Cement is considered the basic component with the highest environmental impact in construction, in terms of CO₂ emissions. As for the aggregates, the process of comminution of rocks, in addition to artificial sand, generates stone powder that ends up being stored outdoors, generating environmental damages. Thus, the replacement of cement by stone powder appears as an attractive alternative towards the sustainable concretes. In this context, the objective of this paper is to determine the maximum packing density in Portland cement, silica fume and stone dust pastes, to determine the optimal cement substitution content for the stone powder. In addition, it is intended to verify the influence of excess water on the consistency of the mixtures produced. The substitution was done in contents equal to 0%, 7%, 14% and 21% by volume and, for each content, the packing density was determined analytically by CPM model and combinations were reproduced experimentally. Excess water was checked by the mini Kantro cone test. The results showed that the higher cement substitution content of the stone powder obtained the higher packing density, experimental and analytical, and the higher workability, allowing economic and environmental advantages. Analyzing each material, the stone powder resulted in the highest packing density and silica fume is the lowest one. Therefore, finer particles resulted in lower packaging densities, due to the greater specific surface area, which demands more water. The agglomeration resulted in more empty gaps between the grains. In addition, mixtures flowability increased with the increase of the stone powder content. As the excess water is responsible for mixture lubrication, a higher packing density for a given volume of water improves the flowability.

This study examines the carbonation and realkalization dynamics of various cementitious systems, with a focus on the influence of cement composition on their susceptibility to carbonation and potential for realkalization. Four cement types were evaluated: CEM I, CEM II/A-LL, CEM II/A-V, and CEM II/B-W. Carbonation depth measurements revealed that blended cements, particularly CEM II/A-LL, showed greater carbonation susceptibility due to their lower portlandite content and increased porosity. In contrast, realkalization experiments demonstrated that blended cements exhibited enhanced ionic transport, resulting in deeper penetration of the alkaline solution. CEM II/A-V showed the highest realkalization depth, while CEM I displayed the lowest, highlighting the role of microstructural characteristics in realkalization efficiency. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) confirmed that carbonation led to portlandite depletion and the formation of calcium carbonate, with limited portlandite regeneration upon realkalization. Thermodynamic simulations further supported the experimental findings, revealing that realkalization only partially restored alkalinity, with no significant dissolution of carbonation products. These results emphasize the need for tailored realkalization strategies, considering cement composition and pore structure, to optimize remediation efforts and enhance the long-term durability of concrete structures.

Corrosion is one of the causes of failure in reinforced concrete structures, and forming a passive film on the steel is essential for protection. Although several studies have looked at passive film formation in concrete pore solutions, few have considered its formation in hardened concrete and the influence of silica fume (SF) in the binder composition. This study aims to evaluate the influence of the SF content on passive film formation time in concrete. Periodic measurements assessed the electrical resistivity and corrosion current density of concrete samples containing 5%, 10%, 15%, and 20% SF. The alkalinity of the mixtures and the kinetics of the pozzolanic reaction were also monitored by XRD and titration tests. The control mixtures exhibited susceptibility to corrosion, regardless of the curing age evaluated. In contrast, the partial replacement of cement with SF accelerated the formation of the passive film on the steel surface, suggesting a delayed onset of corrosion due to modifications in the physical properties of the concrete. Also, the portlandite content and pH can predict passive film formation, with SF significantly accelerating this process.

O livro reúne três capítulos com pontos considerados fundamentais e de interesse da comunidade acadêmica. Com uma abordagem prática, a equipe da Impeta traz os seus conhecimentos através de uma linguagem bem descontraída e, principalmente, com um material com muitos exemplos para facilitar o entendimento do estudante. O maior desafio desta obra é descomplicar a jornada acadêmica e por isso o título deste livro não poderia ser outro, se não, Descomplica com a Impeta.

A durabilidade das estruturas de concreto está diretamente atrelada ao meio no qual os materiais estão expostos. O entendimento dos mecanismos degradantes atuantes nas estruturas é importante, visto que estudos podem ser desenvolvidos para o melhoramento dos materiais, possibilitando que estes sejam mais duráveis sob diferentes condições ambientais. O presente trabalho apresenta um estudo de caso, com o objetivo de analisar a vida útil de uma edificação, localizada em Curitiba-PR, estando a mesma sujeita a continua emissão de CO2, advinda do meio urbano. Considerando o mecanismo de carbonatação como um dos principais responsáveis ao desencadeamento da corrosão de armaduras de edificações, localizadas nos grandes centros urbanos, a pesquisa aplicou dois modelos de previsão de vida útil, Tuutti (1982) e Possan (2010), para determinar a vida útil da estrutura, levando em consideração somente esse fenômeno. Como resultados o trabalho corroborou a hipótese de que os pilares internos estão mais sujeitos ao mecanismo de carbonatação, isto por estes não estarem em contato direto com a água da chuva. Nos casos em que se notou maior agressividade (pilares internos) a vida útil da edificação já está comprometida, com um processo de corrosão instalado. Nos pilares externos, situação mais amena, a vida útil verificada é maior, ficando próximo e até ultrapassando os 50 anos sugeridos pela norma brasileira, NBR 15575 (2013).