3D CONCRETE PRINTING

A free form construction process using a layered manufacturing technology has been developed recently with the aim of fabricating building components and structures directly from Computer-Aided-Design (CAD) data sources. In a free form construction process, components are built up without form work unlike conventional concrete construction methods. Building materials are extruded through a nozzle as self-compacting filaments which form horizontal layers, and these layers when laid down sequentially can create large 3D building components. The free form construction process allows the following possibilities. (a) Reduce materials usage and site work; (b) produce novel internal and external finishes; (c) reduce costly remedial works; and (d) give greater design freedom. Possible applications include acoustic structures, structural insulated walls, and multifunctional cladding panels.

A high-performance printing concrete has been developed for an innovative free form construction process that utilizes digital fabrication methods for building large components. The concrete has a maximum particle size of 2 mm and contains up to 1.2 kg/m3 of polypropylene fiber The fresh concrete was successfully printed through a 9 mm diameter nozzle to build free form concrete components by layers. The fresh state of concrete had an open time of 1.5 hours to let it be printed smoothly. The average compressive strength of the cast and in-situ printed specimens were in the range of 100~110 MPa and 80~88 MPa, respectively whilst the flexural strengths were not significantly different and in the range of 12~13 MPa.