Stability of steel slag as fine aggregate and its application in 3D printing materials

Due to the shortage of natural materials, using steel slag (SS) as replacement for natural sand to manufacture mortar has attracted worldwide attention and becomes a promising technology. This study aims at employing SS as fine aggregate for natural sand substitute in cement mortar synthesis. The measurement of expansion value generated by fine SS aggregate was performed by autoclave test. On the basis of further tests, the optimum content of SS fine aggregate was 25%. The autoclave experiment results indicate that the mortar bar was seriously damaged with higher dosages of SS fine aggregate. The X-ray diffraction (XRD) technique was offered to identify the mineralogical phases of the autoclaved SS. Additionally, this work investigated the printability of 3D printing mortar by assessing its fluidity, slump and mechanical strength. The printing mortar mixed with 25% SS was used in the printing of an actual 3D structure, demonstrating its feasibility to be used in 3D printing field. The microstructure and elements distribution were characterized by scanning electron microscopy (SEM) and the energy dispersive spectroscopy (EDS) techniques. The results showed that it is feasible to incorporate SS in 3D printing mortar, which contributes to the improvement of working properties and the enhancement of mechanical strength. This study provides a novel 3D printing SS mortar with good economic and potentially great environmental benefits. (c) 2021 Elsevier Ltd. All rights reserved.