Effect of expanded perlite on the properties of 3DCP mixtures

Reducing energy consumption for continuous heating and cooling of buildings is currently one of the biggest sustainability challenges. This happens due to the use of materials with low insulation indexes and high thermal losses. As an alternative to minimize this problem, the use of porous aggregates in con-crete dosage stands out. Given this, 3D printing of concrete (3DCP) with light-weight aggregates is an approach that should enable automated formwork-free construction with higher quality, productivity and, at the same time, contribute to better energy efficiency of the structures. As this technology demands very specific rheological requirements, more research needs to be carried out. There-fore, this study aims to investigate the use of different levels of expanded perlite (EP) as a substitute for natural sand in the properties of cementitious composites for 3D printing. Based on a reference mix, EP was used to replace natural aggre-gate at levels of 25%, 50%, 75%, and 100% by volume. In the fresh state, tests were carried out for spreading on the consistency table, bulk density, viscosity (using a viscometer), water retentivity, and shape retention. In the hardened state, printed samples were tested at 7 and 28 days to assess compressive strength. In general, the results show that expanded perlite acts by reducing the density of the mixtures, greatly influencing the other tests carried out. Finally, considering the printing system used, it was possible to find optimized dosages that allow the use of these aggregates in 3DCP mixtures by choosing suitable materials combined with a correct dosage study to meet the criteria of this new construction technique.