Cement is one of the most widely used structural materials and serves as the primary component of concrete. Among the various types, Portland cement is the most commonly utilized due to its excellent strength and corrosion resistance. Recently, efforts have been made to incorporate various functional additives into Portland cement to impart new properties; however, studies on the resulting changes in corrosion resistance remain insufficient. While the existing research has largely focused on impurities in cement, systematic studies on the effects of interstitial elements on the crystallization and electrochemical behavior of cement are scarce. This study investigates the influence of carbon (C) addition on the crystallographic structure and electrochemical properties of Portland cement. C concentrations from 0 to 10 wt.% were added. The microstructure and crystallographic structure with different C concentrations were analyzed using FE-SEM and XRD. The bonding characteristics of cement components according to the C composition were measured using XPS, hardness was measured using Vickers hardness, and electroconductivity was calculated using a 4-point probe. The electrochemical behavior was evaluated according to the ASTM G 61 standards through OCP, EIS, and potentiodynamic polarization tests. As the composition of C increased, the number of voids and cracks decreased, while the electrical conductivity increased from 1.7 × 10⁻⁴ to 4.3 × 10⁻². Additionally, the resistance tended to decrease with the increase in C composition. Therefore, the concentration of C needs to be controlled depending on the required function of the cement.

Portland cement is a critical material widely used in the construction industry, where its crystallization and microstructure are key factors determining its physical and mechanical properties. This study investigated the effect of sulfur on the crystallization and microstructure of Portland cement. Sulfur acts as either an additive or an impurity during the cement production process, influencing the crystal size, distribution, and microstructure formation of major hydration products such as C₃S (tricalcium silicate), C₂S (dicalcium silicate), C₃A (tricalcium aluminate), and C₄AF (tetracalcium aluminoferrite). Through quantitative and qualitative evaluation using XRD, SEM, and EPMA analytical techniques, this study examined changes in the hydration characteristics, crystal structure, and microstructure of Portland cement with varying sulfur concentrations. The results revealed that increased sulfur content promotes the crystal growth of C₃A and the formation of ettringite, which alters the density of the structure during the early stages of hydration and affects its long-term strength properties. These findings suggest that controlling the sulfur content plays a significant role in optimizing the performance and durability of Portland cement. This study highlights the potential for developing high-performance cement by regulating sulfur levels during the production process, contributing to advancements in construction materials.

Portland cement is one of the most widely used construction materials employed in both large-scale structures and everyday applications. Although various materials are often added during production to enhance their performance, NaCl can be introduced in the process for various reasons. Despite this issue, existing studies lack sufficient quantitative data on the effects of NaCl on cement properties. Therefore, this study aims to investigate the physical and chemical degradation mechanisms in cement containing NaCl. Cement specimens were prepared by mixing cement, water, and NaCl, followed by stirring at 60 rpm and curing at room temperature for seven days. Microstructural changes as a function of the NaCl concentration were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were evaluated via open-circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization tests. The results indicate that increasing the NaCl concentration leads to the formation of fine precipitates, the degradation of the cement matrix, and the reduced stability of major hydration products. Furthermore, the electrochemical analysis revealed that higher NaCl concentrations weaken the passive layer on the cement surface, resulting in an increased corrosion rate from 1 × 10⁻⁷ to 4 × 10⁻⁷ on the active polarization of the potentiodynamic polarization curve. Additionally, the pitting potential (E_pit) decreased from 0.73 V to 0.61 V with an increasing NaCl concentration up to 3 wt.%. This study quantitatively evaluates the impact of NaCl on the durability of Portland cement and provides fundamental data to ensure the long-term stability of cement structures in chloride-rich environments.