Low-carbon concrete, from one asset to the next.

Concrete is the most used material on earth after water, and cement is responsible for roughly 8% of global carbon emissions. A building owner who wants a lower-carbon structure has few choices about the concrete itself, because a structural engineer will not accept a mix that has not been proven. This is the account of one method that was proven on one project and then written into the specification of a much larger one.

The method

CO2-mineralised concrete injects captured carbon dioxide into the mix during batching. The gas reacts with the cement to form a mineral, calcium carbonate, that is locked into the concrete permanently and that adds compressive strength. Because the mix gets stronger, the producer can use less cement to reach the same strength, and cement is where the emissions are. The technology was developed by CarbonCure, a Nova Scotia company, and is installed in the supplier's plant rather than on site. An owner chooses it because it lowers embodied carbon without changing how the concrete is placed, cured or inspected, provided the supplier can produce the mix and the engineer will sign it.

Leg one: the Wharf

The Wharf is a mixed-use redevelopment of the Southwest Waterfront in Washington, DC, developed by Hoffman-Madison Waterfront with institutional capital. Phase 2 targeted LEED Neighbourhood Development Gold, and the owner selected CO2-mineralised concrete to support that goal. Vulcan Materials, through Concrete Mixes Inc., supplied the mix.

• 18,891 cu ydConcrete placed at the Wharf Phase 2, about 14,443 cubic metres (CarbonCure project profile, May 2023).
• 134 t CO2Carbon avoided, at minimum, across the pour (same source).

Our lead worked on the Wharf from 2016 to 2019 as a member of the asset-management team at the institutional investor behind the project, and led the adoption of the method from that side: bringing the construction team and the structural engineers together to assess and accept it, and working with the supplier until its plant could produce the mix reliably. The work was not in a laboratory. It was in the meetings where an owner's sustainability target became a line in a concrete specification that a contractor could price.

Leg two: Amazon HQ2

Amazon's second headquarters at Metropolitan Park in Arlington, Virginia was built by Clark Construction, designed by ZGF, and engineered by Thornton Tomasetti, which wrote CO2-mineralised concrete into its low-embodied-carbon structural specification. The concrete came from Miller & Long and from Vulcan, the same supplier that had produced the Wharf mix.

• 106,555 cu ydConcrete placed at HQ2, about 81,467 cubic metres (CarbonCure project profile, June 2026).
• 1,144 t CO2Carbon saved across the project (same source).

Amazon's sustainability lead described the aim as "lowering the carbon footprint of many of our buildings" (Kara Hurst, Amazon, quoted by CarbonCure). The two pours overlapped in time, so the sequence matters less than the scale: proven on the Wharf, delivered at HQ2 at five to six times the volume, with the same supplier, and this time written into the specification from the start rather than negotiated into it.

How a method moves

A new building method does not travel by itself. It travels because someone on the owner's side is willing to carry the risk of the first use, has the standing to bring the engineer and the contractor to the table, and stays with the supplier until the product is reliable. Once that has happened once, the second owner does not have to take the risk; the engineer already has the data, the supplier already has the plant, and the method becomes a line in a specification. Institutional capital did that for this concrete. In March 2021 the same investor anchored a second proptech fund whose first portfolio already held CarbonCure (The Globe and Mail, 15 March 2021). The strategy outlived the individual project.

From offices to homes

Affordable housing needs the same function, and needs it more. Factory-built walls and modules, tighter envelopes, lower-carbon structure and shorter build times each cut what a home costs to build and to run. Each is also a method that a lender, an engineer and a municipal inspector must accept before it can be used on a building people will live in. Groundbreak Ventures, Hopewell's construction-technology affiliate, invests in those methods and proves them on Hopewell's own projects. Doorway carries what has been proven to the next project at scale, with the cost per door reported. The concrete was the rehearsal. The housing is the work.

How we invest in what's next How we build