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The Future of Pre-Stressed Concrete: Replacing Steel and Carbon Rebars with Glass

Reinforced and prestressed concrete (RC and PC) can be used to build many different types of structures and components of structures including slabs, walls, beams, columns, foundations, and frames. RC and PC use steel reinforcement – known as rebar or tendon – embedded within the concrete. The rebars and tendons add strength, allowing the creation of long members and thinner, less-supported slabs

However, steel unalterable properties is that it rusts. When embedded in concrete, steel is protected by the alkaline environment, but moisture, oxygen and chlorides can penetrate concrete catalyzing the corrosion reaction, and ultimately degrading the structure.

Using corrosion-resistant reinforcement represents a widely-recognized effective strategy to ensure long-term durability of reinforced and prestressed concrete structures. PC is a form of concrete which is placed under compression prior to supporting any loads beyond its own weight.

Among composites, carbon fiber reinforced polymer (CFRP) has historically been the preferred solution for prestressed concrete applications. Nevertheless, the high cost of carbon fiber, along with some technological drawbacks, is preventing the wide-spread use of this technology.

Antonio Nanni, PhD, professor and chair of the Department of Civil, Architectural and Environmental Engineering and his team of researchers received funding from the National Cooperative Highway Research Program (NCHRP), Highway IDEA program to develop and test alternatives to CFRPs. “We want to develop a glass fiber reinforced polymer (GFRP) prototype that can effectively replace carbon in mild-prestressed concrete elements,” says Nanni. “Glass fiber is an effective alternative in applications that do not require high levels of concrete prestress.”

“Prestressing, or better pretensioning, as the name suggests, happens before the casting of the concrete,” Nanni explains. “The tendons are stretched before the concrete is cast, and later released once the concrete reaches its required strength. This process results in improved structural capacity and serviceability compared to conventionally reinforced concrete in many situations.”

Prestressed concrete is used in a wide range of building and civil structures where its improved performance can allow longer spans, reduced structural thicknesses, and material savings compared to simple reinforced concrete.

The study will focus on the experimental investigation of GFRP strand protypes, ultimately making them compatible with construction techniques traditionally applied to steel prestressed concrete structures. “The knowledge gained from this study is important not only to the construction industry, but also for Floridian communities,” Nanni explains. “In Florida, 3,600 miles of coast require resilient non-corrosive seawalls. As sea levels rise, coastal communities will increasingly demand sustainable and reliable seawalls that will protect their homes and roads.”

The research project is officially titled, “MILDGLASS: GFRP Strand Prototype for Cost-Effective Mild Prestress.” To learn more about research projects like Nanni’s, please click here.

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