Effect of Lightweight Expanded Clay Aggregate (LECA) On the Printability of Cementitious Compositions for 3D Printing (2025-03)¶

The interest in the development of 3D printing of concrete (3DCP) and its mixtures has significantly increased in recent years. In particular, lightweight mixtures, capable of optimizing the printing process and the thermal comfort of printed structures, still need to be studied. However, it is known that the addition of lightweight aggregates reduces density, providing better resistance to both buckling and plastic collapse during printing. In this sense, the present study aimed at evaluating the influence of the replacement of natural sand by lightweight expanded clay aggregate (LECA) on the fresh state properties of 3DCP mixtures. A 2² factorial design was used, with the replacement content of sand by LECA and the aggregate to binder ratio as independent factors. The squeeze-flow technique, together with the flow-table test, were used to evaluate the rheological behavior of the 3DCP mixtures containing aggregates up to 1.2 mm in maximum diameter. The results showed that replacing sand with LECA increased the flow tension and viscosity of the mix, which resulted in increased constructability preserving the extrudability of to the reference mix. In addition, the mixes with LECA showed up to a 13 % decrease in density in the fresh state, improving the resistance to both local buckling and preventing the plastic collapse during printing.