Life-Cycle Cost-Based Pavement Preservation Treatment Design

Classic engineering economic theory was developed to furnish the analyst with a tool to compare alternatives on the basis of life-cycle cost (LCC). However, tools used to apply theory to transportation focus on new construction projects with relatively long service lives. These tools do not accurately model the economic aspects of short-lived alternatives such as those that pavement managers must evaluate when seeking the most cost-effective pavement preservation treatment. The field of pavement preservation seeks to keep good roads good, and hence pavement preservation treatments are applied to extend the functional service life of the underlying pavement. No significant research has been done to quantify the actual service lives of the pavement preservation treatments themselves nor has a model been furnished to analyze their LCCs. The paper addresses those two gaps in the pavement economics body of knowledge by proposing a methodology for using field test data to quantify the service lives of pavement preservation treatments for both asphalt and concrete pavements. In addition, the paper concludes that an LCC model based on equivalent uniform annual cost, rather than net present value, specifically addresses the relatively short-term nature of pavement preservation treatments and allows the engineer to better relate treatment LCC output to annual maintenance budgets

Evaluation of rutting potential of hot mix asphalt using the asphalt pavement analyzer

A comprehensive study involving rut potential of Hot Mix Asphalt (HMA) was conducted. Both cylindrical and beam specimens of HMA were prepared using a Superpave Gyratory Compactor (SGC) and an Asphalt Vibratory Compactor (A VC), respectively. Mixture rutting performance was determined in the Asphalt Pavement Analyzer (AP A). Initially, rut tests were conducted on three laboratory-prepared HMA for 8000 cycles of loading with I 00 psi hose pressure, 100 lb wheel load, and 50 seating cycles. The rut values (8,000 cycles) varied between 2.0 mm and 6.4 mm. Rut depths were found to be sensitive to temperature when compared that to asphalt content. Subsequently, this study evaluated rut potential of ten plant-produced mixes. Three of these mixes were of type A and six type B insoluble and one Type C. Only one mix showed a rut depth of more than 4 mm. The A VC beam specimens showed higher rut depth compared to cylindrical specimens. The AP A rut test data were analyzed to identify the important contributing factors. Type A mixes were sensitive to percent asphalt content, where as Type B insoluble mixes were sensitive to material passing number 200 sieve. This research investigated the relationship between rheological and mechanical properties for various Oklahoma unmodified and modified binders based on the asphalt mixture's rutting performance. The tests result showed that binder's Performance Grade (PG) affects mixture performance significantly. In general, modified binder showed better performance compared to the unmodified binders. Modified binders of same PG grade did not show the same performance when test parameters were held constant. Binder's viscosity and rut factor (G'/sin8) did not show significant effects on rutting performance of both modified and unmodified binders. Linear and nonlinear regression analyses were performed to investigate the contribution of binder properties to rutting. The nonlinear regression prediction of rutting was better than the linear prediction. This study identified the most significant factors from a number of factors, which affect rut potential of HMA. Seven factors: binders PG, specimen type, test temperature, moisture, wheel load, asphalt content, and hose pressure,. each at two defined levels were incorporated in a Superpave mix. Rut tests were designed to be the elements of an experimental matrix. The matrix test results were analyzed statistically. The analysis results showed that binders PG, specimen type, test temperature, and moisture, affected a mixture's rutting performance significantly. This study developed and described a statistical procedure to design and analyze an experimental matrix of test results. This research investigated the repeatability and reproducibility of laboratory test data. An inter-laboratory study was performed on rut tests using the AP A between the 'asphalt design laboratory' at the Oklahoma Department of Transportation (ODOT) and the 'asphalt laboratory' at the University of Oklahoma (OU). The tests result showed no significant variability in the collected data from two laboratories. This study developed a rut database for future model development. The AP A rut results ofHMA materials, which were used in a road section (funded by ODOT) of the National Center for Asphalt Technology (NCAT) Test Track at Alabama, were also included in the rut database.Final Report (September 1999-September 2001)N

Use of asphalt millings in subbase applications

Asphalt Concrete (AC) pavements, after a certain period of their service life, exhibit various types of deterioration and damage. To remedy these problems and to increase road safety, they are often overlaid with a new layer of asphalt concrete. Sometimes the old asphalt pavement is milled, and the millings, after being treated with certain chemicals, are used as an overlay. However, the asphalt millings are not entirely utilized in producing recycled asphalt pavements (RAP). Due to environmental as well as economical considerations it is necessary to find alternate uses for these millings. The overall objective of this study is to find how asphalt millings are currently used in Oklahoma, the volume of millings produced in the State, and whether the millings could be used in subbase construction. A comprehensive literature search was carried out to obtain articles and reports relevant to asphalt millings. The eight Divisions of ODOT were visited and pertinent people from each Division were interviewed. To enhance the information collection process, a questionnaire was prepared in collaboration with the Research, Development and Technology Transfer unit at ODOT for the Divisional people to fill out. The interviews mainly focused on the current milling operations, recycling of millings, methods followed, current use of millings, and potential future use. Photographs of milling operations and milling applications were taken during certain site visits and are included in this report. Also, milling samples were collected during some of these site visits. The literature survey indicates that processed millings have been used extensively in a variety of applications like shoulder, mailbox turnouts, parking lots, level-up operations, and base/subbase applications in the United States. The divisional interviews revealed that the eight Divisions of ODOT also carry out extensive recycling of asphalt millings. However, due to lack of definite guidelines/specifications for the use of millings in various applications, there have been certain project failures. Aggregate gradation, age of asphalt, milling process, speed of milling operations, age of stockpile and depth of cut primarily affect the quality of millings. Interviews revealed that due to a lack of specific guidelines in subbase application, which are considered critical, the Divisions of ODOT are hesitant in using millings as subbase. From the study it is concluded that a testing methodology must be introduced for determining the quality of millings in terms of their physical and mechanical properties, relative to their intended use.August 1997 - April 1998N

Field evaluation of drainable bases in Oklahoma (FHWA-OK-96-04) 2181

The Oklahoma Department of Transportation (ODOT) Research and Development Division (R&D) installed field data acquisition systems in 1992 on five test pavement sections with a view to evaluate the performance of the drainable base and edge drain systems in Oklahoma. Rainfall, outflow and other data have been collected continuously since that time. The University of Oklahoma (OU), in association with ODOT, analyzed the field data, developed appropriate computer programs (written in SAS 6.08 language) to analyze the data, developed a simple, quick and efficient field test scheme to evaluate the drainage efficiency of the existing pavement sections, and conducted a number of field tests for this purpose. This report presents the results of these studies. The useful data, containing rainfall values and the corresponding outflow values reflecting the drainage characteristics of the pavement drainage system. were identified and grouped into a number of"events." The events were studied to establish any relationship between outflow and rainfall magnitudes, flow rates, time required to initiate flow in different types of pavements, and time required for drainage. This information was combined to determine the drainage efficiency of the corresponding drainable base and edge drain system . Finally, the time for 50% drainage was computed and compared with the AASHTO guidelines to determ ine the drainage quality of the pavements under investigation. This report presents the steps involved in grouping, analyzing and interpreting the field data, and explains the findings with appropriate textual and graphical illustrations. A field test procedure was developed to facilitate a quick examination of the quality of a pavement drainage system . The procedure for this field test, results of the field tests performed, and a comparison with regular rainfall and outflow data are also presented in this report.Final Report October 1991-September 1995N

Cooling properties of asphalt surfaces (FHWA-OK-94-05) 2112

Cooling properties of hot mix asphalt (HMA) are important to transportation agencies and contractors in a surfacing or resurfacing operation. The cooling rate of an HMA overlay dictates how soon a roadway can be opened to traffic without having any potentially serious consequences on the pavement performance. The ease or difficulty of compacting HMA paving mixt?res by rolling is influenced by the viscosity-temperature characteristics of the asphalt cement and the temperature of the mix during compaction. Thus, knowing the cooling rate of HMA provides the contractor information such as the extent of time within which breakdown rolling must be completed to ensure quality of the pavement and also when a roadway can be opened to traffic following a surfacing/resurfacing job without any detrimental consequences. A telephone interview was conducted with selected DOTs. From the interviews, it became evident that although several DOTs do not specify a certain temperature range, they do suggest, based on their experiences, that it is preferable to open a roadway to traffic when the HMA temperature is below l40"F. This temperature is close to the 150"F reported in the Synthesis of Highway Practice by the National Cooperative Highway Research Program (NCHRP). HMA thickness and wind velocity have been rated by the DOTs as the most significant factors that influence the cooling rate of HMA. A finite difference computer code provided in the reference as well as a general purpose finite element program ABAQUS were used to compute the time needed by a HMA layer to cool to 150"'F. In this work, the time to cool to various given average mat temperatures was computed for various laydown (200-300ÁF) and base temperatures (50-120'F). Some field data was collected from a site on 1~35 near its intersection with State Highway 51. The field data compares favorably with that obtained from the numerical model predictions for similar conditions. Therefore, the results reported here can be used, with proper engineering judgement, to determine the time required to open the road to traffic.N

Assessment of resilient modulus testing methods and their application to design of pavements (FHWA-OK-91-08)

Resilient modulus (RM) is an important property of subgrade soils that accounts for repetitive loads due to vehicular traffic. Since AASHTO recommended its use in pavement design in 1986, various transportation agencies have devised procedures for testing and evaluation Of RM. A comprehensive literature search was conducted in this study with two objectives in mind: (i) to obtain information on current practices pertaining to RM testing of subgrade soils; and (ii) to compile information pertaining to the collective experience of various agencies in correlating RM with other engineering soil properties. Practices adopted by different transportation agencies in testing RM are not identical; some follow AASHTO guidelines, while others differ. The differences are centered around deviator stress, rate of loading, confining stress, moisture-density relationship, specimen preparation and stress sequence. The well known relationship between RM and CBR, proposed by AASHTO, does not correlate well for many soils. Efforts have been made by various researchers to correlate RM with other factors including clay, silt and organic carbon contents, plasticity index, liquid limit, group index, compressive strength, initial elastic modulus and confining pressure. Very limited efforts have been directed toward understanding the RM characteristics of bonded materials and aggregate bases.N

Quarterly Technical Progress Report #15302R07

During the seven quarter of the project the research team analyzed some of the acoustic velocity data and rock deformation data. The goal is to create a series of ''deformation-velocity maps'' which can outline the types of rock deformational mechanisms which can occur at high pressures and then associate those with specific compressional or shear wave velocity signatures. During this quarter, we began to analyze both the acoustical and deformational properties of the various rock types. Some of the preliminary velocity data from the Danian chalk will be presented in this report. This rock type was selected for the initial efforts as it will be used in the tomographic imaging study outlined in Task 10. This is one of the more important rock types in the study as the Danian chalk is thought to represent an excellent analog to the Ekofisk chalk that has caused so many problems in the North Sea. Some of the preliminary acoustic velocity data obtained during this phase of the project indicates that during pore collapse and compaction of this chalk, the acoustic velocities can change by as much as 200 m/s. Theoretically, this significant velocity change should be detectable during repeated successive 3-D seismic images. In addition, research continues with an analysis of the unconsolidated sand samples at high confining pressures obtained in Task 9. The analysis of the results indicate that sands with 10% volume of fines can undergo liquefaction at lower stress conditions than sand samples which do not have fines added. This liquefaction and/or sand flow is similar to ''shallow water'' flows observed during drilling in the offshore Gulf of Mexico

Field Performance Monitoring and Modeling of Instrumented Pavement on I-35 in McClain County

Phase 1 of this project was conducted to better understand the cause of pavement failure under actual traffic loading and environmental conditions. A 1,000-ft. long experimental pavement section was constructed on I-35 in McClain County and was instrumented for field data collection. The test section was designed to fail in a relatively short period of time under heavy interstate traffic. After approximately four years (from 2008 to 2012) of exposure to continuous interstate traffic and environment, the test section experienced significant rutting but no fatigue cracking. Therefore, the funding agency decided to monitor the test section for two additional years (from 2012 to 2014) as part of Phase 2 of the project. Additionally, a need for predicting distresses (i.e., rut, based on the site-specific data) using the Mechanistic Empirical Pavement Design Guide (MEPDG) software was expressed. In Phase 2 of this project, the quarterly field testing (FWD, rut measurements, roughness measurements, and crack mapping) was performed on a quarterly basis. Also, the weekly downloading of traffic data and data processing were performed to allow updating of the rut prediction models developed in Phase 1 of this study. Site-specific (Level 1) input parameters for traffic, climate and materials were developed in this study. Furthermore, the rut prediction models in the MEPDG software were calibrated using the developed input parameters and measured rut depths from the test section. Laboratory tests (Hamburg rut, four point beam fatigue, volumetric properties, etc.) were performed on the extracted samples from the test section. Moreover, the contribution of different pavement layers to total rutting was assessed by a forensic investigation involving cutting full-depth trenches at three selected locations of the test section.Final report, October 2012-December 2014N

uarterly Technical Progress Report #15302R05

Three major goals were accomplished during this phase. First, a study was completed of the effects of stress-induced changes in anisotropic elastic moduli in sandstone. Second, a new method for measuring the anisotropic poroelastic moduli from acoustic data was developed. Third, a series of triaxial experiments were conducted on unconsolidated sands to identify pressure/stress conditions where liquefaction occurs under high confining pressures. Stress-induced changes in anisotropic Young's moduli and shear moduli were observed during deformational pathway experiments. A new method was made for the acquisition of compressional and shear wave velocities along a series of 3-dimensional raypaths through a core sample as it is subjected to deformation. Three different deformational pathway experiments were conducted. During the hydrostatic deformation experiment, little or no anisotropy was observed in either the Young's moduli or shear moduli. Significant deformational anisotropies were observed in both moduli during the uniaxial strain test and the triaxial compression experiment but each had a different nature. During the triaxial experiment the axial and lateral Young's moduli and shear moduli continued to diverge as load was applied. During the uniaxial strain experiment the anisotropy was ''locked in'' early in the loading phase but then remained steady as both the confining pressure and axial stress were applied. A new method for measuring anisotropic Biot's effective stress parameters has also been developed. The method involves measuring the compressional and shear wave velocities in the aforementioned acoustic velocity experiments while varying stress paths. For a stress-induced transversely isotropic medium the acoustic velocity data are utilized to calculate the five independent elastic stiffness components. Once the elastic stiffness components are determined these can be used to calculate the anisotropic Biot's effective stress parameters, {alpha}{sub v} and {alpha}{sub h}, using the equations of Abousleiman et al. (1996). A series of experiments have been conducted, on an initially inherently isotropic Berea sandstone rock sample, to dynamically determine these anisotropic Biot's parameters during deformational pathway experiments. Data acquired during hydrostatic, triaxial, and uniaxial strain pathway experiments indicates that Biot's effective stress parameter changes significantly if the applied stresses are not hydrostatic. Variations, as large as 20% between the axial (vertical) and lateral (horizontal) Biot's effective stress parameters, were observed in some experiments. A series of triaxial compression experiments have been conducted on unconsolidated sand (Oil Creek sand) to determine the pressure/stress conditions which would be favorable for liquefaction. Liquefaction of geopressured sands is thought to be one of the major causative mechanisms of damaging shallow water flows. The experiments were developed to determine if: (1) liquefaction could be made to occur in this particular sand at high confining pressures, and (2) the state of liquefication had the same nature at high pressure conditions typical of shallow water flows as it does in low confining pressure soil mechanics tests. A series of undrained triaxial experiments were successfully used to document that the Oil Creek sand could undergo liquefaction. The nature (i.e., the shape of the deformational pathway in mean pressure/shear stress space) was very similar to those observed in soil mechanics experiments. The undrained triaxial experiments also indicated that this sand would strain soften at relatively high confining pressures--a necessary precursor to liquefaction. These experiments serve as a starting point for a series of acoustic experiments to determine the signature of compressional and shear wave properties as the sand packs approach the state of liquefaction (and shallow water flows)