iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Concrete does absorb atmospheric carbon dioxide after installation, but there is no universal percentage for every slab, wall or bridge. Carbonation moves inward from exposed surfaces and turns some cement minerals into calcium carbonate. The amount depends on the cement and supplementary materials, concrete volume, exposed surface area, humidity, coverings, service life and what happens after demolition.
Published estimates illustrate the range rather than define a rule for an individual project. A 100-year lifecycle study estimated uptake at 15.5%–17% of concrete-production emissions (about 18%–21% of ordinary Portland-cement production emissions). A global historical model estimated 4.5 gigatonnes of carbon sequestered in cement materials from 1930 through 2013, offsetting 43% of cement process emissions over that period. Those studies use different boundaries, assumptions and system definitions, so their percentages cannot be applied directly to a particular building.
What happens when installed concrete absorbs CO2?
After concrete hardens, carbon dioxide in air can enter its pore network. It dissolves in the pore moisture and reacts with calcium-bearing hydrated cement phases. The reaction forms calcium carbonate, a process called carbonation:
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minutecalcium-bearing cement phases + CO2 → calcium carbonate + other reaction products
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Carbonation normally starts at exposed faces and advances toward the interior. As the diffusion path gets longer, the rate generally falls. A dense, coated or continuously wet surface can slow gas movement; a surface with suitable moisture and air access can carbonate faster.
The same reaction lowers the alkalinity of the pore solution. That is usually not a structural problem for plain concrete, but it matters in reinforced concrete: if the carbonation front reaches the reinforcing steel’s protective cover, the lower alkalinity can remove part of the steel’s corrosion protection. The carbonation mechanism is well established, but a project-specific corrosion prediction requires cover depth, cracking, moisture, chloride exposure and other data that a general uptake estimate does not provide.
What the reported amount means
Most published figures describe carbon dioxide uptake by the cementitious portion of concrete, not a permanent capture device operating at the construction site. Carbonation is gradual, reversible in some chemical details and strongly controlled by access to air and moisture. A lifecycle result can include the original service period and additional carbonation after demolition, while a test on an intact specimen may cover only one surface and one age.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
How much CO2 does concrete absorb?
The most defensible answer is a range tied to a stated boundary:
| Scope and source | Reported uptake | How to interpret it |
|---|---|---|
| 100-year concrete lifecycle case study (Environmental Impact Assessment Review, 2014) | 15.5%–17% of concrete-production CO2 emissions | Includes lifecycle assumptions; not a universal percentage for every structure. |
| Same study, expressed against ordinary Portland-cement production emissions | About 18%–21% | A different denominator changes the percentage even when the physical uptake is the same. |
| Global historical cement-material model, 1930–2013 (Nature Geoscience, 2016) | 4.5 GtC cumulatively sequestered | Equivalent to an estimated 43% offset of cement process emissions over that period, excluding fossil-fuel emissions. |
| 50-year service-life model under benchmark conditions | Less than 0.3 kg CO2 per m3 of concrete per year after year 20 | Later annual uptake becomes small in that model; it is not a guaranteed threshold for a project. |
| 50-year model by exposure condition | Less than 5% to up to 23% of calcination CO2 uptake | Buried or unexposed concrete was at the low end; favorable outdoor, uncovered, sheltered ordinary Portland cement concrete was at the high end. |
The figures are not contradictory. The first two are lifecycle or global accounting results with different denominators and boundaries. The exposure percentages describe a modeled portion of calcination-related uptake under particular conditions. None should be presented as “concrete always reabsorbs X% of its manufacturing emissions.”
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
How long does concrete keep absorbing carbon dioxide?
Carbonation usually is front-loaded: the largest increments occur while the exposed outer layer is still close to the advancing carbonation front. In a 50-year service-life model, 50% of natural carbonation had occurred by year 12 and 75% by year 28 under the model’s benchmark conditions. After year 20, modeled uptake fell below 0.3 kg CO2 per cubic metre of concrete per year.
That pattern does not mean uptake stops at year 20 or year 28. It means each additional year adds less in that modeled case because carbon dioxide must diffuse farther through already carbonated material. Doubling the assumed service life therefore adds comparatively little uptake in that model compared with the first decades.
Recommended Free Tools
What controls the time curve?
- Carbonation depth: The reaction progresses inward from each exposed surface, and the available uncarbonated depth shrinks over time.
- Moisture: Some pore moisture is needed for CO2 to dissolve, while pores that are fully water-filled restrict gas diffusion. Intermediate relative humidity is often more favorable for carbonation than either extreme.
- Surface condition: Paints, membranes, tiles, dense finishes and other coatings add a diffusion barrier.
- Geometry: Thin sections, edges and members with a high surface-area-to-volume ratio expose more paste per unit of concrete than massive, buried sections.
Why does uptake vary so much between structures?
Exposure and location
Exposure is often the largest practical difference. A cited model estimated less than 5% of calcination CO2 uptake over 50 years for concrete in ground or otherwise unexposed conditions. For outdoor, uncovered, sheltered ordinary Portland cement concrete under favorable conditions, the estimate reached up to 23%. The comparison is a model result, not a guarantee that every outdoor wall will reach 23%.
Rain-washed surfaces are not automatically the fastest-carbonating surfaces. Persistent saturation can impede gas transport, while a sheltered surface with repeated access to air and moderate moisture may carbonate efficiently. Indoor spaces, sealed basements, submerged members and buried foundations each need their own exposure assumptions.
Cement chemistry and supplementary materials
Carbonation capacity depends on the amount and type of cementitious material available to react. Water-to-cement ratio, cement content, curing, temperature and pore structure affect the diffusion path. Supplementary cementitious materials (SCMs) can change both the amount of calcium-bearing material and the permeability of the hardened paste.
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
A 10-year natural-carbonation study found that slag-rich concrete had lower CO2-binding capacity, while greater carbonation depth partly compensated for that lower capacity. This is why a mix cannot be ranked from cement label alone: composition and the measured or modeled carbonation depth must be considered together.
Area, thickness and finish
Two structures made with the same mix can absorb different amounts because one exposes more paste to air. A thin panel, beam edge or crushed particle has a much larger exposed area relative to its volume than a thick, coated foundation. A finish that blocks pores can reduce uptake on the covered face, while cracks and unsealed edges can create additional pathways.
Does concrete reabsorb the CO2 released to make cement?
It reabsorbs some atmospheric CO2 released during cement manufacture, but not necessarily all of it and not on the same timescale. Cement production emissions include process CO2 from calcination, when limestone is heated, as well as emissions from fuel and electricity. Carbonation primarily returns CO2 to calcium-containing cement products; it does not automatically cancel fuel-related emissions.
The 100-year lifecycle estimate of 15.5%–17% of concrete-production emissions (18%–21% against ordinary Portland-cement production emissions) shows why the denominator matters. The global historical estimate of 4.5 GtC and a 43% offset of cement process emissions covers cement materials made over 1930–2013 and excludes fossil-fuel emissions. A project assessment should therefore report the emissions boundary, cement content, time horizon and end-of-life assumptions alongside any uptake figure.
Does crushed or demolished concrete absorb more CO2?
Often, yes. Demolition and crushing expose interior cement paste that was shielded during service. Freshly exposed particle surfaces can then carbonate, so whole-life models commonly include a post-demolition recycling stage.
Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
End-of-life uptake is not a fixed bonus to add to every building. It depends on particle size, how much paste is exposed, moisture, airflow, storage duration, covering, transport and whether the material is reused in a way that keeps surfaces accessible. Fine particles can expose more area, but wet stockpiles or enclosed handling can restrict diffusion. A credible lifecycle calculation models the actual crushing and storage scenario rather than adding a generic percentage.
What to record at demolition
- Whether concrete is crushed, left in large pieces or placed underground.
- Typical and maximum particle size after processing.
- Storage location, duration, rainfall and relative humidity.
- Whether stockpiles are covered, compacted or ventilated.
- The fraction of concrete paste exposed after crushing and the intended recycled use.
How to calculate uptake for a specific project
A project estimate should be based on measured carbonation or a standards-based method, not a single rule of thumb. The 2014 uptake method expresses absorbed CO2 using absorbable CO2 per unit volume, exposed surface area and carbonation depth. In simplified form:
CO2 uptake = absorbable CO2 per unit volume × exposed surface area × carbonation depth
The terms must be defined consistently. “Absorbable CO2 per unit volume” depends on cement chemistry and the fraction of reactive material. “Exposed surface area” should exclude faces blocked by impermeable finishes unless the model explicitly assigns them a reduced rate. “Carbonation depth” must be measured or predicted for the relevant age and environment.
- Define the boundary. Decide whether the result covers installation through service life only or also demolition, crushing, storage and recycled use. State whether the comparison is against concrete-production emissions, cement-production emissions, calcination emissions or process emissions only.
- Inventory the concrete. Record volume, member dimensions, cement content, cement type, SCM proportions, curing history and known mix changes. Separate different mixes and exposure classes instead of averaging them prematurely.
- Map exposed surfaces. Identify outdoor, indoor, buried, submerged, coated, sheltered and cracked faces. Include edges and joints where the geometry materially increases exposure.
- Establish the environment. Use climate, relative-humidity range, temperature, wetting and drying, and surface finish. A single annual humidity value can hide conditions that strongly change diffusion.
- Determine carbonation depth or coefficient. Use field measurements, laboratory testing or an accepted model calibrated to the concrete and exposure. Thermogravimetric analysis and standards-based procedures are preferable to an unsupported generic percentage.
- Calculate service-life uptake by segment. Apply the appropriate depth and exposed area to each member or exposure class, then integrate over the chosen time period. Keep the early, faster phase separate from the later diminishing phase.
- Model end of life. Add only the carbonation expected from the documented demolition, crushing, particle-size and storage scenario. Show this as a separate stage so readers can see how much occurs before and after demolition.
- Report uncertainty. Give a range and identify which assumptions drive it. A result without the cement composition, exposure, time horizon and boundary is not reproducible.
Which standard can support a defensible estimate?
BSI’s PD CEN/TR 17310:2019, Carbonation and CO2 uptake in concrete, provides typical uptake values for structures in different environmental conditions and explains how uptake can be incorporated into whole-life environmental product declarations. It is a framework for consistent accounting, not a promise that every member will match a typical value.
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
For a building, infrastructure owner or environmental product declaration, combine the standard’s approach with project records and measurements. At minimum, retain the cement and SCM composition, dimensions, exposed surfaces, coating or finish, climate and humidity assumptions, service-life period, carbonation depth or coefficient and end-of-life crushing scenario.
How to interpret a concrete CO2 claim
Before accepting a number, ask six questions:
- Is the figure per cubic metre, per tonne, per square metre or for the whole structure?
- Does it describe carbon dioxide mass or carbon mass? One gigatonne of carbon is not one gigatonne of CO2.
- Is the percentage based on concrete-production, cement-production, calcination or process emissions?
- What age and service-life period are included?
- Which surfaces are assumed exposed, and what humidity and finish are used?
- Does the calculation include demolition and crushing, and are those operations actually planned?
Claims that omit these details can look precise while comparing unlike quantities. A lower result for a buried foundation and a higher result for an uncovered outdoor panel may both be reasonable because their exposure histories differ.
Bottom line for designers and owners
Installed concrete does recapture atmospheric CO2 through carbonation, but the amount is structure-specific and arrives gradually. Published lifecycle work places one 100-year estimate at 15.5%–17% of concrete-production emissions, while a separate global historical model reports 4.5 GtC sequestered from 1930–2013 with a 43% offset of cement process emissions. Those values describe different accounting systems, not a universal slab-level percentage.
For a real project, expect the first decades to contribute most of the natural uptake, expect buried or sealed concrete to absorb much less than suitably exposed surfaces, and evaluate crushed concrete separately at end of life. Use PD CEN/TR 17310:2019, measured carbonation data or a calibrated model, and publish the assumptions with the result.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
