# Utilization of Industrial Ferronickel Slags as Recycled Concrete Aggregates
## 3 Results
### Results of Concrete Specimens
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & **Density** & **Water** & \begin{tabular}{c} **Uniaxial Compressive** \\ **Strength of 7 Days** \\ **(Mg/m3)** \\ \end{tabular} & \
\begin{tabular}{c} **Uniaxial Compressive** \\ **Absorption (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Uniaxial Compressive** \\ **Strength of 28 Days** \\ **(MPa)** \\ \end{tabular} \\ \hline S01 & 2650 & 0.32 & 38.00 & 48.50 \\ S02 & 2709 & 0.31 & 36.00 & 47.00 \\ S03 & 2621 & 0.35 & 36.55 & 47.50 \\ SA1 & 3093 & 0.86 & 62.24 & 83.42 \\ SA2 & 3113 & 0.68 & 64.94 & 80.02 \\ SA3 & 3129 & 1.08 & 64.13 & 75.88 \\ SA4 & 3098 & 0.90 & 66.35 & 82.48 \\ SA5 & 3112 & 0.71 & 64.94 & 80.06 \\ SA6 & 3125 & 1.07 & 64.15 & 75.80 \\ SB1 & 3140 & 1.59 & 56.91 & 61.74 \\ SB2 & 3095 & 1.57 & 49.15 & 57.85 \\ SB3 & 3179 & 1.01 & 49.14 & 57.43 \\ SB4 & 3141 & 1.12 & 53.90 & 61.70 \\ SB5 & 3098 & 1.57 & 50.02 & 58.02 \\ SB6 & 3181 & 1.60 & 49.53 & 57.12 \\ SC1 & 3065 & 1.19 & 55.17 & 57.84 \\ SC2 & 3064 & 1.09 & 45.53 & 57.50 \\ SC3 & 3060 & 1.37 & 48.35 & 53.26 \\ SC4 & 3129 & 1.48 & 55.18 & 63.59 \\ SC5 & 3166 & 1.13 & 54.37 & 66.85 \\ SC6 & 3169 & 1.49 & 46.80 & 52.84 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of the physical and mechanical tests of the produced concrete specimens. Figure 8: Results of the physical and mechanical properties of the produced concrete specimens. (**a**) density (kg/m3); (**b**) Water absorption (%); (**c**) Uniaxial compressive strength of 7 days (MPa); (**d**) Uniaxial compressive strength of 28 days (MPa). Figure 9: Textural characteristics of the studied concrete specimens: (**a**) Photomicrograph of sub-hedral spinel (Sp), _w_bsite (W) and anhedral calc-silicate phase (C\({}_{2}\)S) (PPL Nicols, sample SA1). (**b**) Photomicrograph of elogated grain of slag consisting of spinel (Sp) and _w_bsite (W) (PPL Nicols, sample SC2). (**c**) Photomicrograph of subhedral and elogates spinel (Sp) in which scattered cracks are observed which do not penetrate it (PPL Nicols, sample SC5). (**d**) Photomicrograph of an elogated grain of ELECTRIC ARC FURNACE SLAG, which contain calc-silicate phase (C\({}_{2}\)S) and has a good cohesion with the cement paste (PPL Nicols, sample SA4). (**e**) Back-scattered electron image of a spherical grain of _w_bsite (W) which does not have good cohesion with the cement paste and detachments are observed around it (sample SB6). (**f**) Back-scattered electron image of cracks in the cement paste and around a grain of an ELECTRIC ARC FURNACE SLAG that contains calc-silicate phase (C\({}_{2}\)S) and spherical _w_ö_bsite (W) (sample SA6). (**g**) Back-scattered electron image of _w_ö_bsite (W) around which detachments are observed (sample SB2). (**h**) Back-scattered electron image of cracks and detachments between the cement paste and the FeNi slag (sample SC6). All the above are enhanced either through the processing of microscopic images after the 3D depiction or through the study of the transition zone between the aggregate and the cement paste as it is shown in Figure 10a-d. The grains of C\({}_{2}\)S phases and spinels (Figure 10 a,c,d) seem to present good cohesion with the cement paste. In addition, it is observed that the grains of w\(\backslash\)stite have lower microroughness compared to that of the cement paste, where this alternation of the concrete components leads to the better cohesion among them (Figure 10b).