Abstract

Additive manufacturing has enabled the widespread adoption of 3D printable concrete (3DPC) mixtures in the construction industry due to their significant advantages over conventional methods. Compared to traditional formwork systems, 3DPC offers faster production times, reduced labor demands, improved workplace safety and enhanced design flexibility. However, the absence of coarse aggregates and the high proportion of fine materials and binders in these mixtures often result in inferior drying-shrinkage performance. Furthermore, the elevated binder content compromises their sustainability and economic viability relative to traditional concrete. To address these limitations, recent studies have explored the incorporation of fibers, pozzolanic materials, and industrial byproducts to enhance dimensional stability, ecological balance, and cost efficiency. In this study, blast furnace slag (BFS) was used as a partial replacement for cement at 0%, 25, 50 and 75% of the total binder volume to mitigate the environmental impact of 3DPC mixtures.

Additionally, straight steel fibers sourced from waste tires, with lengths of 5, 10 and 15 mm, were incorporated at volumetric ratios of 0%, 0.5% and 1% to improve drying-shrinkage resistance. A total of 27 experimental mixtures, including a control mix, were prepared with a constant water-to-binder ratio of 0.4 and a maximum aggregate particle size of 2 mm. The flow performance of these mixtures was evaluated, revealing a pronounced influence of the BFS substitution rate on flowability. It was determined that the water-reducing admixture requirement of the mixtures decreased with increasing blast furnace slag utilization ratio.