Barriers to Design Optimization: Concrete in the Built Environment

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Concrete remains a resilient and dependable building material; however, the production and manufacturing of this material is one of the largest contributors to CO2 emissions in the built environment. The American Cement Association (ACA, formerly the Portland Cement Association) published its Roadmap to Carbon Neutrality in 2021, with the goal of carbon neutrality for the cement and concrete industry by 2050 (available for download at
www.cement.org). While reductions at the cement plant are underway, further opportunities for carbon reduction exist across the value chain, including optimized structural design to reduce the material use. By intentionally minimizing the volume of concrete used in a project’s design, significant carbon reductions are possible and have been achieved at the project level.
Despite growing momentum, the construction industry is slow to adopt change. The ACA hosted a workshop in June 2025, bringing together structural engineers, architects, general contractors, concrete contractors, and academics. The event featured a series of presentations showcasing the state of the art of optimized design, cutting-edge research, and case studies, followed by collaborative discussions on barriers to implementing structural optimization, and identification of a path forward.

Presented by Caitlin Mueller, MIT

Professor Caitlin Mueller emphasized that “shape matters” when designing with concrete. At MIT’s Digital Structures research group, Mueller’s team combines code-based analytical equations with numerical optimization to generate efficient designs that can be built today.
For example, her research demonstrates that ribbed slab geometries—optimized using analytical equations and numerical modeling—can reduce material mass, cost, and carbon by 60–80% compared to flat slabs. Recent research suggests that structural optimization can bring reinforced concrete buildings to minimal embodied carbon levels as compared to other structural systems.

Mueller’s team has also developed automated tools to simulate concrete behavior and evaluate designs in real time. Their Beam Shape Explorer, an open-source tool, integrates with design tools such as Rhino and Grasshopper, allowing designers to evaluate constraints like ductility, deflection, and geometric form concurrently during early-stage design.

One standout case study featured the Pixelframe system—a reusable, reconfigurable precast concrete system that maintains structural performance across multiple building lifecycles. The system’s first-life carbon efficiency outperforms typical construction, and through reuse, total carbon can be reduced by more than half.

Presented by Jonathan Broyles (MIT) and Michael Hopper (LERA)

Broyles and Hopper presented the embodied carbon performance of post-tensioned voided slabs: flat soffit systems that combine prestressing with internal void formers. These systems achieved 50–60% reductions in concrete volume relative to conventional slabs.

The team advocated for expanding the concept of optimization to incorporate fire rating, acoustic insulation, and structural performance. Their research found that while ribbed systems appear most efficient structurally, voided flat slabs often outperform ribbed systems when considering a holistic analysis—evaluating the trade-offs across multiple building performance goals.

A case study highlighted how an optimized reinforced concrete design was abandoned before the construction phase due to concerns about cost, perceptions of risk, and project politics—underscoring the disconnect between capability and real-world adoption.

Presented by David Whitmore, P+Ex / Vector Corrosion Technologies

Representing the Center of Excellence for Preservation and Service Life Extension (P+Ex), David Whitmore presented a compelling case from Toronto’s Gardiner Expressway, where maintaining over 70,000 cubic yards of concrete avoided 35,000 tons of CO₂ emissions.

P+Ex called for a cultural shift toward valuing repair, preservation, and reuse alongside durability in new construction. Their strategic goals include developing tools and guidelines to embed service-life extension into routine design practice, enabling circularity by keeping structures in use longer.

Presented by Rian Meyers and Tom Vance, Lithko Contracting

Lithko Contracting shared a contractor’s perspective, highlighting the value of early collaboration among the project team. In the case study presented, Lithko worked with all project stakeholders to develop a slab design that saved 7,400 cubic yards of concrete and 15,000 labor hours in rebar installation—all while meeting the stringent requirements of the owner for a perishable goods distribution center.

The team credited their success to proactive design-assist services, optimized concrete mixtures, and strategic preconstruction coordination. They emphasized that practical optimization often depends more on project communication than on technical capability.

Presented by Scott Shell, ClimateWorks

Scott Shell connected design-level decisions with systemic policy trends. He highlighted three high-impact levers:

Shell’s framing emphasized the need for clear performance targets and trust-based collaboration across disciplines. He noted that structural overdesign often stems from institutional risk aversion rather than technical necessity.

Presented by Josephine Carstensen, MIT

Professor Carstensen highlighted how topology optimization can reduce material use while maintaining structural performance. For example, her team evaluated a topology optimized beam design that used 25% less concrete while maintaining elastic performance that was validated through structural testing.

Yet barriers remain. A survey of practicing structural engineers revealed limited familiarity with computational design tools and a widespread perception that architects or cost concerns control key decisions. Even when aware of embodied carbon, many engineers cited lack of tools, budget, or insufficient influence as reasons why optimization strategies are not implemented in practice.

Following the presentations, participants engaged in discussion groups focused on four core topics:

Slab and Member Shape Optimization

Participants discussed a range of strategies—from one-way pan systems to machine-learning-based parametric models, participants shared a diverse array of design strategies. Key enablers included:

• Structural demand-based shape and topology optimization.
• Post-tensioning, prestressing, and voided slabs systems.
• Innovative forming methods, such as 3D-printed and fabric molds.
• Grid and span coordination with programmatic layouts.
• Parametric design tools for evaluating cost, carbon, and constructability.

The consensus was that optimization must be initiated early and be cross-disciplinary. Many cited missed opportunities when decisions were made before mechanical layouts or budgets were defined. A clear call was made for the development of design guides and published case studies to aid the industry in mainstreaming these practices.

Deconstruction and Reuse

Reusing concrete structures or components is feasible, but still a rare practice in many areas of the United States. Participants identified several critical shifts for scaling reuse:

• Design for disassembly, including reversible connections and service-life planning.
• Policy incentives, such as landfill penalties or reuse incentives.
• Case studies and guidelines of best practices.
• Digital inventories or “material passports” to track components.
• Public and private investment in modular systems and circular economies.

Many participants noted the current use of recycled concrete as aggregate or base, while there is a clear desire to move beyond the current practice and begin reuse of whole concrete elements. Cultural perceptions also play a role. Attendees noted the need to “make reuse desirable” through storytelling, showcasing durability, or emphasizing heritage.

Derisking Innovation

Concrete optimization often stalls not because ideas lack merit, but because they feel risky. Participants outlined ways to derisk:

• Pilot projects, mockups, and demonstration sites to test innovations.
• Grant funding or cost-sharing to offset early-stage costs.
• Performance-based specifications that accommodate new approaches.
• Early involvement of code officials and inspectors.
• Centralized databases for test data, construction lessons, and performance history.

Trust and transparency were recurring themes. Early and honest communication about proven—but unfamiliar—methods can help owners and teams move toward accepting novel solutions.

Stakeholder Communication

Across all topics, communication emerged as a central success factor. Key recommendations included:

• Integrated kickoff meetings during schematic design.
• Templates for charrettes, decision logs, and meeting minutes.
• Contracts that incentivize collective problem-solving at all phases of a project.
• Shared language and guidelines to align teams across sectors.

Participants emphasized the need to educate owners, who often default to conventional systems out of caution. Providing clear carbon and cost tradeoffs can unlock flexibility.

The ACA Workshop revealed a clear consensus: the tools and strategies to optimize concrete design already exist—and have been proven at scale. Research has shown that shape optimization, service-life extension, and smarter structural systems can dramatically reduce concrete’s carbon footprint, often with cost savings.

Now, we look to widespread adoption. To bring them into everyday practice, the industry must bridge gaps in education, incentive alignment, and cross-disciplinary engagement. By aligning policies, practices, and project teams around shared goals, the concrete industry can help lead the transformation to a more sustainable built environment. ■

About the Author

Aubrey Smading, PE, is the Director of Concrete Design and Technology at the American Cement Association and works to advance ACA’s Roadmap to Carbon Neutrality. Aubrey leverages her experience as a structural design and forensics engineer to support decarbonization of the industry’s value chain.