Influência da composição química do cimento supersulfatado sujeito à carbonatação natural

• Main Author: Ré, Julia Kich de
• Publication Date: 2025
• Format: Master thesis
• Language: por
• Source: Repositório Institucional da UTFPR (da Universidade Tecnológica Federal do Paraná (RIUT))
• Download full: http://repositorio.utfpr.edu.br/jspui/handle/1/36052
• topic: Concreto - Aditivos; Cimento - Composição; Concreto de alta resistência; Agregados (Materiais de construção); Concrete - Aditives; Cement - Composition; High strength concrete; Aggregates (Building materials); CNPQ::ENGENHARIAS::ENGENHARIA CIVIL; Engenharia/Tecnologia/Gestão

Supersulfated cement (SSC) is a binder composed mainly of blast furnace slag, along with calcium sulfate and an alkaline activator. SSC exhibits various properties, such as good compressive strength at advanced ages, low heat of hydration, and good performance in marine environments with high sulfate content. However, SSC is susceptible to carbonation. Due to its low or negligible portlandite content, ettringite (AFt) and calcium silicate hydrate (C-S-H), the main hydrated phases of SSC, are more prone to carbonation. The behavior of SSC under natural carbonation and the impact of its composition on its hydrated products are not yet fully understood, making it difficult to assess performance and predict the service life of this material. Therefore, the present study aims to evaluate the mechanical and microstructural behavior of different SSC compositions under natural carbonation. Three SSC formulations were analyzed, combining two types of blast furnace slag (EP and EB) and two types of alkaline activators, Portland cement and potassium hydroxide. The samples were exposed in a laboratory environment with a CO₂ concentration of approximately 0.05% for up to 28 weeks. The tests included monitoring compressive strength and measuring carbonation depth over time. Microstructural analyses using X-ray diffraction (XRD) and thermogravimetry (TG/DTG) were conducted to track the carbonation of hydrated phases (AFt and C-S-H) and the formation of calcium carbonates. Additionally, it was observed that EP slag favors the formation of AFt, whereas EB slag promotes the formation of C-S-H. The results indicated that compositions with EB blast furnace slag, which has a higher SiO₂ content, exhibited greater carbonation depth and loss of mechanical strength, whereas the composition with EP blast furnace slag, which has a higher CaO content, showed better performance. Microstructural analyses revealed that C-S-H underwent carbonation more intensely than AFt. The use of KOH as an alkaline activator resulted in the worst mechanical performance and the greatest carbonation depths compared to the other formulations. The findings confirm the high susceptibility of SSC to carbonation, with an accelerated progression of the carbonation front and a significant reduction in mechanical strength, especially in compositions with EB slag. Furthermore, the decomposition of AFt and the decalcification of C-S-H, along with the formation of calcium carbonates, were observed in all formulations. These results highlight the importance of further understanding the carbonation mechanisms in SSC to develop strategies that enhance its durability and performance.