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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1. Results and Discussion In Figure 3, the X-ray diffraction (XRD) pattern of the samples is presented, illustrating the effect of carbonation. In both cases, the peaks corresponding to calcite, the primary product of CO 2 capture, dominate the pattern. For the carbonated steel slag composite (CSSC) sample, shown in Figure 3a, peaks associated with Portlandite are present, indicating incomplete carbonation of calcium hydroxide used as a capture agent. Additionally, a halo representing the amorphous phase is clearly observed. In the composite containing carbonated periwinkle shell, peaks of ettringite and aragonite are detected. These secondary mineral phases indicate the ongoing hydration process of Ordinary Portland Cement (OPC) and suggest a distinct carbonation pathway. Thermogravimetric analysis (TGA) measures the weight loss of a sample as a function of temperature, providing insights into the thermal stability and decomposition characteristics of the materials. Figure 4 presents the weight loss percentages of the samples as a function of temperature, specifically for CSSC (a) and OPCCPS (b). In the low-temperature range (below 105°C), the TGA measurement for OPCCPS reveals a significant mass loss, attributed to the evaporation of bulk water present in the sample. Conversely, the CSSC sample exhibits negligible mass loss in this temperature range, indicating minimal bulk water content in the carbonated steel slag cement. In the intermediate temperature range (around 400°C), both TGA plots display a slight weight loss, indicating the dehydroxidation of portlandite present in the samples. This observation corroborates the presence of such a mineral phase as revealed by the X-ray diffraction (XRD) patterns. The decomposition of calcite results in CO 2 , contributing to the overall weight loss in the high temperature range (above 600°C). In fact, in this temperature region, both samples exhibit significant weight loss associated with the decom position of calcite (CaCO₃) into calcium oxide and carbon dioxide. The release of CO₂ reflects the amount of carbon dioxide captured and stored in the material. Notably, the OPCCPS sample demonstrates a higher weight loss percentage compared to the CSSC sample, indicating that the carbonated periwinkle shell has captured a greater amount of CO₂ than the carbonated steel slag. These results may be the effect not only on of the different composition of the samples, but even due to the different carbonation method.

Figure 5: Reflectance properties of carbonated samples and comparison with OPC cement paste. The yellow area represents the solar window, which encompasses the wavelength range of solar radiation, while the light blue area corresponds to the atmosphere window.

Table 1 Comparison of SRI parameter for materials normally employed in construction and proposed solution for UHI mitigation

Material Asphalt

SRI 0-10