# Physico-Mechanical Properties of Alkali-Activated Based Composites Using Recycled Fire Fibers
## 2 Materials and Methods  
### Materials  
The chemical compositions of FCC and RHA are summarized in Table 1.  
Geopolymer mortars with aggregate were produced [29] at a water/binder (w/b) ratio of 0.6 and an aggregate/binder (a/b) ratio of 2.25, both by weight. The binding material was the spent catalyst residue from catalytic cracking (FCC), an aluminosilicate with high pozzolanic reactivity, a density of 2.44 g/cm\({}^{3}\), and a particle diameter of 17.1 \(\upmu\)m. RHA was used as a source [29] to prepare the alkaline activator, with a density of 1.90 g/cm\({}^{3}\) and a particle diameter of 62.2 \(\upmu\)m. The activator for mortars containing siliceous/limestone aggregate was prepared by mixing 270 g of tap water, 81 g of NaOH (pellets), and 78.75 g of RHA in a 1 L thermal bottle. This mixture was stored in the thermal bottle for 24 h. The suspension was used for mixing with 450 g of FCC and the corresponding quantity of the aggregates and TFs (see Table 2). The activator for mortars with only TFs was prepared by mixing tap water, NaOH, and RHA in the following proportions: water/FCC = 0.6, NaOH/RHA = 1.029, and water/NaOH = 3.33 (see Table 2) and prepared using the same procedure. The mechanical strength measurement of the mortars was then conducted following standard UNE-EN 196-1 [30]. TFs were produced by scraping tire surfaces during retreading, where the majority of fibers and particles were generated. TFs were separated from particles, and the material retained by the #0.63 mm mesh was used (Figure 1). The aggregates used to produce geopolymer mortars were siliceous and limestone aggregates, and the particle size distribution was analyzed by sieving according to the mesh size series of standard UNE-EN 196-1 [30]. The density of aggregates was determined by the pycnometer method for particle sizes between 0.063 mm and 4 mm (UNE-EN 1097-6, [31]). This yielded a density of the siliceous aggregate equaling 2.54 g/cm\({}^{3}\) and limestone aggregate equaling 2.60 g/cm\({}^{3}\). For TFs, the density was determined by the difference in displaced volume using acetone as the fluid. The density obtained for TFs was 1.25 g/cm\({}^{3}\). The particle size distributions of the aggregates used in this study are shown in Figure 2. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & **SiO2** & **Al2O3** & **Fe2O3** & **CaO** & **MgO** & **SO3** & **K2O** & **LOI** & **Na2O** & **P2O5** & **TiO2** \\ \hline FCC & 47.76 & 49.26 & 0.6 & 0.11 & 0.17 & 0.02 & 0.02 & 0.51 & 0.31 & 0.01 & 1.22 \\ RHA & 85.58 & 0.25 & 0.21 & 1.83 & 0.5 & 0.26 & 3.39 & 6.99 & - & 0.67 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The chemical compositions of FCC and RHA as weight percentages. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Motrar Type** & **FCC (g)** &
\begin{tabular}{c} **Activator * (Water+** \\ NaOH + RHA, in g)** \\ \end{tabular} & **TFs (g)** & **Aggregate (g)** \\ \hline \hline CTRLSIL & & & 0 & 1350 \\ \hline \hline CTRLCAL & & & 99.70 \\ \hline TF SIL15 & 450 & 270.00 + 81.00 + 78.75 & 99.70 \\ \hline TF CAL15 & & & 166.16 \\ \hline TF CAL25 & & & 162.55 \\ \hline TF 2/1 & 675.00 & 405.00 + 121.50 + 118.13 & & \\ TF 1.8/1 & 607.50 & 364.50 + 109.35 + 106.31 & & \\ TF 1.6/1 & 540.00 & 324.00 + 97.20 + 106.31 & 337.50 & 0 \\ \hline TF 1.4/1 & 472.50 & 283.50 + 85.05 + 82.69 & & \\ \hline TF 1.2/1 & 405.00 & 243.00 + 72.90 + 70.88 & & \\ \hline TF 1/1 & 337.50 & 202.50 + 60.75 + 59.06 & & \\ \hline \hline \end{tabular} \({}^{*}\)The activating suspension was prepared in a thermal bottle for 24 h.  
\end{table} 
Table 2: Doses of the studied mortars. The geopolymer mortars with TFs were prepared based on the percentage content of TFs (TFaggregate15 and TFaggregate25), which corresponded to replacement with the volume of silicocus or limestone aggregate with TFs (15% and 25% replacement levels).