Investigation on the Rheological Behavior of Lightweight Foamed Concrete for 3D Printing Applications

Unlike ordinary concrete, lightweight foamed concrete (LWFC) has the benefit of decreasing the self-weight of constructive elements while ensuring an efficient thermal insulation and acoustic absorption as well as high fire resistance. A novel version of LWFC has been recently developed by the authors, with the unique property of “extrudability” in a wide density range, meaning that its production process can be carried out without formworks and exploiting innovative 3D printing technologies. The present contribution is focused on the rheological behaviour of this innovative extrudable LWFC (ELWFC). The rheological behaviour in terms of yield stress of the ELWFC is studied via a rotational rheometer in two different modalities, namely constant shear rate and increasing shear rate. Comparison of the rheological behaviour between ELWFC and classical LWFC is also presented. Additionally, the dimensional stability of the cementitious paste at the fresh state having a given yield stress is assessed through an extrusion test. In particular, the experimental investigation is focused on a target dry density of 800 kg/m3, which is identified as a good compromise between insulating features and mechanical strengths. The experimental results show that the considered ELWFC, characterized by a zero slump in the extrusion test, has a yield stress of around 150 Pa (constant shear rate) and 130 Pa (increasing shear rate).