## 2 Experimental Study
### Experimental Program  
The experimental program includes a total of four mixes. The first mix is the control UHPFRC, and the other three are UHPFRC with GCW-GS in different percentages.  
The mixing procedure was as follows. First, the silica sands and the micronized quartz or the corresponding granite waste were put in the mixer. Next, the silica fume and cement were added. The materials were mixed for 30 s before including the water. After 2 min 30 s from the beginning of the mixing, the superplasticizer and the steel fibers were added. The mixing process ended after 25 min.  
The specimens were manufactured according to the specifications of the EN 12390-1 standard [20]. A total of nine specimens were manufactured per mix: three prismatic specimens of 10 \(\times\) 10 \(\times\) 40 cm, three cubic specimens of 10 \(\times\) 10 \(\times\) 10 cm, and three cylindrical specimens of 15 \(\times\) 30 cm. The specimens were removed from the molds after 24 h and transferred to a humid chamber where they remained for 28 days at a temperature of 20 \({}^{\circ}\)C and a relative humidity of 95% (Figure 3), as specified in the EN 12390-2 standard [21].  
The following properties were evaluated: the consistency of the fresh mix, density of hardened concrete, compressive strength, modulus of elasticity, flexural strength, and tensile strength.  
Physical Properties  
The consistency of the fresh UHPFRC was determined once the mixing process was finished and performed according to the NF P 18-470 standard [22]. The density of the hardened UHPFRC was calculated following the specifications of the EN 12390-7 standard [23]. This was done using the three 15 \(\times\) 30 cm cylindrical specimens cast per mix. The  
Figure 3: Preparation and drying of samples.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Specimen** & **Cement** & **Sand (01.5)** & **Sand (0.5/1.6)** & **Micronized** & **Granite Sludge** & **Silica Fume** & **Water** & **SP** & **Steel Fibers** \\ \hline Control & 800 & 302 & 565 & 225 & - & 175 & 175 & 10 & 160 \\
35\% GCW-GS & 800 & 302 & 565 & 146 & 79 & 175 & 175 & 15 & 160 \\
70\% CGW-GS & 800 & 302 & 565 & 68 & 158 & 175 & 175 & 16 & 160 \\
100\% GCW-GS & 800 & 302 & 565 & - & 225 & 175 & 175 & 18 & 160 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Mix proportions of ultra-high performance steel fiber reinforced concrete (UHPFRC) (kg/m\({}^{3}\)).  
compressive strength was determined using the three cubic specimens of 10 \(\times\) 10 \(\times\) 10 cm, following the indications of the EN 12390-3 standard [24]. The modulus of elasticity was determined according to the EN 12390-13 standard [25] using the three 15 \(\times\) 30 cm cylindrical specimens. The flexural strength of the UHPFRC were calculated according to the NF P 18-470 standard [22] on the three prismatic specimens of 10 \(\times\) 10 \(\times\) 40 cm (Figure 4). To determine tensile strength, a new method based on impact loading was proposed in [26], but it is not applicable to this study due to the using of fibers; instead, this property was determined by an inverse analysis from the stress-strain curves obtained from the flexural strength test, following the methodology proposed by [PERSON] in his doctoral thesis [27]. Table 4 shows the mean value of the results obtained from testing three specimens for each percentage of substitution.