The environmental impact of reinforced concrete structures occurs during all phases of the building's life cycle, with emphasis on the stages of extraction and transport of raw materials and concrete production. An effective way to reduce the impact of these structures is to reduce the consumption of materials with the use of optimization techniques. The present study evaluates carbon dioxide emissions of concrete with two different compressive strengths for the region of Chapecó, SC. With these data, the optimization of structural elements was performed aiming to minimize their environmental impact. The carbonation of optimized elements was also evaluated. Among the results, it was observed that concretes with lower strength have better CO2 absorption rates (for the elements analyzed 20MPa concrete absorbed about 90% and 112% more CO2 than 35MPa concrete to columns and beams, respectively). In addition, it was observed that local factors can strongly influence the impacts, with the transport of materials reaching up to 6.4% of total emissions.

Ultra-high performance concrete (UHPC) has emerged as a promising material in civil construction due to its excellent mechanical properties. However, its dense microstructure makes it highly susceptible to explosive spalling under elevated temperatures, limiting its application in fire-exposed environments. The incorporation of polypropylene (PP) fibers has been widely investigated as a strategy to mitigate this phenomenon, although the literature presents a broad range of dosages with varying levels of effectiveness. In this context, the present study evaluated UHPC mixtures containing medium (2.7 kg/m3) and high (8.1 kg/m3) PP fiber contents—based on literature classifications—to assess their influence on workability, mechanical performance, spalling behavior, and residual compressive strength after exposure to 700 °C. The addition of fibers significantly affected the fresh-state consistency, with flow reductions of 13.6% and 44.4% for the medium and high dosages, respectively. Despite these changes, the mechanical performance before heating remained statistically unaffected. In contrast, spalling occurred in all reference specimens (without fibers), while both fiber-reinforced mixtures effectively prevented the phenomenon, indicating that even the medium dosage was sufficient for mitigation. This behavior is attributed to the melting of PP fibers during heating, which promotes microcrack formation and facilitates the release of internal vapor pressure. This mechanism is further supported by the observed mass loss of approximately 9% in both mixtures after thermal exposure.

The building industry is one of the greatest environmental impact causers in the planet. Cement is the second most used material in the world and the consumption of concrete ranges between 20 to 30 Gt yearly. This demand for the materials ten ds to increase for the next 100 years. The increase of concrete strength to reduce the material consumption is one of the options proposed in literature to reduce the environmental impacts in building industry. However, few studies have been carried about the actual advantages of this strategy in building production. In this paper, a 15-storey reinforced concrete building was designed with three different concrete grades for its columns: 30 MPa, 40 MPa and 50 MPa. The results for the volume of concrete and the amount of reinforcing steel to produce the columns were used to perform a cradle-to-gate life cycle assessment (LCA) to determine the alternative with less environmental impacts in the production stage. Results indicate an advantage to adopt higher strength concretes in columns to reduce environmental impacts and the consumption of materials. Direct effects of higher strength in concretes made possible to reduce the consumption of concrete by 15%. There was also a significant reduction caused by indirect effects of higher strengths in concrete, with the reducing of steel consumption up to 22%. With the combination of the direct and indirect effects of higher compressive strengths, it was possible to reduce the environmental impacts of reinforced concrete in all categories studied in the LCA.

The inclusion of carbon nanotubes (CNTs) in cementitious composites has been studied due to their electrical, thermal, and mechanical enhancing properties. Considering the hydrophobic characteristics of CNTs, these nanomaterials need to be well dispersed in the aqueous media in which they are inserted to guarantee those gains. Among the methods applied to produce such composites is the dispersion of CNTs on the surface of anhydrous cement particles using non-aqueous suspensions such as acetone, ethanol, or isopropanol. Even though those non-aqueous media have been individually studied by researchers, comparisons of the efficiency of CNTs dispersion was not found in the literature. Therefore, as a novelty, the present article aims to analyze the influence of the addition of the multi-walled CNTs dispersed in the cited three types of non-aqueous suspensions on the cement paste’s electrical and mechanical properties. Pastes containing 0%, 0.5%, and 1.0% of CNTs were prepared on the surface of anhydrous cement particles using a pre-dispersion technique based on simultaneous sonication and mechanical agitation in the three cited media. Tests to determine electric-volumetric resistivity, compressive strength, and splitting tensile strength were performed. It was observed that acetone dispersion decreases the cement paste’s electrical resistivity, even without the addition of CNTs. The cementitious composites with CNTs demonstrated increased mechanical strength (both compressive and tensile) using all three dispersion media. Statistical analysis (analysis of variance—ANOVA—and Tukey’s Test) was performed to evaluate the significance of the results.

A construção civil responde por aproximadamente 38% das emissões mundiais de CO₂ e a fabricação do cimento Portland é o principal fator gerador desse impacto. Uma alternativa para minimizar as emissões do setor é a utilização de materiais pozolânicos como substituição parcial do cimento. A cinza de casca de arroz, um resíduo da indústria agrícola, é rica em sílica amorfa e pode ser usada como material pozolânico. Este estudo avaliou as propriedades mecânicas e físicas do concreto produzido com 10% e 20% de substituição do cimento pela cinza de casca de arroz, comparando-os com o concreto de referência, cujo aglomerante foi exclusivamente o cimento. Foram analisadas a consistência, o módulo de elasticidade, a resistência à compressão e à tração. Os resultados indicaram que a introdução da cinza reduziu a trabalhabilidade do concreto fresco, não alterou a rigidez das amostras e proporcionou um bom desempenho mecânico após 90 dias de cura.