Composites are growing in applications such as (top left, clockwise) trench and access covers, 3D printed bridges, FRP rebar and marine pilings. Photo Credit: Fibrelite, CEAD, Composite Advantage, Mateenbar
Composites offer light weight, corrosion resistance, high strength and long lifespan — qualities that make them a natural fit for infrastructure projects. Composites are being used to rehabilitate roads, bridges, water/drainage systems and seawalls, to reinforce concrete and to build resilient structures. And while use is growing, composites still comprise less than 1% by volume of structural materials used in infrastructure.
And yet, in August 2020, the U.S. Congress passed the Composite Standards Act, which will establish a design data clearinghouse to disseminate existing guidelines and standards for using composite materials in infrastructure projects. The bill will also direct the National Institute of Standards and Technology (NIST), in consultation with the National Science Foundation (NSF), to carry out a four-year pilot program to assist in assessing the feasibility of adopting composite technology.
In February 2017, NIST released the “Road Mapping Workshop on Overcoming Barriers to Adoption of Composites in Sustainable Infrastructure.” The top three barriers were defined as training and education, codes and standards, and durability and service life prediction. NIST identified three key activities to overcome these barriers: durability testing, design data clearinghouse, and education and training. The 2020 Composite Standards Act will help to overcome the first two while the education and training could be helped by the Innovative Materials for America’s Growth and Infrastructure Newly Expanded (IMAGINE) Act, introduced in 2018. This legislation, which has yet to be passed, is designed to support education about the benefits and properties of composites, which will help designers and engineers rethink infrastructure projects.
Myriad solutions for bridges
Aging infrastructure continues to offer a potentially huge market for composite materials. Decaying bridges and early deterioration of concrete due to corrosion and failure of steel rebar has been well documented. Conventional repairs are time-consuming and disruptive, with a projected cost in the billions. Compared to the often-seen 25-year life of steel-rebar-reinforced concrete, the typical 100-year life of corrosion-resistant composites offers lifecycle cost advantages, in addition to fast installation, reduced disruption and safety benefits. CW’s March 2020 feature “Building bridges with composites” actually includes updates on a wide variety of infrastructure applications, from composite manhole and trench covers to FRP rebar and marine pilings.
According to an April 2020 report from the American Road & Transportation Builders Association (ARTBA), nearly 230,000 bridges in the U.S. require action — 46,000 are structurally deficient and another 81,000 should be replaced. The critical need for bridges that can resist corrosion and extend useful life are part of a growing awareness that composites can play a key role in rehabilitating crumbling infrastructure.
FiberSPAN composite decking rehabilitates Inman Park MARTA station in Atlanta. Photo Credit: Composite Advantage
Projects such as pedestrian bridges continue to slowly help build this case. In 2020, Composite Advantage’s (Dayton, Ohio, U.S.) FiberSPAN fiber-reinforced polymer (FRP) pedestrian bridge system was chosen by the Battery Park City Authority in New York City for the West Thames pedestrian bridge, replacing a temporary structure put in place after the Sept. 11, 2001 terrorist attacks. FiberSPAN FRP bridge decking was also used to rehabilitate two pedestrian overpasses for MARTA stations in Atlanta, Ga., U.S., replacing heavy, decaying concrete. The lightweight, zero-maintenance composite decks allowed contractors to use the original steel trusses, minimizing the repair and labor costs associated with steel upgrades. Using concrete would also have been prohibitive, because it would have taken longer to pour and caused additional disruption and downtime for the rail station.
Composite Advantage is also supplying the lightweight FiberSPAN-C cantilever system to widen bridge sidewalks. Compared to reinforced concrete panels, the prefabricated FRP panels are 80% lighter and much quicker to install, lowering costs. The material’s corrosion resistance to chemicals and water means zero maintenance for a structure that will last nearly 100 years. Installed to accommodate pedestrians and cyclists, the FRP panels can support a 10,000-pound maintenance vehicle for sidewalks that are 7-10 feet wide and a 20,000-pound ambulance for FRP sidewalks wider than 10 feet.
In 2020, Structural Composites (Melbourne, Fla., U.S.) demonstrated the PPP Composite Bridge deck, which was funded by its U.S. Paycheck Protection Program (PPP) funds. This composite bridge deck for an impoverished area in rural Tennessee features the same construction that was tested and validated in a recent Missouri Department of Transportation (MODOT) study. With a 100-year design life, the PPP deck will help provide access for a community in need and provide the field data necessary to support MODOT’s prior testing efforts, supporting the larger goal of highway bridge decks. The PPP deck will also open a market for the many small rural bridges.
Arch bridge system. AIT Bridges uses braided fiber-reinforced polymer (FRP) tubes filled with concrete to create bridges with spans up to 80 feet. Photo Credit: AIT Bridges
A different approach is the composite arch bridge designed by AIT Bridges (Brewer, Maine, U.S.), which uses concrete-filled composite tubes and FRP decking, which reportedly provides an affordable and superior alternative to traditional steel and concrete for small-to medium-sized bridges. In 2020, AIT delivered a 51-foot-span, 20-foot-wide bridge for a stream crossing on state road SR 203 in Duvall, Wash., U.S. Comprising 12 fiberglass composite arches, this bridge will help restore the 5-foot-wide stream to its previous 20-foot width, aiding the return of fish and other wildlife to the area while meeting local road requirements.
The Stuttgart Stadtbahn bridge uses 72 CFRP cable hangars instead of steel. Photo Credit: Teijin
Carbon fiber-reinforced polymer (CFRP) is also being used in bridges. The Stuttgart Stadtbahn bridge, installed over Germany’s A8 motorway in May 2020, is the world's first network arch bridge that hangs entirely on CFRP tension elements called hangers. The 72 cables are produced by Carbo-Link AG (Fehraltorf, Switzerland) using carbon fiber from Teijin (Wuppertal, Germany). They were actually cheaper than the originally-planned steel cables, enabling the crossing of eight freeway lanes without supporting pillars, while their cross-sectional area was only a quarter compared to the steel solution. Further, due to their light weight, the 72 CFRP tension elements could be installed without a crane by just three construction workers. Incorporation of CFRP in the 127-meter-long railway bridge also pioneers sustainability. The EMPA (Federal Material Testing and Research Institute, Switzerland) proved that CO2 emissions during carbon fiber manufacturing are one-third that of steel, and energy consumption is cut by more than 50%.
FiberCore Europe (Rotterdam, Netherlands) has installed more than 1,000 composite bridges worldwide, but its applications in North America have been limited. To address this, parent company FiberCore Holdings (Rotterdam, Netherlands) signed a license agreement in 2020 with Orenco Composites (Roseburg, Ore., U.S.) for the application of FiberCore’s InfraCore technology in the U.S. This collaboration allows Orenco to apply its extensive knowledge in the engineering and production of large composite products while growing applications for the InfraCore technology.
“Bridges with InfraCore Inside
Additively manufactured bridge. 3D-printed, fiber-reinforced polymer (FRP) pedestrian bridge prototype. Photo Credit: CEAD
Technologies such as additive manufacturing are beginning to play a larger role in infrastructure projects as well. For example, Royal HaskoningDHV (Amersfoort, Netherlands), CEAD (Delft, Netherlands) and DSM (Geleen, Netherlands) have designed a lightweight, 3D-printed, fiber-reinforced polymer (FRP) pedestrian bridge prototype. The bridge consists of a glass fiber-filled thermoplastic PET (DSM’s Arnite) reinforced with continuous glass fibers during the 3D printing process. This combination is said to offer high strength, versatility and sustainability. (see “FRP bridge prototype uses large-scale 3D printing”)
Concrete: glass fiber rebar and CFRP grids
“There is a sea change in the use of composites for infrastructure,” says Gregg Blaszak, co-founder of Coastline Composites (Lancaster, Pa., U.S.), a consulting firm that works with FRP composite manufacturers. “We’ve started to see more engineers really take a hard look at these types of materials because they are, for the most part, maintenance free.” One example, he says, is the increasing number of projects specifying fiberglass rebar for reinforcing concrete structures as an alternative to traditional steel rebar.
“I expect to see the continued development of fiberglass rebar in structural applications and increasingly in flatwork applications,” says Christopher Skinner, vice president, Strategic Marketing, Composites for Owens Corning (Toledo, Ohio, U.S.). “Contractors are seeing increased strength and weight reduction versus steel which significantly increases productivity for their crews. I expect that the durability of composite materials will soon be factored into purchase decisions.”
FRP rebar was chosen to reinforce the Jizan Flood Channel in Saudi Arabia. Photo Credit: Mateenbar
Mateenbar, a supplier for the largest FRP rebar project in the world, the 23-kilometer-long and up to 80-meter-wide Jizan Flood Channel in Saudi Arabia, agrees. “With a long and costly history of corrosion worldwide, steel is no longer viewed as a cost-effective option in aggressive environments,” says Mateenbar CEO Nick Crofts. “The ASTM standards and ACI codes were already in place. Saudi Aramco applied them and mandated FRP rebar which, notably, did not increase the cost of the flood channel.” Crofts points out that the project’s installation of FRP rebar was much faster than what contractors and project managers were accustomed to with steel rebar. He sees the Jizan project as a significant turning point in the infrastructure sector, and the anticipated growth in such projects is already justifying its multiple factories in the U.S. and Saudi Arabia.
But glass fiber is not the only reinforcement that can significantly outperform steel in reinforcing concrete. Since 2004, Altus Group (Greenville, S.C., U.S.), an alliance of precast concrete manufacturers, has used CarbonCast high-performance insulated wall panels to enable construction that is lighter, thinner and stronger than most cast-in-place concrete, solid precast concrete and conventional steel-reinforced precast concrete wall systems. The panels comprise two concrete wythes (faceskins) separated by rigid-foam-insulation boards and connected by C-Grid (Chomarat North America, Williamston, S.C., U.S.) carbon fiber composite grid as shear trusses. Offering insulation values of R-37 or higher, CarbonCast panels can be manufactured from 7 to 12 inches thick with widths up to 15 feet and heights of 50 feet or more. Because carbon fiber is much stronger than steel, panel size can be increased, meaning fewer pieces are produced and transported, so installation is faster and the overall carbon footprint during construction is smaller versus conventional precast systems. As of 2020, more than 1,500 CarbonCast projects had been completed, totaling 45 million square feet (4.2 million square meters).
Germany aims to take this technology even further, using carbon fiber-reinforced plastic (CFRP) grids to reinforce solid concrete construction of all kinds, dramatically reducing thickness, weight, installation and CO2 emissions. Established in 2006, the C³ - Carbon Concrete Composite project is the largest research project in the German construction industry, with more than 150 partners and 300 individual projects. Concrete is the world's most widely used material after water, comprising cement, water and aggregate. The production of cement alone is responsible for 6.5% of total CO2 emissions — about three times that from global aviation.
Carbon fiber lattice grid reinforcing concrete is produced by Hitexbau as rolls or sheets from a highly automated production line enabling large dimensions as well as large volumes. Photo Credit: TU Dresden
The German government announced in June 2020 that it will fund a new carbon fiber-reinforced concrete research center, aimed at increasing steel replacement and overcoming barriers to widespread adoption, including government-approved designs and standards. The German effort is led by long-time TU Dresden carbon fiber- and textile-reinforced concrete researcher, Dr. Manfred Curbach, who claims this technology can reduce concrete material use by 50% and CO2 emissions by up to 70%.
Compared to legacy materials like steel, aluminum, iron and titanium, composites are still coming of age, and only just now are being better understood by design and manufacturing engineers. However, composites’ physical properties — combined with unbeatable light weight — make them undeniably attractive.
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