Hot-Mix Bituminous Paving Manual

This training package has been developed to address the area of asphalt pavement construction. It includes as an introduction, the identification of some major pavement distresses. It then addresses the major phases of materials, design, production, placement, and compaction, then concludes with a more detailed look at asphalt pavement performances

Multidisciplinary Data Management Support (MDMS) 101 Overview

The objectives of the Multidisciplinary Data Management Support (MDMS) task order is to provide support to Federal Highway Administration (FHWA) Federal and contract project managers to manage their data and to provide access to and use of data from completed and current FHWA-sponsored projects. The purpose of this task order is twofold: To support the Turner-Fairbank Highway Research Center (TFHRC) Office of Safety and Operations Research and Development (HIRSI) project managers in managing their project data during all stages of their projects. To have a centralized data repository to enable easy identification and access to data that illustrates project benefits. MDMS is a continuation of the Data Resources Testbed (DRT), and all projects under DRT will be stored in the MDMS for the duration of this task order

Ruggedness Testing of the Dynamic Shear Rheometer and the Bending Beam Rheometer Test Procedures

Ruggedness testing of the bending beam rheometer (BBR) and the dynamic shear rheometer (DSR) was performed. Four laboratories participated in this effort. Three materials were used for BBR ruggedness testing and four materials were used for DSR ruggedness testing. Measurement of the creep stiffness and m-value at 60 s with the BBR was found to be fairly repeatable. Of the factors studied, the mold used for casting the beams had a significant effect. Different beam thickness by the two molding techniques was found to be a factor that caused this variation. Other unknown factor(s) also seemed to contribute to this effect. The test temperature also had a significant effect and should be controlled to +/-0.1 deg C. Measurement of the complex shear modulus (G*) and the phase angle (delta) with the DSR was very repeatable. The measurement of G* with 8-mm parallel plates had more variation than the measurement of G* with 25-mm parallel plates. The measurement of delta with both 8-mm and 25-mm plates had lesser variation than the G* measurement. Test temperature was the primary factor that affected the test results for both 8-mm and 25-mm parallel plates, requiring +/-0.1 deg C control. For G* measurements with 8-mm parallel plates, it seemed to make a difference whether asphalt was directly applied to the plates or if it was transferred in the form of a pellet. This effect can probably be accounted for by different thermal history imparted to the pellet. Inconclusive, but definite, effects were observed due to overhang in the case of the 8-mm parallel plates

Intermodal Freight Technology Working Group

The Intermodal Freight Technology Working Group (IFTWG) is a public-private partnership focused on the identification and evaluation of technology-based options for improving the efficiency, safety, and security of intermodal freight movement. Working from this common goal, the IFTWG engages in efforts to marry industry and government priorities in a way that leverages collective experience and shared investment

Pavement Testing Facility -- Phase 1 Final Report

The Pavement Testing Facility (PTF) is a permanent, outdoor, full-scale pavement testing laboratory located at the Federal Highway Administration's (FHWA) Turner-Fairbank Highway Research Center in McLean, Virginia. The purpose of this facility is to quantify the performance of test pavements trafficked under accelerated loading. The facility consists of several instrumented test pavements and the Accelerated Loading Facility (ALF) testing machine. Formal operation of the facility began in October 1986. This report summarizes the work performed during the first phase of research, October 1986 to April 1989. The report includes a discussion of the construction and instrumentation of the PTF test pavements. It describes the operation of the ALF testing machine, and the data collection procedures used at the PTF. The report also summarizes the environmental, and pavement response and performance data collected during the first phase of research. Finally, an analysis of the accelerated pavement testing data was conducted to assess the strengths and weaknesses of accelerated testing with the ALF machine

Comparison of Older and Younger Driver Responses to Emergency Driving Events

This study investigated the responses of older, middle-aged, and younger drivers during performance of emergency maneuvers in an interactive driving simulator. Thirty-six drivers, equally distributed among three age groups (20-29; 35-44; 65-74) participated in the 32.2-km (20-mile) simulated drive, during which they encountered four emergency events at two levels of difficulty. Data were also collected in two baseline segments where no emergency events occurred. The emergency events were situations where other vehicles performed unexpected maneuvers: pulling out in front of the subject's car from a side street, and turning left in front of the subject's car at an intersection. Information on driver performance variables, including avoidance behavior and emergency avoidance response time, was collected. None of the age groups differed in avoidance response time, speed, deviation from the speed limit, brake pedal force, or avoidance behavior. Age differences were found in lateral placement at intersections. Older drivers drove further to the right of the lane center than younger and middle-aged drivers. It is believed that this finding is a result of a higher level of defensive behavior among older drivers. No other differences in driving behavior were found between groups. In this experiment, subjects were not performing turning maneuvers. Future research should be directed, when possible, toward investigating driver behavior when making turning maneuvers across traffic

Evaluation of the Supplemental Procedure of the Maximum Specific Gravity Test for Bituminous Paving Mixtures

The objective of this study was to investigate the effects of performing the supplemental procedure of AASHTO T 209 (or ASTM D 2041) on the percent air voids, the effective aggregate specific gravity, and the maximum specific gravity of a bituminous paving mixture, using both thoroughly coated aggregates and partially coated aggregates. The supplemental procedure should correct the test data for water absorbed into the aggregate during the test. Although the supplemental procedure can be used when designing mixtures, it is most often used for determining the maximum specific gravities of moisture damaged pavement samples, or cores or specimens where sawing has exposed a significant amount of aggregate. The majority of aggregates used in this study had water absorptions below 2.5% and thus were not highly absorptive. It is recommended that the supplemental procedure not be peformed on laboratory mixtures or pavement cores having aggregates with water absorptions below 2.5%. When testing any mixture prepared in the laboratory during the mixture design process, the procedure for determining the maximum specific gravity should only be performed on well coated mixtures so that the supplemental procedure does not have to be used. For highly absorptive aggregates, it is recommended that the test only be performed at high binder contents which provide thick coatings. Only binder contents close to or slightly above the optimal binder content should be used. The maximum specific gravities for the lower binder contents can be calculated using the effective specific gravity of the aggregate. For laboratory mixtures containing highly absorptive aggregates, the supplemental procedure may indicate whether the coating is sufficient

Freight Professional Development: Building a Freight Professional Development Program in the 21st Century

The Federal Highway Administration's (FHWA's) Office of Freight Management and Operations launched the FPD Program in response to the growing need for freight transportation expertise in states and metropolitan areas. Several factors have heightened interest in freight professional development, including increasing freight traffic, an inadequate number of staff devoted to freight, and a lack of understanding of the transportation planning process in both the public and private sectors. The FPD Program assists state departments of transportation (DOTs) and metropolitan planning organizations (MPOs) in developing the skills and knowledge needed co meet the challenges facing freight transportation today and in the near future. The efficient movement of goods is dependent, in large part, on the people who build, maintain, and operate the freight transportation system. Educating and training a skilled and knowledgeable workforce is crucial to improving freight transportation productivity, safety, and security. A series of customer focus group meetings were held to determine what you, our customer, wanted and needed in an FPD Program. Your input helped identify and prioritize FPD products and services to be delivered in 2004 and beyond

Evaluation of Procedures Used to Predict Moisture Damage in Asphalt Mixtures: Executive Summary

Procedures for evaluating the moisture susceptibility of asphalt mixtures were compared by performing them on mixtures having a known history of susceptibility. Data included the retained ratios, visual stripping, mechanical values (tensile strength, stability, etc.), saturation, and swell. The most promising procedures appeared to be the NCHRP 246 and NCHRP 274. Moisture susceptibility was not effectively predicted by the 1-Minute Boiling Water, 10-Minute Boiling Water, Immersion-Compression, Marshall-Immersion, and Dynamic Tumbling procedures. The NCHRP 246 procedure (often referred to as the Lottman procedure) contained two parts: one for short-term pavement performance, and one for long-term pavement performance. The short-term part was not found to be useful with regards to predicting performance. An 80-percent pass/fail criterion was chosen for both tensile strength ratios in the NCHRP 246 and NCHRP 274 procedures, and 70 percent for the M sub r test. Ten percent or greater visual stripping generally indicated unacceptable damage in all procedures performed on compacted mixtures. The data indicated that a freezing period, or higher air void levels, can be beneficial for evaluating moisture susceptibility. The degree of saturation was found to be important in that sufficient water must enter a specimen; however, saturation was not found to be the dominant factor affecting moisture damage. The effects of saturation were masked by other mechanisms such as the type of mechanical test, air void levels, and freezing. There was no conclusive evidence that high saturations or oversaturation due to vacuum conditioning adversely affected the test results

Time-to-Corrosion of Reinforcing Steel in Concrete Slabs, Volume VI: Calcium Nitrite Admixture

Eighteen relatively large reinforced concrete slabs were fabricated in 1980 using calcium nitrite admixture with black (uncoated) steel. Their performance is compared with uncoated steel in concrete without admixtures. The slabs were placed in two lifts: the bottom lift consisted of a bottom mat of reinforcing steel in chloride-free concrete, and a top lift consisting of the top mat rebars in concrete contaminated with various quantities of sodium chloride. All the electrical connections between the reinforcing mats were made exterior to the slabs so that the corrosion current flow could be measured. After curing, the slabs were mounted above ground and exposed to the environment of the Washington, D.C., Northern Virginia area. They were periodically subjected to additional chloride exposure while being monitored for the initial 1-year period. Findings of the study indicate that the calcium nitrite can be effective in reducing rate of corrosion for black reinforcing steel embedded in salt-contaminated concrete up to a chloride/nitrite ratio of 0.9