In a recent article published in Carbon Capture Science & Technology, researchers explored in-situ carbon capture and sequestration (CCS) of CO2 integrated with steam-enabled three-dimensional concrete printing (3DCP).
The technology used a two-step extrusion-based system to capture CO2 and directly inject it into the concrete at the nozzle printhead during deposition. This process accelerated carbonation reactions within the concrete, improving its mechanical properties.
Study: Carbon capture and sequestration with in-situ CO2 and steam integrated 3D concrete printing. Image Credit: sergey kolesnikov/Shutterstock.com
Background
The building and construction (B&C) industry is crucial to the global economic progress across nations. However, it accounts for about 40% of energy-related CO2 emissions and 36% of the world's final energy consumption.
Consequently, 3DCP's transformative potential is gaining prominence as it leverages additive manufacturing principles to redefine traditional construction processes. 3DCP offers multifaceted benefits, including lower demand for natural resources, shorter supply chains due to on-site construction, and a considerable decrease in workplace hazards due to the reduced need for manual labor in high-risk tasks.
Furthermore, permanent sequestration of CO2 in B&C is viable using 3DCP technology. However, the impact of artificial carbonation solutions coupled with 3DCP in improving the concrete’s mechanical performances, CCS capacity, and process scalability requires further investigation. Therefore, this study proposed a two-step extrusion-based 3DCP system and examined its CCS efficacy.
Methods
A three-dimensional (3D) printable concrete mix was prepared using different dry ingredients (silica fume, polycarboxylate superplasticizer, and natural river sand) and Portland cement. Post-printing, the samples were pre-cured for four hours in open-air conditions.
Each sample underwent one of three distinct curing methods:
- Open-air curing: Samples were cured for 28 days in ambient conditions (22±3 °C and 55±10% relative humidity) to replicate typical field construction environments.
- Plastic-sealed curing: Samples were wrapped in plastic to retain moisture during early hydration and cured for 28 days under similar ambient conditions.
- Accelerated carbonation curing (ACC): Samples were exposed to CO2 at 1.4 bars in a sealed tank for two hours, under conditions of 22±3 °C and 55±10% relative humidity. This was followed by 28 days of plastic-sealed curing before testing.
The dynamic rheological properties of freshly printed mortar subjected to CO2-steam integration were assessed. The processed specimens were characterized via thermogravimetric analysis (TGA) to comprehend the influence of printing parameters and curing regimes on their mineralogical compositions past 28 days of curing.
Compression and flexural loading tests were performed to determine the mechanical strength of the prepared specimens. Finally, their macro-pore structures were analyzed using X-ray micro-computed tomography.
Results and Discussion
The 3DCP filament exhibited a smooth surface and maintained shape stability up to 12 layers without an observable slump and deformity.
However, the filament’s surface became rough upon direct integration of CO2 due to intense interactions between the high-pressure gas and the granular medium. Meanwhile, the permissible number of deposited layers increased with elevated CO2 pressure due to rapid setting effects.
Integrating both CO2 and steam significantly improved the printable performance of the concrete mix. This was attributed to the modified water-to-cement (W/C) ratio due to condensation effects near the nozzle, heat dynamics of cement hydration, and volumetric flow rate.
The steam-induced modification in the W/C ratio decreased material viscosity, accounting for enhanced surface roughness and overflow discontinuities.
CO2 integration with 3D printable concrete provided several rheological advantages, including storage modulus, loss modulus, and phase angle of the cementitious fluid. Notably, the 3DCP samples exposed to CO2 exhibited lower phase angles and loss moduli compared to the control samples, facilitated by enhanced hydration kinetics.
The enhancement in mechanical properties of 3D printable concrete depended on curing conditions. For instance, the CO2-injected sample with plastic-sealed curing demonstrated greater compressive strength than the CO2-injected control sample despite its substantially shorter duration of CO2 exposure.
The integration of CO2 and CO2-steam printing configurations substantially reduced the open and total porosities of samples subjected to open-air curing. This indicated the precipitation of carbonates along voids interacting with surface boundaries or interlayer gaps, thereby altering the material permeability to limit the ingress of deleterious agents such as water and chlorides.
Conclusion
Overall, the researchers successfully demonstrated the advantages of incorporating CO2 and steam simultaneously into 3DCP configurations. Samples subjected to CO2-steam integrated printing and open-air curing exhibited maximum carbon uptake with over 38% increase in CCS capability compared to ACC.
Such strengthening effects of CO2-steam were observed even for samples cured under unconfined open-air conditions despite the associated loss of moisture-inducing diminished hydration and pozzolanic activities.
Moreover, up to 50% improvement in 3D printability, 72% in total porosity, 36.8% in compressive strength, and 45.3% in flexural strength was observed depending on curing conditions over the control counterparts of each specimen.
The proposed method offers a promising pathway toward decarbonized construction while expanding viable options for CCS beyond conventional confined curing methods.
Further optimization of mix designs, printing conditions, and the use of flue gases for lower wastage of pure CO2 feedstock can make the process commercially viable.
Journal Reference
Lim, S. G. et al. (2025). Carbon capture and sequestration with in-situ CO2 and steam integrated 3D concrete printing. Carbon Capture Science & Technology, 13, 100306. doi: 10.1016/j.ccst.2024.100306. https://www.sciencedirect.com/science/article/pii/S2772656824001180
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