Concrete footbridge built with concrete from a renovated building

Researchers from EPFL have created a prototype footbridge that used reinforced concrete blocks without pouring concrete for the building project. The concrete blocks were cut from the walls of a building being renovated. The project marks the first time concrete has been recycled in this way.

The concrete walls of the building under renovation were cut into individual blocks on-site and then built into a prestressed arch. Concrete is the most common building material in the world, and as such, has a significant carbon footprint. The project is part of an initiative that aims to shrink the construction industry's carbon footprint by utilizing a circular approach to concrete.

The footbridge will be inaugurated on October 11 at the Smart Living Lab in Fribourg. EPFL assistant professor Corentin Fivet said there is a hesitancy to reuse concrete due to a variety of concerns. One goal of the project was to show that type of concern was unfounded. Part of the purpose of the experiment was to show that repurposed concrete was as reliable and useful as new concrete blocks.

The footbridge built using the repurposed concrete is 10 meters wide and constructed from 25 blocks of concrete cut from walls that would have been torn down and discarded. However, project researchers say if concrete is to be reused effectively, the industry needs new design methods to use existing concrete blocks rather than pouring new ones.

One challenge with the new method is that the properties of existing concrete blocks can't be known ahead of time, unlike pouring new concrete. The team created a computer program automating the process of selecting reclaimed elements from available stock, helping to minimize the carbon footprint of the new construction. On the example project, engineers used 20-centimeter thick concrete blocks, using mortar in some places to smooth out differences in dimensions.