# Fatigue Behaviour of Concrete Using Siderurgical Aggregates
## 2 Methodology  
### Materials and Mix Proportions  
The development of the research is based on the comparison of a concrete with siderurgical aggregates (SA) with a conventional concrete with natural aggregates (NA), which are limestone aggregates, to verify the goodness of siderurgical aggregates. The properties of SA depend on the properties of the scrap and the production process with which the EAFS are obtained, so it is necessary to carry out a complete physical-mechanical characterization of this aggregate. Table 1 shows the composition in oxides by XRF, which was complemented with an analysis by XRD, finding that magnetite, wuestite, magnesioferrite and calcium silicate were the main crystalline phases. Table 2 shows the physical properties of the aggregates used, among which SA's ostensibly higher density (44%) and similar water absorption should be remarked.  
The two mixes (Table 3) were designed by the Fuller method using the same amount of water, cement (CEM 1 52.5R [28]), superplasticizer additive and the same volume of aggregates, to facilitate their comparison. Figure 1 shows the distribution of the granulometric skeleton of the 2 mixes, which are described below:  
1. A reference limestone concrete mix with fines and coarse limestone fractions (LLC).
2. A concrete mix with fine and coarse siderurgical aggregate fractions, which also incorporates limestone sand (SLC) to compensate for the lack of fines of SA (a typical issue for this aggregate [29]).  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Material** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **MnO** & **MgO** & **CaO** & **Na\({}_{2}\)O** & **TiO\({}_{2}\)** & **P\({}_{2}\)O\({}_{5}\)** & **SO\({}_{3}\)** & **V\({}_{2}\)O\({}_{5}\)** \\ \hline
**SA** & 10.57 & 6.19 & 44.79 & 5.95 & 7.09 & 21.99 & 0.03 & 0.51 & 0.29 & 0.27 & 0.36 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Oxide composition of the different fraction of siderurgical aggregates (% wt.).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Size** & **Bulk Density** & **Apparent Density** & **SSD Density** & **Water Absorption** & **Porosity** \\ (**mm/mm)** & **(g/cm\({}^{3}\))** & **(g/cm\({}^{3}\))** & **(g/cm\({}^{3}\))** & **(\% wt)** & **(\% vol.)** \\ \hline NA 12/18 & 2.65 & 2.76 & 2.69 & 1.6 & 4.2 \\ NA 6/12 & 2.67 & 2.78 & 2.71 & 1.4 & 3.7 \\ NA 0/6 & 2.67 & - & - & - & - \\ SA 8/16 & 3.84 & 3.98 & 3.88 & 0.9 & 3.6 \\ SA 4/8 & 3.82 & 4.08 & 3.88 & 2.1 & 7.9 \\ SA 0/4 & 3.87 & - & - & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: Physical properties of the aggregates used.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **LLC** & **SLC** \\ \hline CEM & 340 & 340 \\ Water & 159.8 & 159.8 \\ NA 12/20 & 283.7 & - \\ NA 6/12 & 661.9 & - \\ NA 0/6 & 945.6 & 776.1 \\ SA 8/16 & - & 721.6 \\ SA 4/8 & - & 483.5 \\ SA 0/4 & - & 442.8 \\ Superplasticizer & 3.4 & 3.4 \\ w/c & 0.47 & 0.47 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Concrete mix proportions (kg/m\({}^{3}\)).  
The mixing of the concrete was carried out in three phases. A first phase of mixing for 3 min with the aggregates, cement, and water, a second phase of 3 min rest and a third phase of 2 min with the incorporation of the superplasticizer additive. A needle vibration was performed. The specimens were removed from the mould 24 h after their manufacture, then introduced to cure in a chamber at 95 \(\pm\) 5% humidity and a temperature of 20 \(\pm\) 2 \({}^{\circ}\)C for 28 days, as established by EN-12390-2 [30].