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    Enabling a circular economy in the built environment

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    The amount of waste generated by the construction sector underscores an urgent need for embracing circularity — a sustainable model that aims to minimize waste and maximize material efficiency through recovery and reuse — in the built environment: 600 million tons of construction and demolition waste was produced in the United States alone in 2018, with 820 million tons reported in the European Union, and an excess of 2 billion tons annually in China.This significant resource loss embedded in our current industrial ecosystem marks a linear economy that operates on a “take-make-dispose” model of construction; in contrast, the “make-use-reuse” approach of a circular economy offers an important opportunity to reduce environmental impacts.A team of MIT researchers has begun to assess what may be needed to spur widespread circular transition within the built environment in a new open-access study that aims to understand stakeholders’ current perceptions of circularity and quantify their willingness to pay.“This paper acts as an initial endeavor into understanding what the industry may be motivated by, and how integration of stakeholder motivations could lead to greater adoption,” says lead author Juliana Berglund-Brown, PhD student in the Department of Architecture at MIT.Considering stakeholders’ perceptionsThree different stakeholder groups from North America, Europe, and Asia — material suppliers, design and construction teams, and real estate developers — were surveyed by the research team that also comprises Akrisht Pandey ’23; Fabio Duarte, associate director of the MIT Senseable City Lab; Raquel Ganitsky, fellow in the Sustainable Real Estate Development Action Program; Randolph Kirchain, co-director of MIT Concrete Sustainability Hub; and Siqi Zheng, the STL Champion Professor of Urban and Real Estate Sustainability at Department of Urban Studies and Planning.Despite growing awareness of reuse practice among construction industry stakeholders, circular practices have yet to be implemented at scale — attributable to many factors that influence the intersection of construction needs with government regulations and the economic interests of real estate developers.The study notes that perceived barriers to circular adoption differ based on industry role, with lack of both client interest and standardized structural assessment methods identified as the primary concern of design and construction teams, while the largest deterrents for material suppliers are logistics complexity, and supply uncertainty. Real estate developers, on the other hand, are chiefly concerned with higher costs and structural assessment. Yet encouragingly, respondents expressed willingness to absorb higher costs, with developers indicating readiness to pay an average of 9.6 percent higher construction costs for a minimum 52.9 percent reduction in embodied carbon — and all stakeholders highly favor the potential of incentives like tax exemptions to aid with cost premiums.Next steps to encourage circularityThe findings highlight the need for further conversation between design teams and developers, as well as for additional exploration into potential solutions to practical challenges. “The thing about circularity is that there is opportunity for a lot of value creation, and subsequently profit,” says Berglund-Brown. “If people are motivated by cost, let’s provide a cost incentive, or establish strategies that have one.”When it comes to motivating reasons to adopt circularity practices, the study also found trends emerging by industry role. Future net-zero goals influence developers as well as design and construction teams, with government regulation the third-most frequently named reason across all respondent types.“The construction industry needs a market driver to embrace circularity,” says Berglund-Brown, “Be it carrots or sticks, stakeholders require incentives for adoption.”The effect of policy to motivate change cannot be understated, with major strides being made in low operational carbon building design after policy restricting emissions was introduced, such as Local Law 97 in New York City and the Building Emissions Reduction and Disclosure Ordinance in Boston. These pieces of policy, and their results, can serve as models for embodied carbon reduction policy elsewhere.Berglund-Brown suggests that municipalities might initiate ordinances requiring buildings to be deconstructed, which would allow components to be reused, curbing demolition methods that result in waste rather than salvage. Top-down ordinances could be one way to trigger a supply chain shift toward reprocessing building materials that are typically deemed “end-of-life.”The study also identifies other challenges to the implementation of circularity at scale, including risk associated with how to reuse materials in new buildings, and disrupting status quo design practices.“Understanding the best way to motivate transition despite uncertainty is where our work comes in,” says Berglund-Brown. “Beyond that, researchers can continue to do a lot to alleviate risk — like developing standards for reuse.”Innovations that challenge the status quoDisrupting the status quo is not unusual for MIT researchers; other visionary work in construction circularity pioneered at MIT includes “a smart kit of parts” called Pixelframe. This system for modular concrete reuse allows building elements to be disassembled and rebuilt several times, aiding deconstruction and reuse while maintaining material efficiency and versatility.Developed by MIT Climate and Sustainability Consortium Associate Director Caitlin Mueller’s research team, Pixelframe is designed to accommodate a wide range of applications from housing to warehouses, with each piece of interlocking precast concrete modules, called Pixels, assigned a material passport to enable tracking through its many life cycles.Mueller’s work demonstrates that circularity can work technically and logistically at the scale of the built environment — by designing specifically for disassembly, configuration, versatility, and upfront carbon and cost efficiency.“This can be built today. This is building code-compliant today,” said Mueller of Pixelframe in a keynote speech at the recent MCSC Annual Symposium, which saw industry representatives and members of the MIT community coming together to discuss scalable solutions to climate and sustainability problems. “We currently have the potential for high-impact carbon reduction as a compelling alternative to the business-as-usual construction methods we are used to.”Pixelframe was recently awarded a grant by the Massachusetts Clean Energy Center (MassCEC) to pursue commercialization, an important next step toward integrating innovations like this into a circular economy in practice. “It’s MassCEC’s job to make sure that these climate leaders have the resources they need to turn their technologies into successful businesses that make a difference around the world,” said MassCEC CEO Emily Reichart, in a press release.Additional support for circular innovation has emerged thanks to a historic piece of climate legislation from the Biden administration. The Environmental Protection Agency recently awarded a federal grant on the topic of advancing steel reuse to Berglund-Brown — whose PhD thesis focuses on scaling the reuse of structural heavy-section steel — and John Ochsendorf, the Class of 1942 Professor of Civil and Environmental Engineering and Architecture at MIT.“There is a lot of exciting upcoming work on this topic,” says Berglund-Brown. “To any practitioners reading this who are interested in getting involved — please reach out.”The study is supported in part by the MIT Climate and Sustainability Consortium. 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      Admir Masic: Using lessons from the past to build a better future

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      As a teenager living in a small village in what was then Yugoslavia, Admir Masic witnessed the collapse of his home country and the outbreak of the Bosnian war. When his childhood home was destroyed by a tank, his family was forced to flee the violence, leaving their remaining possessions to enter a refugee camp in northern Croatia.It was in Croatia that Masic found what he calls his “magic.”“Chemistry really forcefully entered my life,” recalls Masic, who is now an associate professor in MIT’s Department of Civil and Environmental Engineering. “I’d leave school to go back to my refugee camp, and you could either play ping-pong or do chemistry homework, so I did a lot of homework, and I began to focus on the subject.”Masic has never let go of his magic. Long after chemistry led him out of Croatia, he’s come to understand that the past holds crucial lessons for building a better future. That’s why he started the MIT Refugee Action Hub (now MIT Emerging Talent) to provide educational opportunities to students displaced by war. It’s also what led him to study ancient materials, whose secrets he believes have potential to solve some of the modern world’s most pressing problems.“We’re leading this concept of paleo-inspired design: that there are some ideas behind these ancient materials that are useful today,” Masic says. “We should think of these materials as a source of valuable information that we can try to translate to today. These concepts have the potential to revolutionize how we think about these materials.”One key research focus for Masic is cement. His lab is working on ways to transform the ubiquitous material into a carbon sink, a medium for energy storage, and more. Part of that work involves studying ancient Roman concrete, whose self-healing properties he has helped to illuminate.At the core of each of Masic’s research endeavors is a desire to translate a better understanding of materials into improvements in how we make things around the world.“Roman concrete to me is fascinating: It’s still standing after all this time and constantly repairing,” Masic says. “It’s clear there’s something special about this material, so what is it? Can we translate part of it into modern analogues? That’s what I love about MIT. We are put in a position to do cutting-edge research and then quickly translate that research into the real world. Impact for me is everything.”Finding a purposeMasic’s family fled to Croatia in 1992, just as he was set to begin high school. Despite excellent grades, Masic was told Bosnian refugees couldn’t enroll in the local school. It was only after a school psychologist advocated for Masic that he was allowed to sit in on classes as a nonmatriculating student.Masic did his best to be a ghost in the back of classrooms, silently absorbing everything he could. But in one subject he stood out. Within six months of joining the school, in January of 1993, a teacher suggested Masic compete in a local chemistry competition.“It was kind of the Olympiads of chemistry, and I won,” Masic recalls. “I literally floated onto the stage. It was this ‘Aha’ moment. I thought, ‘Oh my god, I’m good at chemistry!’”In 1994, Masic’s parents immigrated to Germany in search of a better life, but he decided to stay behind to finish high school, moving into a friend’s basement and receiving food and support from local families as well as a group of volunteers from Italy.“I just knew I had to stay,” Masic says. “With all the highs and lows of life to that point, I knew I had this talent and I had to make the most of it. I realized early on that knowledge was the one thing no one could take away from me.”Masic continued competing in chemistry competitions — and continued winning. Eventually, after a change to a national law, the high school he was attending agreed to give him a diploma. With the help of the Italian volunteers, he moved to Italy to attend the University of Turin, where he entered a five-year joint program that earned him a master’s degree in inorganic chemistry. Masic stayed at the university for his PhD, where he studied parchment, a writing material that’s been used for centuries to record some of humanity’s most sacred texts.With a classmate, Masic started a company that helped restore ancient documents. The work took him to Germany to work on a project studying the Dead Sea Scrolls, a set of manuscripts that date as far back as the third century BCE. In 2008, Masic joined the Max Planck Institute in Germany, where he also began to work with biological materials, studying water’s interaction with collagen at the nanoscale.Through that work, Masic became an expert in Raman spectroscopy, a type of chemical imaging that uses lasers to record the vibrations of molecules without leaving a trace, which he still uses to characterize materials.“Raman became a tool for me to contribute in the field of biological materials and bioinspired materials,” Masic says. “At the same time, I became the ‘Raman guy.’ It was a remarkable period for me professionally, as these tools provided unparalleled information and I published a lot of papers.”After seven years at Max Planck, Masic joined the Department of Civil and Environmental Engineering (CEE) at MIT.“At MIT, I felt I could truly be myself and define the research I wanted to do,” Masic says. “Especially in CEE, I could connect my work in heritage science and this tool, Raman spectroscopy, to tackle our society’s big challenges.”From labs to the worldRaman spectroscopy is a relatively new approach to studying cement, a material that contributes significantly to carbon dioxide emissions worldwide. At MIT, Masic has explored ways cement could be used to store carbon dioxide and act as an energy-storing supercapacitor. He has also solved ancient mysteries about the lasting strength of ancient Roman concrete, with lessons for the $400 billion cement industry today.“We really don’t think we should replace ordinary Portland cement completely, because it’s an extraordinary material that everyone knows how to work with, and industry produces so much of it. We need to introduce new functionalities into our concrete that will compensate for cement’s sustainability issues through avoided emissions,” Masic explains. “The concept we call ‘multifunctional concrete’ was inspired by our work with biological materials. Bones, for instance, sacrifice mechanical performance to be able to do things like self-healing and energy storage. That’s how you should imagine construction over next 10 years or 20 years. There could be concrete columns and walls that primarily offer support but also do things like store energy and continuously repair themselves.”Masic’s work across academia and industry allows him to apply his multifunctional concrete research at scale. He serves as a co-director of the MIT ec3 hub, a principal investigator within MIT Concrete Sustainability Hub, and a co-founder and advisor at the technology development company DMAT.“It’s great to be at the forefront of sustainability but also to be directly interacting with key industry players that can change the world,” Masic says. “What I appreciate about MIT is how you can engage in fundamental science and engineering while also translating that work into practical applications. The CSHub and ec3 hub are great examples of this. Industry is eager for us to develop solutions that they can help support.”And Masic will never forget where he came from. He now lives in Somerville, Massachusetts, with his wife Emina, a fellow former refugee, and their son, Benjamin, and the family shares a deep commitment to supporting displaced and underserved communities. Seven years ago, Masic founded the MIT Refugee Action Hub (ReACT), which provides computer and data science education programs for refugees and displaced communities. Today thousands of refugees apply to the program every year, and graduates have gone on to successful careers at places like Microsoft and Meta. The ReACT program was absorbed by MIT’s Emerging Talent program earlier this year to further its reach.“It’s really a life-changing experience for them,” Masic says. “It’s an amazing opportunity for MIT to nurture talented refugees around the world through this simple certification program. The more people we can involve, the more impact we will have on the lives of these truly underserved communities.” More

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      in Environment

      MIT announces 2024 Bose Grants

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      MIT Provost Cynthia Barnhart announced four Professor Amar G. Bose Research Grants to support bold research projects across diverse areas of study, including a way to generate clean hydrogen from deep in the Earth, build an environmentally friendly house of basalt, design maternity clothing that monitors fetal health, and recruit sharks as ocean oxygen monitors.

      This year’s recipients are Iwnetim Abate, assistant professor of materials science and engineering; Andrew Babbin, the Cecil and Ida Green Associate Professor in Earth, Atmospheric and Planetary Sciences; Yoel Fink, professor of materials science and engineering and of electrical engineering and computer science; and Skylar Tibbits, associate professor of design research in the Department of Architecture.

      The program was named for the visionary founder of the Bose Corporation and MIT alumnus Amar G. Bose ’51, SM ’52, ScD ’56. After gaining admission to MIT, Bose became a top math student and a Fulbright Scholarship recipient. He spent 46 years as a professor at MIT, led innovations in sound design, and founded the Bose Corp. in 1964. MIT launched the Bose grant program 11 years ago to provide funding over a three-year period to MIT faculty who propose original, cross-disciplinary, and often risky research projects that would likely not be funded by conventional sources.

      “The promise of the Bose Fellowship is to help bold, daring ideas become realities, an approach that honors Amar Bose’s legacy,” says Barnhart. “Thanks to support from this program, these talented faculty members have the freedom to explore their bold and innovative ideas.”

      Deep and clean hydrogen futures

      A green energy future will depend on harnessing hydrogen as a clean energy source, sequestering polluting carbon dioxide, and mining the minerals essential to building clean energy technologies such as advanced batteries. Iwnetim Abate thinks he has a solution for all three challenges: an innovative hydrogen reactor.

      He plans to build a reactor that will create natural hydrogen from ultramafic mineral rocks in the crust. “The Earth is literally a giant hydrogen factory waiting to be tapped,” Abate explains. “A back-of-the-envelope calculation for the first seven kilometers of the Earth’s crust estimates that there is enough ultramafic rock to produce hydrogen for 250,000 years.”

      The reactor envisioned by Abate injects water to create a reaction that releases hydrogen, while also supporting the injection of climate-altering carbon dioxide into the rock, providing a global carbon capacity of 100 trillion tons. At the same time, the reactor process could provide essential elements such as lithium, nickel, and cobalt — some of the most important raw materials used in advanced batteries and electronics.

      “Ultimately, our goal is to design and develop a scalable reactor for simultaneously tapping into the trifecta from the Earth’s subsurface,” Abate says.

      Sharks as oceanographers

      If we want to understand more about how oxygen levels in the world’s seas are disturbed by human activities and climate change, we should turn to a sensing platform “that has been honed by 400 million years of evolution to perfectly sample the ocean: sharks,” says Andrew Babbin.

      As the planet warms, oceans are projected to contain less dissolved oxygen, with impacts on the productivity of global fisheries, natural carbon sequestration, and the flux of climate-altering greenhouse gasses from the ocean to the air. While scientists know dissolved oxygen is important, it has proved difficult to track over seasons, decades, and underexplored regions both shallow and deep.

      Babbin’s goal is to develop a low-cost sensor for dissolved oxygen that can be integrated with preexisting electronic shark tags used by marine biologists. “This fleet of sharks … will finally enable us to measure the extent of the low-oxygen zones of the ocean, how they change seasonally and with El Niño/La Niña oscillation, and how they expand or contract into the future.”

      The partnership with sharks will also spotlight the importance of these often-maligned animals for global marine and fisheries health, Babbin says. “We hope in pursuing this work marrying microscopic and macroscopic life we will inspire future oceanographers and conservationists, and lead to a better appreciation for the chemistry that underlies global habitability.”

      Maternity wear that monitors fetal health

      There are 2 million stillbirths around the world each year, and in the United States alone, 21,000 families suffer this terrible loss. In many cases, mothers and their doctors had no warning of any abnormalities or changes in fetal health leading up to these deaths. Yoel Fink and colleagues are looking for a better way to monitor fetal health and provide proactive treatment.

      Fink is building on years of research on acoustic fabrics to design an affordable shirt for mothers that would monitor and communicate important details of fetal health. His team’s original research drew inspiration from the function of the eardrum, designing a fiber that could be woven into other fabrics to create a kind of fabric microphone.

      “Given the sensitivity of the acoustic fabrics in sensing these nanometer-scale vibrations, could a mother’s clothing transcend its conventional role and become a health monitor, picking up on the acoustic signals and subsequent vibrations that arise from her unborn baby’s heartbeat and motion?” Fink says. “Could a simple and affordable worn fabric allow an expecting mom to sleep better, knowing that her fetus is being listened to continuously?”

      The proposed maternity shirt could measure fetal heart and breathing rate, and might be able to give an indication of the fetal body position, he says. In the final stages of development, he and his colleagues hope to develop machine learning approaches that would identify abnormal fetal heart rate and motion and deliver real-time alerts.

      A basalt house in Iceland

      In the land of volcanoes, Skylar Tibbits wants to build a case-study home almost entirely from the basalt rock that makes up the Icelandic landscape.

      Architects are increasingly interested in building using one natural material — creating a monomaterial structure — that can be easily recycled. At the moment, the building industry represents 40 percent of carbon emissions worldwide, and consists of many materials and structures, from metal to plastics to concrete, that can’t be easily disassembled or reused.

      The proposed basalt house in Iceland, a project co-led by J. Jih, associate professor of the practice in the Department of Architecture, is “an architecture that would be fully composed of the surrounding earth, that melts back into that surrounding earth at the end of its lifespan, and that can be recycled infinitely,” Tibbits explains.

      Basalt, the most common rock form in the Earth’s crust, can be spun into fibers for insulation and rebar. Basalt fiber performs as well as glass and carbon fibers at a lower cost in some applications, although it is not widely used in architecture. In cast form, it can make corrosion- and heat-resistant plumbing, cladding and flooring.

      “A monomaterial architecture is both a simple and radical proposal that unfortunately falls outside of traditional funding avenues,” says Tibbits. “The Bose grant is the perfect and perhaps the only option for our research, which we see as a uniquely achievable moonshot with transformative potential for the entire built environment.” More

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      in Environment

      Think globally, rebuild locally

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      Building construction accounts for a huge chunk of greenhouse gas emissions: About 36 percent of carbon dioxide emissions and 40 percent of energy consumption in Europe, for instance. That’s why the European Union has developed regulations about the reuse of building materials.

      Some cities are adding more material reuse into construction already. Amsterdam, for example, is attempting to slash its raw material use by half by 2030. The Netherlands as a whole aims for a “circular economy” of completely reused materials by 2050.

      But the best way to organize the reuse of construction waste is still being determined. For one thing: Where should reusable building materials be stored before they are reused? A newly published study focusing on Amsterdam finds the optimal material reuse system for construction has many local storage “hubs” that keep materials within a few miles of where they will be needed.

      “Our findings provide a starting point for policymakers in Amsterdam to strategize land use effectively,” says Tanya Tsui, a postdoc at MIT and a co-author of the new paper. “By identifying key locations repeatedly favored across various hub scenarios, we underscore the importance of prioritizing these areas for future circular economy endeavors in Amsterdam.”

      The study adds to an emerging research area that connects climate change and urban planning.

      “The issue is where you put material in between demolition and new construction,” says Fábio Duarte, a principal researcher at MIT’s Senseable City Lab and a co-author of the new paper. “It will have huge impacts in terms of transportation. So you have to define the best sites. Should there be only one? Should we hold materials across a wide number of sites? Or is there an optimal number, even if it changes over time? This is what we examined in the paper.”

      The paper, “Spatial optimization of circular timber hubs,” is published in NPJ Nature Urban Sustainability. The authors are Tsui, who is a postdoc at the MIT Senseable Amsterdam Lab in the Amsterdam Institute for Advanced Metropolitan Solutions (AMS); Titus Venverloo, a research fellow at MIT Senseable Amsterdam Lab and AMS; Tom Benson, a researcher at the Senseable City Lab; and Duarte, who is also a lecturer in MIT’s Department of Urban Studies and Planning and the MIT Center for Real Estate.

      Numerous experts have previously studied at what scale the “circular economy” of reused materials might best operate. Some have suggested that very local circuits of materials recycling make the most sense; others have proposed that building-materials recycling will work best at a regional scale, with a radius of distribution covering 30 or more miles. Some analyses contend that global-scale reuse will be necessary to an extent.

      The current study adds to this examination of the best geographic scale for using construction materials again. Currently the storage hubs that do exist for such reused materials are chosen by individual companies, but those locations might not be optimal either economically or environmentally. 

      To conduct the study, the researchers essentially conducted a series of simulations of the Amsterdam metropolitan area, focused exclusively on timber reuse. The simulations examined how the system would work if anywhere from one to 135 timber storage hubs existed in greater Amsterdam. The modeling accounted for numerous variables, such as emissions reductions, logistical factors, and even how changing supply-and-demand scenarios would affect the viability of the reusehubs.

      Ultimately, the research found that Amsterdam’s optimal system would have 29 timber hubs, each serving a radius of about 2 miles. That setup generated 95 percent of the maximum reduction in CO2 emissions, while retaining logistical and economic benefits.

      That results also lands firmly on the side of having more localized networks for keeping construction materials in use.

      “If we have demolition happening in certain sites, then we can project where the best spots around the city are to have these circular economy hubs, as we call them,” Duarte says. “It’s not only one big hub — or one hub per construction site.”

      The study seeks to identify not only the optimal number of storage sites, but to identify where those sites might be.

      “[We hope] our research sparks discussions regarding the location and scale of circular hubs,” Tsui says. “While much attention has been given to governance aspects of the circular economy in cities, our study demonstrates the potential of utilizing location data on materials to inform decisions in urban planning.”

      The simulations also illuminated the dynamics of materials reuse. In scenarios where Amsterdam had from two to 20 timber recycling hubs, the costs involved lowered as the number of hubs increased — because having more hubs reduces transportation costs. But when the number of hubs went about 40, the system as a whole became more expensive — because each timber depot was not storing enough material to justify the land use.

      As such, the results may be of interest to climate policymakers, urban planners, and business interests getting involved in implementing the circular economy in the construction industry.

      “Ultimately,” Tsui says, “we envision our research catalyzing meaningful discussions and guiding policymakers toward more informed decisions in advancing the circular economy agenda in urban contexts.”

      The research was supported, in part, by the European Union’s Horizon 2020 research and innovation program. More

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      in Energy

      Jackson Jewett wants to design buildings that use less concrete

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      After three years leading biking tours through U.S. National Parks, Jackson Jewett decided it was time for a change.

      “It was a lot of fun, but I realized I missed buildings,” says Jewett. “I really wanted to be a part of that industry, learn more about it, and reconnect with my roots in the built environment.”

      Jewett grew up in California in what he describes as a “very creative household.”

      “I remember making very elaborate Halloween costumes with my parents, making fun dioramas for school projects, and building forts in the backyard, that kind of thing,” Jewett explains.

      Both of his parents have backgrounds in design; his mother studied art in college and his father is a practicing architect. From a young age, Jewett was interested in following in his father’s footsteps. But when he arrived at the University of California at Berkeley in the midst of the 2009 housing crash, it didn’t seem like the right time. Jewett graduated with a degree in cognitive science and a minor in history of architecture. And even as he led tours through Yellowstone, the Grand Canyon, and other parks, buildings were in the back of his mind.

      It wasn’t just the built environment that Jewett was missing. He also longed for the rigor and structure of an academic environment.

      Jewett arrived at MIT in 2017, initially only planning on completing the master’s program in civil and environmental engineering. It was then that he first met Josephine Carstensen, a newly hired lecturer in the department. Jewett was interested in Carstensen’s work on “topology optimization,” which uses algorithms to design structures that can achieve their performance requirements while using only a limited amount of material. He was particularly interested in applying this approach to concrete design, and he collaborated with Carstensen to help demonstrate its viability.

      After earning his master’s, Jewett spent a year and a half as a structural engineer in New York City. But when Carstensen was hired as a professor, she reached out to Jewett about joining her lab as a PhD student. He was ready for another change.

      Now in the third year of his PhD program, Jewett’s dissertation work builds upon his master’s thesis to further refine algorithms that can design building-scale concrete structures that use less material, which would help lower carbon emissions from the construction industry. It is estimated that the concrete industry alone is responsible for 8 percent of global carbon emissions, so any efforts to reduce that number could help in the fight against climate change.

      Implementing new ideas

      Topology optimization is a small field, with the bulk of the prior work being computational without any experimental verification. The work Jewett completed for his master’s thesis was just the start of a long learning process.

      “I do feel like I’m just getting to the part where I can start implementing my own ideas without as much support as I’ve needed in the past,” says Jewett. “In the last couple of months, I’ve been working on a reinforced concrete optimization algorithm that I hope will be the cornerstone of my thesis.”

      The process of fine-tuning a generative algorithm is slow going, particularly when tackling a multifaceted problem.

      “It can take days or usually weeks to take a step toward making it work as an entire integrated system,” says Jewett. “The days when that breakthrough happens and I can see the algorithm converging on a solution that makes sense — those are really exciting moments.”

      By harnessing computational power, Jewett is searching for materially efficient components that can be used to make up structures such as bridges or buildings. These are other constraints to consider as well, particularly ensuring that the cost of manufacturing isn’t too high. Having worked in the industry before starting the PhD program, Jewett has an eye toward doing work that can be feasibly implemented.

      Inspiring others

      When Jewett first visited MIT campus, he was drawn in by the collaborative environment of the institute and the students’ drive to learn. Now, he’s a part of that process as a teaching assistant and a supervisor in the Undergraduate Research Opportunities Program.  

      Working as a teaching assistant isn’t a requirement for Jewett’s program, but it’s been one of his favorite parts of his time at MIT.

      “The MIT undergrads are so gifted and just constantly impress me,” says Jewett. “Being able to teach, especially in the context of what MIT values is a lot of fun. And I learn, too. My coding practices have gotten so much better since working with undergrads here.”

      Jewett’s experiences have inspired him to pursue a career in academia after the completion of his program, which he expects to complete in the spring of 2025. But he’s making sure to take care of himself along the way. He still finds time to plan cycling trips with his friends and has gotten into running ever since moving to Boston. So far, he’s completed two marathons.

      “It’s so inspiring to be in a place where so many good ideas are just bouncing back and forth all over campus,” says Jewett. “And on most days, I remember that and it inspires me. But it’s also the case that academics is hard, PhD programs are hard, and MIT — there’s pressure being here, and sometimes that pressure can feel like it’s working against you.”

      Jewett is grateful for the mental health resources that MIT provides students. While he says it can be imperfect, it’s been a crucial part of his journey.

      “My PhD thesis will be done in 2025, but the work won’t be done. The time horizon of when these things need to be implemented is relatively short if we want to make an impact before global temperatures have already risen too high. My PhD research will be developing a framework for how that could be done with concrete construction, but I’d like to keep thinking about other materials and construction methods even after this project is finished.” More

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      in Environment

      3 Questions: Boosting concrete’s ability to serve as a natural “carbon sink”

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      Damian Stefaniuk is a postdoc at the MIT Concrete Sustainability Hub (CSHub). He works with MIT professors Franz-Josef Ulm and Admir Masic of the MIT Department of Civil and Environmental Engineering (CEE) to investigate multifunctional concrete. Here, he provides an overview of carbonation in cement-based products, a brief explanation of why understanding carbonation in the life cycle of cement products is key for assessing their environmental impact, and an update on current research to bolster the process.

      Q: What is carbonation and why is it important for thinking about concrete from a life-cycle perspective?

      A: Carbonation is the reaction between carbon dioxide (CO2) and certain compounds in cement-based products, occurring during their use phase and end of life. It forms calcium carbonate (CaCO3) and has important implications for neutralizing the GHG [greenhouse gas] emissions and achieving carbon neutrality in the life cycle of concrete.

      Firstly, carbonation causes cement-based products to act as natural carbon sinks, sequestering CO2 from the air and storing it permanently. This helps mitigate the carbon emissions associated with the production of cement, reducing their overall carbon footprint.

      Secondly, carbonation affects concrete properties. Early-stage carbonation may increase the compressive strength of cement-based products, enhancing their durability and structural performance. However, late-stage carbonation can impact corrosion resistance in steel-reinforced concrete due to reduced alkalinity.

      Considering carbonation in the life cycle of cement-based products is crucial for accurately assessing their environmental impact. Understanding and leveraging carbonation can help industry reduce carbon emissions and maximize carbon sequestration potential. Paying close attention to it in the design process aids in creating durable and corrosion-resistant structures, contributing to longevity and overall sustainability.

      Q: What are some ongoing global efforts to force carbonation?

      A: Some ongoing efforts to force carbonation in concrete involve artificially increasing the amount of CO2 gas present during the early-stage hydration of concrete. This process, known as forced carbonation, aims to accelerate the carbonation reaction and its associated benefits.

      Forced carbonation is typically applied to precast concrete elements that are produced in artificially CO2-rich environments. By exposing fresh concrete to higher concentrations of CO2 during curing, the carbonation process can be expedited, resulting in potential improvements in strength, reduced water absorption, improved resistance to chloride permeability, and improved performance during freeze-thaw. At the same time, it can be difficult to quantify how much CO2 is absorbed and released because of the process.

      These efforts to induce early-stage carbonation through forced carbonation represent the industry’s focus on optimizing concrete performance and environmental impacts. By exploring methods to enhance the carbonation process, researchers and practitioners seek to more efficiently harness its benefits, such as increasing strength and sequestering CO2.

      It is important to note that forced carbonation requires careful implementation and monitoring to ensure desired outcomes. The specific procedures and conditions vary based on the application and intended goals, highlighting the need for expertise and controlled environments.

      Overall, ongoing efforts in forced carbonation contribute to the continuous development of concrete technology, aiming to improve its properties and reduce its carbon footprint throughout the life cycle of the material.

      Q: What is chemically-induced pre-cure carbonation, and what implications does it have?

      A: Chemically-induced pre-cure carbonation (CIPCC) is a method developed by the MIT CSHub to mineralize and permanently store CO2 in cement. Unlike traditional forced carbonation methods, CIPCC introduces CO2 into the concrete mix as a solid powder, specifically sodium bicarbonate. This approach addresses some of the limitations of current carbon capture and utilization technologies.

      The implications of CIPCC are significant. Firstly, it offers convenience for cast-in-place applications, making it easier to incorporate CO2 use in concrete projects. Unlike some other approaches, CIPCC allows for precise control over the quantity of CO2 sequestered in the concrete. This ensures accurate carbonation and facilitates better management of the storage process. CIPCC also builds on previous research regarding amorphous hydration phases, providing an additional mechanism for CO2 sequestration in cement-based products. These phases carbonate through CIPCC, contributing to the overall carbon sequestration capacity of the material.

      Furthermore, early-stage pre-cure carbonation shows promise as a pathway for concrete to permanently sequester a controlled and precise quantity of CO2. Our recent paper in PNAS Nexus suggests that it could theoretically offset at least 40 percent of the calcination emissions associated with cement production, when anticipating advances in the lower-emissions production of sodium bicarbonate. We also found that up to 15 percent of cement (by weight) could be substituted with sodium bicarbonate without compromising the mechanical performance of a given mix. Further research is needed to evaluate long-term effects of this process to explore the potential life-cycle savings and impacts of carbonation.

      CIPCC offers not only environmental benefits by reducing carbon emissions, but also practical advantages. The early-stage strength increase observed in real-world applications could expedite construction timelines by allowing concrete to reach its full strength faster.

      Overall, CIPCC demonstrates the potential for more efficient and controlled CO2 sequestration in concrete. It represents an important development in concrete sustainability, emphasizing the need for further research and considering the material’s life-cycle impacts.

      This research was carried out by MIT CSHub, which is sponsored by the Concrete Advancement Foundation and the Portland Cement Association. More

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      in Energy

      MIT engineers create an energy-storing supercapacitor from ancient materials

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      Two of humanity’s most ubiquitous historical materials, cement and carbon black (which resembles very fine charcoal), may form the basis for a novel, low-cost energy storage system, according to a new study. The technology could facilitate the use of renewable energy sources such as solar, wind, and tidal power by allowing energy networks to remain stable despite fluctuations in renewable energy supply.

      The two materials, the researchers found, can be combined with water to make a supercapacitor — an alternative to batteries — that could provide storage of electrical energy. As an example, the MIT researchers who developed the system say that their supercapacitor could eventually be incorporated into the concrete foundation of a house, where it could store a full day’s worth of energy while adding little (or no) to the cost of the foundation and still providing the needed structural strength. The researchers also envision a concrete roadway that could provide contactless recharging for electric cars as they travel over that road.

      The simple but innovative technology is described this week in the journal PNAS, in a paper by MIT professors Franz-Josef Ulm, Admir Masic, and Yang-Shao Horn, and four others at MIT and at the Wyss Institute for Biologically Inspired Engineering.

      Capacitors are in principle very simple devices, consisting of two electrically conductive plates immersed in an electrolyte and separated by a membrane. When a voltage is applied across the capacitor, positively charged ions from the electrolyte accumulate on the negatively charged plate, while the positively charged plate accumulates negatively charged ions. Since the membrane in between the plates blocks charged ions from migrating across, this separation of charges creates an electric field between the plates, and the capacitor becomes charged. The two plates can maintain this pair of charges for a long time and then deliver them very quickly when needed. Supercapacitors are simply capacitors that can store exceptionally large charges.

      The amount of power a capacitor can store depends on the total surface area of its conductive plates. The key to the new supercapacitors developed by this team comes from a method of producing a cement-based material with an extremely high internal surface area due to a dense, interconnected network of conductive material within its bulk volume. The researchers achieved this by introducing carbon black — which is highly conductive — into a concrete mixture along with cement powder and water, and letting it cure. The water naturally forms a branching network of openings within the structure as it reacts with cement, and the carbon migrates into these spaces to make wire-like structures within the hardened cement. These structures have a fractal-like structure, with larger branches sprouting smaller branches, and those sprouting even smaller branchlets, and so on, ending up with an extremely large surface area within the confines of a relatively small volume. The material is then soaked in a standard electrolyte material, such as potassium chloride, a kind of salt, which provides the charged particles that accumulate on the carbon structures. Two electrodes made of this material, separated by a thin space or an insulating layer, form a very powerful supercapacitor, the researchers found.

      The two plates of the capacitor function just like the two poles of a rechargeable battery of equivalent voltage: When connected to a source of electricity, as with a battery, energy gets stored in the plates, and then when connected to a load, the electrical current flows back out to provide power.

      “The material is fascinating,” Masic says, “because you have the most-used manmade material in the world, cement, that is combined with carbon black, that is a well-known historical material — the Dead Sea Scrolls were written with it. You have these at least two-millennia-old materials that when you combine them in a specific manner you come up with a conductive nanocomposite, and that’s when things get really interesting.”

      As the mixture sets and cures, he says, “The water is systematically consumed through cement hydration reactions, and this hydration fundamentally affects nanoparticles of carbon because they are hydrophobic (water repelling).” As the mixture evolves, “the carbon black is self-assembling into a connected conductive wire,” he says. The process is easily reproducible, with materials that are inexpensive and readily available anywhere in the world. And the amount of carbon needed is very small — as little as 3 percent by volume of the mix — to achieve a percolated carbon network, Masic says.

      Supercapacitors made of this material have great potential to aid in the world’s transition to renewable energy, Ulm says. The principal sources of emissions-free energy, wind, solar, and tidal power, all produce their output at variable times that often do not correspond to the peaks in electricity usage, so ways of storing that power are essential. “There is a huge need for big energy storage,” he says, and existing batteries are too expensive and mostly rely on materials such as lithium, whose supply is limited, so cheaper alternatives are badly needed. “That’s where our technology is extremely promising, because cement is ubiquitous,” Ulm says.

      The team calculated that a block of nanocarbon-black-doped concrete that is 45 cubic meters (or yards) in size — equivalent to a cube about 3.5 meters across — would have enough capacity to store about 10 kilowatt-hours of energy, which is considered the average daily electricity usage for a household. Since the concrete would retain its strength, a house with a foundation made of this material could store a day’s worth of energy produced by solar panels or windmills and allow it to be used whenever it’s needed. And, supercapacitors can be charged and discharged much more rapidly than batteries.

      After a series of tests used to determine the most effective ratios of cement, carbon black, and water, the team demonstrated the process by making small supercapacitors, about the size of some button-cell batteries, about 1 centimeter across and 1 millimeter thick, that could each be charged to 1 volt, comparable to a 1-volt battery. They then connected three of these to demonstrate their ability to light up a 3-volt light-emitting diode (LED). Having proved the principle, they now plan to build a series of larger versions, starting with ones about the size of a typical 12-volt car battery, then working up to a 45-cubic-meter version to demonstrate its ability to store a house-worth of power.

      There is a tradeoff between the storage capacity of the material and its structural strength, they found. By adding more carbon black, the resulting supercapacitor can store more energy, but the concrete is slightly weaker, and this could be useful for applications where the concrete is not playing a structural role or where the full strength-potential of concrete is not required. For applications such as a foundation, or structural elements of the base of a wind turbine, the “sweet spot” is around 10 percent carbon black in the mix, they found.

      Another potential application for carbon-cement supercapacitors is for building concrete roadways that could store energy produced by solar panels alongside the road and then deliver that energy to electric vehicles traveling along the road using the same kind of technology used for wirelessly rechargeable phones. A related type of car-recharging system is already being developed by companies in Germany and the Netherlands, but using standard batteries for storage.

      Initial uses of the technology might be for isolated homes or buildings or shelters far from grid power, which could be powered by solar panels attached to the cement supercapacitors, the researchers say.

      Ulm says that the system is very scalable, as the energy-storage capacity is a direct function of the volume of the electrodes. “You can go from 1-millimeter-thick electrodes to 1-meter-thick electrodes, and by doing so basically you can scale the energy storage capacity from lighting an LED for a few seconds, to powering a whole house,” he says.

      Depending on the properties desired for a given application, the system could be tuned by adjusting the mixture. For a vehicle-charging road, very fast charging and discharging rates would be needed, while for powering a home “you have the whole day to charge it up,” so slower-charging material could be used, Ulm says.

      “So, it’s really a multifunctional material,” he adds. Besides its ability to store energy in the form of supercapacitors, the same kind of concrete mixture can be used as a heating system, by simply applying electricity to the carbon-laced concrete.

      Ulm sees this as “a new way of looking toward the future of concrete as part of the energy transition.”

      The research team also included postdocs Nicolas Chanut and Damian Stefaniuk at MIT’s Department of Civil and Environmental Engineering, James Weaver at the Wyss Institute, and Yunguang Zhu in MIT’s Department of Mechanical Engineering. The work was supported by the MIT Concrete Sustainability Hub, with sponsorship by the Concrete Advancement Foundation. More

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      in Environment

      3 Questions: Leveraging carbon uptake to lower concrete’s carbon footprint

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      To secure a more sustainable and resilient future, we must take a careful look at the life cycle impacts of humanity’s most-produced building material: concrete. Carbon uptake, the process by which cement-based products sequester carbon dioxide, is key to this understanding.

      Hessam AzariJafari, the MIT Concrete Sustainability Hub’s deputy director, is deeply invested in the study of this process and its acceleration, where prudent. Here, he describes how carbon uptake is a key lever to reach a carbon-neutral concrete industry.

      Q: What is carbon uptake in cement-based products and how can it influence their properties?

      A: Carbon uptake, or carbonation, is a natural process of permanently sequestering CO2 from the atmosphere by hardened cement-based products like concretes and mortars. Through this reaction, these products form different kinds of limes or calcium carbonates. This uptake occurs slowly but significantly during two phases of the life cycle of cement-based products: the use phase and the end-of-life phase.

      In general, carbon uptake increases the compressive strength of cement-based products as it can densify the paste. At the same time, carbon uptake can impact the corrosion resistance of concrete. In concrete that is reinforced with steel, the corrosion process can be initiated if the carbonation happens extensively (e.g., the whole of the concrete cover is carbonated) and intensively (e.g., a significant proportion of the hardened cement product is carbonated). [Concrete cover is the layer distance between the surface of reinforcement and the outer surface of the concrete.]

      Q: What are the factors that influence carbon uptake?

      A: The intensity of carbon uptake depends on four major factors: the climate, the types and properties of cement-based products used, the composition of binders (cement type) used, and the geometry and exposure condition of the structure.

      In regard to climate, the humidity and temperature affect the carbon uptake rate. In very low or very high humidity conditions, the carbon uptake process is slowed. High temperatures speed the process. The local atmosphere’s carbon dioxide concentration can affect the carbon uptake rate. For example, in urban areas, carbon uptake is an order of magnitude faster than in suburban areas.

      The types and properties of cement-based products have a large influence on the rate of carbon uptake. For example, mortar (consisting of water, cement, and fine aggregates) carbonates two to four times faster than concrete (consisting of water, cement, and coarse and fine aggregates) because of its more porous structure.The carbon uptake rate of dry-cast concrete masonry units is higher than wet-cast for the same reason. In structural concrete, the process is made slower as mechanical properties are improved and the density of the hardened products’ structure increases.

      Lastly, a structure’s surface area-to-volume ratio and exposure to air and water can have ramifications for its rate of carbonation. When cement-based products are covered, carbonation may be slowed or stopped. Concrete that is exposed to fresh air while being sheltered from rain can have a larger carbon uptake compared to cement-based products that are painted or carpeted. Additionally, cement-based elements with large surface areas, like thin concrete structures or mortar layers, allow uptake to progress more extensively.

      Q: What is the role of carbon uptake in the carbon neutrality of concrete, and how should architects and engineers account for it when designing for specific applications?

      A: Carbon uptake is a part of the life cycle of any cement-based products that should be accounted for in carbon footprint calculations. Our evaluation shows the U.S. pavement network can sequester 5.8 million metric tons of CO2, of which 52 percent will be sequestered when the demolished concrete is stockpiled at its end of life.

      From one concrete structure to another, the percentage of emissions sequestered may vary. For instance, concrete bridges tend to have a lower percentage versus buildings constructed with concrete masonry. In any case, carbon uptake can influence the life cycle environmental performance of concrete.

      At the MIT Concrete Sustainability Hub, we have developed a calculator to enable construction stakeholders to estimate the carbon uptake of concrete structures during their use and end-of-life phases.

      Looking toward the future, carbon uptake’s role in the carbon neutralization of cement-based products could grow in importance. While caution should be taken in regards to uptake when reinforcing steel is embedded in concrete, there are opportunities for different stakeholders to augment carbon uptake in different cement-based products.

      Architects can influence the shape of concrete elements to increase the surface area-to-volume ratio (e.g., making “waffle” patterns on slabs and walls, or having several thin towers instead of fewer large ones on an apartment complex). Concrete manufacturers can adjust the binder type and quantity while delivering concrete that meets performance requirements. Finally, industrial ecologists and life-cycle assessment practitioners need to work on the tools and add-ons to make sure the impact of carbon is well captured when assessing the potential impacts of cement-based products in buildings and infrastructure systems.

      Currently, the cement and concrete industry is working with tech companies as well as local, state, and federal governments to lower and subsidize the code of carbon capture sequestration and neutralization. Accelerating carbon uptake where reasonable could be an additional lever to neutralize the carbon emissions of the concrete value chain.

      Carbon uptake is one more piece of the puzzle that makes concrete a sustainable choice for building in many applications. The sustainability and resilience of the future built environment lean on the use of concrete. There is still much work to be done to truly build sustainably, and understanding carbon uptake is an important place to begin. More

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      in Energy

      Integrating humans with AI in structural design

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      Modern fabrication tools such as 3D printers can make structural materials in shapes that would have been difficult or impossible using conventional tools. Meanwhile, new generative design systems can take great advantage of this flexibility to create innovative designs for parts of a new building, car, or virtually any other device.

      But such “black box” automated systems often fall short of producing designs that are fully optimized for their purpose, such as providing the greatest strength in proportion to weight or minimizing the amount of material needed to support a given load. Fully manual design, on the other hand, is time-consuming and labor-intensive.

      Now, researchers at MIT have found a way to achieve some of the best of both of these approaches. They used an automated design system but stopped the process periodically to allow human engineers to evaluate the work in progress and make tweaks or adjustments before letting the computer resume its design process. Introducing a few of these iterations produced results that performed better than those designed by the automated system alone, and the process was completed more quickly compared to the fully manual approach.

      The results are reported this week in the journal Structural and Multidisciplinary Optimization, in a paper by MIT doctoral student Dat Ha and assistant professor of civil and environmental engineering Josephine Carstensen.

      The basic approach can be applied to a broad range of scales and applications, Carstensen explains, for the design of everything from biomedical devices to nanoscale materials to structural support members of a skyscraper. Already, automated design systems have found many applications. “If we can make things in a better way, if we can make whatever we want, why not make it better?” she asks.

      “It’s a way to take advantage of how we can make things in much more complex ways than we could in the past,” says Ha, adding that automated design systems have already begun to be widely used over the last decade in automotive and aerospace industries, where reducing weight while maintaining structural strength is a key need.

      “You can take a lot of weight out of components, and in these two industries, everything is driven by weight,” he says. In some cases, such as internal components that aren’t visible, appearance is irrelevant, but for other structures aesthetics may be important as well. The new system makes it possible to optimize designs for visual as well as mechanical properties, and in such decisions the human touch is essential.

      As a demonstration of their process in action, the researchers designed a number of structural load-bearing beams, such as might be used in a building or a bridge. In their iterations, they saw that the design has an area that could fail prematurely, so they selected that feature and required the program to address it. The computer system then revised the design accordingly, removing the highlighted strut and strengthening some other struts to compensate, and leading to an improved final design.

      The process, which they call Human-Informed Topology Optimization, begins by setting out the needed specifications — for example, a beam needs to be this length, supported on two points at its ends, and must support this much of a load. “As we’re seeing the structure evolve on the computer screen in response to initial specification,” Carstensen says, “we interrupt the design and ask the user to judge it. The user can select, say, ‘I’m not a fan of this region, I’d like you to beef up or beef down this feature size requirement.’ And then the algorithm takes into account the user input.”

      While the result is not as ideal as what might be produced by a fully rigorous yet significantly slower design algorithm that considers the underlying physics, she says it can be much better than a result generated by a rapid automated design system alone. “You don’t get something that’s quite as good, but that was not necessarily the goal. What we can show is that instead of using several hours to get something, we can use 10 minutes and get something much better than where we started off.”

      The system can be used to optimize a design based on any desired properties, not just strength and weight. For example, it can be used to minimize fracture or buckling, or to reduce stresses in the material by softening corners.

      Carstensen says, “We’re not looking to replace the seven-hour solution. If you have all the time and all the resources in the world, obviously you can run these and it’s going to give you the best solution.” But for many situations, such as designing replacement parts for equipment in a war zone or a disaster-relief area with limited computational power available, “then this kind of solution that catered directly to your needs would prevail.”

      Similarly, for smaller companies manufacturing equipment in essentially “mom and pop” businesses, such a simplified system might be just the ticket. The new system they developed is not only simple and efficient to run on smaller computers, but it also requires far less training to produce useful results, Carstensen says. A basic two-dimensional version of the software, suitable for designing basic beams and structural parts, is freely available now online, she says, as the team continues to develop a full 3D version.

      “The potential applications of Prof Carstensen’s research and tools are quite extraordinary,” says Christian Málaga-Chuquitaype, a professor of civil and environmental engineering at Imperial College London, who was not associated with this work. “With this work, her group is paving the way toward a truly synergistic human-machine design interaction.”

      “By integrating engineering ‘intuition’ (or engineering ‘judgement’) into a rigorous yet computationally efficient topology optimization process, the human engineer is offered the possibility of guiding the creation of optimal structural configurations in a way that was not available to us before,” he adds. “Her findings have the potential to change the way engineers tackle ‘day-to-day’ design tasks.” More