How Skyscrapers Turn Captured Carbon Dioxide Into Concrete

Skyscrapers have always been good at two things: touching clouds and making humans feel financially inadequate.
Now they’re learning a third trickhelping store carbon dioxide (CO2) inside the very concrete that holds
them up. Yes, the same gas we keep arguing about in comment sections can get locked into stone-like minerals and
quietly mind its own business for decades (or centuries), which is more than we can say for most group chats.

The headline idea is simple: capture CO2 from an industrial source (or even the air), then use it in concrete
production so it becomes a stable mineraloften calcium carbonate (basically the family of limestone). The
reality is more interesting: there are multiple pathways, different performance tradeoffs, and a growing set of
codes, specs, and verification tools that determine whether your “green concrete” is actually greeneror just
wearing a leafy badge on LinkedIn.

Why Concrete Is the Main Character in High-Rise Carbon Math

If you’re building tall, you’re building heavyand that usually means a lot of concrete in foundations, cores,
slabs, columns, and sometimes precast facade panels. Concrete’s climate problem mostly comes from cement:
producing cement releases CO2 both from high-temperature fuel use and from the chemical process of turning
limestone into clinker. That’s why “low-carbon concrete” is basically a choose-your-own-adventure book where
every chapter starts with: “Use less cement.”

Captured-CO2 concrete doesn’t magically erase cement’s footprint, but it can help in three big ways:
(1) make cement work more efficiently, enabling cement reduction, (2) replace parts of the mix with
carbon-storing ingredients, and/or (3) capture CO2 from cement plants and reuse it to make cement-like products.
For skyscraperswhere volume and repetition are hugesmall percentage improvements can scale into meaningful
embodied-carbon reductions across a project.

From Smokestack (or Air) to Mixer Truck: Where the CO2 Comes From

“Captured CO2” can mean a few different supply stories:

• Point-source capture from industrial facilities (cement kilns, refineries, steel, ammonia, ethanol, etc.).
• Biogenic CO2 from processes like ethanol fermentation (often considered “short-cycle” carbon).
• Direct air capture (DAC), which pulls CO2 straight from ambient air (energy-intensive, but flexible).

For concrete applications, CO2 generally needs to be delivered in a controlled waytypically compressed and metered.
That can mean tanks at a ready-mix plant, cylinders feeding a precast curing chamber, or a dedicated mineralization
facility that converts CO2 into aggregates or cementitious products before the concrete is ever batched.

One important reality check: climate benefit depends on the full chaincapture energy, compression, transport
distance, and whether the concrete process lets you reduce cement (or other high-carbon inputs). In other words,
“CO2 in concrete” is not automatically a climate win; it has to be designed as one.

The Chemistry Trick: Turning CO2 Into Stone (So It Can’t Escape)

Concrete is full of calcium-rich compounds. When CO2 is introduced under the right conditions, it reacts to form
stable carbonate mineralsoften calcium carbonate (CaCO3). Think of it as converting a gas into a solid crystal
that becomes part of the concrete matrix. Once mineralized, the CO2 is no longer a gas that can leak; it’s
chemically bound in a rock-like form.

This “carbon mineralization” is the umbrella concept. Under that umbrella, the industry is using three practical
routes that show up in real projectsincluding high-rise construction.

Route 1: Inject CO2 During Mixing (Ready-Mix Concrete’s “Spark Notes” Version)

In CO2-injected mixing, a small, measured amount of captured CO2 is added during batching (or sometimes into the
ready-mix truck). The CO2 reacts quickly with calcium ions to form tiny calcium carbonate particles. Those
nano- to micro-scale minerals can improve early-age properties and, crucially, allow producers to tweak mix
designs to use less cement while keeping strength on target.

How this fits skyscraper construction

Skyscrapers love ready-mix because it’s fast, scalable, and compatible with pumping concrete hundreds of feet
upward. CO2 injection is attractive here because it can be integrated without changing how crews place and finish
concrete. For high-rise slabs and cores, engineers typically care about strength gain, workability retention, and
predictable set timesso CO2-injected mixes are usually positioned as “same concrete, lower footprint,” not “new
weird concrete that behaves like a moody sourdough starter.”

What engineers and contractors watch

• Strength profile: especially early strength for cycle times (forms, post-tensioning schedules, etc.).
• Pumpability: high-rise pumping is unforgiving; consistency matters more than marketing.
• Verification: environmental product declarations (EPDs) and third-party accounting for embodied carbon.

Route 2: Cure Concrete in a CO2-Rich Chamber (Precast’s Superpower)

If ready-mix is the improv comedy of construction, precast is the scripted Broadway showcontrolled environment,
repeatable quality, and fewer surprises. CO2 curing takes advantage of that control. Fresh concrete products (like
blocks, pavers, panels, or certain structural elements) are placed in a sealed chamber where CO2 is introduced.
The CO2 reacts with calcium-bearing materials, accelerating carbonation and forming stable carbonates that can
contribute to strength development.

Why it’s a big deal for high-rises

Many skyscrapers use precast componentsarchitectural panels, some structural elements, or hybrid systems.
CO2 curing can reduce curing time and sometimes cut the cement requirement, which helps embodied carbon.
It also pairs well with alternative binders and industrial byproducts (like steel slag), creating a pathway to
“cement-free” or “cement-reduced” concrete products in certain applications.

One real-world twist: “dilute CO2” can be enough

Some mineralization approaches can work with CO2 streams that don’t require the same level of purification as
other utilization pathways. That matters because purification can add cost and emissionsespecially if the
electricity powering it isn’t clean.

Route 3: Make CO2-Storing Aggregates (Concrete’s “Hidden Storage Compartment”)

Cement gets most of the climate attention, but aggregates (sand and stone) make up most of concrete by volume.
CO2-mineralized aggregates aim to store carbon at scale by converting CO2 into carbonate rock that can replace
conventional aggregate. Instead of digging and crushing fresh stone, the process creates a synthetic limestone-like
material where CO2 is part of the rock itself.

For skyscrapers, the appeal is twofold: (1) the potential to store meaningful amounts of CO2 in a high-volume
ingredient, and (2) the chance to reduce emissions linked to mining and transportespecially if the synthetic
aggregate is produced near major urban concrete markets.

Where this shows up on a project

• Structural concrete (when performance matches spec and supply is consistent).
• Non-structural mixes (fill, sidewalks, site concrete) as an easier first step.
• Precast products that can qualify aggregates through standardized testing before mass adoption.

Bonus Route: Capture CO2 at Cement Plants and Turn It Into a Cement-Like Product

Some emerging processes capture CO2 from cement kilns and reuse it to produce supplementary cementitious
materials or cement-like binders. This is exciting because it targets emissions at the source and creates a product
that can be blended into cement or concretepotentially reducing overall clinker content while recycling CO2.

For high-rise teams, this route matters because it can fit existing procurement patterns: you’re still buying cement
or cementitious materialsjust with a lower embodied carbon profile. Adoption often hinges on standards,
approvals, and the slow-but-steady evolution of building codes (which move at the speed of a committee meeting
scheduled for “sometime after lunch”).

How Skyscrapers Actually “Use” CO2 Concrete: A Practical Flow

1) The design team sets embodied carbon goals

This typically happens through performance specs (global warming potential targets), EPD requirements, or
low-carbon concrete codes and guidance. High-rise projects increasingly treat embodied carbon like a real design
parameterright alongside fire rating, vibration criteria, and “don’t make the lobby look like a dentist’s office.”

2) The contractor and suppliers qualify mixes

Trial batches confirm strength, slump/workability, set time, pump performance, and finishing. For CO2-based
approaches, suppliers also validate dosing control, curing protocols (for precast), and any mix adjustments that
reduce cement without sacrificing performance.

3) Verification is baked into submittals

The grown-up version of “trust me, bro” is third-party documentation: product data sheets, EPDs, and sometimes
project-level accounting that tracks CO2 mineralized and cement reduced. The goal is to prove that carbon is
actually being stored and/or avoidednot just discussed enthusiastically in kickoff meetings.

Benefits (and the Fine Print Everyone Should Read)

What you can realistically gain

• Lower embodied carbon via cement reduction, mineralized materials, or both.
• Comparable performance when properly qualified (strength, durability, constructability).
• Scalability because concrete supply chains already serve huge volumesespecially in urban cores.

The fine print

• Net benefit depends on the whole system: CO2 source, energy, transport, and how much cement you truly avoid.
• Not every route fits every element: high-strength core concrete may have different constraints than site paving.
• Standards and approvals matter: adoption accelerates when materials map cleanly to existing specs and test methods.

Specifying CO2 Mineralized Concrete for a High-Rise: A Quick Checklist

1. Start with performance targets: strength, durability exposure, pump requirements, finish needs, schedule constraints.
2. Ask what changes: Is CO2 added during mixing, used in curing, or embedded in aggregates/binders?
3. Demand documentation: EPDs, test reports, and clear accounting of CO2 stored vs. emissions avoided.
4. Confirm supply reliability: consistency beats novelty on a tower pour.
5. Run trials early: don’t wait until the first mat foundation pour to “see how it goes.”

FAQ

Does CO2 in concrete make it weaker?

Not necessarily. Many approaches are designed to maintain strength or even improve certain early-age properties.
The key is proper mix qualification and adherence to curing/mixing protocols.

Is the CO2 permanently stored?

When CO2 is mineralized into stable carbonates (like calcium carbonate), it’s effectively locked into a solid form.
Verification and measurement methods vary by technology and project requirements.

Can this replace all cement in a skyscraper?

Not today. Some products can be cement-free in specific precast applications, but a full high-rise structural system
typically uses multiple complementary strategies: cement reduction, alternative binders, optimized design, and
(in some cases) CO2 mineralization.

Conclusion: The Tall-Building Future Might Literally Be Set in Stone

Skyscrapers won’t single-handedly solve climate change. But they can stop being passive carbon piggy banks and
start acting like carbon storage devicesone mix design at a time. Captured CO2 can be injected during mixing,
used in controlled curing, transformed into synthetic aggregates, or even recycled into cement-like materials from
cement-plant emissions. The most successful projects treat this as an engineering and procurement strategy, not
a slogan: qualify performance, verify carbon impacts, and scale what works.

And if nothing else, it’s comforting to know that while humans keep releasing hot air, our buildings can at least
learn to lock some of it away.

On-the-Ground Experiences: What It’s Like Using CO2 Concrete on a Skyscraper Project

The first “experience” most teams have with CO2 mineralized concrete is a meeting where someone says,
“So… the concrete eats carbon?” and someone else replies, “Yes, but only a little, and we have to document it.”
That’s the tone-setting moment. After that, the work becomes surprisingly practical.

On a typical high-rise, the early wins happen in places where the project already has flexibility: site concrete,
non-critical slabs, or early procurement packages for precast elements. Teams will often start there because the
risk is lower and the learning curve is gentler. You get to practice the new submittal languageEPDs, global
warming potential targets, mineralization claimswithout betting the structural core on Day One.

If the project uses CO2 injection during mixing, the “jobsite experience” is less dramatic than people expect.
The concrete truck still shows up. The pump still groans like it’s doing CrossFit. Finishers still complain about
everything (as is tradition). The difference is upstream: the supplier is controlling a CO2 dose, tracking it, and
often adjusting cement content slightly while meeting strength requirements. The most noticeable change on
site is paperworkmore of it, and more specific. Instead of “here’s the mix,” it becomes “here’s the mix, here’s
the verified performance history, here’s the carbon accounting method, and here’s the EPD that proves it.”

For precast elements using CO2 curing, the experience feels more like adopting a new manufacturing protocol.
You’ll hear about curing chambers, cycle times, and quality control in a way that resembles semiconductor
manufacturingexcept the product is a concrete panel the size of a studio apartment. Teams often report that
the biggest benefit is predictability: controlled curing can tighten schedules, speed up strength gain, and reduce
water curing needs. The biggest challenge is coordination: you need early alignment between architect,
structural engineer, fabricator, and contractor so that the product qualifies under the right standards and doesn’t
get value-engineered out during a budget squeeze.

Aggregates that store CO2 introduce a different kind of experience: supply chain diplomacy. You’re no longer
just asking “Can we get stone?” You’re asking “Can we get this aggregate, consistently, at scale, with stable
gradation and performance data, delivered on a schedule that matches tower pours?” When it works, it feels like
a cheat code because aggregates are such a huge portion of concrete by volume. When it doesn’t, teams learn
quickly that pilots and prototypes are not the same thing as city-scale logistics.

The most valuable lesson teams tend to carry forward is that CO2 mineralization is not a single productit’s a
category. The best results come from stacking strategies: optimize structural design to use material efficiently,
reduce cement with supplementary cementitious materials where appropriate, and add CO2 mineralization where it
can be verified and scaled. In practice, this looks like an embodied-carbon playbook: different mixes for different
elements, supplier partnerships locked in early, and a verification plan that survives contact with real-world
construction chaos.

And yes, there is always one momentusually during a late-night pourwhen someone jokes that the building is
“breathing in CO2.” At that point, you know the concept has officially made it onto the jobsite. That’s when it
starts to sticklike, you know, calcium carbonate.