Zhichao Liu

Carbonatable binders offer a promising route for CO2 utilization and low-carbon cementitious materials, but their carbonation behavior is complicated by the asynchronous responses of coexisting mineral phases. This study developed a mineral-phase-informed machine-learning framework to interpret and regulate the time-resolved wet carbonation response of multimineral carbonatable binders. Using a dataset comprising 163 experimental samples, an artificial neural network was used to predict mineral-phase composition from synthesis parameters, while an XGBoost model predicted the pH-decrease-rate curve from mineral-phase composition and normalized reaction time. Model interpretation indicated that in γ-C2S-dominated binders, C3S2 was associated with an enhanced intermediate-stage response, whereas β-C2S was associated with a delayed and more sustained response. These patterns were qualitatively supported by pH and conductivity measurements of high-purity mineral phases. Inverse optimization further translated the model-inferred phase-response relationship into binder design. Compared with the nonoptimized sample, optimized binders showed higher compressive strength, increasing from 55.78 to 61.04–66.33 MPa, and slightly higher mean CO2 uptake, increasing from 156.36 to 161.81–164.27 kg/t. These results demonstrate that mineral-phase-informed machine learning can guide the design of carbonatable binders with tailored carbonation responses and improved engineering performance.

1. The cement industry accounts for approximately 5-8% of global anthropogenic CO2 emissions, presenting a critical decarbonization challenge [1,2]. Carbonatable binders, which harden by chemically...

γ-dicalcium silicate (γ-C₂S) is a carbonatable binder with excellent carbonation reactivity. However, its extremely low hydration activity prevents the paste from setting and hardening properly, making it difficult to be directly cast and molded. This study introduces β-hemihydrate gypsum as an early-strength regulating agent, which utilizes its rapid hydration to form dihydrate gypsum, thereby imparting early-age strength to the composite system and enabling subsequent carbonation curing after demolding. The experimental investigation examined the effects of β-hemihydrate gypsum content on the fluidity, setting time, and carbonation performance of γ-C₂S paste. The results indicate that when the β-hemihydrate gypsum content is not less than 10%, the paste can obtain sufficient early-age strength to achieve smooth demolding. At a β-hemihydrate gypsum content of 10%, after pre-drying treatment, samples subjected to carbonation curing for 24 h under a CO₂ partial pressure of 0.3 MPa achieved a peak absolute dry compressive strength of 117.29 MPa with a softening coefficient of 0.92. Further increases in β-hemihydrate gypsum content lead to reductions in both strength and water resistance. Microstructural analysis reveals that at a gypsum content of 10%, the crystalline network of dihydrate gypsum interlocks and coexists with calcium carbonate and silica gel generated from γ-C₂S carbonation, forming a compact structure. In contrast, the framework formed by excessive gypsum before carbonation restricts the continuous interlocking and overall development of calcium carbonate products generated from γ-C₂S, resulting in deterioration of structural integrity and mechanical properties. This study provides theoretical foundation and technical support for the engineering application of γ-C₂S-based carbon mineralization materials.

Despite significant advances in the synthesis of biomimetic materials, the scalable fabrication of high‐performance bulk materials under ambient conditions remains a formidable challenge— particularly when it comes to achieving rapid processing while preserving superior mechanical properties. Herein, inspired by nacre's “brick‐and‐mortar” structure, this work develops an energy‐efficient approach that utilizes ice‐templating technology as the structure framework and carbon mineralization for rapid CaCO₃ production, resulting in a strong yet tough carbon mineralized material (CMM) while also fixing CO₂. This material replicates both the hierarchical microstructure and chemical composition of nacre. By precisely controlling the freezing dynamics with dual temperature gradients, this work creates an ordered lamellar skeleton composed of γ‐dicalcium silicate (γ‐C₂S). The rapid, in situ carbon mineralization under mild conditions generates interspersed CaCO₃ grains within this structure, which are then infiltrated with gelatin to form a nacre‐like CMM with exceptional mechanical properties. The resulting material exhibits a flexural strength of 45 MPa (eight times that of a cement‐hydrogel composite) and a fracture toughness of 2.03 MJ m⁻³ (a 20‐fold improvement over unmodified CMM), while maintaining a density of only 1.2 g cm⁻³. The enhanced performance stems from multiscale toughening mechanisms, including crack deflection, secondary crack formation, and strong interfacial bonding, all of which facilitate efficient energy dissipation. This work establishes a new paradigm for designing high‐performance synthetic materials through the synergistic integration of biomimetic principles with carbon mineralization, offering promising applications in the development of sustainable infrastructure and carbon neutrality.

Traditional high-temperature fabrication methods for ceramics suffer from significant energy consumption and limit the development of advanced ceramics incorporating temperature-sensitive materials. While bioinspired mineralization provides an effective strategy to realize the room-temperature preparation of ceramics, scaling up production remains a challenge. Herein, we demonstrate a room-temperature procedure for the fabrication of large-scale ceramics by using the carbonation reaction of sodium alginate (SA)-doped γ-dicalcium silicate (γ-C₂S) compacts. This bioinspired in situ mineralization process regulates molecular interactions and microscopic crystal alignment, resulting in the formation of CO₂ mineralized ceramics with specifically oriented mesocrystals and exceptional mechanical properties rivaling those of biological materials. Through this strategy, we demonstrate that the advanced ceramic composites with compressive strength approaching 300 MPa can be fabricated at a large scale, with the additional benefits of fixing about 200 kg of CO₂ per ton of CO₂ mineralized ceramics. Our innovative approach shows great potential for the efficient and cost-effective fabrication of large-scale and high-performance bioceramics, aligning with the goals of sustainable development involving reducing the energy consumption and achieving carbon neutrality.

Steel slag as an alkaline industrial solid waste, possesses the inherent capacity to engage in carbonation reactions with carbon dioxide (CO₂). Capitalizing on this property, the current research undertakes a systematic investigation into the fabrication of high-carbonation precast concrete (HCPC). This is achieved by substituting a portion of the cementitious materials with steel slag during the carbonation curing process. The study examines the influence of varying water–binder ratios, silica fume dosages, steel slag dosages, and sand content on the compressive strength of HCPC. Findings indicate that adjusting the water–binder ratio to 0.18, adding 8% silica fume, and a sand volume ratio of 40% can significantly enhance the compressive strength of HCPC, which can reach up to 104.9 MPa. Additionally, the robust frost resistance of HCPC is substantiated by appearance damage analysis, mass loss rate, and compressive strength loss rate, after 50 freeze–thaw cycles the mass loss, and the compressive strength loss rate can meet the specification requirements. The study also corroborates the high-temperature stability of HCPC. This study optimized the preparation of HCPC and provided a feasibility for its application in precast concrete.