with joints spaced at a minimum of 0.92 to 1.22 m (3 to 4 ft) on center. From 1992 to 1995, seven cities in Tennessee participated in UTW demonstrations. The field tests were so successful that synthetic fiber-reinforced UTW is now being bid on many state and local projects. Presently, the primary use of UTW is to rehabilitate high average daily traffic intersections. Other potential uses include overlays of residential streets, parking lots, and airport aprons.
Synthetic Fiber-Reinforced Concrete Bridge Decks: Redefining Bridge Deck Design and Behavior
Authors: Newhook John P. , Mufti Aftab A.
Published: August 2018

Researchers at the Technical University of Nova Scotia have pioneered the development of concrete slab on girder bridge decks totally devoid of all internal steel reinforcement. The decks are constructed of synthetic fiber-reinforced concrete on composite steel girders restrained by external steel straps. The discrete reinforcing fiber used is a collated fibrillated polypropylene fiber. The major benefit of this approach is the reduction of long-term maintenance costs and the increase in bridge deck lifespan. An overview of the concepts behind this technology, theoretical and experimental work that has been undertaken, and some the practical aspects of designing a fiber-reinforced concrete mix with high volume fractions of synthetic fiber are presented.
Properties of Polymeric Fiber-Reinforced Concrete
Authors: Balaguru P. , Khajuria Anil
Published: August 2018

The mechanical properties of lightweight and normal concrete containing nylon polymeric fibers are presented. Fiber reinforced concrete made with nylon fibers was evaluated. The 19-mm-long fibers were in single filament form. The control concrete was designed for a compressive strength of 20 MPa. The primary independent variable was fiber volume fraction. The response variables were air content, unit weight of fresh concrete, compressive strength, modulus of rupture (flexural strength) and toughness, splitting tensile strength, and impact strength. The addition of fibers decreased the slump values. The decrease was negligible at fiber contents of 0.45 and 0.6 kg/m3. The fibers distributed well in the matrix. Fibers could be directly added in the mixer. The effect fibers had on unit weight of concrete is negligible. Addition of fibers up to 2.4 kg/m3 did not change the compressive, flexural, and splitting tensile strengths appreciably. Impact strength and flexural toughness increased consistently with the increase of fiber volume fraction.
Effect of Aggregate Contamination on Concrete Pavement Durability
Authors: Wojakowski John , Hossain Mustaque
Published: August 2018

Durability is a prerequisite for satisfactory performance of concrete pavements in freeze-thaw environments. The Kansas Department of Transportation (KDOT) has been experiencing durability problems of limestone aggregates since the 1930s and, finally, has developed stringent specifications for concrete aggregates through a series of field and laboratory studies in the mid-1980s. Recently, pavements that potentially are nondurable because of contamination of limestone aggregates have been detected on three projects on I-35 and US-50. These projects involved more than 500,000 yd2 of concrete pavement, worth approximately $10,000,000. The suspected contamination was first detected by a geological investigation on slices of cores and beam samples randomly taken from the project as well as on loose coarse aggregate samples larger than 4.75 mm (U.S. No. 4) sieve size. Freeze-thaw tests (ASTM C-666; Procedure B) on the cores and beams retrieved from these projects indicated that the samples with higher percentages of aggregate contamination did not meet the KDOT specifications for durable concrete. Results of ASTM C-666 (Procedure B) tests on the beam samples prepared with increasing percentages of nondurable aggregate (contaminant) show that higher expansion and lower durability correlate very well with the increasing percentage of contaminants. An analysis of service life adjustments made because of the ranges of contamination detected in the project cores indicates a reduced service life of 5.1 percent for the I-35 concrete pavement and 5.5 percent for the concrete pavement placed on US-50.
Permeability of Concrete Subjected to Cyclic Loading
Authors: Tawfiq Kamal , Armaghani Jamshid , Vysyaraju Janaki Ramprasad
Published: August 2018

The effect of microcracking development and propagation on the permeability of concrete was investigated in this study. Large numbers of single-edge–notched beams as well as unnotched beams were prepared in the laboratory and in the field from different concrete mixes and subjected to dynamic loading at various stress ratios. During the cyclic loading, stress-strain and air permeability measurements were simultaneously recorded using strain gauges and the poroscope apparatus. Obtained strain and the air permeability measurements were used to evaluate the deterioration of concrete during crack initiation and further propagation. After fatigue testing, other sets of samples were cored from the fractured beams for water permeability testing. Results from these samples were used to correlate with the air permeability as well as with the compressive strength of the beams. Findings indicated that at the first stage of cyclic loading the beam samples exhibited large strains along with a rapid deterioration in the permeability values. Scanning electron microscope images on a specimens obtained from cracked sections in Stages I and II corresponded with the severity of the strain measurements and the air permeability values in these zones. It was also found that compressive strength influenced the transport characteristics of concrete. Another relationship was derived for the air permeability ratio versus the ratio of number of cycles. This relationship can be used as a tool to predict the remaining fatigue life of a structure by measuring its permeability.
Neural Network Interpretation of Ultrasonic Response for Concrete Condition Assessment
Authors: Shoukry Samir N. , Martinelli D.R.
Published: August 2018

Ultrasonic testing of concrete structures using the pitch-catch method is an effective technique for testing concrete structures that cannot be accessed on two opposing surfaces. However, the ultrasonic signals so measured are extremely noisy and contain a complicated pattern of multiple frequency-coupled reflections that makes interpretation a difficult task. In this investigation, a neural network modeling approach is used to classify ultrasonically tested concrete specimens into one of two classes: defective or nondefective. Different types of neural nets are used, and their performance is evaluated. It was found that correct classification of the individual ultrasonic signals could be achieved with an accuracy of 75 percent for the test set and 95 percent for the training set. These recognition rates lead to the correct classification of all the individual test specimens. The study shows that although some neural net architectures may show high performance using a particular training data set, their results might not be consistent. In this paper, the consistency of the network performance was tested by shuffling the training and testing data sets.
Temperatures and Related Behavior in Segmental Retaining Wall System
Authors: Buttry Kenneth E. , McCullough Earl S. , Wetzel Richard A.
Published: August 2018

A segmental retaining wall reinforced with geosynthetics was constructed on the University of Wisconsin-Platteville campus from October to December 1993. It was 3.5 m high and 36.6 m long and was instrumented to measure movements, earth pressures, forces between segmental units, temperatures, and strains in the geogrid reinforcement. Monitoring of the instrumentation was done during construction and is continuing. The results of the monitoring program pertaining to temperatures, geogrid strains, and normal forces acting between adjacent layers of facing units of the wall are reported. The maximum temperature recorded in the wall was 28°C, and the minimum was −4°C. Maximum strains in the geogrid were 0.50 percent. Load cell measurements of the normal force acting on a facing unit were initially about twice the weight of the units above the load cell. With time the measured normal forces decreased to approach the weight of the units above. Wall behavior appears to be related to seasonal temperature changes, and these relationships are discussed.
Frost-Thaw Effects on Ballasted Track
Authors: Raymond Gerald P.
Published: August 2018

The multiple failures of a ballasted track 877 m long built to guide the wheels of a heavy gantry crane used in a logging yard in northern Alberta, Canada, are described. At the time of construction the crane was claimed to be the heaviest, and its wheels were supported by a ballasted track with wood lateral members (ties). The track was built in 1985 but exhibited excessive differential vertical and lateral deformations in subsequent years. The focus is on failure of a track related to freeze-thaw conditions and the solution to track instability problems, which was achieved geotextiles.
Effect of Geotextiles on Permanent Deformation in Salt-Encrusted Subgrade Soils
Authors: Bayomy Fouad M. , Al-Shaikh Abdul-Karim M. , Abduljauwad Sahl N.
Published: August 2018

The effectiveness of using geotextiles on top of salt-encrusted soil, known as sabkha in the Arabian Gulf area, used as a subgrade layer was investigated. A specific characteristic of this soil is that when it is dry (at or below the optimum moisture content) it possesses a sufficient bearing capacity and is hard enough to resist permanent deformation. However, when saturated it loses its strength and causes very large pavement deformations. An experimental model was developed in the laboratory to test and evaluate the bearing capacity and resistance to permanent deformation of the soil–fabric-reinforced system. The laboratory model consists of a cylindrical mold 320 mm in diameter and 420 mm in height in which a sabkha subgrade and a granular base are compacted and separated by a nonwoven geotextile. The testing variables considered in the study are thickness of the base layer on top of the sabkha sub-grade, the presence and types of geotextiles, the applied dynamic stress, and the moisture condition of the soil (at optimum dry versus saturated). The results indicate that the use of geotextiles significantly improved the bearing capacity and resistance to permanent deformation of the base layer on top of a sabkha subgrade. The improvement achieved is more significant for saturated conditions and is a function of the tensile strength of the geotextile. Increasing the base thickness resulted in higher levels of resistance to permanent deformation. A generalized linear regression model was developed to evaluate the permanent deformation of the soil–fabric–aggregate systems. The model is laboratory based, and its validity is restricted to the conditions investigated.
Effect of Reinforcement on Fatigue Life of Asphalt Beams
Authors: Saraf Chhote L. , Majidzadeh Kamran , Tribbett William O.
Published: August 2018

A study was conducted to determine the effect of reinforcement on the fatigue lives of asphalt beams of size 76 × 76 × 610 mm, which were prepared in the laboratory with a typical surface layer asphalt mix. Three sets of nine beams each contained no reinforcement (control beams) and reinforcements consisting of nonwoven paving fabric and composite (woven grid and nonwoven fabric composite). Each set of beams was subjected to three different load levels (three beams were tested at each load level), and their fatigue lives were determined. The fatigue testing of these beams was carried out by placing the beam on an elastic foundation (approximately 150 mm deep, 76 mm wide, and 660 mm long) and loading the beam at the center. A fatigue load at a frequency of 2 cycles/sec was applied to each beam. Each load cycle consisted of a half sine wave of 0.1-sec duration and a rest period of 0.4 sec. The total number of fatigue loads to crack the entire depth of beam was recorded as its fatigue life. The data obtained from three different sets of the beams were analyzed to determine the effect of reinforcement on the fatigue lives of the beams. These analyses indicated that the beams reinforced with composite performed significantly better than the beams containing paving fabric alone, and the beams reinforced with fabric alone performed better than the unreinforced control beams. Further details of the study and the results are described.
Field Tests and Numerical Analyses of Subgrade Soil Reinforced with Grids of Stabilized Granular Columns
Authors: Lawton Evert C. , Mokashi Anagha A. , Fox Nathaniel S.
Published: August 2018

Field tests and numerical analyses conducted to establish the feasibility of reinforcing soft, loose, or otherwise inadequate subgrade soils with a grid of small-diameter, stabilized, vertical granular columns to support traditional pavement systems are described. This technique may prove to be cost-effective if it is used to improve subgrade soils so that the sub-base or base courses can be reduced in thickness or eliminated. Field plate bearing tests were carried out on unreinforced cohesionless silty sand and on the same soil reinforced with vertical reinforcing columns constructed of four materials: crushed granitic gneiss, silica sand, cement-stabilized native soil, and cement-stabilized silica sand. The field tests indicated that the columns made of the two cement-stabilized materials substantially increased the subgrade modulus of the native soil. In contrast, the two unstabilized columnar reinforcing materials produced no substantial improvement in stiffness. The field tests were modeled by using an axisymmetric finite-element (FE) program and hyperbolic constitutive relationships for the native soil and the columnar reinforcing materials. Triaxial tests were performed on reconstituted specimens of the native soil and compacted specimens of cement-stabilized native soil to determine the stress–strain–strength parameters required for the FE analyses. The FE analyses modeled the plate bearing tests on the reinforced soil to a reasonable degree, indicating that the FE method used has the potential to simulate a complete pavement system (including a wearing surface) in which the subgrade soil is reinforced with columns of stabilized granular materials.
Zero-Shear Viscosity of Bituminous Binder and Its Relation to Bituminous Mixture's Rutting Resistance
Authors: Sybilski Dariusz
Published: August 2018

When testing viscosity of polymer-bitumen systems a question arises about interpretation of results as those systems behave as non-Newtonian liquids. A simple equation modeling non-Newtonian behavior of polymer-bitumens was proposed (which is a simplified version of the CROSS model). The equation used enables the calculation of zero-shear viscosity η0 from viscosity measurements conducted under various shear conditions, that is, with rotational viscometer at different shear rates (stresses). Test results are presented of several polymer-modified bituminous binders before and after Thin film oven test aging and discussion of non-Newtonian behavior. The wheel tracking test (Laboratoric Central des Ponts et Chaussées) was conducted for asphalt concrete with several bituminous binders, either plain bitumens or polymer modified. To estimate bituminous mixture's rutting resistance, a new relationship has been proposed to calculate N10 (wheel passes number to rut depth 10 mm). Close correlation was found between N10 and zero-shear (or absolute) viscosity of binders at 60°C, both conventional and polymer modified.
Influence of Air-Blowing on the Performance-Related Properties of Paving Asphalt
Authors: allagher Kevin P. G , Bahia Hussain U. , Guerra Jason D. , Keating Jay
Published: August 2018

A comprehensive experiment was designed to compare the performance-related properties of a wide range of air-blown asphalt binders with those of straight run asphalt binders of similar viscosity grades. The binders were evaluated using the concepts of the Superpave binder specifications. In contrast to the prevailing perception in the industry, all performance-related properties of the air-blown binders were found to be as good as or better than conventional straight run asphalt binders.
Microstructure, Morphology, and Failure Modes of Polymer-Modified Asphalts
Authors: Shin E. Eugene , Bhurke Alekh , Scott Edward , Rozeveld Steve , Drzal Lawrence T.
Published: August 2018

The effects of polymer modification on microstructure, morphology, and failure modes of asphalt binders and their concretes were investigated using various test methodologies that have been newly developed or modified. Results from the good and bad samples (i.e., a new Marshall concrete specimen and an aged road core, flexible pavement that showed signs of stripping, respectively) confirmed the reliability and applicability of the test methods. Two different viscosity-graded asphalt binders, AC-5 and AC-10, with two types of network thermoplastics, styrene-butadiene-styrene and styrene-ethylene-butadiene-styrene block copolymers, were studied for void morphology, binder phase morphology, statistical void image analysis, and failure modes as a function of polymer concentration and test temperature. One of the most striking results is that a highly entangled fibrillar network structure has been observed from both straight and polymer-modified asphalt binders after an electron beam etching. It was also observed that the morphology of the network altered with prestraining or binder aging. Void morphology and statistical void analysis were well characterized with the methods developed, but no significant effect of polymer modification was observed. From the fracture studies, however, the polymer modification indicated strong influence on both microdeformation behavior and failure mode of the asphalt concretes.
Effect of Asphalt Film Thickness on Short- and Long-Term Aging of Asphalt Paving Mixtures
Authors: Kandhal Prithvi S. , Chakraborty Sanjoy
Published: August 2018

It is generally believed that an asphalt paving mixture should have an adequate asphalt film thickness around the aggregate particles to ensure reasonable durability (resistance to aging) of the mixture. The minimum asphalt film thickness generally recommended ranges from 6 to 8 μm. However, no significant background research data are available in the literature to support these recommended minimum asphalt film thicknesses. Some states specify minimum asphalt film thickness for mix designs. This study was undertaken to quantify the relationship between various asphalt film thicknesses and the aging characteristics of the asphalt paving mix so that an optimum film thickness desirable for satisfactory mix durability could be established. Mixes prepared with asphalt binder film thickness ranging from about 4 to 13 μm were subjected to accelerated aging using Strategic Highway Research Program (SHRP) procedures to simulate both short- and long-term aging. Both the aggregate (RD) and the asphalt cement (AAM-1) used in this study were obtained from the SHRP Materials Reference Library. The aged, compacted mix was tested for tensile strength, tensile strain at failure, and resilient modulus. The aged asphalt cement was recovered and tested for penetration, viscosity, complex modulus, and phase angle. Aging indexes were obtained from these tests, and the relationship between film thickness and the aged mix/aged asphalt cement properties were determined using regression analysis. For the particular aggregate/asphalt cement combination used in this study, it was found that accelerated aging would occur if the asphalt binder film thickness was less than 9 to 10 μm in an asphalt paving mixture compacted to 8 percent air void content.
Modeling of Oxidative Aging Behavior of Asphalts from Short-Term, High-Temperature Data as a Step toward Prediction of Pavement Aging
Authors: Huh Jung-Do , Robertson Raymond E.
Published: August 2018

The oxidative aging data collected during the Strategic Highway Research Program have been analyzed in terms of kinetics of viscosity change with time and temperature. Changes in viscosity have been used as the measure of the progress of aging. The objective is to model viscosity increases accurately enough to be able to predict aging (in terms of viscosity changes) at pavement temperatures from short-term test data acquired at high temperature. This involved constituting a mathematical model, based on oxidative reactions, and a nonlinear regression of the data to test predictability of the proposed model. Clearly, there is a point beyond which viscosity change becomes independent of time, but no data were collected to that extent. Separately, it has been shown that oxidation of aliphatic sulfide to sulfoxide and oxidation of benzylic carbon to carbonyl are the principal chemical reactions that contribute to an increase in viscosity. The data fit the proposed equation sufficiently well to allow calculation of rate constants of viscosity increases for both reactions, and, hence, allow development of an Arrhenius temperature relationship. Finally, it is hoped that the proposed equation will provide reasonable estimates of rates of oxidative aging of asphalts at pavement temperatures from short-term, high-temperature oxidative aging data measured in a laboratory.
Asphalt-Aggregate Interactions Characterized by Zeta Potential and Retained Strength Measurements for Natural and Organosilane-Treated Aggregates
Authors: Hagen Arnulf P. , Lee William D. , Jones Tisha M.
Published: August 2018

Zeta potentials in water have been measured for a poorly performing, easily stripped hard limestone, a well-performing hard limestone, a sandstone, a rhyolite, soda lime glass beads, and for eight AC-20 asphalt binders. Four of the binders selected to represent a range of zeta potentials were combined with the sandstone, the limestones, and the glass beads according to Oklahoma Department of Transportation mix formulas and tested for retained strength. The good hard limestone was the best overall performer with retained strengths of 96 to 100 percent, the poor hard limestone was acceptable, overall the sandstone was unsatisfactory; and the glass beads did not survive the retained strength preconditioning procedure. The aggregates were then treated with organosilane derivatives to chemically modify their surfaces and to change the aggregate zeta potential. For example, the zeta potential of the poor hard limestone was made to be closer to that of the good hard limestone. The modified aggregates were then used in the same mix and the retained strengths measured. The good hard limestone mix exhibited no change in retained strength; however, the poor hard limestone, the sandstone, and the glass bead mixes gave excellent retained strengths.
Use of Lime in Recycling Asphalt
Authors: Wisneski M. L. , Chaffin J. M. , Davison R. R. , Bullin J. A. , Glover C. J.
Published: August 2018

Two Strategic Highway Research Program asphalts were aged in a pressure oxygen vessel (POV) with and without admixture of CaO and Ca(OH)2 at several concentrations. These same asphalts were then aged by low-temperature air blowing, and the resulting materials were softened by mixing with three recycling agents obtained by supercritical extraction of asphalts. These rejuvenated asphalts were mixed with varying amounts of CaO and aged in the POV. Oxidation rates and hardening were measured at various temperatures, and the resulting kinetic parameters were used to estimate hardening at road conditions. The hardening rate was always reduced by lime addition. The oxidation rate was sometimes reduced. The recycling agents alone reduced the hardening rates relative to those of the original asphalts, but the effect was further enhanced by CaO additions.
Permeability of Asphalt Surface Seals and Their Effect on Aging of Underlying Asphalt Concrete
Authors: Button Joe W.
Published: August 2018

Asphalt surface seals are defined as slurry seals, micro-surfacings, and chip seals (seal coats). The relative aging abatement effects of surface seals on the upper 13 mm (½ in.) of an asphalt pavement were estimated. A laboratory aging experiment was devised wherein a surface seal was simulated by a membrane that could be easily removed after the artificial aging process without affecting the uppermost layer of asphalt in the asphalt concrete. By comparing laboratory aging data with existing field data on aged asphalt pavements it was possible to make inferences about the number of years an asphalt surface seal will delay hardening of an underlying asphalt concrete layer. Compacted asphalt concrete slab specimens (40 × 60 × 13 mm) were prepared in the laboratory. Half of each slab was covered with an impermeable membrane; then the specimens were exposed to hot air to accelerate oxidative aging. Following the heat exposure, asphalt was extracted and physical and chemical tests were performed to measure hardening of the covered and uncovered specimens. Permeabilities of laboratory prepared slurry seal, micro-surfacing, and seal coat specimens were measured. By knowing the amount of oxidative aging that occurred in uncovered and covered specimens of asphalt concrete and the permeability of the surface seals, the effects of the surface seals on aging of an underlying asphalt concrete layer were interpolated. Testing indicated that a surface seal can retard oxidative hardening of an underlying asphalt concrete layer by 0 to 2 years, depending on the situation. However, most of the oxidative aging in the upper stratum of an asphalt concrete pavement occurs during the first 4 years after construction. After this period, the asphalt aging rate decreases significantly. Therefore, for a surface seal to significantly delay oxidative hardening of the underlying pavement, it must be placed during the first 2 years (approximately) of the pavement's life. It was demonstrated that ultraviolet (actinic) light penetrates asphalt cement only a few microns and, therefore, does not contribute materially to hardening of the uppermost 13 mm of an asphalt concrete pavement. Permeability of a slurry seal or micro-surfacing after sufficient traffic to effect maximum compaction is less than 1 × 10−5 cm/sec. Permeability to water and air of an asphalt seal coat (chip seal) is essentially zero. For practical purposes, these three surface seals will protect the top 13 mm of an underlying pavement from oxidation as if they were impermeable to air and water.
Procedure to Estimate Loading from Weigh-in-Motion Data
Authors: Wu Shie-Shin
Published: August 2018

Truck weight data collected from weigh-in-motion (WIM) sites were used to develop a procedure to estimate truck load factors for pavement design purposes. A conceptual procedure that uses WIM data to derive equivalent single-axle load factors for different types of trucks is presented. Sets of load factors can be developed for different types of facilities. An example is provided to illustrate how these factors can be used by engineers to calculate project design loading. Applying these factors to traffic classification counts collected from the statewide traffic monitoring program, engineers can also compute network traffic loading history.
Investigation of Bonding Materials for Traffic Monitoring Equipment: Properties of Selected Formulated Materials
Authors: Rue Agata J. Wiackowska-La , Fowler David W. , Ueber Eric J.
Published: August 2018

Planning for new construction and rehabilitation requires accurate knowledge of traffic volume, vehicle classification, and axle loads. Monitoring and controlling the movements of cars and other vehicles will grow increasingly important in the foreseeable future. To estimate the number of vehicles, truck weights, and speed, piezoelectric axle detectors placed into pavements are used. In Texas several thousand devices at over 1,000 sites are maintained and regularly monitored online. It is essential that the installation of monitoring devices be fast, easy, usable in all types of pavements, and reliable without requiring maintenance or reinstallation for a reasonable length of time. Bonding materials are needed to install the monitoring devices in the pavement. A study was conducted to select materials that would perform satisfactorily. Several chemically different materials were tested. Descriptions of the laboratory testing program, field installations, test results, and conclusions are presented.
Considerations for Designing Commercial Vehicle Monitoring Facilities
Authors: Stamatiadis Nikiforos , Graves R. Clark , Schmidt James
Published: August 2018

Commercial vehicle monitoring facilities provide the highway community with the means of supervising truck traffic. The technological advancements of the last few decades have allowed the realization of electronic clearances and can provide more effective ways to monitor and inspect truck traffic. However, in an era with limited funds and space for roadway expansion, some consideration must be given to what types of facilities are needed and what is the most efficient way to spend the available funds. Hence, a research effort was conducted to determine successful practices for designing a new facility or retrofitting or upgrading an existing one. The issues that need to be considered and addressed when designing or upgrading a commercial vehicle facility are discussed, and a checklist of critical factors, considerations for facility components, and typical facility layouts are provided. The findings indicate that a systems approach should be undertaken, all agencies affected by the operation of these facilities should be consulted and included in all phases of the project, and the development of a vision of the commercial vehicle operations goals is essential.
Development of Integrated Traffic Monitoring System for Delaware
Authors: Faghri Ardeshir , Glaubitz Martin , Parameswaran Janaki
Published: August 2018

The establishment of a comprehensive statewide traffic counting program is discussed. The program comprises automatic traffic recorder (ATR), automatic vehicle classification (AVC), and weigh-in-motion (WIM) sites for the state of Delaware. The program was undertaken to review, establish, and implement effective statistical and procedural methods. The second phase of a two phase project, which implements the methodologies that were derived in the first phase, is presented. Using descriptive analysis and seasonal grouping, the number and location of sites needed for each of the three types of traffic monitoring devices were determined. Existing field data from Delaware's current ATR locations allowed for a statistical determination of the necessary number and road-type group distribution for the ATR sites. The absence of field data for AVC and WIM sites, however, necessitated alternative methods for determining the number and location of the traffic monitoring devices. As a result, a combination of statistical analysis and engineering judgment must be used for the establishment of any statewide traffic monitoring system.
Survey of State Practices to Control Skid Resistance on Hot-Mix Asphalt Concrete Pavements
Authors: Jayawickrama P. W. , Prasanna R. , Senadheera S. P.
Published: August 2018

A nationwide survey on design methods for achieving adequate skid resistance on hot-mix asphalt concrete pavements was conducted. Information was collected on the design practices used by 48 state departments of transportation (DOTs) in the contiguous United States. Survey findings show that the emphasis placed on the skid resistance aspects in various state DOT design procedures vary considerably. Based on the data collected, 21 out of 48 state highway agencies either do not have any design guidelines specifically addressing pavement skid behavior or assume that adequate skid resistance may be ensured through proper mix design. The general approach used by these agencies involves frequent monitoring of pavements to identify pavements with skid-related problems so that appropriate action may be taken. Survey findings indicated that state DOTs that consider skid resistance in their design procedures emphasize controlling the quality of coarse aggregates used in pavement surface course construction. The procedures used for aggregate qualification, however, vary significantly from one state agency to another. Some state DOTs rely on simple aggregate classification methods based on aggregate type, whereas others perform detailed laboratory evaluation. The laboratory test procedures that are most commonly used in evaluating aggregate frictional properties are the polish value test, acid insoluble residue test, and petrographic analysis. In addition to laboratory testing, Florida, Kentucky, Pennsylvania, and Texas use alternative procedures to qualify aggregates based on their field skid performance.
Using the International Roughness Index for Profilograph Trace Reduction
Authors: Cumbaa Steven L.
Published: August 2018

Current Louisiana acceptance specifications for 100 percent payment require Profile Indexes (PIs) completed pavement surface to as low as 3.0 in./mi for flexible pavements and 6.0 in./mi for rigid pavements. These acceptance specifications are currently among the most stringent in the United States. Requiring an acceptance PI value of less than 7.0 in./mi when using the California-style profilograph and the 0.2 in. blanking band is unacceptable unless the blanking band is eliminated from the procedure. Louisiana's efforts to replace the blanking-band evaluation procedure with a procedure that inputs the profile trace into the quarter-car-based International Roughness Index (IRI) model are presented. The key step in this process is the scanning and digitization of the profilo-gram before determining the IRI based on the filtered profile trace. A much better correlation exists between the rideability of the finished surface and the profilograph IRI than that of the profilograph PI. New profilograph IRI specifications are recommended to replace the existing PI specifications.
Performance of Flexible and Rigid Pavements in Ohio
Authors: Mukhtar Hamid , Abdulshafi Osama
Published: August 2018

Deviations in traffic and performance prediction parameters and overall standard deviations applicable to Ohio were determined. Pavement test sites were selected to represent the statewide distribution of pavement designs in Ohio, characterized by such factors as material type, functional classification, and different climatic and soil regions. Core samples were obtained and several laboratory tests were conducted to determine the as-constructed material properties and variability of the design input parameters. Comparison of predicted and observed performances based on approximately 4 years of data indicated that the AASHTO equation does not predict the performance of flexible pavements in Ohio. The predicted and the observed performances for rigid pavement sites were essentially the same, that is, no change in the observed and the predicted pavement serviceability index (PSI); however, these observations were based on short-term performance data. The overall variance estimates for flexible and rigid pavements were not obtained due to lack in the change of performance data for most sections.
Development of Automated Algorithms for Pavement Condition Survey
Authors: Chou Chia-pei J. , Liau Tz-kai
Published: August 2018

Image processing and analysis techniques have been successfully applied to the evaluation of some types of pavement surface distress, including longitudinal, transverse, and alligator cracking. Many efforts have been made to develop automated evaluation for other types of distress patterns, but, due to the complexities of these distress types, the results were not as positive as for those distresses mentioned above. The main objectives are to develop image segmentation and classification methods to isolate distress features, and to develop the back-propagation neural network model to recognize block cracking and potholes, in addition to alligator, longitudinal, and transverse cracking. It was observed that longitudinal, transverse, alligator, and block cracking were accurately recognized, and the analytical system has a success rate of 93 percent for potholes. Preliminary results indicate that the proposed approach is very positive and has great potential for integration into an automated system for pavement distress evaluation.
Estimation of Rideability by Analyzing Longitudinal Road Profile
Authors: Sayers Michael W. , Karamihas Steven M.
Published: August 2018

A method for estimating pavement rideability by computing a statistic called ride number (RN) from measured longitudinal profiles of the pavement is presented. The computational algorithm was developed with two objectives in mind: (a) relevance, as established by correlation between RN and mean panel ratings obtained for profiled pavements, and (b) portability, as determined by the ability of different profiling systems to obtain comparable RN values for profiles taken on the same pavement. Experimental data show that the new algorithm is comparable to previously developed RN algorithms in terms of its correlation with panel ratings. The new algorithm is much more portable; comparable RN values can be obtained from different profilers and the quasi-static Dipstick device. However, measures from ultrasonic profilers are not as accurate, and in some cases these devices are not acceptable for measuring RN. Although the fundamental relationships between profile characteristics and the human perception of rideability are still not understood, the algorithm is recommended as the best way to apply the results of past research investigating rideability.