# A Review of the Influence of Steel Furnace Slag Type on the Properties of Cementitious Composites
## 5 Requirements for SFS Characterization
### Chemical and Mineralogical Characterization  
The chemical composition alone should not be used as a predictor of SFS behavior, since there is often substantial elemental substitution. A combination of chemical and mineralogical classifications will initiate a more complete analysis of the SFS chemical properties.  
The chemical composition of SFS is typically assessed by X-ray fluorescence (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES), atomic absorption spectroscopy (AAS), or a combination thereof [261; 262; 263; 264; 265; 266]. Typically, these data are represented in the oxide form, as shown in Table 1.  
The crystalline mineral composition of SFS can be assessed by X-ray diffraction (XRD) [263; 264; 266; 267; 268]. Very commonly, XRD is used to qualitatively assess the SFS composition, as discussed in Section 1.2 with typical mineral compositions. While there is a list of minerals commonly identified in SFS (e.g., larnite, wustite, hematite, brownmillerite, lime, merwinite, and pericase), the composition can vary with a wide range of minor or trace compounds; for instance, one partial  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Mix**} & \multirow{2}{*}{**Compressive Strength (MPa)**} & **Split Tensile** & **Longitudinal Dynamic** \\  & & **Strength (MPa)** & **Modulus (GPa)** \\ \hline Control & 41.1 \(\pm\) 2.2 & 4.5 \(\pm\) 0.4 & 32.9 \(\pm\) 1.0 \\ EAF & 49.8 \(\pm\) 2.2 & 5.1 \(\pm\) 0.6 & 43.6 \(\pm\) 0.5 \\ BOF & 38.5 \(\pm\) 1.1 & 4.3 \(\pm\) 0.7 & 40.4 \(\pm\) 1.8 \\ LMF & 43.0 \(\pm\) 4.3 & 5.1 \(\pm\) 0.3 & 41.3 \(\pm\) 1.1 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Twenty-eight-day mortar properties (average \(\pm\) standard deviation) for four equivalent mixes with full replacement of aggregate with matched gradations of dolomite (control), EAF slag, BOF slag, or LMF slag [10].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Mix**} & \multirow{2}{*}{**Compressive Strength (MPa)**} & **Critical Mode I** & **Total Fracture** & **Free Drying** \\  & & **Stress Intensity** & **Energy (N/m)** & **Shrinkage (\(\pm\)**)** \\  & & **Factor (MPa-m\({}^{2}\))** & & \\ \hline Control & 46.1 \(\pm\) 1.4 & 1.00 \(\pm\) 0.12 & 101.6 \(\pm\) 15.9 & \(-\)437 \(\pm\) 21 \\ EAF & 48.3 \(\pm\) 0.5 & 1.39 \(\pm\) 0.06 & 124.0 \(\pm\) 8.1 & \(-\)517 \(\pm\) 55 \\ BOF & 40.1 \(\pm\) 2.0 & 1.21 \(\pm\) 0.06 & 118.5 \(\pm\) 6.5 & \(-\)537 \(\pm\) 60 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Twenty-eight-day concrete properties (average \(\pm\) standard deviation) for three equivalent mixes with full replacement of coarse aggregate with dolomite (control), EAF slag, or BOF slag [9].  
review of the literature found 59 different mineral compounds reported for various EAF and BOF slags [25], which demonstrates the need for mineralogical characterization for SFS.  
One complication with laboratory XRD is that Cu K\(\alpha\) radiation is very common, which will induce fluorescence in iron and iron-containing minerals [269], resulting in a higher background in the diffractogram. The higher background may overwhelm smaller peaks (i.e., present for low phase contents, poorly crystalline phases, etc.), diminishing the accuracy of qualitative or quantitative XRD analysis. The typical phase detection limit for powder XRD is reported to be around a few percent up to 10% [270; 271; 272]. Therefore, for XRD experiments where fluorescence is a potential issue, it is important to consider an appropriate X-ray source [273]. For SFS and iron-containing minerals, Co K\(\alpha\) or Cr K\(\alpha\), for instance, has shown to be more reliable [267; 268; 269; 274]; indeed, quantitative XRD, such as by Rietveld analysis, is possible for SFS by using Co K\(\alpha\) radiation [268; 33]. Quantitative XRD can also be used to estimate the relative amounts of each crystalline phase and amorphous phase(s) [275].