The markets: Civil infrastructure (2017)

Aging infrastructure offers a potentially huge market for composite materials but civil projects are publicly owned, subject to regulatory oversight and, therefore, decision makers are change-resistant and decisions are, in part, cost-driven. Composites nevertheless continue to make headway.

Aging infrastructure offers a potentially huge market for composite materials. According to a report by the coalition Transportation for America (Washington, DC, US), titled The Fix We’re In For: The State of our Nation’s Busiest Bridges, there are 69,223 structurally deficient highway bridges in the US alone — 11.5% of all US highway bridges — that require rehabilitation or replacement. These numbers have stimulated development of a number of composites-enabled technologies.

            The early deterioration of concrete due to the corrosion and failure of steel rebar has been well documented. Conventional repairs could cost billions. In many locales, the useful life of corrosion-prone steel-rebar-reinforced concrete is limited to 25 years, rather than the 75-100 years once promised by its advocates. Therefore, the lifecycle cost advantages, not to mention the safety benefits, of using composite rebar continue to overcome resistance among change-averse municipalities. That said, once significant activity among composites fabricators looking to replace entire bridge structures has quieted, replaced by a more conservative focus on replacing vulnerable, corrosion-prone concrete bridge decks with robust composite replacements on steel truss bridges.

Progress is still halting. Faced with limited annual budgets, state and local transportation executives have the choice to replace a certain number of bridges with concrete that could last 30-40 years at best, or half as many using composites that could last up to 100 years. In both cases, their careers will be long finished before anyone will hold them to account, so the easy answer is twice as many low-cost bridges. In the bridge world, therefore, says Scott Reeve, president of Composite Advantage LLC (Dayton, OH, US), the day cannot be won on the classic lifecycle-cost argument alone. Reeve, whose company is among the most successful fabricators of composite bridge decks, confirms that the “upfront cost” problem continues to exist. “A composite vehicle deck is about twice the price of a concrete deck,” he points out. “Until we can get that differential down to around 15%, market penetration will remain slow.”

But projects still make the news, particularly in pedestrian bridges. In 2016, a fully bio-composite footbridge, for example, has been installed on the Eindhoven University of Technology campus in The Netherlands. This 14m long “bio-bridge” is made from a hemp- and flax-fiber base and is the result of collaboration between a large number of knowledge institutions and companies. Students from TU/e, Delft University of Technology (TU Delft, Delft, The Netherlands) and the Eindhoven region’s vocational colleges, among others, worked on building the bridge. Fibers of hemp and flax are the basic material of the bridge. In order to develop the bio-composite, the fibers were stuck to a biological PLA foam (polylactic acid) core and then a bio-resin was sucked into the fiber layers using a vacuum, which produced a very strong support beam when hardened.

The plan is for this bridge to remain up for a year and about 28 sensors in the bridge will measure the bending that occurs. The initiators hope that this bridge will show the potential of bio-composite as a sustainable alternative for existing construction materials. The bridge is the result of the 4TU Lighthouse research project “B3: Fully Bio-Based Composite Pedestrian Bridge.” Partners in The Netherlands were TU/e (chair Innovative Structural Design), TU Delft, composite company NPSP Composieten BV (Werkendam) and the Center of Expertise Biobased Economy, a collaboration between Tilburg-based Avans Hogeschool and HZ University of Applied Sciences (Vlissingen). The project was co-funded by Stichting Innovatie Alliantie (SIA, The Hague).

Composites are, however, beginning to compete directly with concrete and demonstrate such value in marine civil infrastructure applications. A case in point is the all-composite dock system for the city of Jacksonville’s (FL, US) Fire & Rescue Department (JFRD) Station 40. Like the new station structures, the proposed dock structures to be able to survive Category 3 hurricanes — 205-241 kph winds and 2.74-3.66m of sea storm surge. Early bids, based on reinforced concrete, were up to 50% over a budget determined by a federally funded Homeland Security grant. Register Marine (Jacksonville, FL, US) reoriented the program to use pultruded glass/polyester composite pilings, beams and planking to build fixed and floating dock structures and were able to meet all of the technical and grant-funding requirements, including budget and timeline (see “Related Suppliers").

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