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Bendable concrete and other CO2 infused cement mixes could dramatically reduce global emissions
The bendable concrete created at the University of Michigan allows for thinner structures with less need for steel reinforcement. Joseph Xu / University of Michigan College of Engineering One of the biggest contributors to climate change is right under your feet, and its transformation could be a powerful solution to preventing greenhouse gases from entering the atmosphere. The production of cement, the binding element of concrete, accounted for 7% of total global carbon dioxide emissions in 2018. Concrete is one of the most used resources on Earth, with around 26 billion tonnes produced worldwide each year. . This production is not expected to slow down for at least two more decades. Given the scale of the industry and its greenhouse gas emissions, technologies that can reinvent concrete could have profound impacts on climate change. As engineers working on infrastructure and construction issues, we have engineered the next generation of concrete technology that can reduce the carbon footprint of infrastructure and increase sustainability. This includes CO2 impregnated concrete which traps greenhouse gases and can be stronger and even pliable. The industry is ripe for radical change, especially with the Biden administration’s promise to invest heavily in infrastructure projects and cut US emissions at the same time. However, to make CO2 work in concrete on a large scale in a way that drastically reduces emissions, all related emissions must be taken into account. Rethinking Concrete Concrete is made up of aggregate materials – mostly rocks and sand – as well as cement and water. Because about 80% of concrete’s carbon footprint comes from cement, researchers are striving to find alternative materials. Industrial byproducts such as iron slag and coal fly ash are now frequently used to reduce the amount of cement needed. The resulting concrete can have considerably lower emissions due to this change. Alternative binders, such as calcined calcareous clay, can also reduce cement usage. A study found that using limestone and calcined clay could reduce emissions by at least 20% while lowering production costs. Besides the development of mixed cements, researchers and companies are focusing on ways to use the captured CO2 as an ingredient in the concrete itself, locking it in and preventing it from entering the atmosphere. The CO2 can be added as aggregates – or injected during mixing. Carbonation hardening, also known as CO2 hardening, can also be used after concrete has been poured. These processes convert CO2 from a gas into a mineral, creating solid carbonates which can also improve the strength of concrete. This means that structures may need less cement, which reduces the amount of associated emissions. Companies such as CarbonCure and Solidia have developed technologies to use these processes for poured concrete on construction sites and in precast concrete, such as cinder blocks and other building materials. Carbon dioxide can constitute a significant percentage of the mass of concrete. Lucca Henrion / University of Michigan, CC BY-ND The Kitahama Building, the tallest residential tower in Japan, is constructed with pliable concrete to withstand earthquakes. MC681 / Wikimedia Commons At the University of Michigan, we’re working on composites that produce a pliable concrete material that allows for thinner, less brittle structures that require less steel reinforcement, further reducing associated carbon emissions. The material can be designed to maximize the amount of CO2 it can store by using smaller particles that easily react with CO2, turning it into a mineral. The CO2-based bendable concrete can be used for general buildings, water and energy infrastructure, as well as transport infrastructure. Bendable concrete was used in the 61-story Kitahama Tower in Osaka, Japan, and road bridge slabs in Ypsilanti, Michigan. The Lifecycle Emissions Challenge These advanced technologies may begin to tackle the carbon footprint of concrete infrastructure, but barriers still exist. In a study released on February 8, three of us looked at life cycle emissions from infusing CO2 into concrete and found that the estimates did not always take into account emissions from capture, transport and use of CO2. Together with colleagues, we have developed strategies to ensure that carbon drying has a strong emissions benefit. Overall, we recommend developing a standard CO2 hardening protocol. Laboratory experiments show that CO2 hardening can improve the strength and durability of concrete, but results vary depending on specific hardening procedures and concrete mixes. Research can improve the conditions and timing of steps in the curing process to increase concrete performance. Electricity consumption – the biggest source of emissions during curing – can also be reduced by streamlining the process and possibly using waste heat. [Deep knowledge, daily. Sign up for The Conversation’s newsletter.] Advanced concrete mixes, bendable concrete in particular, are already starting to solve these problems by increasing durability. Merging of infrastructure and climate policy In 2020, a wide range of companies announced measures to reduce their emissions. However, government investment and procurement policies are still needed to transform the construction industry. Local governments are taking the first steps. “Low carbon embedded concrete” rules and projects to reduce the amount of cement in concrete have sprung up across the country, including in Marin County, California; Hastings-on-Hudson, New York; and a sidewalk driver in Portland, Oregon. In New York and New Jersey, lawmakers proposed state-level policies that would offer price discounts in the bidding process for proposals with the lowest emissions of concrete. These policies could serve as a model for reducing carbon emissions from the production of concrete and other building materials. Much of North America’s infrastructure is in poor condition. Achim Herring / Wikimedia Commons, CC BY Nationally, the crumbling of federally managed infrastructure has been a growing crisis. The Biden administration could begin to tackle these issues, as well as climate change, and create jobs through a strategic infrastructure program. Transportation Secretary Pete Buttigieg recently said there was “enormous potential for job creation, equity and climate success when it comes to advancing America’s infrastructure.” This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Lucca Henrion, University of Michigan; Duo Zhang, University of Michigan; Victor C. Li, University of Michigan, and Volker Sick, University of Michigan Read more: Biden plans to tackle climate change in ways that no US president has done before. Some cities are starting to adapt Lucca Henrion is working as a researcher in the Global CO2 Initiative at the University of Michigan. He volunteers with the Open Air Collective. Duo Zhang works as an Assistant Research Scientist at the University of Michigan. He is researching carbon-sequestering concrete materials. Victor C. Li receives research funding from the Department of Energy (ARPA-E) and Aramco Corporation. He is James R. Rice Professor Emeritus at the University of Michigan, Ann Arbor. Professor Li heads the Center for Low Carbon Built Environment (CLCBE) at the University of Michigan. Volker Sick receives funding from the US Department of Energy and the University of Michigan’s Global CO2 Initiative.
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