Federal Highway Administration (FHWA) - Turner-Fairbank Highway Research Center (TFHRC)

Purpose: The Arens Photometric and Visibility Laboratory conducts evaluations of the photometric and colorimetric properties of traffic control devices, including signing and pavement marking materials and traffic signal lights, and supports human factors research used to establish the required levels that meet the visual needs of drivers. Laboratory Description: The laboratory develops recommendations for the specification of materials, both in photometric and colorimetric terms. The laboratory also evaluates transport-related lighting and signing equipment, including automobile headlamps (as they affect the visibility of signs and markings) and traffic control devices (particularly the light-e mitting diode and fiber-optic types). Validation of field instruments used for measurement of traffic control devices can be performed by comparison with laboratory instruments. Laboratory Capabilities: In addition to basic photometric and colorimetric measurements, the Arens Photometric and Visibility Laboratory evaluates fluorescence and retroreflective properties of materials. Results of these evaluations support Federal guidelines issued in the Manual on Uniform Traffic Control Devices as well as the development of consensus standards promulgated by the American Society for Testing and Materials International. Laboratory Equipment: Gamma Scientific 940D Computerized Photometric Range System; an auto-ranging, gonio-p hotometer that includes a three-axis goniometer for placement and orientation of samples and a two-axis Observation Angle Positioner (OAP), which provides precise angular separation of the light source and photometer, as measured at the sample. The goniometer is mounted on a rail, allowing the distance between the goniometer and the OAP to be adjusted from 1 meter to approximately 30 meters. The second axis on the OPA ensures that the photometer is oriented toward any device under test. The system is primarily used in the measurement of retroreflective materials, but may also be used for photometric measurement of small light sources, such as headlights and traffic control signal lights; Optronic Laboratory Type OL-754 double-m onochromator spectroradiometer; Konica-MinoltaCS-2000 spectroradiometer; Photo Research Model 1980A Pritchard Photometer (luminance meter) with Cassegrain lens, with an effective aperture of 0.2 minutes of arc; Gamma Scientific GS-BFC-450 bispectral fluorescence colorimeter; handheld illuminance and luminance meters; NIST-calibrated luminous intensity standards, precision shunts, and voltmeters for calibration purposes; NIST-traceable Standard Calibration Source (luminance and color temperature). Laboratory Services: The Arens Photometric and Visibility Laboratory directly conducts or supports human-factors studies on roadway visibility issues, such as the impact of roadway lighting on driver performance. The laboratory has conducted in-h ouse studies and investigations in support of contract research studies, the development by the Operations Core Business Unit staff of the new edition of the Manual on Uniform Traffic Control Devices, and the work of other government agencies on topics, including the measurement of the color characteristics of retroreflective materials for the revision of the 1979 Federal Highway Administration Color Tolerances, evaluation of pavement markings under automobile headlamps, photometric evaluation of a mobile sign retroreflectometer, evaluation of fluorescent signing materials and ultraviolet headlighting, and design of a universal, multipurpose, computer-controlled roadway lighting system for the Smart Road in Blacksburg, VA.

Purpose: The Binder Laboratory studies the flow and deformation of paving materials. The laboratory's primary mission is to characterize the behavior of paving materials properly such as asphalt binder and fine aggregate mastic. Laboratory Description: The Binder Laboratory is equipped to enable evaluation of the strength, stiffness, and ductility of paving materials and emerging test methods and equipment. Work conducted in the laboratory provides the basis for improved material specifications (e.g., the Superpave performance-based binder specifications) that enable improvement of the durability, longevity, quality, and cost-effectiveness of pavements. Laboratory Capabilities: The Binder Laboratory is equipped with state-of-the-art rheology instrumentation and the latest asphalt binder test equipment in order to test binders at various conditions and temperatures. Cracking of pavements takes place mostly at intermediate ambient and low temperatures, while rutting (permanent deformation) takes place mostly at high pavement temperatures. Dynamic Shear Rheometers are used for rheological characterization of paving asphalts in the intermediate to high temperatures ranging from 7 degrees Celsius (42 degrees Fahrenheit) to temperatures approaching 100 degrees Celsius (212 degrees Fahrenheit). The Rotational Viscometer is used to determine the steady-state viscosity of asphalt binders at high temperatures above 100 degrees Celsius (212 degrees Fahrenheit), such as 115 degrees Celsius (240 degrees Fahrenheit) to 220 degrees Celsius (424 degrees Fahrenheit). The Pressure Aging Vessel is used with the Rolling Thin Film Oven to simulate long-term aging of asphalts and, hence, pavements. Rheological properties of asphalt binders may thus be measured indicative of pavement conditions after years of service. The Ductility Meter DDA-3 Instrument is being advanced to determine the strain tolerance of binders at intermediate temperatures with the Double Edge Notch Test (DENT). The binder strain tolerance in the ductile state has been found to be a good indicator for fatigue performance. The Bending Beam Rheometer and Direct Tension Tester are used both individually and in combination to determine the low-temperature (thermal) cracking temperatures of asphalts. The latest asphalt binder testing equipment, the Asphalt Binder Cracking Device (ABCD), was developed using FHWA's Highways for Life funds. The ABCD is used to determine the low temperature cracking temperature for asphalt binders. The residue of emulsified asphalts for pavement layer bonding tack coats and pavement preservation treatments can be recovered with updated methodologies and characterized with performance grading instruments. The laboratory is accredited by the American Association of State Highway and Transportation Officials for competency in construction materials testing. Laboratory Equipment: Dynamic Shear Rheometers, Bending Beam Rheometer, Asphalt Binder Cracking Device, Ductility Meter DDA-3, Pressure Aging Vessel, Rolling Thin Film Oven, Rotational Viscometer, Evaporative Recovery of Bituminous Emulsions.

Research projects conducted within the CRF support both the goals of the Federal Highway Administration and provide assistance to State agencies and industry partners. MAJOR COMPONENTS CRF is composed of the following three laboratories: The Chemistry Laboratory synthesizes and characterizes highway materials and evaluates their susceptibility to in-service damage. This synthesis includes evaluating the susceptibility of highway materials to weathering, moisture damage, oxidation, deleterious aggregates, and ASR gel formation, as well as studying the harmful effects of deicing chemicals on the materials. The Analytical Laboratory uses highly specialized equipment for the identification and chemical analysis of materials used in paving structures and for the development of standard test methods for the paving industry. Instrumentation includes the following: The Infrared Spectrometer is used for the identification of coatings and asphalt binders and the rapid determination of the type and quantity of additives in binders as well as their degree of aging. The uses for the Ion Exchange Chromatograph include the quantitative determination of additives for forensic tests in paving systems and the effects of additives on the environment surrounding highway systems. The Atomic Absorption Spectrometer is used in forensic studies to determine the amounts of trace metals present in paving systems such as lime in hot mix asphalt. The Elemental Analyzer determines the amount of carbon, hydrogen, nitrogen, oxygen, and sulfur present in organic systems. It is used to study the structure and aging of asphalt binders. The solvent separation of asphalt binders into their component Saturates Aromatics, Resins, and Asphaltenes (SARA analysis) by thin layer chromatography is accomplished using the Iatroscan Spectrometer. This technique is very useful in determining how the structures of asphalt binders are affected by additives and aging. The Raman microscope is used to study the structure of aggregates, fly ash, and other materials used in concrete production. It is also used to study the formation of ASR (Alkali Silica Reaction) gels in concrete. The X-Ray Fluorescence spectrometer is used to measure the elemental composition of materials, in particular aggregates, fly ash, and concrete. The Materials Characterization Laboratory contains several microscopes including a scanning electron microscope with an Energy Dispersive X-ray Microanalysis (EDAX-ray) fluorescence spectrometer. These microscopes enable researchers to identify the compositions of highway related materials and study the morphological properties of polymer modified asphalt binders. The Turner-Fairbank Highway Research Center (TFHRC) has more than 24 laboratories for research in the following areas: safety; operations, including intelligent transportation systems; materials technology; pavements; structures; and human centered systems. The expertise of TFHRC scientists and engineers covers more than 20 transportation-related disciplines. These laboratories are a vital resource for advancing this body of knowledge created and nurtured by our researchers. The Federal Highway Administration's Office of Research, Development, and Technology operates and manages TFHRC to conduct innovative research to provide solutions to transportation problems both nationwide and internationally. TFHRC is located in McLean, Virginia. Information on TFHRC is available on the Web at www.fhwa.dot.gov/research/tfhrc/ . RECENT ACCOMPLISHMENTS Developed a test method to detect and measure the presence of lime in hot mix asphalt. This method is being adopted by American Association of State Highway and Transportation Officials (AASHTO) as a standard procedure. Developed a simple test method to demonstrate the presence of phosphoric acid in asphalt binders. Provided technical assistance to a number of State agencies in forensic investigations. These investigations included the use of lime as an antistrip additive, the use of phosphoric acid as an asphalt modifier, and various cases of contaminated binders and aggregates.

Purpose: Researchers in the Concrete Laboratory evaluate new test methods, conduct concrete materials research, develop mixture design and analysis procedures for concrete pavements, and provide concrete forensics. Laboratory Description: The Concrete Laboratory has facilities for evaluating plastic and hardened concrete properties, including rheology, setting, and calorimetry; concrete curing and volume change; concrete durability, including freezing, and thawing, and alkali-silica reaction; and mechanical properties, including strength and modulus of elasticity. Laboratory Capabilities: The laboratory batches, mixes, and conducts tests on cement paste, mortar, and concrete. A curing room is available for curing concrete specimens under standard or other controlled conditions, and for assessing curing-related properties, such as degree of hydration, maturity, and shrinkage. The Concrete Laboratory includes facilities for investigating the effects of chemical and environmental exposure on concrete, as well as capabilities for assessing a number of distress mechanisms, including alkali-aggregate reaction, sulfate attack, chloride penetration, freezing and thawing, and thermal effects. The Concrete Laboratory also has an aggregate materials and sample preparation room. Facilities are available for testing the mechanical properties of concrete, steel, and composites. These facilities are inspected by the Cement and Concrete Reference Laboratory and accredited by the American Association of State Highway and Transportation Officials Materials Reference Laboratory. Laboratory Equipment: Several concrete, mortar, and paste mixers of various sizes and types are available in the Concrete Laboratory, including a high-shear paste mixer and a high-intensity concrete mixer (Figure 1). Figure 1. High-Intensity Concrete Mixer. Equipment for evaluating early-age mixtures includes a Vebe Consistometer, a Dynamic Shear Rheometer (Figure 2), a semi-adiabatic calorimeter, and an isothermal calorimeter (Figure 3). Figure 2. Dynamic Shear Rheometer. Figure 3. Isothermal Calorimeter. Concrete curing equipment includes three controlled curing tanks and two walk-in environmental chambers. Equipment for evaluating the durability of concrete includes an automated freeze-thaw chamber (Figure 4) with the capacity for 17 specimens, coefficient of thermal expansion test frames (developed in-house and obtained commercially), computer-controlled chloride penetration test equipment, and a surface resistivity apparatus (Figure 5). Figure 4. Freeze-Thaw Chamber. Figure 5. Surface Resistivity Apparatus. The Concrete Laboratory also performs shrinkage tests that include restrained shrinkage tests and autogenous shrinkage tests. The mechanical properties measurement equipment includes a universal testing machine with a capacity of 4,500 kilonewtons (1,000,000 pounds) and a beam tester with a capacity of 130 kilonewtons (30,000 pounds), a compressometer/extensometer, and four creep frames. Laboratory Services: The Concrete Laboratory provides support in the following areas: Evaluates and develops new or improved equipment and procedures for assessing the properties and performance of concrete, including materials selection, mixture proportioning, and construction of concrete. Mixes, casts, and tests concrete test specimens in support of other researchers at the Turner-Fairbank Highway Research Center. Investigates the properties and performance of concrete and its component materials (cement, aggregate, and supplementary and alternative cementitious materials admixtures, etc.). Performs specialized testing and forensic investigations on concrete to assist State departments of transportation and other research offices and divisions within the Federal Highway Administration.