Investigation on applicability of spherical electric arc furnace slag as fine aggregate in superplasticizer-free 3D printed concrete.

• Less dependence on PCE for 3DPC with EAFS fine aggregates. • 3DPC with EAFS possesses better flowability and buildability. • The spherical model of EAFS contributes to improved mechanical properties. • EAFS fine aggregates dense packing reduced the 3DPC pore volume. Polycarboxylate ether superplasticizer (PCE) is a popular option for improving the flowability of 3D printed concrete (3DPC). However, the side effects and high cost of PCE impede the development of 3DPC. In recent years, a spherical electric arc furnace slag (EAFS) was produced by a novel production method. It is, therefore, imperative to investigate the usage of EAFS's ball-rolling effect to improve 3DPC flowability. In this paper, the rheological properties, flowability, buildability, mechanical properties, and pore structure of superplasticizer-free 3DPC were determined with EAFS replacing 25%, 50%, 75%, and 100% of river sand (RS). The results were compared with the control sample which contains PCE and 100% RS. The rheological properties proved that both EAFS and PCE improved 3DPC flow initiation, but 3DPC with EAFS achieved a lower viscosity loss rate, which is beneficial to buildability. Under consistent printability conditions, the average flowability value of 3DPC with EAFS was 180 mm, which exceeded the control sample by 15 mm, and the optimum buildability was achieved when 50%–75% of RS was replaced. Furthermore, the EAFS spherical model allowed for significant improvements in 3DPC mechanical properties while also reducing the pore volume. Overall, utilizing EAFS to improve 3DPC flowability successfully eliminates dependence on PCE, while optimizing buildability and mechanical properties, among other benefits. [ABSTRACT FROM AUTHOR]