Mechanical and Mineralogical Properties of Concrete Incorporating Low-Lime Calcium Silicate Cement Under Accelerated...

Low-lime calcium silicate cement (CSC) offers the potential to reduce CO₂ emissions during cement production and sequester CO₂ through carbonation curing. However, the relationship between CSC replacement, strength development, and CO₂ uptake requires clarification at the concrete scale. This study evaluated the effects of replacing OPC with 0%, 25%, and 50% CSC on compressive strength, carbonation behavior, phase evolution, and CO₂ sequestration in concrete. Following initial steam curing, specimens underwent carbonation curing under 20% CO₂ for up to 14 days. Compressive strength and carbonation depth were measured, while phase evolution and CO₂ uptake were examined using X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis (TGA). After 14 days, compressive strengths were 35.46, 29.84, and 27.95 MPa, respectively. Although final strength decreased with increasing CSC replacement, the 50% mixture exhibited an approximately 398% increase from its pre-carbonation strength of 5.61 MPa. Corresponding carbonation depths were 8.8, 18.2, and 27.1 mm, and TGA-based net CO₂ uptakes were 18.2, 34.0, and 50.5 kg CO₂/t-concrete. Calcite and vaterite were identified, while infrared spectral changes suggested the formation of silica-rich reaction products. Thus, 50% OPC replacement achieved approximately 28 MPa and 2.8 times the CO₂ uptake of the control under the investigated conditions. These findings demonstrate the potential to combine OPC substitution with mineral CO₂ sequestration, while highlighting a trade-off between compressive strength and CO₂ uptake. Further mechanical and durability evaluations and a comprehensive life-cycle assessment are required to establish structural applicability and net greenhouse gas emission reductions.