Concretos com altos teores de filer calcário em misturas binárias e ternárias com cinza volante: resistência à compressão mecânica, microestrutura e sustentabilidade

Abstract

The cement industry produces about 5% of all CO2 emissions that contribute to greenhouse gases, which represents a significant number compared to the worldwide magnitude of its production, with the respective effects of the use of natural resources and the increase in temperature from the earth. The higher the contents of mineral additions (MA) to Portland cement (PC), the lower the clinker contents, making the PC more sustainable due to the lower consumption of resources and energy. Among inert MA, the most used in cement factories are limestone fillers (LF) ground together with clinker, as they are found almost everywhere in the world. Current research points to the increase in the use of LF to replace PC at levels greater than those provided for in standards, including in ternary mixtures with pozzolans, in order to obtain more resistant, sustainable concretes with a cheaper unit cost, without loss of its durability characteristics. This thesis aims to use high levels of PC substitution (50 to 80%) in binary, ternary and quaternary mixtures of MA (LF and Fly Ash - FA) and addition of Hydrated Lime (HL), with the study of probable useful life, through carbonation and sustainability through Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). It was possible to observe the changes that occurred in the concrete mixes due to the variation in the PC, LF, FA and HL content and its implications on compressive strength, carbonation, formation of carbonated compounds, combined water, Portlandite and carbonate contents, as well as the consequences of these changes in the sustainability parameters (LCA and LCC). In this sense, it was possible to verify the feasibility of preparing concrete through the use of a hyperplasticizer additive that allowed the reduction of the w/b content (0.25), together with the optimization of particle packing, resulting in a workability of 100+20 mm and compressive strengths ranging from 51.8 to 88.6 MPa at 91 days of age. The highlights are the mixtures FC50 and FC60CH10 with compressive strength (at 91 days) and carbonation coefficient (kc) of 87.8/88.6 MPa and 0.22/0.34 mm.t-05, respectively. Another trait worth mentioning is FC70CV10P, with only 20% PC and a consumption of 87 kg.m-3 and 104 L.m-3 of clinker and water, respectively, obtained a compressive strength, at 91 days, of 51, 8 MPa, as well as a carbonation coefficient (kc) of 0.27 mm.t-0.5, leading to a service life 55 times longer than the maximum used in this study (100 years). Regarding the useful life, it was found that, with the exception of the FC70CV10 and FC70CV10CH10 traits, all the others had a useful life greater than 100 years, taking the FC50, FC60 and FC60CH10 traits to the first position in relation to LCA and LCC.