Gi-Joon Park

Pilot-scale validation of controlled CO₂ curing for reinforced concrete members remains limited. This study developed a 2400 L high-temperature CO₂ curing chamber integrating control of temperature, relative humidity (RH), CO₂ concentration, and pressure with real-time monitoring and automated CO₂ regulation. Its applicability was evaluated using commercial concrete bricks and a reinforced concrete slab through mass monitoring, compressive strength testing, phenolphthalein-based carbonation assessment, thermogravimetric analysis (TGA), flexural testing, and carbonation depth measurement. Real-time mass monitoring showed a net mass gain of 50.7 g after 1 h, corresponding to 2.8% of the initial mass. The CO₂-cured bricks achieved a compressive strength of 9.77 MPa, with a calculated CO₂ uptake of 5.72% based on TGA. The CO₂-cured slab exhibited a compressive strength of 41.9 MPa, comparable flexural load capacity to the steam-cured slab, and a higher ductility index of 6.86. Carbonation remained within the concrete cover without reaching the reinforcement. Within the scope of the investigated materials and curing conditions, these results demonstrate the pilot-scale feasibility of controlled CO₂ curing for commercial concrete products and reinforced concrete members and provide a basis for further member-scale validation and process optimization.

Mineral carbonation offers a pathway for permanent CO₂ storage in construction materials while, in many systems, improving product performance and enabling the reuse of cementitious wastes. However, laboratory-scale carbonation efficiencies often decline during pilot- and industrial-scale implementation because conversion is governed not only by reaction chemistry but also by spatially heterogeneous transport conditions. Local velocity, CO₂ concentration, residence time, temperature, moisture, and phase distribution collectively determine the reaction environment experienced by each specimen, particle, or slurry region. This review develops a unified computational fluid dynamics (CFD) framework linking material carbonation with reactor hydrodynamics, reactive transport, model selection, validation, and scale-up. Four representative processes—accelerated carbonation curing, CO₂ injection during mixing, recycled-concrete-aggregate carbonation, and aqueous mineral carbonation—are interpreted as humid gas–porous solid, gas–liquid–solid non-Newtonian suspension, packed-bed, and gas–liquid–solid slurry systems, respectively. A Reynolds–Damköhler framework, extended through a local Damköhler number, Da(x), is proposed to characterize spatial variations in transport–reaction competition. Three coupled mechanisms are identified as essential for predictive modelling: reaction-induced CO₂ depletion, two-way moisture exchange between gas and cementitious phases, and thermal feedback on reaction kinetics and CO₂ solubility. Process-specific modelling strategies, coupling requirements, and validation criteria are then synthesized. The resulting framework enables CFD-informed reactor design, diagnosis of flow-induced non-uniformity, and more reliable scale-up by linking hydrodynamic performance to material conversion, product uniformity, energy demand, and process-level carbon efficiency.

Reclaimed water generated during concrete production contains suspended cementitious solids that can serve as reactive phases for CO2 mineralization. This study investigates the carbonation behavior of reclaimed water and evaluates its applicability for CO2 sequestration and reuse in cementitious materials at both laboratory and pilot scales. Carbonation experiments were conducted under varying CO2 injection rates and solid contents to examine their influence on carbonation kinetics and CO2 uptake. The results showed that increasing the CO2 injection rate significantly accelerated carbonation due to enhanced gas-liquid mass transfer, while excessive solid content introduced transport limitations that reduced effective carbonation efficiency. To enable real-time monitoring of the carbonation process, an in-line density measurement approach was developed and validated against thermogravimetric analysis (TG). The density-based method exhibited strong correlation with TG-derived CO2 uptake at laboratory scale and remained reliable under pilot-scale conditions, although slight deviations were observed due to compositional heterogeneity in actual reclaimed water. Mineralogical and microstructural analyses confirmed that carbonation converted calcium-bearing phases into stable calcium carbonate, with calcite identified as the dominant carbonation product. Pilot-scale experiments using a 1000 L carbonation reactor demonstrated consistent carbonation behavior and confirmed the scalability of the process. Concrete mixtures prepared with carbonated reclaimed water exhibited mechanical performance comparable to those prepared with conventional mixing water. These results indicate that carbonation of reclaimed concrete wash water provides a feasible pathway for simultaneous CO2 mineralization and recycling of wash water in concrete production systems.

In this study, cementless concrete was produced by completely replacing cement with ground granulated blast furnace slag (GGBFS) and using calcium hydroxide (CH) as the alkali activator. The effects of silica fume (SF) substitution (0%, 10%, and 20%) and curing conditions (ambient, high-temperature steam, and high-temperature water) on the fundamental properties of cementless concrete were examined. Higher SF content reduced slump flow but maintained adequate filling ability. The lower pH of CH delayed setting, particularly at higher SF substitution levels. Under high-temperature curing, pozzolanic reactions improved strength development, resulting in compressive and flexural strengths of 106.1 MPa and 28.3 MPa, respectively, at 20% SF substitution with high-temperature steam curing. The developed cementless concrete is expected to serve as a high-strength, low-carbon structural member for use in precast and modular concrete industries that use high-temperature curing processes.

This study investigates the carbonation degree of reclaimed water (RW) and its potential use as mixing water for cementitious materials under controlled laboratory conditions using a simplified CO₂ injection method. To reproduce the chemical environment of actual RW, a synthetic reclaimed water (SRW) system with a cement-to-sand ratio of 8:2 was prepared and used throughout the evaluation. Thermogravimetric analysis revealed that the cementitious solids suspended in SRW exhibit high reactivity with CO₂, achieving a net CO₂ uptake of 16.8%, equivalent to 8.31 g of CO₂ sequestered per kilogram of RW. The use of untreated RW as mixing water slightly reduced flowability and increased superplasticizer demand compared with distilled water, whereas carbonation treatment of RW improved workability and mitigated the rapid initial setting typically observed with untreated RW. Notably, replacing 3% of the cement with carbonated RW solids did not cause any reduction in compressive strength, indicating that the carbonated solids can be incorporated without compromising mechanical performance. These results confirm that the CaCO₃ formed during RW carbonation remains stably retained within mortar and concrete, demonstrating the feasibility of using carbonated RW as a dual-function material—serving both as mixing water and as a medium for CO₂ sequestration.