Development of fibre reinforced engineered cementitious composite using polyvinyl alcohol fibre and activated carbon powder for 3D concrete printing

3D concrete printing (3DCP) technology offers a revolutionary technique of building modern structures with lower costs, less construction wastes, and higher efficiency compared to traditional construction processes. Concretes produced by 3DCP exhibit better performance in various aspects, compared to traditionally cast concretes. This study proposes a polyvinyl alcohol (PVA) fibre reinforced engineered cementitious composite (ECC) coupling activated carbon powder (ACP), which is preferred for 3DCP. To develop a preferred mix that has both competitive mechanical strength and printability for 3DCP, seven mixes with varying contents of PVA (1 vol% and 1.5 vol%) and ACP (0.5 wt% and 1 wt%) were prepared and tested by traditional casting. To evaluate the performance of each mix, fresh properties such as slump flow and mechanical properties, including compressive strength and flexural strength, were assessed. A preferred mix with the highest flexural strength was then chosen and optimised through the re-calibration of the use of chemical admixtures. A group of samples of the adjusted mix was then prepared by 3DCP and the aforementioned properties tested and compared with the cast ones. Results show that the printed samples had less compressive strength but still remained competitive compared to cast samples, while their flexural strength was substantially enhanced. Moreover, the structure's anisotropy of printed mix was also studied, leading to the finding that when the filament was perpendicular to the loading direction, higher compressive strength and flexural strength were obtained, compared to the parallel position of the filament vis-à-vis the loading direction.