Architecture

Bottles to bridges: Glass-based concrete makes for a greener crossing

Bottles to bridges: Glass-based concrete makes for a greener crossing
The Darwin Bridges project was constructed using concrete containing recycled glass equivalent to 70,000 wine bottles
The Darwin Bridges project was constructed using concrete containing recycled glass equivalent to 70,000 wine bottles
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The Darwin Bridges project was constructed using concrete containing recycled glass equivalent to 70,000 wine bottles
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The Darwin Bridges project was constructed using concrete containing recycled glass equivalent to 70,000 wine bottles
The Darwin Bridges are located on Montreal's Nuns' Island and replace a pair of bridges that previously stood on the site for almost 60 years
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The Darwin Bridges are located on Montreal's Nuns' Island and replace a pair of bridges that previously stood on the site for almost 60 years
The Darwin Bridges have improved accessibility for pedestrians and cyclists
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The Darwin Bridges have improved accessibility for pedestrians and cyclists
The Darwin Bridges' concrete utilizes 10% finely ground recycled glass in place of traditional cement, reducing its carbon emissions significantly
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The Darwin Bridges' concrete utilizes 10% finely ground recycled glass in place of traditional cement, reducing its carbon emissions significantly
The Darwin Bridges are expected to last over 125 years of operation
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The Darwin Bridges are expected to last over 125 years of operation
Darwin Bridges' crossings span a length of 37 m (121 ft) each
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Darwin Bridges' crossings span a length of 37 m (121 ft) each
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Production of the cement used in concrete is a major cause of CO2 emissions worldwide, so Provencher Roy architects used a greener alternative for a pair of bridges in Canada. The bridges were built from concrete that incorporated locally sourced recycled glass, reducing its greenhouse gas footprint significantly.

The Darwin Bridges are located on Nuns' Island in Montreal, and replaced a pair of bridges that had been used for almost 60 years. Their sidewalks were inadequately narrow and the passage under the crossings was starting to collect puddles of water.

The new bridges were built using cast-in-place concrete, which utilized a mixture of 10% finely ground recycled glass as a binder to replace the cement. Provencher Roy says it reduced greenhouse gas emissions by an impressive 40 tonnes (44 US tons). However, it's worth noting that there are other teams using glass to make greener concrete, including the Nanyang Technological University and Deakin University – so this is not a totally new idea, but a new application of it.

"This ground-breaking project builds upon 17 years of research on the integration of ground glass into civic infrastructures, in collaboration with the Université de Sherbrooke and Ville de Montréal," stated Provencher Roy. "A world premiere, this 100% Québécois patented GGP [ground-glass pozzolans] invention was added as a ternary binder, enabling the project to make a direct environmental impact by reducing greenhouse gas emissions. The GGP used replaced the cement typically used, constituting 40,000 kilograms [88,185 lb] of locally recycled glass and representing 70,000 wine bottles."

The Darwin Bridges' concrete utilizes 10% finely ground recycled glass in place of traditional cement, reducing its carbon emissions significantly
The Darwin Bridges' concrete utilizes 10% finely ground recycled glass in place of traditional cement, reducing its carbon emissions significantly

The gently curving new bridges – each of which spans a length of 37 m (121 ft) – are a major improvement over their predecessors. They boast improved safety and accessibility for pedestrians and cyclists, with new LED lighting and wider walkways. Additionally, a new lush greenery-filled area was added to enliven the exposed concrete.

The new Darwin Bridges have been in use for a while now, but only recently officially opened. All being well, they're expected to remain in operation for over 125 years.

Source: Provencher Roy

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3 comments
3 comments
Karmudjun
Interesting. I have heard of glass as an ingredient but have no reference to it's subsequent concrete characteristics or cost profile. Presumably the glass is practically free for the grinding which requires greenhouse gas energy in our current energy model. Is this a cost prohibitive formulation? Is this a weaker or stronger building medium? Are there self-healing (as in long-term Roman style concrete crack resolution due to their formulations?) properties in GGP, or does it have a limited lifespan like current concrete? I guess I'll have to do my own research, but thanks for the article. I do see from the source article they anticipate 125 yr. lifespan rather than 75 yr. w/ traditional concrete.
TechGazer
Are the glass particles actually functioning as a binder (chemically bonding), or is their addition just increasing the strength of the mix enough that they can use less cement? If they mixed the glass with sand and stones, would the glass bind those aggregates together even weakly?
Peter Forte
As stated, ground glass is used as a binder to replace concrete. Alternative energy could be used to grind the glass. Apart from building construction, there are many different uses for this, down to pedestrian walkways.