Determinação da ecoeficiência de concretos reciclados em função do consumo de ligantes

Abstract

The cement industry CO2 emissions represent about 7 % of total greenhouse gases emissions worldwide. Cement production is expected to increase by 12 – 23 % above the level of 2014 until 2050, and traditional strategies to mitigate such emissions focusing on cement production will not be able to compensate for this growth. Thus, new alternatives must be developed, which includes increasing the efficiency of cement consumption in concretes. The use of recycled aggregates from CDW as a substitute for natural aggregates generally increases the cement content in recycled concrete (RC) to obtain the same performance. This fact can compromise the principle of sustainability in the use of this residue. Thus, this study aims to establish an overview of the binder’s consumption of RC, whose data are available in the literature, and to measure the efficiency of these mixtures through the Binder Intensity (bi) and CO2 Intensity (ci). In addition, the study aims to establish benchmarks and guidelines that can contribute to increasing ecoefficiency in the RC binder’s consumption. In general, RC show high cement consumption with an increase in compressive strength at 28 days. The lowest values of bi observed range from 6 to 7 kg.m-3.MPa-1, which occurs for RC with strengths above 50 MPa, and the lowest values of ci range from 2 to 4 kg.m-3. MPa-1, for strengths less than 50 MPa and mixtures that use cements with low clinker contents. Such bi and ci ranges reveal significant potential for RC gains reducing CO2 emissions within the RC chain, since the vast majority of bi and ci results are above the upper limit of these ranges. Based on the panorama, a bi  7 kg.m-3.MPa-1 and a ci  5 kg.m-3.MPa-1 are identified as possible benchmarks for RC. Some of the main guidelines drawn were: to reduce the w/b ratio of RC, limiting the binder's consumption; to use mineral additions, preferably the active ones; improve the dispersion and the particle packaging; to use high-strength Portland cements, limiting the clinker-factor.