PSI - Issue 67

G. Goracci et al. / Procedia Structural Integrity 67 (2025) 30–38 G. Goracci/ Structural Integrity Procedia 00 (2024) 000 – 000

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2.1 Sample preparation

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b

Figure 2 : Photographs of Carbonated Samples a) Carbonated periwinkle shell with Ordinary Portland Cement (OPCCPS) b) : Carbonated steel slag composite (CSSC).

2.1.1 Preparation of Carbonated Periwinkle Shell (CPS) The raw materials used for this sample type were OPC CEM-1 52.5R (Rezola) and Periwinkle shell (PS) ash. To prepare CPS, a mixture of 5 g of PS ash and 87.5 mL of distilled water was placed in a sealed plastic tube. CO 2 gas with a pressure of 0.4 bar was bubbled into the mixture while stirring at a speed of 1700 rpm for 15 minutes at room temperature. Subsequently, the sample was immersed in a water-rich CO 2 environment overnight, following a wet carbonation method. The resulting carbonated Periwinkle powder was obtained by centrifugation for 10 minutes followed by drying at 80 °C overnight. 2.1.2 Production of Carbonated concrete (OPCCPS) The cement was first mixed with CPS using a cement-to-ash ratio of 0.3. Water was then added at a water-to cement (w/c) ratio of 1, along with a superplasticizer at a concentration of 6 wt% relative to that of the OPC. The mixture was stirred for 90 seconds, allowed to rest for 60 seconds, and then stirred again for an additional 90 seconds. The resulting mixture was poured into a silicon mold and left to cure in a desiccator with a relative humidity of 100% for 24 hours. 2.1.3 Preparation of Carbonated Steel Slag Composite (CSSC) The raw materials used for this sample type were steel slag (NIPPON STEEL) and Portlandite (SIGMA ALDRICH). The steel slag was mixed with 75% by weight of Portlandite and water at a ratio of 0.15. The mixture was then subjected to a 5-ton load to form pellets. The pellets were carbonated in a 100% CO 2 atmosphere for 5 minutes in a desiccator, following a semi-dry carbonation method. After carbonation, the pellets were sealed in plastic bags and stored for 7 days. Following the storage period, the pellets were dried overnight at 60 °C.2.2 2.2 Characterization Methods The carbonation efficiency of the samples was evaluated using thermogravimetric analysis (TGA) with a TGA 500 instrument (TA Instruments). Approximately 10 mg of powder was heated from room temperature to 900 °C at a rate of 10 °C/min under a flow of nitrogen gas. Diffraction experiments were conducted using a Bruker X-ray diffractometer (D8 ADVANCE, US) with Cu Kα radiation (λ = 1.5418 Å), to identify the mineral phases of the