Wood-Based Support Material for Extrusion-Based Digital Construction (2019-02)¶

Extrusion-based digital construction (DC) approaches make it feasible to overcome constraints of conventional construction, namely, high formwork costs, long total construction times, low productivity and geometrical inflexibility. However, to date, no satisfactory solutions for extruding strongly inclined and horizontal elements are available. A wood-starch-composite has been systematically developed as a sustainable support material (SM) for extrusion-based DC. Material and process-specific requirements were identified for this purpose, and a feasible process chain was developed. A parametric study was conducted to determine the influence of SM composition on its extrusion feasibility and compressive strength. Various compositions with two starch types and two wood particle shapes were tested. New, specific testing methods were developed. Selected compositions were tested using a 3D-printing device to verify extrudability and form stability. Relationships between material compositions of SM and its rheological and mechanical properties were identified. All mixtures showed sufficient compressive strength in respect of the loading conditions analysed. However, their flow properties varied significantly. A mixture of native maize starch and wood floor was identified as the best variant (compressive strength 2.3 MPa). Comprehensive investigations of possible process chains, as well as full-scale demonstration and optimisation of the process parameters, were not in the scope of this paper. Such investigations are intended in further studies. Practical implications – The general applicability of wood-based SM for DC with cement-based construction materials was proved. The findings offer a novel and promising solution for 3D-printing of non-vertical concrete elements. Experimental setup and material compositions are detailed to ensure reproducibility.