bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital Imaging Techniques for Assessment of Homogeneity of Granular Materials
Authors: Al-Shibli Khalid , Macari Emir José , Sture Stein
Published: January 2019

This study focuses on the use of digital image techniques to evaluate and develop quantitative measures of fabric for fine-grained granular materials to assess degrees of homogeneity and isotropy. The description of a procedure performed to prepare homogeneous cylindrical sand specimens is presented. Two techniques were performed to investigate the homogeneity. The specimens were preserved with an ultralow viscosity embedding epoxy resin, and they were allowed to cure prior to dissection for subsequent detailed analysis of the internal fabric. Digital imaging techniques were used to process and analyze various sections of the specimens. The analysis consisted of studying two specific fabric characteristics of the soil: particle orientation and local void ratio. Frequency distribution charts were plotted to assess the degrees of homogeneity and isotropy. Other invasive techniques were also used in some cases to assess the repeatability of the specimen preparation technique. Results indicate that the specimens were prepared with a high degree of homogeneity. Some degree of spatial variation was observed in the local void ratio evaluation.
Digital-Image-Based Computer Modeling and Visualization of Cement-Based Materials
Authors: Bentz Dale P. , Garboczi Edward J.
Published: January 2019

Over the past several years, digital-image-based computer models and subsequent visualization of microstructure have proven valuable in studying processing-microstructure-property relationships in cement-based materials. This paper reviews the computer modeling techniques used to simulate the microstructure of hydrating cement paste at the micrometer level and the microstructure of concrete and mortar at the millimeter level. In the former case, digital-image-based models using cellular automata offer many advantages in simulating the reactions occurring during the hydration of cement paste. In the latter case, a continuum hard core-soft shell percolation model appears to be most efficient for modeling the aggregates in a mortar or concrete, each surrounded by an interfacial transition zone (ITZ). Here, digitization is employed to compute the volume fractions occupied by aggregate, bulk cement paste, and ITZ cement paste. The influence of microstructure on the diffusivity of these materials is addressed within the overall framework of this multiscale modeling approach.
New Approach to Interpretation of Noninvasive Surface Wave Measurements for Soil Profiling
Authors: Poran Chaim J. , Rodriguez-Ordoñez Jorge A. , Satoh Takenori , Borden Roy
Published: January 2019

Noninvasive shear wave velocity (SWV) profiling of soil deposits has long been recognized as a cost-effective approach to obtain SWV data essential for seismic response analysis including site amplification and liquefaction. The controlled-source measurement of surface wave dispersion (CXW) is a relatively new noninvasive method that is used for site characterization in the United States, Japan, and other countries. The CXW method uses harmonic-controlled sources to produce steady state Rayleigh waves in order to measure the dispersion characteristics of soil and rock. Several interpretation techniques may be used to obtain SWV structure from Rayleigh wave dispersion data (in a process that is referred to as the Vf-VS method). CXW measurement data from more than 200 soil and rock sites were analyzed. These results were used to formulate a new approach for the Vf-VS interpretation method based on the new concept of reference profiles that describes the average dispersion curve and SWV structure. The reference profile is based on SWV dependency on confining pressure (depth) in soils. Simple equations were developed for direct inversion of the reference profile. The new procedure is completed by considering the effects of single layers with properties that are different from the reference profile. This new interpretation procedure is rapid and computationally efficient, and its results are more representative of actual soil structure than results obtained from other noninvasive methods. This study indicates inversion that is based on surface waves dispersion can provide a good estimate of average SWV variation.
Methodology for Creating Defensible Three-Dimensional Visualizations
Authors: Burnetti James , Massimini Patricia
Published: January 2019

Commercial-off-the-shelf three-dimensional (3-D) modeling and visualization tools make it relatively easy to produce 3-D renderings of data. It is much more difficult to ensure that 3-D renderings honor the original data points, that they take into account the heterogeneity of the medium in which the data were collected, and that they convey the uncertainty inherent in interpolating between and extrapolating from the original data points. This study offers practical advice by describing three steps necessary to produce defensible 3-D visualizations: defining the problem to be solved, selecting the appropriate software tools, and applying the tools in a systematic manner.
Three-Dimensional Characterization of Contaminant Plumes
Authors: Jones Norman L. , Davis R. Jeffrey
Published: January 2019

Before remediation of a site with contaminated soil or groundwater, the contaminant plume must first be characterized. This involves sampling the contaminant concentration at a set of locations in and around the contaminated area. To present the measured concentrations in a meaningful form, the concentrations are typically interpolated to the nodes of a three-dimensional grid, and the plume is visualized by constructing iso-surfaces from the gridded data. The critical step in this process is the interpolation stage. Improper application of an interpolation scheme can result in grossly misleading three-dimensional plume maps. There are a number of problems that often occur when interpolating contaminant plume data, including generation of negative concentrations, oscillation of interpolated values, improper estimation of maximum concentrations, and skewing of the results due to data clustering. These and other difficulties associated with plume characterization are discussed, along with a simple set of guidelines for detecting and overcoming these problems.
Three-Dimensional Stratigraphic Characterization for Geotechnical Exploration
Authors: Kinnicutt Patrick , Einstein Herbert , Noack Carlos
Published: January 2019

In current geotechnical engineering practice, soil or rock stratigraphy is usually obtained from borehole data. Interpolation between boreholes is performed by projecting borehole data on a cross-sectional plane, either by hand drawings or by using CAD or GIS software, then manually interpolating between the boreholes. This methodology for obtaining the geology of a site does not truly represent the three-dimensional nature of the data, and it does not capture the uncertainties in the interpolation. This study describes NOMAD, a three-dimensional ground profiler developed for education and research that runs on the UNIX platform. The focus is on features available in NOMAD for visualizing uncertainties, creating ground profiles from site data, and updating the model with new subjective and objective data. One such feature, which will be described in detail, is the ability to modify a cross section of the site and have this modification automatically propagated to the site model and other cross sections, allowing users to visualize how changes in one cross section affect other cross sections. Also discussed is a model incorporated in NOMAD for creating ground profiles from borehole data. This model makes use of Indicator CoKriging and Bayesian Updating for modeling both the subjective and objective information about a site, taking into account the true three-dimensional nature of the data.
Three-Dimensional Characterization with Limited Data: An Example from Playa-Lake Basin, Southeast Arizona
Authors: Rucker Michael L. , Keaton Jeffrey R.
Published: January 2019

Limited data of variable quality provided the basis for characterizing a proposed waste disposal site with an earth fissure in support of an aquifer protection permit. The data included driller's logs of water wells, down-hole and surface geophysical surveys, and repeated topographic survey profiles. Three-dimensional characterization of the site, located near the margin of a playa lake, based on the limited data was accomplished with methods appropriate for the amount and quality of subsurface information. These included application of Quaternary geology and sedimentology and percolation theory. A predictive model of groundwater decline and aquifer mechanics was based on an engineering geologic model of the playa-lake basin. Two two-dimensional finite element models constructed perpendicular to the earth fissure along the sides of the site were calibrated and used to predict growth of the fissure as a function of future groundwater decline.
Application of Neural Network Technology to Highway Maintenance Management
Authors: Randolph Dennis A.
Published: January 2019

Modern maintenance management systems provide detailed information for managers. However, this information and the detailed descriptions of work and production do not reflect the influence that people have on each other. Team composition is critical to the attainment of productivity goals, but managers must depend upon intuitive skills to make team assignments. The objective of this work was to develop a system that managers could use to assist them in making team assignments. Neural network techniques were used to develop predictive models for team productivity. Historic data on team composition and productivity were used to train neural networks, and then the trained networks used to estimate production. Team productivity tables can be developed using the trained neural networks, and managers can use these tables to guide the assignment of workers to crews. Neural networks can be used to replace the intuitive skills that managers often lack. Because neural networks use historic data to train, the predictive models produce intuitively comfortable results. Moreover, because neural network programs take advantage of modern computer power and use brute force to generate results, the limits of other statistical techniques are avoided.
Final Results of Road Traffic in Winter Project: Socioeconomic Effects of Winter Maintenance and Studded Tires
Authors: Leppänen Anne
Published: January 2019

Finland is a sparsely populated country where the road network provides access even to the most remote areas of the country. All public roads maintained by the Finnish National Road Administration (FinnRA) are kept in good condition day and night throughout the year. Sodium chloride is the main substance used for chemical deicing; sanding is used only on roads with little traffic. In Finland the use of studded tires began in the early 1960s. Finland is the leading country in the use of studded tires: in winter, 95 percent of passenger cars have studded tires. The simultaneous use of salt and studded tires causes problems. To solve these problems, FinnRA launched a large research program called “Road Traffic in Winter” to evaluate alternative winter maintenance scenarios for improving social benefits. The project had nine future scenarios, representing permutations of three alternatives each for studded tire use and salting. None of the examined scenarios was more favorable than the baseline situation (current usage). When searching for the socioeconomic optimum, the accident costs become the most important factor, and the accident costs strongly support retention of the baseline situation: the use of salt and studded tires should be continued at current levels despite their drawbacks.
Estimation of Effects of Reduced Salting and Decreased Use of Studded Tires on Road Accidents in Winter
Authors: Kallberg Veli-Pekka , Kanner Heikki , Mäkinen Tapani , Roine Matti
Published: January 2019

The effect on road accidents of reduced salting was estimated on the basis of accident risks on bare (free of ice and snow) and slippery roads and the changes that decreased salting causes in the proportions of vehicle kilometers driven on different road surface conditions. That the risk in slippery conditions may depend on the frequency of such conditions was also taken into account. The effects of studded tires on accidents were estimated on the basis of data from mail surveys and case study accidents. The effects of the use of studded tires on driving behavior were studied in real traffic so that drivers were unaware that their driving was being monitored. The final conclusions were drawn by combining results from a number of studies. Even though the results from a single study were often more indicative than conclusive, the studies together resulted in reasonably clear implications of the direction and magnitude of the effects. It was concluded that decreasing the use of salt or studded tires from the present level (approximately 95 percent of cars use studded tires and approximately 10 T of salt is used per road kilometer each winter) would increase injury accidents in winter. Accidents would increase 26 to 30 percent if salting were decreased by 80 percent and only 20 percent if cars were equipped with studded tires.
Deicing Chemicals as Source of Constituents of Highway Runoff
Authors: Granato Gregory E.
Published: January 2019

The dissolved major and trace constituents of deicing chemicals as a source of constituents in highway runoff must be quantified for interpretive studies of highway runoff and its effects on surface water and groundwater. Dissolved constituents of the deicing chemicals—sodium chloride, calcium chloride, and premix (a mixture of sodium and calcium chloride)—were determined by analysis of salt solutions created in the laboratory and are presented as mass ratios to chloride. Deicing chemical samples studied are about 98 and 97 percent pure sodium chloride and calcium chloride, respectively; however, each has a distinct major and trace ion constituent signature. The greatest impurity in sodium chloride road salt samples was sulfate, followed by calcium, potassium, bromide, vanadium, magnesium, fluoride, and other constituents with a ratio to chloride of less than 0.0001 by mass. The greatest impurity in the calcium chloride road salt samples was sodium, followed by potassium, sulfate, bromide, silica, fluoride, strontium, magnesium, and other constituents with a ratio to chloride of less than 0.0001 by mass. Major constituents of deicing chemicals in highway runoff may account for a substantial source of annual chemical loads. Comparison of estimated annual loads and first flush concentrations of deicing chemical constituents in highway runoff with those reported in the literature indicate that although deicing chemicals are not a primary source of trace constituents, they are not a trivial source, either. Therefore, deicing chemicals should be considered as a source of many major and trace constituents in highway and urban runoff.
Forward-Lighting Configurations for Snowplows
Authors: Bajorski Peter , Dhar Suman , Sandhu Deniz
Published: January 2019

Snow and ice control is a critical maintenance operation for New York State: each winter, up to 68 500 km (42,500 lane-mi) of highways must be cleared. Visibility during plowing operations is often poor and is further diminished by backscatter glare from the snowplow's own headlights as well as glare from lights of oncoming traffic. Results are summarized of a pilot study to identify forward (front-end) lighting configurations that might improve visibility for plow operators during such operations. During the 1993–1994 winter, eight lighting configurations were tested, two of which were identified as potential improvements over the existing pattern. Simple procedures and forms were developed for collecting reliable data. Methodological issues in performing such experiments are discussed. A statistical methodology is presented that is suitable for comparison of lighting configurations but is also applicable in other, broader contexts in which a number of items are compared by several evaluators.
Applications of Classification and Regression Tree Methods in Roadway Safety Studies
Authors: Stewart J. Richard
Published: January 2019

In recent years a number of nonparametric regression-type statistical procedures have been developed. Classification and regression trees (CART) is one such method that can be used as a classifier for a discrete-valued response variable or as a regression model for a continuous response variable. Advantages of CART over many other methods are its ability to include a relatively large number of independent variables and to identify complex interactions among these variables. A brief description of the CART procedure is given, and its application as a classifier and as a regression model to highway safety analyses is illustrated.
Reliability of Statistical Road Accident Injury Severity Models
Authors: Saccomanno F. F. , Nassar S. A. , Shortreed J. H.
Published: January 2019

The reliability of different statistical road accident severity models is assessed using a number of criteria, such as goodness of fit, robustness of risk factor coefficients, and intuitive acceptability and consistency of output. The results of this analysis suggest that model reliability is not sensitive to the number of injury classes specified in the model or to the level of model aggregation. All models consistently identified the same risk factors as explaining most of the variation in injury experience in the data. These factors are (a) dynamics of the accident, (b) seating position of occupant, (c) use of seat belts, and (d) age of occupant involved. There is no indication that a significant transfer of error takes place from one severity level to another in a sequential model structure. The results suggest that reliability of statistical road accident severity models depends primarily on the accuracy of information provided in the accident data.
Statistical Test of Difference between Expected Accident Frequencies
Authors: Hauer Ezra
Published: January 2019

A primer on the testing of some common statistical hypotheses in road safety is presented. The basic notions of statistical hypothesis testing are reviewed and applied to the specific circumstance when one wishes to test a statistical hypothesis about a change in the expected accident frequency beyond what is the result of a change in traffic and similar influences. The hope is that this exposition will illumine the meaning and intricacy of such tests, inform the decision about when such tests are called for, help users choose the right significance or power, and, because software is now available, improve practice in this matter. A companion paper on the detection of deterioration in safety makes use of the foundation provided.
Detection of Safety Deterioration in a Series of Accident Counts
Authors: Hauer Ezra
Published: January 2019

The task is to develop a workable procedure with the object of detecting sites where the mean accident frequency has increased over time to more than what can be attributed to changes in traffic or to general trends. Two kinds of increase are to be detected: a steady but gradual deterioration and a sudden increase in mean accident frequency at an unknown time. The procedure is to be applied to many sites, with the detected sites subsequently examined in detail. Both the gradual and the sudden increase in accident frequency are to be detected by a statistical test of significance for the difference between the means of two Poisson random variables. The software for doing such tests of significance has been developed and is available. An identification procedure is suggested to take account of (a) the number of sites that can be practically subjected to detailed examination and (b) the marginal yield of correctly identified sites.
Methodology for Identifying Highway Safety Problem Areas
Authors: Tarko Andrzej P. , Sinha Kumares C. , Farooq Omer
Published: January 2019

Safety programs can provide benefits only if they apply effective countermeasures to the locations and areas that really need safety treatment. A methodology of areawide safety analyses is presented to detect these areas (states, counties, townships, etc.) that should be considered for safety treatment. The method is implemented for Indiana at the county level. The method uses regression models to estimate the normal number of crashes in individual counties. The above-norm numbers of crashes calculated for several past years are used to predict the above-norm value for the future year when the safety treatment is to be applied. The counties are priority ranked using the combined criterion including both the above-norm number of crashes and the confidence level. Above-norm crashes represent the magnitude of the problem—specifically, how many crashes could be avoided if the safety level was normal. A confidence level represents the chance that the observed excessive number of crashes is not just a random effect, but indicates a real safety problem. The example analysis is performed for the alcohol-related crashes to illustrate and test the method. The results are promising and in conformance with the results obtained in the previous study.
Identification of Sites with Promise
Authors: Hauer Ezra
Published: January 2019

Procedures for the identification of black spots, or hazardous locations, are attempts to select some sites out of many to improve safety. These are sites with promise. The historical and conceptual development of such procedures is reviewed. On the basis of this review, an attempt is made to create some order in the thinking. Suggestions are made to improve identification. It is noted that the status of the stage that follows identification, the stage of site safety diagnosis and remediation, is underdeveloped.
Twenty-Five Years of Pavement Smoothness Specifications in Georgia
Authors: Collins Ronald , Gulden Wouter , Brown Dan R.
Published: January 2019

The traveling public generally recognizes the smoothness of a pavement as a major indicator of quality. A newly constructed pavement can have excellent materials, mix design, compaction, and so forth, but if the public considers the ride rough, the quality is considered poor. While continually striving to improve the quality of paving materials in mix designs, the Georgia Department of Transportation (GDOT) began an effort in 1968 to attain the ability to accurately measure the smoothness of a pavement so that this indicator of quality could be measured and specified during construction. GDOT has been using response-type smoothness-measurement systems in its construction specifications for acceptance of projects since 1972 and since 1979 for both rejection and acceptance. The evolution of the pavement smoothness-measuring program in Georgia, the program operating procedures, and the current smoothness specifications are described. The long-term benefits of smoothness specification for pavement construction are also discussed, as is GDOT's effort to replace the Mays Meter trailer systems currently used with South Dakota–type, laser-based road profilers.
Evaluation of Surface Treatment Practices in United States
Authors: Ksaibati Khaled , Cole Michael , Farrar Michael
Published: January 2019

The University of Wyoming and the Wyoming Department of Transportation are performing a comprehensive research study on the performance of surface treatments. A survey consisting of 16 questions about the maintenance, construction, agency policies, evaluation procedures, and testing equipment of surface treatments was distributed to all 50 state departments of transportation; 47 of these agencies responded. The responses were summarized and analyzed for trends.
Skidding Characteristics of Pavement Surfaces Incorporating Steel Slag Aggregates
Authors: Stock A. F. , Ibberson Colin M. , Taylor I. F.
Published: January 2019

Steel slag, a by-product of the steel industry, has been used in road construction in South Yorkshire and its environs for the past 60 years. Local highway engineers have anecdotal evidence of good long-term antiskid performance from road surfacings that incorporate steel slag aggregate, and these materials have remained popular with users. In view of the move toward performance measurements for paving materials, a systematic study of the performance of paving materials incorporating slag has been set up as a combined industry-university project with the assistance of the Teaching Company Directorate. The evaluation of the skid resistance characteristics of steel slag aggregates and the skidding characteristics of pavement surfaces incorporating steel slag aggregate are reported. The research program developed a modified specimen preparation procedure that significantly reduced the scatter in polished stone value (PSV) results. The field data showed that all steel slag surfaces provided good long-term skid resistance and that the 14-mm chippings exceed the performance expectations of rock chippings with similar PSVs.
Analysis of Thermal Fatigue Distress of Asphalt Concrete Pavements
Authors: Jackson N. Mike , Vinson Ted S.
Published: January 2019

Thermal cracking of asphalt concrete pavements is responsible for millions of dollars in annual maintenance and rehabilitation costs in the United States and Canada. Thermal cracking typically is associated with low temperatures in northern climates and at high elevations. Another form of thermal cracking, known as thermal fatigue cracking, has been proposed by several researchers as a potential mode of distress in regions with relatively moderate climates. The objectives were to evaluate the possibility of the occurrence of the thermal fatigue cracking mode of distress and to identify a suitable laboratory test procedure to facilitate a mechanistic analysis of this mode of distress. The most promising test procedures evaluated included the direct tensile creep test and the thermal stress restrained specimen test. The results suggest that thermal fatigue distress in asphalt concrete mixtures is not a viable mode of distress in the absence of environmental aging. From the data presented and results documented by others, it is evident that distress often attributed to thermal fatigue cracking is more likely the result of low-temperature cracking of environmentally aged mixtures or subgrade-related distress. It is concluded that fatigue distress due to thermal loading of semirestrained pavements does not occur.
Characterizing Properties of Asphalt Cement at Cold Temperatures
Authors: Stroup-Gardiner Mary , Newcomb Dave , DeSombre Rachel
Published: January 2019

A range of binder test results for Strategic Highway Research Program (SHRP) Materials Reference Library asphalts were used to identify critical low-temperature behavior. Test results were obtained from in-house testing, Minnesota Department of Transportation (Mn/DOT) testing, and previously reported SHRP research reports. Tests used were the Fraass brittle point, bending beam, a dynamic shear rheometer (DSR), and differential scanning calorimetry (DSC) glass transition temperature. A good correlation between the Fraass brittle point and the bending beam rheometer limiting stiffness indicated that the Fraass brittle point represented the behavior of a binder at a stiffness of approximately 200 MPa. Because the traditional method of using the DSR to obtain the glass transition temperature, Tg, from the peak of the loss modulus curve did not provide sufficiently specific results, the temperature at which a minimum phase angle was used to define the Tg instead. These results showed a good correlation with the bending beam results and a strong correlation with the Fraass brittle point. The DSC results were not well correlated with either the rheometer results or the Fraass brittle point. This appears to be due to the intricacies related to interpreting DSC data. Binder results were compared with results reported by SHRP researchers for the indirect tensile creep and thermal stress restrained specimen test. Results indicated that cold-temperature mixture properties are predominantly due to binder properties. Results also indicated that the asphalt source was more important than the asphalt grade in defining cold-temperature properties. The two binders used to construct the Minnesota Road Research facility on I-94 in Otsego were classified by Mn/DOT as PG 58-28 and PG 58-22, respectively. The Canadian SHRP researchers’ equation for estimating the minimum design pavement temperature indicated a cold-temperature design temperature of —28°C, but the SHRP 90 percent reliability grading indicated that a PG 58-40 was needed. Evaluation of the pavement performance over two winters—the first of which was extremely cold even by Minnesota standards—showed that the PG 58-28 had no thermal cracks while the PG 58-22 test sections had 12 transverse cracks. This indicates that the Canadian SHRP equation may be considered a high-reliability minimum design temperature.
Minimum Voids in Mineral Aggregate in Hot-Mix Asphalt Based on Gradation and Volumetric Properties
Authors: Hinrichsen John A. , Heggen John
Published: January 2019

The use of voids in mineral aggregate (VMA) criteria for proper mix design of hot-mix asphalt is a time-honored and fairly successful tool. Recent developments in the field of asphalt mix design have encouraged the use of mixtures with a coarse aggregate structure to resist the effect of heavy traffic loads. By using the equations presented, which account for both aggregate gradation and the volumetric properties of the materials, the mix designer is able to judge the proper VMA requirement for each unique blend of materials. By applying the new equations, the most economical mix may be selected without great risk of reduced durability. Supporting data from field application are presented to illustrate the use of the equations.
Structural Analysis of Aggregate Blends Using Strategic Highway Research Program Gyratory Compactor
Authors: Seward Dan L. , Hinrichsen John A. , Ries Jennifer L.
Published: January 2019

The Iowa Department of Transportation (IDOT) received a Strategic Highway Research Program (SHRP) gyratory compactor in December 1994. Since then IDOT has been studying the ability of the compactor to analyze fundamental properties of aggregates such as shape, texture, and gradation by studying the volumetrics of the aggregate blends under a standard load using the SHRP gyratory compactor. This method of analyzing the volumetrics of aggregate blends is similar to SHRP's fine aggregate angularity procedure, which analyzes void levels in noncom-pacted aggregate blends, which in turn can be used to evaluate the texture or shape of aggregates, what SHRP refers to as angularity. Research is showing that by splitting the aggregate blend on the 2.36-mm (#8) sieve and analyzing the volumetrics or angularity of the separated blend, important fundamental properties can be determined. Most important is structure (the degree and location of aggregate interlock). In addition, analysis of the volumes of the coarse and fine portions can predict the voids in the mineral aggregate and the desired asphalt content. By predicting these properties, it can be determined whether the combined aggregate blend, when mixed with asphalt cement, will produce a mix with structural adequacy to carry the designed traffic load.
Development and Evaluation of Dynamic Flexural Beam Fatigue Test System
Authors: Tayebali Akhtarhusein A. , Deacon John A. , Monismith Carl L.
Published: January 2019

Although both mix variables and environmental variables are known to affect the fatigue response of asphalt-aggregate mixes, other factors—including specimen fabrication procedure and test equipment and procedures—are equally important. The development of a dynamic flexural beam fatigue test system is described, and the effects of specimen compaction method and equipment type on the precision of in situ fatigue lives of asphalt-aggregate mixes predicted by using laboratory strain-life relationships are discussed. Results indicate a coefficient of variation of 41 percent in fatigue life for the new fatigue equipment compared with one of 93 percent for an earlier electropneumatic version. The specimen compaction method was also found to influence significantly the precision of the predicted fatigue life. A 33 percent difference in coefficients of variation between the fatigue response of rolling wheel–compacted specimens and kneading-compacted specimens was observed. Consequently, twice as many specimens are required to achieve a given level of precision in in situ predicted fatigue life if kneading compaction is used instead of rolling wheel compaction. Similarly, if a pneumatic system and associated test procedure are used, approximately 12 times as many specimens are required to achieve similar precision in predicted fatigue life compared with the new servohydraulic fatigue test system.
Dynamic Properties of Fiber-Modified Overlay Mixture
Authors: Huang Haiming , White Thomas D.
Published: January 2019

Cores and slabs of fiber-modified asphalt overlay were taken from a series of test sections constructed on two highways in Indiana. Extensive laboratory investigations were conducted to evaluate the fiber-modified asphalt mixtures. Laboratory tests included physical properties, beam fatigue, and complex modulus. Because of a lack of a standard method for fiber extraction, three fiber extraction methods were evaluated. Test results show that more than 95 percent of fiber can be extracted from paving mixtures. Actual fiber contents in test sections were found to be different from target fiber contents by a significant amount. Physical property tests show that the addition of fibers is related to a higher percentage of air voids in the in situ pavement. Results of fatigue tests indicate that fibers increase the fatigue life of overlay mixture. There are inconsistencies in the significance of fiber on both dynamic modulus and phase angle. However, the results do indicate that the addition of fibers will change the viscoelastic properties of mixtures. There is no statistical difference in dynamic modulus and phase angle among the mixtures with different fiber contents.
Comparative Field Evaluation of Shale Oil–Modified Asphalt with Polymer-Modified Asphalts
Authors: Thomas Kenneth P. , Harnsberger P. Michael , Robertson Raymond E. , Lukens Larry A. , Peters Victoria J.
Published: January 2019

Since the discovery, patenting by Western Research Institute, and licensing to The New Paraho Corporation of a concept for the use of an asphalt modifier that can be produced from western shale oil, nine test strips have been constructed in five states in the United States. Performance evaluations were conducted on three shale oil–modified asphalt (SOMAT) test pavements that were laid in Utah and Wyoming. In all cases the performance of the test pavements was compared with pavement sections that were constructed using polymer-modified asphalts. The results of the evaluation of the pavement performance at the three project sites in general show that rutting, fatigue cracking, and thermal cracking properties of the SOMAT (test) pavements are comparable to the AC-20R and PBA-6a (control) pavements. However, with respect to moisture susceptibility and in-service aging, the SOMAT pavements are less prone to moisture damage and are aging at a slower rate than the control pavements. A life cycle cost analysis was conducted on the SOMAT and AC-20R pavements laid south of Moab, Utah, on U.S. Highway 191. The projected terminal service life for the two pavements, assuming that no remedial actions are taken, is 28 years for the SOMAT test strip and 7 years for the AC-20R control section. The cost of these remedial actions was estimated on the basis of the realization that remedial actions would be conducted and assuming a 30-year service life. The total estimated cost for the SOMAT pavement was $171,218/lane-mile, and for the AC-20R pavement it was $315,639/lane-mile.
Effect of Specimen Size on Compaction and Volumetric Properties in Gyratory Compacted Hot-Mix Asphalt Concrete Specimens
Authors: Hall Kevin D. , Dandu Satish K. , Gowda Gary V.
Published: January 2019

Gyratory compaction is the centerpiece of the Strategic Highway Research Program asphalt mixture design procedure Superpave. A number of factors could potentially affect the behavior of asphalt mixes in the gyratory compactor. One of these is specimen size. Four specimen sizes each of one unmodified and two rubber-modified hot-mix asphalt concrete mixes were compacted in the Superpave gyratory compactor to determine the effect of specimen size on compaction and volumetric properties of the mixes. All specimens were compacted using a 150-mm-diameter mold. Specimens of each of the mix types were prepared using three gradations and three binder contents. Densification curves and plotting number of gyrations versus percent of theoretical maximum density were developed for each mix type/gradation/binder content combination. A strong trend in the densification data was observed, in which curves representing specimen sizes of 3500, 5000, and 6500 g were grouped together, apart from the curve representing a 2000-g specimen size. This trend, the grouping of larger specimen data apart from small specimen data, was also observed in volumetric data (optimum asphalt content, voids in mineral aggregate, and voids filled with asphalt). These trends were observed in most of the mix type/ gradation/binder content combinations. The data presented suggest that for specimens of sufficient size, for example, greater than 3500 g, specimen size does not significantly affect the volumetric or compaction properties of hot mix specimens, which supports the ruggedness of the gyratory compaction procedure.
Complex Modulus Testing of Asphaltic Concrete: RILEM Interlaboratory Test Program
Authors: Francken L. , Partl M. ,   Technical Committee on Bitumen and Asphalt Testing
Published: January 2019

An interlaboratory test on bituminous materials was initiated in 1990 to promote and develop mix design methodologies and associated significant measuring methods. The exercise was carried out on materials obtained from a full-scale test site. Repeated loading tests were performed in this program by 15 participating laboratories to determine two basic material properties: the complex modulus and the fatigue law. The main conclusions derived from the analysis of complex modulus measurements and further discussions of the summary report with the participants are summarized. This intensive common effort has allowed several participants to make substantial improvements in their procedures and equipment. Recommendations are expected to induce further progress in the harmonization of different test methods.
Polymer-Modified Asphalt Pavements in Ontario: Performance and Cost-Effectiveness
Authors: Ponniah Joseph , Kennepohl Gerhard
Published: January 2019

Two trial sections were constructed to investigate the rutting resistance and low temperature performance of different polymer-modified asphalt (PMA) mixes at sites representative of highways experiencing rutting as a result of heavy traffic loading in cold climatic regions. The two-way average annual daily traffic for both sites was >35,000 (6,000 vehicles per day). Modified asphalts used in the trial sections include engineered bitumen type 306, premium asphalt, reprocessed polyethylene (Novophalt), Neoprene, scrap tire rubber, Vestoplast-S, Kraton 4460, Styrelf, and polyethylene. Representative test samples of aggregates, asphalt cement, modified asphalts, and hot mixes were taken for routine testing during production. In situ quality control tests were done by taking plate samples while laying the mix and by coring after compaction. Additional laboratory tests were done at temperatures ranging from 0°C to —35°C to evaluate the materials’ low temperature cracking resistance. Field performance of trial sections was monitored yearly by crack mapping and measuring transverse profiles at 30-m spacing on each test section. Levels were taken at 100-mm intervals by using a dipstick. A computer program was written to process the data and calculate the rut depths for each wheelpath. Crack mapping was done to assess the crack growth in each test section. The performance of the sections was compared with respect to average rut depth and crack growth. The following are described: (a) the modified mix design chosen specifically to produce accelerated test results, (b) the experience gained in the construction of trial sections, (c) the results of laboratory testing to evaluate the low temperature performance of the PMAs, (d) the field performance evaluation with respect to rutting and cracking, and (e) the life cycle cost analysis. Average rut depth measurements 5 to 7 years after construction show that PMA pavement sections are performing better than conventional asphalt with respect to rutting. With regard to cracking, polymers with 85 to 100 penetration (pen) base asphalt did not perform better than control sections. However, there is an indication that PMA, which has a soft grade (150 to 200 pen) base asphalt, tends to improve low-temperature performance comparable to the control section. In other words, PMA generally performs better than conventional asphalt, provided it contains a soft grade (150 to 200 pen) base asphalt. Life cycle cost analysis indicates that PMA is cost-effective in extending pavement life by 2 to 3 years if the cost of polymer modification does not exceed the cost of conventional asphalt by 100 percent.
Use of Georgia Loaded Wheel Tester to Evaluate Rutting of Asphalt Samples Prepared by Superpave Gyratory Compactor
Authors: Collins Ronald , Shami Haroon , Lai James S.
Published: January 2019

The Georgia loaded wheel tester (LWT) developed by the Georgia Department of Transportation has been used since 1985 in the laboratory during the design stage to evaluate rutting susceptibility of asphalt concrete mixtures. In the LWT testing, asphaltic concrete is subjected to an elevated temperature in a loaded wheel system under repetitive loading conditions, and the permanent deformation induced under the wheelpath is measured. This approach to assess rutting susceptibility was thought to be much more representative than the current test methods and can provide a fast and more accurate means of assessing rutting susceptibility of asphalt concrete under actual field conditions. The asphaltic beam samples used for the LWT testing are prepared by a rolling compaction machine. The new LWT developed in 1992 is described. To promote the concept of using Georgia LWT as a supplement to the Superpave Level 1 design procedure for evaluating permanent deformation of hot-mix asphalt (HMA), a test method utilizing Superpave gyratory compactor-prepared samples to evaluate the rutting resistance of HMA by the LWT was developed. The gyratory samples placed in a specially designed mold can be tested in the LWT identical to that for performing the LWT testing on the beam samples. A test program was conducted to evaluate the applicability of the testing procedure and to develop correlations between the rut depth of asphalt mixes using the beam samples and the gyratory samples. The test program used three asphalt mixes of different degrees of rutting resistance ranging from high to low rut susceptibility. Both types of samples were tested at 40°C, 50°C, and 60°C temperatures for 8,000 cycles under the standard LWT testing procedure. The rut depth results from the beam samples and the gyratory samples showed good correlations for all three mixes tested. The test results also showed a strong relationship between the rut depth values and the air void content in the mixes.
Integrating Transportation and Environmental Planning: Extending Applicability of Corridor and Subarea Studies and Decisions on Design Concept and Scope
Authors: McLeod Douglas S.
Published: January 2019

FHWA and FTA have proposed a combined process for integrating transportation and environmental planning. A major feature of the process is conducting corridor and subarea studies to reach a decision on design concept and scope in planning before a project enters a preliminary engineering phase. These corridor and subarea studies facilitate decisions by metropolitan planning organizations (MPOs) and refinement of their long-range plans, analyses of alternatives, and analyses of demand reduction and operations required of congestion management systems. As developed to date, the combined process is seen primarily as applying to major investment studies. As part of its congestion management system, Florida (the Department of Transportation, MPOs, and others) addressed corridor and subarea studies, major investment studies, and the proposed combined process. Furthermore, the Florida congestion management system task team found that the combined process may have many beneficial aspects, addressed state and MPO institutional roles in reaching decisions on design concept and scope, and is evaluating the extension of the combined process to arterial investments and interchange justification analyses. By extending the process to these other projects and reaching a decision on design concept and scope in planning, the needs and alternatives analyses required by the National Environmental Policy Act could be obtained earlier, possibly improving and shortening the decision-making process. Overviews of the combined process and Florida actions that may lead to extending the process beyond major investment studies are presented. Florida actions include supporting pilot arterial investment studies to be coordinated by MPOs with funding provided by the state.
Distinguishing Wide and Local Area Business Impacts of Transportation Investments
Authors: Weisbrod Glen
Published: January 2019

Although transportation system investments are made for a variety of reasons (including improvements to capacity, traffic flow, safety, and economic development), they almost always involve social, environmental, or business impact tradeoffs, whereby some class of travelers, businesses, or area residents believe that they are made better-off and some that they are made worse-off by new facilities or new traffic activity patterns. The challenge for transportation planning is to recognize benefits and anticipate adverse local impacts so that the tradeoffs do not undermine the capability to make larger system improvements. Business impacts are the focus here. An analysis process for identifying and distinguishing the potential wide area and small area business impacts of highway improvements is described. A similar format can also be applied to other modes of travel.