# On the Stability of Graphene-Based Aqueous Dispersions and Their Performance in Cement Mortar
## 2 Materials and Methods
### Mix Design  
Mix designs of all mortars produced during the experimental campaign are reported in Table 3, with the percentages of carbon nanomaterials reported by weight of cement. Preliminary investigation has allowed us to fix the proper SP/c ratio at 0.009 to guarantee adequate workability for most of the mortars functionalized with the carbon nanomaterials over the tested concentration range. Only mortars containing more than 0.3 wt% of Gr-SG required an amount of SP that exceeded the allowed limit provided by the manufacturer; therefore, they were not included in the experimental campaign. Mortar C, which does not contain any GPNs or GO, was used as a reference. All mortars were produced according to the UNI EN 196-1 standard, modified to take into account the addition of graphene-based dispersions and SP. Water containing the SP and the graphene-based dispersion was mixed with cement and stirred in a Hobart mixer at 140 \(\pm\) 5 rpm for 30 s. The sand was then added and mixed for 30 s at 285 \(\pm\) 10 rpm. After 30 s, the mechanical mixing was stopped for 90 s, and the mortar adhered to the container was hand-mixed; then the mixing continued at 285 \(\pm\) 10 rpm for 120 s. Each mix was finally poured in two steps into steel prismatic formworks with dimension of 40 mm \(\times\) 40 mm \(\times\) 160 mm, vibrating after each step for 30 s to eliminate air bubbles. Finally, moulds were stored for 24 h in the climatic chamber at 20 \({}^{\circ}\)C and R.H. \(\geq\) 90%. After that, mortar specimens were de-moulded and cured for 28 days in the climatic chamber under the same conditions.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Additive** & **Additive** & **SC/Additive** & **HT** & **LPE** \\
**Label** & **Type** & **Concentr.** & **Ratio** & **Treat.** & **Treat.** \\  & & **(wt\%)** & **Ratio** & **(h\(\sim\)\({}^{\circ}\)C)** & **(h)** \\ \hline D-TGA & Gr-TG & 1.53 & 1/5 & 6–180 & 6 \\ D-TGb & Gr-TG & 2.50 & 1/5 & 6–180 & 6 \\ D-SGa & Gr-SG & 1.53 & 1/5 & 6–180 & 6 \\ D-GOa & GO & 1.53 & 0 & 0 & 6 \\ D-GOb & GO & 2.50 & 0 & 0 & 6 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Composition of the graphene-based dispersions and related pretreatments. Labelling explanation: “D” denotes “dispersion”, “a” and “b” the minimum and maximum concentration, respectively.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mortar** & **Dispersion** & **Carbon Nanomaterial** & **w/c** & **s/c** & **SP/c** \\
**Label** & **Type** & **(wt\% *)** & **Ratio by wt.** & **Ratio by wt.** & **Ratio by wt.** \\ \hline C & - & 0 & 0.475 & 2.5 & 0.009 \\
01 TG & D-TGA & 0.1 & 0.475 & 2.5 & 0.009 \\
03 TG & D-TGA & 0.3 & 0.475 & 2.5 & 0.009 \\
05 TG & D-TGb & 0.5 & 0.475 & 2.5 & 0.009 \\
1 TG & D-TGb & 1.0 & 0.475 & 2.5 & 0.009 \\
01 SG & D-SGa & 0.1 & 0.475 & 2.5 & 0.009 \\
03 SG & D-SGa & 0.3 & 0.475 & 2.5 & 0.009 \\
01 GO & D-GOa & 0.1 & 0.475 & 2.5 & 0.009 \\
05 GO & D-GOb & 0.5 & 0.475 & 2.5 & 0.009 \\
1 GO & D-GOb & 1.0 & 0.475 & 2.5 & 0.009 \\ \hline \hline \end{tabular} \({}^{*}\)by weight of cement  
\end{table}
Table 3: Mix designs of mortars.