Contribuição à avaliação do desempenho técnico e ambiental de cimentos com elevados teores de adições minerais

Abstract

Regarding the cement production challenges in a demanding scenario to reduce environmental impacts, the use of mineral additions allows, in addition to achieving technical advantages, to reduce greenhouse gases emissions, the depletion of nonrenewable resources and the fossil fuels use. In view of this scenario, there is a worldwide trend towards the normalization of composite cements produced with more than one type of mineral addition, resulting in ternary and quaternary cements with a low-clinker factor. In this dissertation, thirteen binders with clinker factors ranging from 40% to 50% were studied, constituted by the combination of at least two types of mineral additions, namely blast-furnace slag, fly ash, calcined clay and limestone filler. The binders were studied for physical, chemical, mechanical and environmental performance. For physical, chemical and mechanical performance, the mandatory requirements and criteria of ABNT NBR 16697: 2018 were evaluated. For environmental performance, GHG emissions (in CO2eq) were estimated through life cycle assessment, and verified with the national cement industry recommendations for reducing CO2 emissions , outlined in the Cement Technology Roadmap Brazil for 2050. The results showed that ten of the studied binders met the mandatory criteria and requirements described in ABNT NBR 16697: 2018, while the other three, with a higher limestone content, did not meet the loss on ignition criterion. Among the studied binders, the highlight was the combination of calcined clay, blast-furnace slag and limestone filler, which presented compressive strength at 3 days close to 23MPa and 41MPa at 28 days of age, proving that there is synergy between the mineral additions, explored in this quaternary cement. Furthermore, it is noteworthy the binder constituted by the combination of calcined clay and limestone filler, in the proportion provided by Limestone Calcined Clay Cement (LC3), which presented compressive strength at 3 days close to 29MPa and 41MPa at 28 days of age; however, the emission associated with this binder does not meet the recommendations outlined in the Cement Technology Roadmap Brazil for 2050. Some cements may present emissions higher than the recommendation, provided that the cement produced and consumed, on average, meets the recommendation.