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OR Adopting Concrete Environmental Standards
Earlier this month, the City of Portland, Oregon, announced the approval of recommendations to add Concrete Embodied Carbon Threshold requirements for city construction projects. The recommendations were approved by chief engineers from the Environmental Services, Water and Transportation infrastructure bureaus.
“Most of us don’t think much about the concrete beneath our feet. As the most widely used building material in the world, it has a significant environmental impact,” said Stacey Foreman, who leads the project as the City’s Sustainable Procurement Program Manager. “Portland is a leader in establishing these thresholds and in our approach of bringing multiple stakeholders together to develop them.”
According to the City of Portland’s release, the new standards are in line with its commitment to climate action and leadership.
New City Standards
While cement is the largest component of concrete, cement production along reportedly generates 8% of global greenhouse gas emissions. Lower-carbon mixes can be designed to perform as well, or better, than conventional concrete and are competitive in cost, the city notes.
Concrete is used in a high volume of projects in Portland, including sidewalks and ADA ramps, bicycle and pedestrian paths, fire hydrant pads, retaining walls for parks, and large infrastructure projects such as the Water Bureau’s Bull Run filtration facility and the Bureau of Environmental Services’ wastewater and stormwater infrastructure. The new sustainability standards will accelerate the bureaus’ use of concrete that is durable but manufactured with lower climate impacts.
Projects that are currently underway and are using low-carbon concrete include:
Implementing the new threshold requirements will reportedly result in a range of 3%-35% reduction in greenhouse gas emissions over historically used concrete mixes. For example, a new water reservoir project would result in a 19% reduction in concrete-embodied carbon, saving approximately 3.5 kg-CO2e which is the equivalent of removing 754 gasoline-powered cars of the road.
“This has been a unique and thoughtful process that has taken stakeholder recommendations into account through the implementation at every stage,” said Michael Bernert, Vice President, at Wilsonville Concrete Products, a member of the stakeholder committee. “This process involved engineers, contractors and suppliers, which is not always the case.”
“The Water Bureau’s filtration project has been evaluating ways to maximize the use of low-carbon concrete in an industry where standards are sometimes slow to change,” said Jodie Inman, the Portland Water Bureau’s Chief Engineer.
“These thresholds demonstrate that the City of Portland is a large customer that cares about concrete performance and reducing our carbon footprint. This creates an incentive for suppliers and contractors to provide materials that meet our new, stricter standards.”
The new city standards will take effect in January. Current Sustainable Procurement Initiatives, including the Low-Carbon Concrete Initiative and the new Embodied Carbon Thresholds for Concrete Mixes, can be found here.
Low-Emission Concrete Research
In August, Swedish multinational power company Vattenfall developed what it’s calling a “climate-smart hydropower concrete” that can reportedly use less cement, reducing its overall carbon dioxide emissions by about a quarter.
The company reports by reducing its cement content in structural concrete, there is a direct reduction in the strain on what otherwise would be inputted to the environment. To achieve this reduction in cement quantity and heat development, Vattenfall is using by-products that react with cement in combination with lessons learned from the company’s major periods of expansion in the 1950s and '60s to develop a modern, climate-smart concrete concept.
In wake of the development, Vattenfall is planning to utilize the climate-smart hydropower concrete to replace parts of an existing dam at its Lilla Edet power station in Göta älv near Gothenburg, Sweden. The company plans to complete the dam replacement project by 2024.
In November, a study conducted by current and former researchers at Massachusetts Institute of Technology’s Concrete Sustainability Hub looked at how concrete emissions could be reduced in U.S. buildings and pavements.
The MIT Concrete Sustainability Hub is a team of researchers from several departments across MIT working on concrete and infrastructure science, engineering and economics. Its research is supported by the Portland Cement Association and the Ready Mixed Concrete Research and Education Foundation.
According to their findings, the team predicts that concrete buildings and pavement emissions could be reduced by roughly 50%, even as concrete use increases. Currently, concrete production is estimated to contribute around 1% of emissions in the nation and remains one of several carbon-intensive industries globally.
In predicting that the use of the material will only continue to increase in the future, researchers looked at how environmental impacts of concrete could be reduced.
To estimate how greenhouse gas reduction strategies could minimize the cumulative emissions of each sector and how they compare to national GHG reduction targets, researchers took extensive life-cycle assessments of the structures and pavements. In doing so, the team reported that if reduction strategies were implemented, the emissions for pavements and buildings between 2016 and 2050 could fall by up to 65% and 57%, respectively.
Most recently, in what is being touted as a “world’s first,” three engineers from Cambridge, England, have reportedly created a zero-emissions cement. The trio, comprised of Dr. Cyrille Dunant, Dr. Pippa Horton and Julian Allwood, have already filed a patent for the material and have since been awarded additional research funding.
Inspired by the chemistry involved with used cement and lime-flux from conventional steel recycling processes, Dunant embarked on the invention of Cambridge Electric Cement. According to reports, the zero-emissions cement is made by utilizing a recycling loop that eliminates the emissions of cement production, saves raw materials and reduces the emissions needed to make lime-flux.
To create the material, the engineers started with demolition waste from an old building, which is made up of stones, sand, cement powder and water. Once the team is able to gather the old cement power, it is used to replace lime-flux in steel recycling.
Then, as the steel melts, the flux forms a slag that floats on the liquid steel, to protect it from oxygen in the air. After the recycled steel is tapped off, the liquid slag can cool rapidly in air. The remaining material is ground into a powder, which the team argues is virtually identical to the clinker, or the basis of the new cement.
