# Internal Curing Effect of Waste Glass Beads on High-Strength Cement Composites
## 2 Materials and Methods
### Testing Methodology  
For each specimen, the compressive strength was measured at the ages of 1, 3, 28, and 56 d; the density was measured at the age of 28 d; and XRD, TGA, and MAS NMR spectroscopy were conducted at the ages of 3 and 56 d. HSCC fluidity was measured in the unhardened state before a specimen was placed in the mold. The flow table method (ASTM C 1437) was used in which the mixture in a fresh state was placed on a flow table and measured after the flow stopped. The density of HSCC specimens was measured according to ASTM D 792. For compressive strength measurements, the compressive strengths of three cylindrical specimens were measured, and the average was selected as the compressive strength in accordance with ASTM C109/C109a. Powder samples that passed through a 75 \(\upmu\)m sieve were collected from the specimens used for compressive strength and hydrate composition measurements. When WGB was added, a 50 \(\times\) 100 mm area was selected at the center of the \(\mathcal{O}\)100 \(\times\) 200 mm specimen, and then paste powder samples were collected. A flake-type sample was taken from the specimen destroyed by a compressive strength test using stainless steel tweezers. Subsequently, WGB was removed from the flake-type sample with stainless steel tweezers and was powdered using a mortar. To stop further hydration of the collected samples for Rietveld-refinement-based quantitative analysis, the solvent exchange method using isopropanol and ethyl ether was used as the standard condition. The samples were kept dry using silica gel until testing. The test conditions for hydration product composition analysis are as follows. XRD was performed using a PANalytical X'Pert PRO-MPD device (DA101 at the KBSI Daegu Center), and the scan range was set to 0.02\({}^{\circ}\). Measurements were obtained over a range of 5\({}^{\circ}\) to 70\({}^{\circ}\) at intervals of 3.0\({}^{\circ}\). Figure 3 shows the XRD patterns of the binders used in this study. TGA was conducted at a heating rate of 10 K/min in a N\({}_{2}\) environment using a thermal analyzer (TA Instrument, Q600, PH407, KBSI Pusan Center). Solid-state \({}^{29}\)Si MAS NMR was analyzed using an INOVA 600 spectrometer (KBSI Western Seoul Center). The \({}^{29}\)Si MAS NMR spectrum was obtained at a rotation speed of 10.0 kHz, pulse width of 2.2 \(\upmu\)s, and relaxation delay of 22 s using a 5 mm HX-CPMAS probe and 5 mm zirconia rotor. To estimate the extent of hydration, thermodynamic modeling was performed based on the clinker reactivity obtained using the Gibbs energy minimization software GEM-Selektor v3.3 and CEMDATA 18.01 database [28]. The reactivity model of UHPC mixed with WGBs was designed using the Rietveld refinement method and [PERSON]'s hydration model [29]. This method, which tracks hydration dynamics as a function of hydration time, was used to model HSCC mixed with WGBs. The aforementioned database contains thermodynamic data as well as data for cement minerals, such as ettrinigite (Aft), single-phase aluminum-iron (Afm), hydrotalcite, hydrated garnet, and calcium silicate hydrate (C-S-H). The chemical composition of cement and the hydration reaction conditions defined and entered in GEMS were combined with the Parrot-K \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Mixture ID.** & **Cement** & **Silica Fume** & **Silica Powder** & **Water** & **Superplasticizer** & **WGB** \\ \hline SP & & & & & 0 \\ \hline S5 & & & & & 21 \\ \hline S10 & & & & & 42 \\ \hline S20 & & & & & 81 \\ \hline RP & 322 & 106 & 128 & 304 & 20 & 0 \\ \hline R5 & & & & & 21 \\ \hline R10 & & & & & 42 \\ \hline R20 & & & & & 81 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Mix proportions of specimens (per cubic meter of specimens, kg/m\({}^{3}\)). relationship between cement hydration degree and time. The Parrot-Killoh empirical model is expressed in Equations (1)-(3). Equation (1) concerns nucleation and growth. Equation (2) concerns diffusion, and Equation (3) concerns the formation of hydration phase.