# Susceptibility to Expansive Reactions of a _Greener_ Uhpc: Micro to Macro-Scale Study
## 2 Materials and Methods  
### Raw Materials and Mix Design  
The author developed the UHPFRC [53; 54; 55] using locally available materials in Portugal/Europe. The mixture design included a local waste material, the spent equilibrium catalyst (ECat) from the fluid catalytic cracking unit of Sines Refinery in Portugal. A breakthrough of the work was using ECat, for the first time, as an internal curing agent proving engineering benefits with additional cost and eco-efficiency outputs. More information can be found elsewhere [53; 54; 55]. It follows a brief description of constituent raw materials and mixture proportions. The binder fraction is constituted by a ternary blend of Portland cement CEM I 42.5 R, dry fume silica fume, and limestone filler, whose main oxide composition and physical properties are shown in Table 1. The aggregate fraction corresponds to (in volume): 85% fine sand with a maximum diameter of 1 mm, density of 2580 kg/m\({}^{3}\): and water absorption of 0.02%, and 15% of ECat with a density of 2660 kg/m\({}^{3}\) and absorption of 30%. A superplasticiser based on modified carboxylates with a density of 1080 kg/m\({}^{3}\) and a solid content of 40% was employed to ensure self-compactability and adequate cementitious particle dispersion. Figure 1 presents the secondary electron mode SEM images of particle morphology of cement, silica fume, limestone filler, and ECat. Steel fibres 0.2 mm in diameter and 13 mm in length (lf/df = 65) were incorporated to produce UHPFRC mixtures (UHPC with 3% fibre reinforced in volume), with tensile strength and modulus of elasticity 2750 MPa and 200 GPa, respectively.  
Even though the UHPFRC developed presents lower cement and silica fume dosage than the commercially available blends (see Appendix A), it presents a compressive strength in the range expected for this cement-based materials family, see Figure 2. Moreover, no special curing treatments were applied, and UHPC specimens remained under standard water curing at 20 \(\pm\) 2 \({}^{\circ}\)C.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & & **Cement** & **SF** & **LF** & **ECat** \\ \hline \multirow{6}{*}{Main oxide composition (\%)} & SiO\({}_{2}\) & 19.80 & \(>\)90 & & 40.30 \\ \cline{2-5}  & CaO & 61.32 & & 99.0 & 0.06 \\ \cline{2-5}  & Fe\({}_{2}\)O\({}_{3}\) & 3.16 & & 0.02 & 0.45 \\ \cline{2-5}  & Na\({}_{2}\)O & 0.15 & & 0.43 \\ \cline{2-5}  & Al\({}_{2}\)O\({}_{3}\) & 5.08 & & 54.45 \\ \cline{2-5}  & MgO & 1.82 & & 0.15 \\ \cline{2-5}  & K\({}_{2}\)O & 0.58 & & 0.02 \\ \cline{2-5}  & SO\({}_{3}\) & 2.90 & & 0.00 \\ \cline{2-5}  & LOI (\%) & 2.54 & & 1.05 \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Pozzolanic activity \\ (NF P18\(-\)513) \\ \end{tabular} } & \multirow{2}{*}{mg Ca(OH)\({}_{2}\)/g} & \multirow{2}{*}{1577} & \multirow{2}{*}{1540} \\ \cline{2-5}  & Density (kg/m\({}^{3}\)) & 3310 & 2200 & 2680 & 2660 \\ \cline{2-5}  & Specific surface (m\({}^{2}\)/kg) & 440 & 19632 & 550 & 150,070 \\ \cline{2-5}  & Initial setting time (min) & 141 & & \\ \cline{2-5}  & Final setting time (min) & 201 & & \\ \cline{2-5}  & D10 (\(\mu\)m) & 1.40 & 0.11 & 1.12 & 50.00 \\ \cline{2-5}  & D50 (\(\mu\)m) & 10.00 & 0.32 & 4.55 & 90.00 \\ \cline{2-5}  & D90 (\(\mu\)m) & 25.00 & 0.84 & 15.36 & 120.00 \\ \hline \multirow{2}{*}{Mechanical properties} & Rc,2 (MPa) & 32.20 & & \\ \cline{2-5}  & Rc,7 (MPa) & 47.40 & & \\ \cline{2-5}  & Rc,28 (MPa) & 60.80 & & \\ \hline \end{tabular}
\end{table}
Table 1: Main oxide composition, LOI, and physical properties of cementitious materials.  
The current durability study was performed in UHPC (with no fibres), and the mixture proportions are presented in Table 2.  
Figure 1: SEM images of (**a**) cement, (**b**) silica fume, (**c**) limestone filler, and (**d**) ECat.  
Figure 2: Compressive strength and standard deviation bars of UHPFRC between 2 and 90 days.