3D-printable lightweight foamed concrete and comparison with classical foamed concrete in terms of fresh state properties and mechanical strength

This paper presents a novel type of foamed concrete that is termed “3D-printable lightweight foamed concrete” (3DP-LWFC). Unlike classical lightweight foamed concrete (C-LWFC), this novel material is able to keep its shape at the fresh state due to enhanced consistency and viscosity. This peculiarity lends itself to being implemented in automated extrusion production process and 3D printing applications without the use of formwork, which is particularly convenient in the building industry. These unique fresh state properties of 3DP-LWFC are demonstrated through a specific extrusion test conceived and used in this experimental campaign, and highlighted by comparison with results related to C-LWFC. Despite the remarkably different behavior of the novel material at the fresh state, the mechanical strength of 3DP-LWFC is even slightly higher than C-LWFC. This is demonstrated through a wide experimental campaign focused on the compressive and flexural strength of 3DP-LWFC, which includes different dry densities, curing conditions, cement types, water/cement ratios. Additionally, the effect of the mixing conditions on the mechanical strength of 3DP-LWFC, in particular the rotational speed of the mixer during the preparation of the paste, is also analyzed and discussed. It is found that the increase of mixing intensity from 1200 rpm to 3000 rpm resulted in a considerable increase of mechanical strength values of 3DP-LWFC, up to more than 70% for the compressive strength and up to around 100% for the flexural strength.