This paper reviews the potential use of silico-manganese slag (SiMnS) as binder and aggregate in Portland cement and geopolymer concrete. SiMnS is a byproduct of alloy steel production. Depending on the process of solidification, the slag is available in crystalline hard stone type and granulated glassy form. The latter one is more reactive due to the presence of amorphous phases. Therefore, granulated slag has been mostly used as supplementary cementitious material, either blending with clinker or as a precursor for alkali activated binder. Whereas the former is less reactive, and has been mostly used as aggregate, which can enhance the properties of the concrete. The reactive component such as CaO and SiO2 improve the binding capability of the cement gel. The leaching of toxic and heavy metals from the SiMnS reacted binder matrix is not reported. This paper also highlights the future potential of this slag by a process called slag engineering to modify its chemistry similar to granulated blast furnace slag (GBFS), to be utilized more effectively.