U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: Date: Sept/Oct 1998|
Issue No: Vol. 62 No. 2
Date: Sept/Oct 1998
The Virginia Department of Transportation (VDOT) has the enormous job of maintaining 90,000 kilometers of highways - the third largest state-maintained highway system in the United States. Another 16,000 kilometers of urban streets are maintained by cities and towns with the help of state funds. VDOT's system includes approximately 13,000 bridges meeting the requirements of the National Bridge Inspection Standards and another 8,000 smaller structures. More than 30 percent of Virginia's bridges are structurally deficient or functionally obsolete.
To address the deficient bridges and maintain its other structures, VDOT must get the most for its bridge dollars. This means making the correct decisions on whether to maintain, rehabilitate, replace, load restrict, close, or do nothing to a bridge. Each bridge must be considered in relation to all other system demands, and a rational method of comparison must be used. The key to a successful bridge program is to identify the trade-offs so that bridge projects can be developed by priority and funds can be allocated efficiently. To best determine which projects should receive the highest priority and what improvements are the most appropriate, bridge engineers, researchers, and managers must provide the tools needed to make accurate decisions.
A strong research program is part of the effort. Research is necessary both to evaluate new technologies before they are implemented and to help solve problems we are currently experiencing. In the future, the challenge of meeting the demand for cost-effective bridges will depend not only on new technologies but also on innovative ideas for the use of current and past technologies.
VDOT is unique in that it has a research organization that is currently celebrating 50 years of excellence in research. The Virginia Transportation Research Council (VTRC) was established in 1948 with the central goal "to discover, to innovate, to teach, and to learn." Its mission today is "to bring innovation to transportation." VTRC promotes excellence in transportation through objective research and superior technical services.
VTRC is organized with four research teams: the Pavement and Structures Team; the Materials Team; the Socio-Economics, Environmental, and Transportation Systems Team; and the Safety Team. The Pavement and Structures Team and the Materials Team provide the primary support for the bridge program. The Socio-Economics, Environmental, and Transportation Systems Team provides support for historic preservation and hydraulics.
VTRC works closely with the operations personnel of VDOT. More than 200 of VDOT's management and technical personnel participate in the research effort as members of research advisory committees. For the bridge program, there is close coordination with VDOT's Structure and Bridge, Materials, Construction, and Maintenance divisions; the nine field districts; and the Federal Highway Administration (FHWA) through three key research advisory committees. They are the bridge committee, the concrete committee, and the geotechnical committee. These committees have members from the operational divisions, field districts, VTRC, FHWA, industry associations, and academia to advise and direct the research and to facilitate the implementation of the recommendations of the teams and committees.
The research and technology programs for VDOT encompass the rehabilitation and replacement of bridges as well as the design and construction of new structures. VTRC's assistance ranges from the simple to the complex and addresses the assessment of the physical conditions of bridges and different methodologies for treatment.
Assessment and Rehabilitation of Structures
Nondestructive Evaluations of Structures
Major emphasis is placed on evaluating and minimizing the deterioration of all types of existing structures. Considerable progress has been made in recent years in the development, refinement, and advancement of nondestructive evaluation techniques.
Acoustic Emission Monitoring
A recently completed study shows that acoustic emission monitoring can be used to remotely monitor cracks in steel bridge elements. It is the only method that can distinguish between active and benign cracks. The real-time monitoring of steel bridge deterioration can reduce the number of visual inspections and provide for more efficient inspection, repair, and replacement decisions.
Crawling Robotics System
A crawling robotics system is being developed for the remote visual and ultrasonic inspection of steel bridge members. A third-generation robot can rapidly climb a steel high-mast light pole and allow for the inspection of connections that are subject to cracking. A fourth-generation robot (Robo Snake) is expected to traverse obstacles such as stiffeners and diaphragms and allow for inspection of steel beams and box girders. The work has the potential to reduce the cost of the inspection of structures and improve safety. The research was co-sponsored with FHWA's Office of Technology Applications (OTA) funds and is being conducted in conjunction with the University of Virginia's (UVA) School of Engineering and Applied Science.
High-Tech Alternatives for Removing Structural Steel Paint
There are two very different technologies for removing bridge paint (typically lead-based systems) that Virginia is actively examining.
ElectroStripT is a proprietary method that uses an electro-chemical reaction to cause paint to debond from its metal substrate. The process uses high current and low direct current (DC) voltage to cause the paint to lift from the steel. The paint is retained in a pad material that serves as the anode. The pad material with the paint residue is packaged and transported to an appropriate disposal or recycling site. Compared to conventional grit blasting, the process is very clean, quiet, more worker-friendly, and much less expensive. Containment requirements are much less than for conventional methods of paint removal. It will permit full removal in situations in which conventional methods would not be practicable. A full-scale field trial was recently demonstrated on a bridge on I-66 over a local street in Arlington County.
A less-developed technology being examined uses high-energy physics plasma techniques to remove paint from bridge steel. Called a pulsed plasma jet, operating repetitively, it removes paint by ablating it. That is, the plasma - ionized gases at very high temperatures (more than 3,000 degrees Celsius) - "cooks" the paint off of the steel but doesn't last long enough (as little as 1/1000th of a second) to damage the steel. The plasma jet is designed to operate in a continuous mode with multiple devices for production purposes. The cyclic rate will vary from 10 to 1,000 hertz. A vacuum arrangement around the device will collect the paint debris for appropriate disposal and/or recycling.
Engineering and design is ongoing, and the company is working toward a trial with real bridge steel early in 1999.
Rehabilitation of Reinforced Concrete Structures
Various activities have been undertaken in the last several years to address the expensive problem of chloride-induced corrosion of reinforcing steel in concrete bridges. To prevent ongoing reinforcing steel corrosion from causing structures to deteriorate prematurely, the following rehabilitation methods are under study:
Electrochemical Treatments of Concrete Bridges
Recent experiences by state highway agencies with rehabilitation of concrete bridges show that once the concrete is contaminated with sufficient chloride ions to cause steel corrosion and concrete delamination, rehabilitation procedures consisting of repair of the damaged concrete and subsequent application of an overlay, sealer, or membrane are not effective in stopping corrosion unless all chloride-contaminated concrete is removed. Electrochemical imbalances between the new and contaminated concrete often have sufficient potential differences to sustain corrosion again in the steel bars. Consequently, the electrochemical measures such as CP and ECE are the only rehabilitation methods that are known to overcome this electrochemical imbalance phenomenon.
This method controls the flow of electrons in the steel/concrete system so that anodic current from the reinforcing steel is prevented. Cathodic protection can be applied on a structure in two ways: (1) by use of impressed current, and (2) by use of galvanic current. Both require the installation of a suitable anode - either applied on the surface of the concrete or embedded just below the surface of the concrete, depending on the anode systems involved. In the first approach, a rectifier is used to provide a controlled amount of direct current to flow between the anode and the reinforcing steel, which becomes the cathode. In the second approach, a suitable anodic metal is used to provide a flow of natural direct current between the metal and the steel, in accordance with the potential difference between the two materials.
Proper selection of anode systems is critical to the effectiveness of any CP system, regardless of the approach selected, and efforts at VTRC have been directed at identifying the best anode systems for each possible situation or environment.
Impressed-Current CP of Bridge Decks
In addition to having long service life and the ability to effectively distribute the direct current across a concrete deck, anodes for use in this type of CP also have to be strong enough to withstand traffic loads and have to be compatible with the other more conventional rehabilitation procedures. For this purpose, slotted titanium mesh anode systems without overlays were tested on some concrete decks. The testings confirmed observations made elsewhere that the titanium mesh is by far the best anode for use in impressed-current CP of bridge decks.
Impressed-Current CP of Inland Bridge Piers
Because the surfaces of concrete piers are not exposed to traffic wear, anodes do not need to be embedded in the concrete. Consequently, VTRC field-tested a metallized zinc coating and a conductive sprayable polymer coating developed by the Brookhaven National Laboratory under the sponsorship of FHWA. Although the materials were found to be promising to varying degrees, testing raised concerns about the service life, the exposure of the workers, or the environmental issue.
The solution turned out to be electrically conductive paints - both organic-solvent and water-based. These paints are essentially paints mixed with sufficient graphite particles to enhance its conductivity. Field installations, some very sizeable and as old as 10 years, have indicated that these types of paints can provide a service life of probably at least 15 years.
In addition, testing of a new sacrificial or galvanic anode system, zinc-hydrogel, is underway on some inland concrete. The current comes from the difference in potential between the steel and the zinc anode, which is available as a foil with an adhesive backing of a conductive gel, to create the necessary current flow.
Galvanic CP of Marine Concrete Piles
Finally, several different galvanic anode systems (metallized Al-Zn coating, Zn-hydrogel, zinc-grout jacket, and zinc-compressed panel) are being tested on several concrete piles in Willoughby Bay, Norfolk, Va. Galvanic CP is ideal for use in concrete piles located in seawater because the corrosion is concentrated around the splash zone, where the concrete is often wet and, therefore, very conductive.
Development of New Concrete-Embeddable Reference Electrodes
Possibly just as important as the anode and the rectifier in a CP system are concrete-embeddable reference electrodes. In contrast to portable copper/copper-sulfate electrodes being used to measure the steel-to-concrete potentials across the surface of a concrete structure, these electrodes can be embedded in concrete to allow for long-term monitoring of the operation of any CP system. Unfortunately, there are concerns that the present-day embeddable reference electrodes (such as silver/silver-chloride, molybdenum/molybdenum-oxide, graphite, etc.) may not have sufficient service life. Consequently, research efforts have been initiated with UVA's Center for Electrochemical Science and Engineering to explore the application of the concept of potential-stable galvanic couples (PSGC) in the design of an entirely new class of electrodes that can be embedded in concrete. In addition to providing a very stable reference potential, this new class of electrodes can be fabricated in any desirable sizes. The results of the first-phase of research efforts have identified three good candidate PSGC reference electrodes.
Hydraulic Cement Concrete Overlays for Bridge Decks and Pavements
This project, in the fourth year of a five-year study, included the construction of high-performance concrete overlays on six three-span bridges on I-95 near Emporia, two 28-span bridges on Route 60 in Virginia Beach, and 610-meter (m) sections of pavement overlays on I-295 near Richmond, I-81 near DeWitt, and Route 29 near Charlottesville. Bridge overlays are 32 millimeters (mm) in minimum thickness, and the pavement overlays are 50, 75, and 100 mm thick. The Route 29 project demonstrated whitetopping. (See article on page xx.) The I-85 and I-295 projects demonstrated overlays on continuously reinforced-concrete pavements. Overlay concretes consisted of 32 combinations of ingredients, including silica fume, latex, corrosion-inhibiting admixtures, a shrinkage-reducing admixture, steel, polypropylene and polyolefin fibers, types II and III portland cement, slag, fly ash, and topical applications of corrosion-inhibiting admixtures. Overlays are performing well and demonstrating the various technologies.
Field Evaluation of Corrosion Inhibitors for Concrete
For field evaluation, 156 exposure slabs, three bridge deck overlays, and substructure patches have been constructed with and without a variety of combinations of corrosion-inhibiting admixtures and topically applied inhibitors. The slabs and structures are being monitored over a five-year period for corrosion activity as part of a $250,000 FHWA-administered pooled-fund study. Measurements are being made on the slabs for macrocell current, macrocell potential, resistance between top and bottom rebar mats, half-cell potentials, and rates of corrosion. After approximately one year of exposure, measurements on the slabs show that as the chloride ion content in the slabs increases the macrocell current, macrocell potential, half-cell potential, and rate of corrosion increase and the resistance decreases. The measurements also show no significant difference between the slabs repaired with and without corrosion-inhibiting admixtures and topical treatments. Slabs repaired with 7-percent silica fume showed half-cell potentials that were less negative than those repaired without silica fume.
Virginia's research efforts include an assessment of the value of her historic bridges as well as implementation of the latest technology. Efforts to properly manage the state's historic bridges began in the 1970s with its initial survey of Virginia's metal-truss bridges. In the 1980s, Virginia's concrete and masonry arches, built prior to 1932, were surveyed. The 1990s have seen the revisiting and updating of the prior surveys to include all remaining examples of each bridge type and new surveys of non-arched concrete bridges built prior to 1950 and of all moveable-span bridges. At the conclusion of each survey, the bridges were evaluated by the Historic Structures Task Group - an interdisciplinary group made up of representatives of VDOT, VTRC, the Virginia Department of Historic Resources, and FHWA. Now that an inventory of significant bridges has been established, the task group is working to develop a plan to manage and treat these historic structures to ensure their future survival.
Leaking joints are the major cause of deterioration of superstructure elements below the decks and the substructures. VDOT is using more continuous spans and integral abutments to eliminate as many deck expansion joints as possible to reduce future maintenance expenditures. However, current integral designs are often conservative and based on empirical values. The design of integral bridges is complicated by the soil-structure interaction associated with thermal movements. To optimize the future designs, more data on the soil pressures and on the magnitude and distribution of the stresses induced in the structure are needed.
VTRC conducted an analysis of an integral backwall bridge on Route 257 over I-81. The bridge was instrumented during construction and monitored for 2.5 years. The results indicated that the bridge performed satisfactorily during the monitoring period although some settlement problems were encountered with the approach fill. VTRC is looking at ways to minimize the settlement behind the backwalls. Also, additional research is planned on the resistance of pile caps and integral abutments to lateral loading and on the performance of integral bridges.
Heated Bridge Decks
In the fall of 1996, VTRC constructed a bridge with a heated deck on Route 60 over the Buffalo River in Amherst County to improve winter-driving safety. The site is located in the eastern foothills of the Blue Ridge Mountains, where road conditions during winter storms can often be treacherous. The bridge has 241 chemical-filled steel heat pipes and approximately three kilometers of piping embedded in the concrete deck and approach slabs.
VTRC has been evaluating the performance of the heated bridge. Data collected from various deck and environmental sensors and from video acquired by an infrared camera are periodically transferred to VTRC for analysis. In addition, a Web page has been set up to monitor the project.
Thus far, the heating system has not performed adequately. Problems were observed with the heat distribution across the deck surface and with heat output generated by the system. A series of experiments were conducted using different heating fluids, including Freon 123, Freon 134a, and ethanol. Recent tests using ammonia as a heat-transfer liquid showed promise for an effective operation. It appears that the heat output at the deck surface will be adequate for winter operations if ammonia is placed in the entire heating system. VTRC remains committed to ensuring a successful monitoring of this project.
Prevention of Reinforcement Corrosion in New Concrete Bridges
The very harsh service environments that many bridges are exposed to may require a combination of protection systems to prevent reinforcement corrosion. Although high-performance concrete and adequate concrete cover over reinforcement provide a long service life, research is continuing to determine the additional benefits to be obtained from improving the quality of concrete, using corrosion-inhibiting admixtures and adopting corrosion-resistant reinforcement.
Shrinkage and Creep
Cracks in concrete allow the infiltration of chlorides and water and the early age corrosion of reinforcement. Concretes that have high shrinkage and low creep are more prone to cracking, but shrinkage and creep are rarely included as specification requirements. The objective of this three-year project being done by the Virginia Polytechnic Institute and State University (Virginia Tech) is to identify, refine, and develop equipment, test procedures, and specifications that can be implemented, thereby reducing cracking in concrete structures.
A study has recently been initiated to examine the rheology of a variety of concrete mixtures, particularly high-performance concrete mixtures. The intent is to develop and refine test procedures that measure the fresh properties of concrete and thereby minimize placement problems and enhance the quality of concrete structures. Conventional slump measurements often do not provide a good indication of the workability of high-performance concrete mixtures.
Pulsed Ultrasonic Interferometer
The study using a pulsed ultrasonic interferometer to evaluate the consolidation of concrete found a correlation between the degree of consolidation of concrete and ultrasonic velocity. The system can provide an indicator of the degree of consolidation when measurements are made on fresh and hardened concrete and thereby provide a way to know when consolidation equipment or concrete mixtures need to be adjusted to improve consolidation. More research is needed to implement the technique.
The long-term benefits for concrete offered by commercially available corrosion-inhibiting admixtures are not certain. For example, calcium nitrite, which is an anodic inhibitor, is ineffective when the chloride-to-nitrite ratio exceeds approximately 1.0. In addition, this inhibitor is water-soluble and, therefore, is leachable from the concrete and should become less effective with time. Because the chloride ions will continue to build up in the concrete while the admixed nitrite may slowly leach out, eventually the nitrite will not likely inhibit corrosion. Other products have not been evaluated long enough to assess their potential.
Consequently, VTRC has started to search the new inhibitors that have been developed for other industries looking for inhibitors that can be used in concrete. Using tests conducted in a simulated concrete pore solution, two promising new inhibitors have been identified. Research efforts are underway to investigate other new inhibitors and to evaluate commercially available inhibitors.
Epoxy-Coated Reinforcing Steel
A five-year study done by Virginia Tech under contract with VTRC has shown that the epoxy coating on reinforcing steel used in bridge decks and substructures in Virginia begins to debond after as little as four years in service. The study involved the evaluation of cores taken from 21 bridge decks and the piles in three bridges ranging in age from two to 20 years and the evaluation of the reinforcement in exposed specimens and pour-water solutions with various chloride contents. It was concluded that because the coating debonds, the investigation of alternative rebar materials providing better corrosion protection at a more favorable cost/benefit ratio is desirable.
A new reinforcement that promised such potential is the stainless steel-clad bar. Efforts are underway to use this new bar on an experimental basis in a new bridge deck and to evaluate the corrosion resistance and mechanical properties of this material.
High-Performance Grouts for Post-Tensioning Strands
One completed project and a recently initiated project provide insight into the problems associated with using something other than portland cement and water to grout post-tensioning ducts. A grout mixture containing 7-percent silica fume was used to grout the ducts in the pier caps of a major river crossing, and a mixture containing 20-percent silica sand and 30-percent fly ash is specified for the ducts in a segmental bridge on Virginia's experimental Smart Highway. A high-range, water-reducing admixture must be used to obtain the fluidity required to pump the grouts. The high-performance grouts can provide lower permeability to chloride ions and lower shrinkage and thereby should provide greater protection for the strands than grouts that are made of only portland cement and water.
VDOT is developing and using high-performance concrete (HPC) for safe, cost-effective structures. Seven such structures were constructed between 1995 and 1997. Compressive strengths of 48 megapascals (MPa), 55 MPa, and 69 MPa were used in the beams of six of the structures, and/or low-permeability special provision was used in five. The bridge with the 69-MPa beams also had the large diameter, 15-mm strands at 50-mm spacing. Six of the structures are carrying traffic, and the seventh will be open to traffic upon completion of the connecting road.
High-strength, durable air-entrained concretes have been developed at two Virginia plants using portland cement and slag at one plant and using portland cement and silica fume in the other. In the other, higher strengths in beams have led to economy due to a smaller section or reduced number of beams.
VDOT experience to date shows that air-entrained HPC with high early strengths, a 28-day strength of 48 to 69 MPa , and low permeability can be manufactured on a production basis with locally available materials. VDOT's HPC program is progressing successfully, and 12 more structures have been selected, increasing the total number of HPC bridges to 19.
High-performance steel (HPS), developed under an agreement between FHWA, the American Iron and Steel Institute (AISI), and the U.S. Navy, became available in 1996. HPS has been promoted as having unique chemical and physical properties, including improved weldability using minimum preheat to obtain sound welds, that allow more economical fabrication practices to be employed. Tennessee and Nebraska were the first states to use HPS-70W grade. Building on their lessons learned, Virginia decided to construct two HPS bridges and to conduct additional research funded by FHWA OTA to evaluate the base metal and weld material properties and their performance.
Two structures have been designed with HPS-70W steel. One structure has a seven-span, continuous arrangement of 62 - 5@80 - 62 m. The second structure has a five-span, continuous arrangement of 54.5 - 3@70 - 49.5 m, and it has an identical sister bridge to be fabricated with ASTM A709M Grade 345W steel for comparison with the HPS structure. Documentation of the entire project from design through fabrication and erection is planned. Evaluation of the overall bridge performance under live load as well as long-term monitoring is essential for expanded use of this material.
Fiber-Reinforced Polymer Composites
The Tom's Creek Bridge in Blacksburg is an experimental structure designed with a timber deck and innovative, all-composite-material beams. The bridge, erected in the summer of 1997, is one of the first applications of composite materials in the United States for the primary load-carrying elements of a bridge subjected to vehicular traffic.
Composite materials, produced from polymer resins and high-strength fibers, have the potential to be effective construction materials because of their corrosion resistance and high strength-to-weight ratio. However, very little data exists on the synergistic effects of vehicular loads and actual environmental conditions that cannot be duplicated in the laboratory. Consequently, a team of civil engineers, chemists, and composite materials engineers from Virginia Tech, VTRC, and the VDOT Structure and Bridge Division have collaborated to develop a testing protocol to examine the durability of the Tom's Creek Bridge composite beams under actual field conditions. The goals of this project are:
In a cooperative spirit to work with industry to promote the bridge application of aluminum, VDOT committed to construct several bridges with aluminum deck systems. The new aluminum deck is comprised entirely of extrusions welded together at the sides, providing continuity in the top and bottom flanges. After welding, the webs of the extruded parts form repeating triangles, creating trusses perpendicular to the extruded direction. The extrusions generally run longitudinally (parallel to the girders and traffic flow). The completed proprietary deck is connected securely to the underlying girders so that composite action is developed between the deck and the girders. The difference in thermal expansion coefficients between steel and aluminum induces stresses in both materials that are accounted for in the design. The decks could be fabricated in panels as large as can be shipped, which for highway shipment is about 4.3 m wide by 36.6 m long. The decks are shop-coated with an epoxy-based wearing surface with a 9.53-mm nominal thickness.
VTRC, with support from the FHWA OTA, initiated a three-part study to evaluate the aluminum deck system. The first phase involved structural testing and evaluation of a 2.74-m by 3.66-m deck panel by the Structures Laboratory at FHWA's Turner-Fairbank Highway Research Center. Several tests were conducted in which the panel was loaded to its design limit under various support conditions. In addition, a test to failure was conducted. The second phase involves a series of static and dynamic load tests on a completed structure. The third phase will focus on the long-term durability of the deck system.
To meet the growing demand for better, more efficient, cost-effective, and appealing bridges with extended service lives, Virginia is moving boldly forward with both new technologies and improvements upon current technologies. VDOT is not rushing forward carelessly; the department is working with its industry partners to do laboratory and field testing and evaluations to ensure that the technologies are functionally, economically, and aesthetically acceptable.
VTRC has nurtured an excellent working relationship with its operational divisions and field districts, FHWA, industry, and academia to promote technology and research. The research advisory committees are key to the success in identifying needs, providing direction, and implementing technologies. Also, there has been an outstanding partnership with FHWA's Virginia Division, the Region 3 Office, the Office of Technology Applications, and the Turner-Fairbank Highway Research Center in supporting, implementing, and evaluating new technologies and conducting research.
There is a commitment by upper management to promote the use of technology and research to maintain and enhance Virginia's transportation system. VDOT employees and managers are working together to ensure that Virginia's transportation system represents the highest standards of safety and quality and that VDOT is a leader in using innovation and technology to move Virginia's bridge program into the 21st century. This commitment and effort was recognized in March 1998 when VDOT received the Federal Highway Administrator's Public Service Award for the initiative and leadership demonstrated by VDOT in implementing innovative design and high-performance-material technologies in bridge construction under Section 6005, Applied Research and Technology Program, of the Intermodal Surface Transportation Efficiency Act of 1991.
The citation reads, in part, "Your organization's proactive effort in fostering and applying new bridge technologies in the Commonwealth of Virginia is commendable. Virginia is the only State to have built bridge projects using the heated bridge deck, the thin bonded overlays, the high-performance materials (steel, concrete, aluminum, and fiber-reinforced polymer composites), the nondestructive evaluation/testing, and the jointless bridge technologies. These innovative technologies have great potential to improve and enhance the effectiveness and efficiency of the Nation's transportation system."
Claude S. Napier Jr. is the division bridge engineer in FHWA's Virginia Division Office in Richmond, Va. He is responsible for the FHWA bridge program, including bridge, concrete, and geotechnical technology and research. He has 28 years of bridge design, construction, and maintenance experience, including 20 years with FHWA. Napier is a registered professional engineer in Virginia. He received his bachelor's and master's degrees in civil engineering from Virginia Polytechnic Institute and State University.
Wallace T. McKeel Jr. is the research manager for the VTRC Pavement and Structures Team in Charlottesville, Va. He manages VDOT's research program in the structural, pavement, geotechnical, maintenance, and field operations areas. He has 39 years of bridge design and research experience, including 35 years with VTRC. McKeel is a registered professional engineer in Virginia. He received his bachelor's degree in civil engineering from the Virginia Military Institute and his master's degree in civil engineering from the University of Virginia. He has written numerous papers and reports primarily on the design, evaluation, and maintenance of bridges and on the durability of drainage structures.
Michael M. Sprinkel is the research manager for the VTRC Materials Team in Charlottesville, Va. He specializes in materials and construction methods for the protection, repair, rehabilitation, and replacement of bridge decks and other concrete structures. He has 26 years of research experience. Sprinkel is a registered professional engineer in Virginia, and he has published more than 40 papers. He received his bachelor's and master's degrees in civil engineering from the University of Virginia.