Canadian architectural form Provencher Roy used concrete with incorporated locally sourced recycled glass to reduce the carbon footprint of two bridges.

The new bridges replace the Darwin Bridges on Nuns’ Island in Montreal, which had served for 60 years. The new ones were built using cast-in-place concrete. In the mixture, 10 per cent ground recycled glass (ground glass pozzolan or GGP) was used, to replace part of the cement as a binder. This came down to 40,000 kilograms of locally recycled glass for the bridges, the equivalent of 70,000 wine bottles. Using glass instead of cement is said to have reduced the emissions by 40 tonnes (44 US tons).

The architectural firm claims to be the first in the world to use glass powder cement. The material is patented and derives from 17 years of research carried out by the University of Sherbrooke and Ville de Montréal.

Each of the two bridges spans a length of 37 metres (121 ft). They have improved safety and accessibility for pedestrians and cyclist, LED lighting, and wider walkways compared to the old bridges. The bridges’ lifespan is expected to extend over 125 years, compared to 75 years for a conventional concrete structure.

Photos: Stéphane Brügger