Innovative usages of stainless steel slags in developing self-compacting concrete

• Stainless steel slags (SSOS and SSRS) were employed to develop SCC.
• Effects of SSOS and SSRS flowability and viscosity of SCC were observed.
• Mechanical and durability properties of the SCC were investigated.
• Strength formula for the stainless steel slags-based SCC was successfully provided.
• Relationships between compressive strength, UPV, RN, and surface resistivity were established.

This paper deals with development of self-compacting concrete (SCC) containing stainless steel oxidizing slag (SSOS) and stainless steel reducing slag (SSRS) – byproducts of the stainless steel makings. The oxidizing slag was employed as fine and coarse aggregates in substituting to conventional materials (sand and gravel) with various percentages (i.e. 0%, 50%, and 100%). Meanwhile, the reducing slag was used as a part of ordinary Portland cement (e.g. 0%, 10%, 20%, and 30%). As a result, a total of 12 mixtures with a fixed water–binder ratio (w/b = 0.4) were prepared for experiment; and its properties obtained in fresh state including density, flowability, viscosity, passing ability, and setting time and in hardened state such as compressive strength, ultrasonic pulse velocity, rebound hammer, length change, and surface resistivity were examined accordingly. The results indicate that incorporating SSOS aggregates or SSRS cement in SCC mixtures apparently reduces the workability besides effectively enhancing its viscosity. Mixture with SSOS increased shows a higher fresh density than the control, while containing high level of SSRS results in lowering that density. More interestingly, the stainless steel slags-based SCC can accelerate the hardening process, which shortening a setting time of 25% and 36%, corresponding for mixture with 50% and 100% SSOS aggregates. For hardened properties, compressive strength of SCC prepared with SSOS replacement in full exhibits slightly better or at least similar to that of the control, considerable improvement in surface resistivity, and potentially volumetric instability. Strength development models, modifying from ACI-209, have also been provided for the slags-based SCC. In addition, relationships between UPV, rebound number, and electrical resistivity versus compressive strength within 91 days have been further established.