Mix design, optimization and performance evaluation of extrusion-based 3D printable concrete

Abstract

3D concrete printing (3DCP) is a cutting-edge construction method that has recently received much attention. Most of the 3DCP research works focused on printer development, printable material mix design, and the complexity of the geometry shapes. This research primarily focuses on determining appropriate mix proportions and suitable 3D printable concrete (3DPC) mix design using a trial and error approach. The experimental tests are performed on 27 mix trials with different materials to determine the printable properties such as flowability, buildability, extrudability, and open time. Also, printed and cast samples were tested for compressive strength. The 3DPC mix with 19% OPC, 23% of fly ash, 7% of silica fume, 13% of GGBS, 4% limestone and 0.22% superplasticizer (% by mass of total binder) was found as identified mix proportion, which exhibits the required 3DPC characteristics such as good buildability, easy extrusion, less setting time, cohesiveness of mix, and reduction in deformation. The proposed mixing protocol and suggested 3DPC mix design were encouraging for large-scale 3DCP. To demonstrate the application of the 3DPC mix, the 3D printed concrete furniture was printed with a nozzle of size 30 mm, extrusion speed of 100mm/s and a printing speed of 60mm/s.