Desenvolvimento de compósitos para impressão 3D com consumo de cimento reduzido por meio de adições minerais

Abstract

Recently, 3D concrete printing (3DCP) has been gaining prominence in the construction industry. However, in order to meet the extrusion requirements, 3DCP mixtures are usually dosed with high Portland cement contents. Thus, a solution seen as promising to make this technology more sustainable is the reduction of cement consumption through partial replacement by mineral additions. In view of this, the present research aims to develop composites for 3D printing containing different percentages of limestone filer and metakaolin as binder fraction of the analysis compositions. The proposed mixtures encompass replacement contents in 30% limestone filer, 40% limestone filer, and 30% limestone filer with 10% metakaolin. In the fresh state, these composites were evaluated through the tests of spreading, slump, bulk density, incorporated air content, squeeze-flow and buildability. In the hardened state, flexural strength, compressive strength, interlayer adhesion, specific mass, void index, and water absorption by immersion were analyzed. In general, the mixtures demonstrated compliance with the requirements of the printer handled. A highlight is given to the composite containing 30% filer with 10% metakaolin that, with the ideal amount of water, evidenced good print quality and excellent buildability of the printed part. The mixes containing only filer showed higher deformability of the mixture, and this characteristic is directly proportional to the content of incorporation of this material. The behavior in the hardened state, in turn, indicated that it was related to cement consumption. The higher this parameter, the better was the mechanical performance. In relation to the reference mixture, the mixes containing 30% filer, 40% filer, and 30% filer with 10% metakaolin showed behaviors of, respectively, -24,5%, -34,4% and -31,4% (flexural strength), -43,8%, -50,2% and -36,5% (compressive strength) and -2,2%, -19,5% and +0,5% (interlayer adhesion strength) at 7 days of age. Moreover, the content of void index and water absorption by immersion were higher as the value of specific mass of these composites was lower. It is possible to conclude, therefore, that there is the possibility of obtaining printable mixtures with reduced cement consumption and that are in compliance with requirements necessary for the printing system used.