Development of composites for 3D printing with incorporation of limestone filler and metakaolin as partial replacement for cement
3D printing, cement, limestone filer, metakaolin, building capacity
3D printing of concrete (3DCP) based on additive manufacturing techniques has been gaining prominence in the construction industry, despite the great difficulty in supplying cementitious materials with characteristics suitable for the extrusion system. To meet such criteria, 3DCP mixtures are usually dosed with high levels of Portland cement which, in turn, is a retainer of a manufacturing process that consumes a lot of energy and releases high amounts of CO2 into the atmosphere. Therefore, a solution seen as promising to make the 3DCP methodology more sustainable is the reduction of cement consumption through the partial replacement by supplementary cementitious materials (SCM). Given the above, the objective of this work is to develop composites for 3D printing containing different percentages of limestone filer and metakaolin as binder fraction of the analysis compositions. These mixtures were evaluated both in the fresh state - through the tests of spread, slump, bulk density, incorporated air content, squeeze-flow and buildability - and in the hardened state - taking into account the behavior of flexural strength, compressive strength, adhesion between layers, specific mass, porosity and water absorption. The results show that it is possible to obtain printable composites with reduced cement consumption due to the incorporation of supplementary cementitious materials in the mixtures. In the fresh state this is evidenced by the FC30MK10h12 mix, which best met the extrusion criteria. In the hardened state, the FC30 mixture provided the best mechanical performance among the compositions containing SCM. In general, it was found that the use of limestone filer and metakaolin as partial replacement for cement is a relevant alternative by meeting the requirements necessary for printing and minimizing the high consumption of cement normally used in this new construction technique.