## 2 Materials and Methods  
The following components were used to make the self-compacting concrete mixes for testing: Portland cement CEM I 52.5R with a density of 3.10 g/cm\({}^{3}\), which meets the requirements of PN-EN 197-1 [21] and has the chemical and phase composition shown in Table 1; an innovative third-generation superplasticizer (SP) Glenium Sky 600 produced by BASF, based on polycarboxylic ether (PCE) polymers, with a density of 1.08 g/cm\({}^{3}\), used in a quantity equal to 4.0% of the cement weight; potable tap water; a granite aggregate with an average density of 2.61 g/cm\({}^{3}\), supplied by Tampereen Kovakivi Oy, which had fractions of 10-5, 5-2, 2-1, 1.2-0.5, 0.6-0.1 mm, and one fraction with a grain size \(<\)0.1 mm acting as a fine filler. The fine aggregate, with a fraction of up to 2 mm, constituted 48% of the total aggregate. The particle size distribution curve of the granite aggregate that was used for testing is shown in Figure 1. For the designed concrete mixes, the water to cement W/C ratio was equal to 0.42. The composition of the concrete mix was modified with the following nanoparticles in the form of dry powder in the amount of 4.0% of the cement weight: SiO\({}_{2}\) (Figure 2a) with particle size \(<\)20 nm, density of 2.4 g/mL at 25 \({}^{\circ}\)C, purity of 99.5%, and specific surface area equal to 450 m\({}^{2}\)/g; TiO\({}_{2}\) (Figure 2b), with particle size \(<\)25 nm, density of 3.9 g/mL at 25 \({}^{\circ}\)C, purity of 99.7%, and specific surface area equal to 50 m\({}^{2}\)/g; Al\({}_{2}\)O\({}_{3}\) (Figure 2c), with particle size \(<\)50 nm and specific surface area of 40 m\({}^{2}\)/g. The authors decided to use the highest content of nanoparticles (4.0%) used in previous studies [22] to see if a significant modification of SCC composition with the addition of nanoparticles has an impact on the properties of the hardened cement matrix. Generally speaking, using a lower content of nanoparticles (0.5% and 2.0%) resulted in slightly visible effects in previous tests [22], while using more than 4.0% of nanoparticles required a bigger amount of superplasticizer (\(>\)4.0%, which is not reasonable) to obtain the proper characteristics of a self-compacting concrete mix (slump flow \(>\) 550 mm). The nanoparticles used in the tests were provided by Sigma Aldrich. Four self-compacting concrete mixes were designed and made with the above ingredients, one of which was prepared without the addition of nanoparticles, as a control. The compositions of all the designed mixes per 1 m\({}^{3}\) are presented in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline
**Component** & **[wt. \%]** & **Phase** & **[wt.\%]** \\ \hline CaO & 65.0 & C\({}_{3}\)S & 56.3 \\ SiO\({}_{2}\) & 22.0 & C\({}_{2}\)S & 20.8 \\ Al\({}_{2}\)O\({}_{3}\) & 5.4 & C\({}_{3}\)A & 8.7 \\ Fe\({}_{2}\)O\({}_{3}\) & 3.3 & C\({}_{4}\)AF & 10.0 \\ MgO & 3.2 & & \\ Cl- & \(\leq\)0.08 & & \\ Loss of ignition & 3.0 & & \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical and phase composition of Portland cement CEM 152.5R. Figure 1: Grading curve of the aggregate. From each mix, with the designation and composition given in Table 2, a series of 12 cuboid specimens with dimensions of \(40\times 40\times 160\) mm were made. They were then matured in a climatic chamber at an air temperature of 20 \({}^{\circ}\)C (\(\pm\) 1 \({}^{\circ}\)C) and a relative humidity of 95% (\(\pm\) 5%). These series were marked identically as mixes S0, S1, S2, and S3. After one year, cylindrical samples of 25 mm in diameter and 20 mm in height were cut from the previously prepared cuboid specimens. The samples were cut from the centre of the specimens to avoid the boundary effect. In order to properly prepare the surface for the creep tests using the indentation method, the cylindrical samples were first immersed in epoxy resin in a vacuum machine that had an inside pressure of 0.07 bar, and their surfaces were then ground using 320 grit sandpaper and a 9, 3, and 1 \(\upmu\)m graded diamond slurry until a smooth surface was obtained.