Next-Generation Reinforced Concrete Supports Structures, Emits Less CO2

Amir Hajiesmaeili (pictured) testing the properties of a new material designed to reinforce concrete structures. Photo courtesy of Alain Herzog/EPFL.

A researcher from École Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland, has created a modified version of an ultra high-performance fiber-reinforced concrete (UHPFRC) designed to extend the life span of bridges, monuments, and other structures.

The newest UHPFRC material was developed by Amir Hajiesmaeili of EPFL’s Laboratory for Maintenance and Safety of Structures (MCS). Hajiesmaeili’s next-generation material retains the mechanical properties of conventional concrete, but exchanges steel fiber for stiff synthetic polyethylene fiber and replaces half of the cement mixture with limestone. “The trick was to find a material that’s very strong and produces the right consistency,” says Hajiesmaeili.

As a result of these modifications, UHPFRC is 10% lighter and releases 60-70% less carbon dioxide (CO2) than the previous generation of fiber-reinforced concrete. Over the past 15 years, the MCS lab has overseen more than 100 projects to reinforce bridges and buildings in Switzerland that use first-generation UHPFRC. “With this material, we can add value to age-old structures by ensuring they will last for a long, long time,” says MCS Head Eugen Brühwiler.

After earning a Master’s in civil engineering, Hajiesmaeili joined EPFL to complete his PhD. He worked in the Swiss National Science Foundation's NRP “Energy Turnaround" project, where he spent nearly four years “cooking” a modified version of UHPFRC that retained the strength of the previous generation material but produced less CO2. “After three years of this trial-and-error,” says Hajiesmaeili, “we finally found the right recipe—one that also meets stringent building standards.”

As a testament to his efforts, Hajiesmaeili’s UHPFRC material is scheduled to be used for a 2020 bridge reinforcement project. “This solution is also much more financially and environmentally sound than razing and rebuilding existing structures like bridges and historical monuments,” says Brühwiler.

Source: École Polytechnique Fédérale de Lausanne,