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90 PREPUBLICATION COPYâUncorrected Proofs APPENDIX B DEFINITIONS AND INTENDED BENEFITS OF IBRC TECHNOLOGIES The Committee classified the innovative materials and other technologies used in the Innovative Bridge Research and Construction (IBRC) projects in 17 categories (see Box B.1). Definitions of each technology are presented in the following section, along with explanations of the intended benefits of applying the technologies in bridge construction and examples of IBRC projects that demonstrated the technology. =========================================================================== Box B.1 IBRC Technology Categories Concrete: 1. High-performance concrete (HPC) 2. Self-consolidating concrete (SCC) 3. Ultra-high performance concrete (UHPC) Fiber reinforced polymers (FRP): 4. Externally bonded FRP reinforcement 5. FRP deck elements 6. FRP superstructure elements 7. FRP rebar 8. FRP prestressing tendons (strand or bar) Corrosion control technologies: concrete reinforcement: 9. Low-chromium steel (ASTM A1035/1035M steel) rebar 10. Galvanized rebar 11. Stainless steel rebar (solid or clad) Corrosion control technologies: coating and anodes: 12. Metallizing 13. Cathodic protection anodes and electrochemical chloride extraction 14. Galvanic protection and other corrosion control technologies Other IBRC technologies: 15. High-performance steel (HPS gr 50, 70) 16. Accelerated bridge construction (ABC) technologies, methods, or procedures 17. Monitoring and instrumentation technology ===========================================================================
91 PREPUBLICATION COPYâUncorrected Proofs CONCRETE 1. High-Performance Concrete (HPC) Definition HPC is designed to add strength and durability to bridge elements. The mix design includes supplementary cementitious materials (for example, fly ash, silica fume, ground-granulated blast furnace slag) for a concrete with low permeability that slows or stops the ingress of chlorides that can corrode steel reinforcement. HPC may include the use of high-range water-reducing admixtures for a low water- to-cementitious materials ratio to achieve higher strength while maintaining workability and finishability. Higher-strength HPC is typically used in bridge girders. Normal-strength HPC is typically used in bridge decks and substructures because of its enhanced durability. Intended Benefits The use of HPC is intended to extend the service life of the bridge by reducing cracking and permeability. Use of the material also promises benefits during bridge construction and element fabrication. The use of HPC for precast prestressed girders is typically associated with high early concrete compressive strength. The ability of HPC to achieve high strengths at early ages can lead to faster turnover of precasting beds, and thus allow for increased production. High final concrete compressive strengths in conjunction with additional reinforcement in precast prestressed girders can also enable wider girder spacings and longer span lengths, potentially eliminating or reducing the number of piers and reducing the number of girders per span. These capabilities can lead to savings in construction costs and time. HPC can also allow for shallower girder cross sections that reduce the required height of approach spans or increase underpass clearances with savings in earthwork. By replacing a percentage of the cement, the supplementary cementitious materials used in HPC can lower the cost of the concrete mix and reduce the projectâs carbon footprint.
92 PREPUBLICATION COPYâUncorrected Proofs Example Projects In the IBRC program, HPC was used in girders, decks, superstructure spans, abutments, piers, and overlays. Two examples are: The Church Street South Extension Bridge in New Haven, Connecticut (CT-2000-1). The bridge, which provides a direct link between downtown New Haven and the Long Wharf and waterfront areas, was constructed with an 8.25-in.-thick cast-in-place HPC deck, which was also reinforced with low-chromium steel rebar. The Mackey Bridge, also known as the Marsh Rainbow Arch Bridge, on 120th Street over Squaw Creek in Boone County, Iowa, outside Des Moines (IA-2004-01). HPC was used for all of the precast concrete on the job, including the prestressed I-beams, full-depth deck panels, pile caps, and integral abutment footings supported on steel piles. 2. Self-Consolidating Concrete (SCC) Definition SCC, sometimes referred to as self-compacting concrete, is typically produced by adjusting traditional mix designs with the use of superplasticizers and viscosity modifiers. These admixtures create a flowing concrete that can fill in complex structural shapes and around congested steel reinforcing while resisting separation and maintaining uniform suspension of solids, eliminating the need for mechanical vibration. Amounts of these admixtures can be balanced to meet shrinkage and other standard performance requirements and to control undesirable effects like bleeding and segregation based on project needs. Intended Benefits SCCs benefits derive from its flowability and consolidation. Structural concrete elements that have restricted worker access need highly workable concrete to ensure consolidation around congested rebar and posttensioning. The long-term performance of these elements using traditional low-slump concrete mixes is affected in part by the quality of the mechanical vibration process during placement. SCC is
93 PREPUBLICATION COPYâUncorrected Proofs formulated to self-consolidate during placement, thus eliminating the human factor to ensure complete consolidation. Compared to conventional concrete mixtures, SCC will have a small increase in material-related costs due to some of the ingredients and the need for more and higher dosages of chemical admixtures. However, the materialâs flowability and consolidation can result in reduced placement labor and increased speed of construction. The reduction in labor requirements can also have the added benefit of enhancing worksite safety. These savings during construction can offset the increased material cost of SCC. Further, the improved consolidation of SCC mixes is expected to improve surface appearance, strength, and durability. Example Projects Applications of SCC in IBRC projects can be found in drilled shafts, foundations, girders, decks, and overlays. Examples are: Route I-280/Garden State Parkway Interchange 145 project in New Jersey. SCC was used in four 6- ft-diameter drilled shafts. The M-50 Bridge over the Grand River, Jackson, Michigan (MI-2004-01). The project used SCC to construct bridge beams. 3. Ultra-High Performance Concrete (UHPC) Definition UHPC has mechanical and durability properties that exceed that of conventional concrete (Graybeal 2011, Haber et al. 2018). By using an optimized particle size distribution, a low water to cementitious material ratio, and a high percentage of discontinuous internal fiber reinforcement, UHPC exhibits significantly higher compressive and tensile strengths as compared to conventional concrete. Conventional concrete is weak in tension, with the tensile strength on the order of one-tenth of the compressive strength. Because
94 PREPUBLICATION COPYâUncorrected Proofs of its discontinuous pore structure, UHPC reduces water ingress, which enhances durability as compared to conventional concrete or HPC. Intended Benefits In the FHWA state-of-the-art report on UHPC, Russell and Graybeal (2013) identified four primary characteristics that distinguish UHPC from conventional concrete: higher compressive strength, higher tensile strength with ductility, increased durability, and higher initial unit cost. Based on these characteristics, they indicated that UHPC is well-suited for applications in which compressive strength is the predominant design factor or for use in outdoor or severe exposure environments due to its durability. In addition, the high tensile strength of UHPC can be advantageous for both service and strength design for flexure, shear, and torsion. The addition of the fibers in UHPC enables the concrete to exhibit ductile behavior even after initial cracking without the addition of traditional rebar. Elimination of the reinforcing steel can greatly simplify construction. In addition, UHPC exhibits superior durability due its dense matrix created by a combination of fine powders (that is, grain size maximum of 600 micrometer as reported by PCA) and chemical reactivity. This results in the small disconnected pores that prevent deleterious solutions from penetrating into the matrix, which can cause conventional concrete to deteriorate (Russell and Graybeal 2013). Enhanced durability stems from increased resistance to freezing and thawing, alkali-silica reaction (ASR), scaling, and abrasion; and decreased permeability and carbonation depth. The higher initial unit cost of UHPC requires consideration of the life-cycle costs of the applications to be considered viable. The reduced labor and material costs associated with the elimination of mild reinforcement in UHPC systems is also a potential benefit. Example Projects In the IBRC program, UHPC projects are mixed among some of the other categories and in some cases classified as HPC. Example projects are:
95 PREPUBLICATION COPYâUncorrected Proofs The single-span Mars Hill bridge in Wapello County, Iowa (over Little Soap Creek on 100th Avenue, Keokuk Township), which contains UHPC bridge girders. The UHPC girders were smaller and eliminated the need for transverse shear reinforcement. Virginia Route 58 Business over Route 58 Bypass (Route 624 over Cat Point Creek). In this new construction, the superstructure consisted of prestressed bulb tee girders that used UHPC. FIBER-REINFORCED POLYMER (FRP) COMPOSITE TECHNOLOGY 4. Externally bonded FRP reinforcement 5. FRP deck elements 6. FRP superstructure elements 7. FRP rebar 8. FRP prestressing tendons (strand or bar) Definition FRP composites consist of polymeric material systems (for example, epoxy, vinylester, polyester, and phenolic) reinforced with fibers such as carbon, glass, and aramid. State transportation agencies have integrated FRP composites into a wide range of bridge applications. Externally bonded FRP technology is used to repair and strengthen concrete, steel, and timber bridges. FRP materials are also used for modular bridge decks, prefabricated superstructure elements, concrete reinforcement, and prestressing tendons. Intended Benefits In general, FRP materials are intended to provide durable solutions for the construction of new bridges and for the rehabilitation and strengthening of existing bridges. Because of its light weight, FRP composites can lead to reduced material transportation costs and faster erection times. In the case of externally bonded FRP composite materials, their light weight, high tensile strength, and ease of installation have the potential to reduce the cost and expedite the repair and strengthening of bridges that have suffered deterioration or that do not meet current load requirements. Modular FRP bridge decks have
96 PREPUBLICATION COPYâUncorrected Proofs the potential to be rapidly installed in the field with less labor and lighter weight construction equipment than conventional deck replacements. These attributes facilitate accelerated bridge construction with reduced impact on the traveling public. The reduced weight of the deck may allow the bridge to carry additional vehicle loads, thereby allowing for an upgraded classification of the bridge. Prefabricated FRP decks and superstructures offer the potential for accelerated bridge construction and lower maintenance. FRP rebar and prestressing tendons have the advantage of not being susceptible to corrosion, which is a primary source for the deterioration of reinforced concrete bridge members. For precast prestressed concrete members such as precast girders, and posttensioned members such as bridge box-girders that use internal or external tendons, corrosion of the prestressing is a source of premature deterioration. Again, the light weight of the FRP materials promises to accelerate bridge construction and reduce the weight of the structure. Example Projects The following are examples of the use of FRP in IBRC projects: West Virginia Market Street Bridge in Wheeling, West Virginia (WV-1999-02), was originally constructed in 1930 as a two-span riveted steel structure. A bridge condition assessment by the West Virginia Department of Transportation (WVDOT) during the late 1990s revealed that the existing bridge deck was in poor condition. In addition, one of the bridge sidewalks had been closed (Whipp 2001). Due to its economic importance to local businesses, the WVDOT decided to replace the bridge with one in which the deck was made of FRP composites manufactured by the pultrusion process. As a result of reducing the weight of the bridge superstructure, it was possible to eliminate the construction of the middle pier from the original bridge and, thus, to replace the two78.66-ft-span bridges with a single 177-ft-span bridge. As of 2015, the WVDOT inspection record showed that the bridge was in good condition. New York Route 418 Bridge over Schroon River (NY-1999-07) is located in the town of Warrensburg of Warren County, New York. The bridge was built in 1933, and its original deck was
97 PREPUBLICATION COPYâUncorrected Proofs constructed from steel gratings filled with concrete. In 2000, the New York State Department of Transportation restored the roadway to unrestricted traffic by replacing the original concrete-infill steel grate deck with a lightweight FRP deck that had a high initial installed cost of $75/ft2. According to state personnel, the periodic inspection report of August 2018 indicated that the FRP deck was still in service and had a Fair rating. The Bridge Street Bridge spanning the Rouge River in Southfield, Michigan (MI-1999-02), was the first U.S. vehicular concrete bridge constructed with objectives of (1) demonstrating the use of noncorrosive FRP prestressed tendons, (2) extending the service life of highway bridges, and (3) reducing construction-related safety concerns and maintenance costs (Grace et al. 2002). In the state's most recent inspection report, several full-length reflective cracks in the deck were observed. However, the bridge was reported to be in âFairâ condition. The information available to the committee does not indicate whether the cracks reported are related to the use of FRP prestressed tendons or are from other sources. Texas FM 1362 over Sue Creek in Burleson County (TX-2001-01) is a two-span bridge that carries the highway over water. The bridge had a low load rating and was in need of strengthening, which was accomplished by using externally bonded FRP reinforcement. The Texas Department of Transportation was able to reduce design and construction time while avoiding road closure (Yang and Jahedkar 2003). CORROSION CONTROL TECHNOLOGIES: CONCRETE REINFORCEMENT 9. Low-chromium steel rebar 10. Galvanized rebar 11. Stainless steel rebar (solid or clad) General Definition Low-chromium steel (also known as ASTM A1035/1035M steel) is a low-carbon, chromium, microcomposite steel. Galvanized steel is a type of steel that has been coated with a layer of zinc coating.
98 PREPUBLICATION COPYâUncorrected Proofs Stainless steel (solid or clad) is an alloy that contains chromium and other elements. All three materials can be used as rebar in concrete bridges. Intended Benefits The main benefits of all three materials when used as rebar is to reduce susceptibility to corrosion that leads to higher bridge maintenance and repair costs from spalling and surface damage to concrete elements. Example Projects The following are examples of IBRC projects that used corrosion-resistant rebar materials: Iowa used low-chromium steel rebar on a bridge constructed in 2001. The structure, eastbound IA 520 over South Beaver Creek, contains a 274-ft-long, 39 ft-wide deck on prestressed concrete I- beams. Low-chromium steel was used for deck reinforcement. The westbound structure was built with conventional epoxy-coated rebar. Electrodes were installed at various locations to monitor for corrosion activity in each direction. In Missouri, two bridges were constructed to evaluate the performance of stainless steel rebar (MO- 2000-01, Route 6 in Galt, and MO-2001-02, Route 86 over Hickory Creek). The control bridge was constructed with epoxy-coated rebar. Performance was documented using nondestructive fiber optic chloride sensors, permeability testing, half-cell potential readings, and visual inspection. A project in Illinois (IL-1999-07, City of Quincy, 18th Street over Cedar Creek) incorporated galvanized rebar in the substructure and deck. Galvanized steel was also used for other applications on the bridge, including as structural steel in girders. CORROSION-CONTROL TECHNOLOGIES: COATING AND ANODES 12. Metallizing 13. Cathodic protection anodes and electrochemical chloride extraction 14. Galvanic protection and other corrosion-control technologies
99 PREPUBLICATION COPYâUncorrected Proofs Definition Metallizing is the application of a sprayed-on galvanic cathodic system as a means of extending the life of embedded reinforcement in structural concrete. The system is typically composed of a zinc-rich thermally applied spray. It also acts to some degree as a coating as it can assist in mitigating the ingress of aggressive elements. Another means of providing galvanic protection to mitigate the spread of corrosion is by connecting sacrificial anodes to the exposed reinforcement steel. Deteriorated areas of concrete are removed and discrete sacrificial anodes, usually zinc, are connected to the exposed reinforcement. The anodes cathodically protect the surrounding concrete area that may be chloride contaminated. Chloride extraction removes chloride ions from contaminated concrete and reestablishes the passivity of steel reinforcement. The extraction is carried out by temporarily applying an electric field between the concrete reinforcing and an externally mounted anode mesh. During the process, chloride ions are transported back through the concrete toward the surface. Intended Benefits The long-term intended benefit of coatings and anode technologies is a reduction in the deteriorating effects of corrosion of steel reinforcement in concrete to enable longer service life. Coatings are also primarily used for existing construction to provide a physical barrier on the surface of repaired concrete to mitigate the further intrusion of moisture, oxygen, and chloride ions into concrete. Coatings can also be used in new construction, but there has not been widespread use for this category. The anode technologies primarily benefit existing concrete construction and are used where corrosion of reinforcing steel has reached the initiation phase. Example Projects Examples of IBRC projects that used coating and anode technologies are the following:
100 PREPUBLICATION COPYâUncorrected Proofs In a project in Illinois (Il-2000-02, I-474 FR 174 to Illinois River), three types of zinc-based metals were tested in a cathodic protection application to protect against corrosion. Evaluation results indicated that the systems did not perform as intended. Electrochemical chloride extraction was used by Minnesota (MN-1999-02, I-94 and Glenwood Avenue) to protect against corrosion in concrete bridge piers. Evaluation found that the process reduced average chloride levels in the treated structures by approximately 50 percent, but that chloride concentrations remained above the acceptable level at some locations. OTHER TECHNOLOGIES 15. High-Performance Steel Definition High-performance steel (HPS) is higher in strength than conventional steel and can improve the cost- effectiveness of steel bridges that take advantage of the superior properties of the material. The three most common types of HPS are: HPS100W, HPS70W, and HPS50W. The number following HPS designates the strength of the material in ksi units. HPS is produced by two different processes: thermo-mechanical control process and quenched and tempered plates. The selected method of manufacture may limit the overall length and thickness of the HPS plates. Intended Benefits The high strength of HPS may allow longer spans without increasing the depth of the beams, eliminating or reducing the number of piers and increasing horizontal clearance while maintaining vertical clearance. Alternatively, the strength of HPS may allow reducing the depth of beams, increasing vertical clearance while maintaining the existing approach roadway profile. Applications for HPS found in the IBRC projects include folded plates, beams and girders, corrugated webs, and an investigation regarding bracing requirements for HPS girders. Advantages of
101 PREPUBLICATION COPYâUncorrected Proofs HPS in IBRC projects, as reported by the states that conducted the projects in the HDR report (HDR 2013), were the following: Higher yield strength. Less material needed to provide required strength. Expected service life as high as 75 years. Ability to accommodate tight vertical clearances. Improved toughness (ability to resist cracking). Example Projects Californiaâs (CA-2001-05) Whiteâs Hill Sidehill Viaduct project used HPS in plate girders of the new bridge for high strength; longer spans allowed for eliminating piers in an active landslide area. Nebraskaâs (NE-2002-01) Highway N-79 over Wagon Tongue Creek project demonstrated the use of folded plate technology in which the bridge girders are fabricated by bending flat plates into an inverted steel box shape. The new shape reduces the cost of girder fabrication and provides an alternative for short span bridges. 16. Accelerated Bridge Construction Definition Accelerated bridge construction (ABC) uses innovative planning, design, materials, and construction methods to reduce the on-site construction time when building new bridges or replacing and rehabilitating existing bridges. ABC technologies can be divided into the categories of project planning, geotechnical solutions, and structural solutions. Examples of technologies in the project planning category include early environmental clearance and permitting, alternative technical concepts, and A plus B bidding, where âAâ is the traditional bid for the contract items and âBâ is the time estimated by the bidder to complete the work. Examples in the geotechnical solutions category include micropiles and lightweight fill.
102 PREPUBLICATION COPYâUncorrected Proofs Examples in the structural solutions category include prefabricated bridge elements such as modular decked beams and precast substructures and prefabricated bridge systems such as superstructure spans moved into place using self-propelled modular transporters or lateral slides. Intended Benefits Bridge owners use ABC in their projects for a number of reasons. These include reduced traffic impacts, reduced on-site construction time, improved work zone safety, improved site constructability, improved material quality and product durability, and minimized environmental impacts. Other reasons include contractor-initiated change, maintenance of existing alignment, limitation of right-of-way take, emergency replacement, ability to use local contractor or county workforce to construct, need to minimize business and other commercial impacts, and maintenance of essential services such as emergency response, police, mail delivery, transit, and garbage collection. Direct construction costs of ABC using prefabricated bridge elements and systems are expected to be more economical than conventional cast-in-place construction after the use of ABC becomes standard practice. A historical example of such cost savings for prefabrication versus cast-in-place construction is the use of pretensioned concrete I-shaped beams, which became standard practice more than half a century ago because of their economy and quality control relative to cast-in-place beams. During the current transition stage of moving standard practice from conventional to ABC, the construction cost of ABC projects is frequently higher. Construction contractorsâ bid prices for ABC projects are frequently higher due to the increased risk perceived by the contractor when using unfamiliar means and methods. Also, additional mobilization costs are incurred with system moves such as when using self-propelled modular transporters to quickly install superstructure spans. Even so, construction contractors are field-changing ABC technologies into conventionally bid projects because of the various advantages offered by ABC, including cost savings for fabricating repetitive precast concrete elements, reduced environmental impacts that can speed a project
103 PREPUBLICATION COPYâUncorrected Proofs and thereby save costs, and increased safety because of the reduced time in the work zone, which can also cut costs. Although a number of reasons may drive the use of ABC, the original and primary reason for the use of ABC is reduced traffic disruption. This is because bridge construction in the United States has changed from the capacity-building focus needed in the mid-1900s when the Interstate was being built to the preservation and maintenance focus required today as the average bridge is reaching its design life and requiring upgrade while still maintaining traffic flow. When user costs are included for high-traffic- volume locations, ABC is usually the least costly solution due to the reduced onsite construction time that reduces traffic delay. Example Projects Two examples of ABC projects in the IBRC program are as follows: Mill Street Bridge over the Lamprey River Epping, New Hampshire. ABC elements for this project are the adjacent pretensioned concrete box beams and the precast concrete abutment walls, wingwalls, and spread footings.. The Live Oak Creek Bridge on Texas State Highway 290 over Live Oak Creek in Crockett County. ABC elements on this project are the full-depth precast concrete deck panels. The superstructure consists of I-shaped pretensioned concrete beams with an 8-in.-thick full-depth precast concrete deck. 17. Monitoring and Instrumentation Technology Definition Monitoring and instrumentation technology includes advanced sensors and data acquisition systems to monitor the performance of new and existing bridges. Data from these systems are used to evaluate the safety and integrity of bridges and to evaluate the progression of deterioration and damage. Data from the in-place sensors are typically stored on site and downloaded at regular intervals over an Internet connection or by wireless transmission for engineering analysis of performance.
104 PREPUBLICATION COPYâUncorrected Proofs Typically, sensors are used to monitor integrity by observing changes in strain, deformation, acceleration, and vibration as affected by vehicular traffic, temperature, and other load effects. Sensors can also be used to assess the fatigue damage that occurs at critical details in structural steel bridge elements. Sensors are also available to monitor changes in corrosion activity of reinforcing steel in concrete and embedded steel piles in soil. Intended Benefits The intended benefit of monitoring and instrumentation of bridges is to establish ongoing performance and safety. Changes in structural behavior can be associated with deterioration or other risk factors that can be evaluated to assess remaining service life and to ensure ongoing safety of a bridge. In recent years, instrumentation and monitoring has evolved to discussion of âsmart bridgesâ in which measured field data is fed into analytical models of anticipated behavior to determine real-time assessment of ongoing safety and integrity. Example Projects Examples of monitoring and instrumentation technology in IBRC projects include the following: New single-span precast prestressed concrete bulb tee bridge on State Route 36 in California (CA- 2001-03) in which passive sensors were cast into the concrete to monitor the ingress of chloride ions into the concrete. The devices consisted of a chloride sensor and a radio-frequency identification tag that could be interrogated remotely. In the replacement of a bridge over Kealakaha Stream on Route 19 in Hawaii (HI-2000-01), a three- span posttensioned concrete segmental bridge, fiber optic sensor technology was installed for dynamic monitoring of deformations and strains during earthquake shaking and traffic vibrations.