Resumo O concreto é um dos materiais mais usados na construção civil no Brasil, e seu uso difundido advém da grande facilidade de execução e adaptação às mais diversas formas. Reduzir o consumo dos materiais envolvidos na produção do concreto é uma das maneiras de buscar uma maior sustentabilidade da construção civil. Estas reduções de consumo de materiais, se avaliadas levando-se em conta também os impactos que a produção e o transporte dos mesmos geram no meio ambiente, podem vir a aprimorar ou redirecionar as conclusões ou decisões a serem tomadas em relação à busca de uma maior sustentabilidade ambiental. Dentro deste enfoque foram levantadas e avaliadas as emissões de dióxido de carbono (CO2), impactos ambientais gerados quando da extração/produção e transporte até o local de utilização das matérias primas do concreto. Juntamente foram levantadas e avaliadas as emissões na produção e transporte do concreto até a obra. Dentre as conclusões do estudo constatou-se que menores resistências características do concreto produzirão menores emissões de CO2, e que a influência do transporte nas emissões é significativa devido às longas distâncias percorridas pela maior parte das matérias primas.

Concrete is one of most used materials in construction and also one of the main responsible for the emission of carbon dioxide, or CO 2 , in the atmosphere. Thus, in order to study ways to reduce this impact, it is important to evaluate the influence of each raw material of the reinforced concrete, as well as the phases of the life cycle in which these impacts are more relevant. This paper presents a review of recent studies related to carbon dioxide emissions of the materials of reinforced concrete. In this review, we sought to identify the phases of the life cycle of reinforced concrete most focused by researches. It was found that the cement production stage is the most contemplated in the studies, many of them focusing on the additions of complementary cementitious products, since cement is among the materials that contributes decisively to the total CO 2 emissions. The structure sizing, with the definition of concrete strength to be adopted in the design, were also extensively investigated, since these are phases in which it is identified a greater possibility of contribution, by the researchers, for the minimization of the impacts.

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.

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.