NAE Perspectives offer practitioners, scholars, and policy leaders a platform to comment on developments and issues relating to engineering. 

Naresh Thadhani is Jefferson Science Fellow, Bureau of Overseas Buildings Operations, U.S. Department of State, and professor, School of Materials Science and Engineering, Georgia Institute of Technology  

US embassies are impressive feats of architecture and engineering. They are more than ordinary buildings; they are multifunctional campuses serving as centralized headquarters for American diplomats and foreign-service officials.  

Each embassy represents a unique embodiment of US values and the best in architecture, design, engineering, technology, art, culture, and environmental sustainability. Addison “Tad” Davis, former director of the Bureau of Overseas Buildings Operations (OBO) of the Department of State, aptly remarked, “If you have seen one embassy, you have only seen one embassy” [1]. With OBO presently overseeing assets in 290 global locations, the task of building, operating, and maintaining facilities in every climate, time zone, and political environment presents a range of complex challenges. These encompass ensuring safety and security through site isolation and protective measures, maintaining adaptability within code-compliant structural designs, and accounting for the economic, environmental, and social impact on local communities. The complexities amplified by shifting geopolitical landscapes, climate fluctuations, urban expansion, and escalating costs of ownership and maintenance require transformative changes and add to the imperative that materials matter in the building and construction of the embassy of the future. 

Legacy Materials and Challenges

For years, materials used for building construction have primarily addressed challenges scoped and defined by structural engineers, architectural designers, and building construction specialists within the constraints of code-based designs. However, these legacy materials come with challenges that must be addressed. For instance, the embodied energy for producing metals like aluminum (~180 MJ/kg) and steel (~110 MJ/kg) ranks among the highest. Additionally, the usage of concrete surpasses all other materials combined and requires the highest total embodied energy (~220 GJ) due to its overall consumption in building an average housing unit [2]. Today, second only to water, concrete is the most consumed material: each person in the world uses about three tons of concrete per year.  

Concrete's popularity is attributed to its abundant global availability and versatile usage in prefabricated or cast-in-place forms, providing high strength, durability, energy savings, and resistance against natural and manmade disasters. However, its main ingredient, cement, produced through pyro-processing in a rotary kiln, consumes 3,150 MJ/ton of energy and emits approximately 800 kg of CO2 per ton, contributing to about 8% of all emissions [3]. 

Steel is another widely used structural material, with a global production of approximately 1.9 billion tons. Fifty-two percent of it is used in buildings and infrastructure [4]. Steel is a scientist’s dream material for researching the fascinating structure-property alterations under various extreme chemical, mechanical, and thermal environments. It is an engineer’s go-to material for all things structural due to its availability in a wide range of commercial grades with desirable properties. However, steel is susceptible to corrosion, which has significant societal impacts on safety, costs, and resource depletion. According to a National Association of Corrosion Engineers impact study, the annual cost of corrosion is estimated to be $276 billion, or 2.7% of US GDP (2013) and about 3.4% of global GDP. With US embassies increasingly being built in coastal areas and hot and humid climates, the effects of corrosion on exposed structures and mechanical equipment can be pervasive, requiring intentional and decisive choices of expensive materials, coatings, and preventive maintenance protocols. Furthermore, iron and steel production, mainly involving carbothermic reduction of iron ore using blast furnace technologies, accounts for 1.9 tons of CO2 emitted per ton of steel, representing 11% of global emissions [5]. 

Security threats and natural disasters require building materials that provide the necessary protection for embassies. Major damage to buildings can be sustained from extreme weather, direct-fire weapons, and explosive blast waves. Progressive collapse of buildings, though a rare event, can have catastrophic consequences and is another worrisome threat. Triggered by local or inadvertent material failure or structural instability, progressive collapse can spread as a cascading progression of damage, causing a building to collapse or disproportionately fail. Building codes define materials and structural designs to prevent disproportionate damage propagation by reducing system susceptibility, increasing robustness via redundant load transfer paths and effective interconnections. Steel and concrete serve as optimal choices for meeting the requirements of these extreme events. 

Sustainability Advances in Concrete and Steel

In response to the challenges posed by legacy materials, innovative strides have been made to enhance the sustainability and efficiency of concrete and steel production. Ultra-high-performance concrete, reinforced with fibers, silica fume, titanium oxide (TiO2), carbon nanotubes (CNT), and locally available fines and nano-additives, offers increased durability, self-cleansing properties, and radiofrequency (RF) attenuation functionalities [6]. The addition of fines makes concrete flowable and rapidly curable, ensuring predictable strength properties and low water permeability. Silica fume, TiO2, and CNT also reduce shrinkage, facilitate hydration, resist pollution and corrosion, and increase durability to about 75 years. On the other hand, green concrete, derived from eco-friendly waste materials such as fly ash, blast furnace slag, silica fume, metakaolin, red mud, and rice husk ash, significantly lowers the energy requirements for manufacturing and reduces CO2 emissions by 30%. Mineral admixtures can chemically react with calcium hydroxide, a product of cement hydration, to form stronger calcium silicate hydrates, enhancing strength and refining the pore structure for reduced permeability, thermal resistance, and fire resistance. Admixtures that cause swelling can stop water and air permeation, enabling self-healing characteristics and requiring less overall maintenance of concrete structures. Such advancements in concrete formulation have facilitated the use of 3-D printing [7] for complex concrete structures and components, leading to faster, more efficient, automated, and modular construction processes. Integration of IoT sensors and GPS trackers with drones can further enhance construction efficiency.  

Advancements are also being made in steel production, with the goal of achieving zero CO2 emissions by 2050 [8], as mandated by the 2022 Bipartisan Infrastructure Investment and Jobs Act. Electric arc furnace technology, utilizing fully recycled scrap or direct hydrogen-reduced steel, represents a pathway towards a more environmentally friendly steel industry [9]. Clean electricity, value-chain innovation involving alternative sources of iron ores such as locally available taconite, and the use of electrolysis or non-carbon renewable reducing agents can drive these sustainable steel production methods. Additionally, in-situ process monitoring and modeling of oxide reduction and impurity oxidation chemistries, combined with artificial intelligence (AI) and machine learning (ML) tools, promise improved materials production efficiency through alternative feedstock materials and additive manufacturing. 

Mass Timber as a Competitive Alternative Material for Building Construction

Mass timber, an engineered composite of wood-derived products, is emerging as a competitive alternative material for building construction due to its high strength-to-weight ratio [10]. Beyond its environmental benefits as a renewable, thermally insulating, and energy-efficient material, mass timber is less carbon-intensive to manufacture, transport, and erect in comparison to conventional construction materials. As such, mass timber presents an attractive consideration for the OBO's building construction portfolio while advancing environmental stewardship goals for the US State Department.  

Incorporating mass timber into new office buildings can potentially reduce embodied carbon by 20-40%, shift material construction and labor costs to US companies, and enable more efficient construction schedules with cost savings of 30-55%. The weight savings of approximately 45% relative to baseline reinforced concrete structures also result in using 50-60% less concrete and steel. The two main forms of mass timber are cross-laminated timber (CLT), consisting of layers of solid-sawn kiln-dried lumber boards adhesively bonded to form structural panels, and glue-laminated timber (GLT) or glulam, which involves solid-sawn lumber members layered parallel on their wide faces with adhesive between layers. CLTs are mainly used for walls, roofs, and floor separations as a sustainable alternative to concrete, while GLTs or glulam can replace steel in columns, beams, rafters, and trusses. 

The introduction of new fire-resistant, mass-timber-based structural building materials in the 2021 International Building Code has sparked increased interest among architects, designers, and builders. However, there are challenges that need to be addressed before mass timber can be widely adopted, particularly for use as building materials in extreme environments. For instance, the transversely isotropic mechanical properties of mass timber increase its vulnerability to progressive collapse and its performance against blast and ballistic threats. Hygrothermal behavior stemming from moisture infestation can lead to susceptibility to biological attack and biodegradation. Additionally, the effects of aging and climate conditions on the thermal stability of wood, adhesively bonded joints, and structural member connections remain areas of concern that require further research. 

Change Drivers Affecting the Future of Building Construction

The future of building construction will be shaped by significant change drivers, which include rapid urbanization, the imperative for sustainable materials, and the impacts of climate change. By 2023, the world's population is projected to reach 8 billion, and this number is expected to surpass 10 billion by 2050 and exceed 11 billion by the end of the century [11]. As more than 70% of the population migrates to and resides in megacities, covering only 2% of the earth's land, and about 40% of the population lives within 100 km of the coast, extreme weather events, heatwaves, droughts, sea-level rise, and flooding will have multiplicative effects. Over 10% of US embassies, consulates, and other diplomatic assets are in the highest category of climate disaster risk. Deforestation and ecosystem destruction from mining activities for minerals, metals, and even sand for concrete will make it challenging to maintain the status quo. Sustainable materials, advances in processing and green manufacturing technologies, and significant reductions in embodied energy and CO2 emissions will be necessary. 

The digital revolution for "materials by design" will be essential to aid in transforming the material-architecture reciprocity from “materials providing solutions for architectural and engineering challenges” to “novel sustainable materials guiding architectural and engineering designs” for building construction. The Materials Genome Initiative (MGI)[1], a federal multi-agency program aimed at accelerating the pace from material discovery to development and deployment, can play a vital role in this transformation. By integrating and iterating knowledge across the entire materials development continuum, the MGI provides a framework for seamless information flow and knowledge exchange among stakeholders contributing to materials research and development. Embracing the MGI can accelerate the availability of sustainable materials with desired properties, thereby reshaping the future of building construction. 

Additionally, automating building construction through building information modeling (BIM) has the potential to revolutionize the industry. BIM serves as a software platform for integrated design, modeling, planning, and collaboration involving all stakeholders throughout an asset's life cycle [12]. The use of BIM streamlines workflow, improves communication, identifies production and cost-saving strategies, provides greater visibility between disciplines, and enhances decision-making. Furthermore, the integration of structural finite element analysis (FEA) of the mechanical behavior of materials, performance-driven personalized design options, AI-enabled evaluation of iterative processes, and additive manufacturing will lead to more efficient on-site execution and automation of management, planning, design, and construction. The integration of performance-based design and modeling through the use of BIM and sustainable new and legacy materials [13] will offer an abundance of opportunities for building the embassy of the future as a remarkable feat of architecture and engineering. 

[1] www.mgi.gov 

Concluding Remarks

Building the embassy of the future requires sustainable, high-performance construction materials that can withstand extreme environments, that can be manufactured with low embodied energy and net-zero CO2 emission, and that can employ judicious use of resources amidst the challenges posed by climate change and urbanization. Sustainable innovations in concrete, steel, and mass timber offer solutions to engineering and construction challenges. However, achieving transformative changes will require adopting performance-based approaches to architecture and engineering design and leveraging the MGI to rapidly manufacture and deploy sustainable materials with desired functionalities. Additionally, the integration of BIM and the automation of construction processes will play a crucial role in shaping the embassy of the future. Materials matter in building the embassy of the future, as they form the foundation for sustainable, innovative, and resilient construction. 

References 

[1]      Davis A “Tad.” 2020. Setting Conditions for Embassy after Next. The Military Engineer 112(729):72-76. 

[2]      Bechtold M, Weaver JC. 2017. Materials Science & Architecture. Nature Reviews: Materials 2, article 17802:1-19. 

[3]      Hertwich EG. 2021. Increased carbon footprint of materials production driven by rise in investments. Nat. Geosci. 14:151–155. 

[4]      World Steel in Figures 2022. 2022. Worldsteel. Available at https://worldsteel.org/wp-content/uploads/World-Steel-in-Figures-2022-1.pdf.   

[5]      Hasanbeigi A. 2022. Steel Climate Impact: An international benchmarking of energy and CO2 intensities. Global Efficiency Intelligence. St. Petersburg, Florida.   

[6]      Sanchez F, Sobolev K. 2010. Nanotechnology in Concrete – A Review. Construction Building Materials 24:2060-2071. 

[7]      Khan MS, Sanchez F, Zhou H. 2020. 3-D printing of Concrete: Beyond Horizons. Cement and Concrete Research 133, article 10670. 

[8]      International Energy Agency. 2020. Iron and Steel Technology Roadmap. International Energy Agency. Paris. Available at https://www.iea.org/reports/iron-and-steel-technology-roadmap.    

[9]      Chang C. 2021. The Technology Whitespace for Deep Decarbonization of Steel Production. ARPA-E workshop, August 31. 

[10]   Woodworks and Think Wood. 2022. Mass Timber Design Manual – Volume 2. WoodWorks, Wood Products Council. Available at https://www.woodworks.org/resources/mass-timber-design-manual/. 

[11] World City Populations 2023. 2023. World Population Review. Available at https://worldpopulationreview.com/world-cities.  

[12]   Gerbert P, Castagnino S, Rothballer C, Renz A, Filitz R. The Transformative Power of Building Information Modeling. Boston Consulting Group . Available at https://www.bcg.com/publications/2016/engineered-products-infrastructure-digital-transformative-power-building-information-modeling.  

[13]   Enabling innovation: the future of materials. 2022. Economist Impact. Available at https://impact.economist.com/sustainability/circular-economies/enabling-innovation-the-future-of-materials.  

Disclaimer

The views expressed in this perspective are those of the author and not necessarily of the author’s organizations, the National Academy of Engineering (NAE), or the National Academies of Sciences, Engineering, and Medicine (the National Academies). This perspective is intended to help inform and stimulate discussion. It is not a report of the NAE or the National Academies. 

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