# Performances of the Synergy of Silica Fume and Waste Glass Powder in Ternary Blended Concrete
## 3 Discussion of Results
### Effect of Elemental Ratio on the Concrete Characteristics  
Generally, the spectrum of blended silica-fume paste indicates that the Ca/Si ratio decreased with the increase in the amount of amorphous silica present in the products, as  
Figure 9: FTIR spectra of blended silica-fume/glass (ternary) cement (CGS\(-\)bottom), blended silica-fume (binary) cement (CS\(-\)middle) and hydrated cement (CC\(-\)top) paste. shown in Table 4 by the energy dispersion spectroscopy (EDS) results. Region 8 (Figure 10) comprises both calcium silica hydrate (CSH) and calcium aluminosilicate hydrate (CASH). The interaction of amorphous silica with tetracalcium aluminosilicate (C\({}_{4}\)AF) and tricalcium silicate (C\({}_{3}\)A) led to the formation CASH, as indicated in region 8 of the blended silica-fume paste. Spectra 9 and 23 have the presence of Fe but spectra 8 and 24 do not. The Ca/Fe ratio was 19.73 in the ternary blended paste, but drastically reduced to 2.04 in the absence of glass powder. This suggests that glass induces the reactivity of C\({}_{4}\)AF hydrations that could lead to the formation of hydrogarnet (CASH). Moreover, a lower calcium-carbon ratio (Ca/C = 2.75) in the blended silica binder in contrast to 3.78 in the blended glass/silica-fume (ternary) samples indicates that glass cha \begin{table}
\begin{tabular}{c c c} \hline \hline
**Elements** & **Silica-Cement** & **Glass-Silica-Cement** \\ \hline Ca/Si & 3.34 & 3.78 \\ Si/Al & 7.11 & 4.20 \\ Ca/C & 2.75 & 3.98 \\ Ca/F & 2.04 & 19.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Elemental ratio in silica fume and glass-blended silica-fume paste. Figure 10: X-ray diffraction spectroscopy of the silica fume and glass/silica-fume binder. (**a**) Silica-fume blended paste (**b**) Glass/silica-fume ternary blended paste. of the hydration products within the matrix through the infusion of amorphous silica into portlandite to form CSH by preventing or limiting the occurrence of Equation (2). \[\text{Ca(OH)}_{2}+\text{CO}_{2}\rightarrow\text{CaCO}_{3}+\text{H}_{2}\text{O} \tag{2}\]  
This explains why carbonation was noted to have reduced by the incorporation of glass in the blended silica-fume- or OPC-based concrete. Similarly, the microstructure shown in Figure 10 in the glass/silica binder was found to be non-uniform and full of micropores due to the heterogeneity or incompatibility of the glass particle with both the cement and silica-fume particle sizes thereby causing more ITZs within the crack region (Figure 10b). Figure 11 shows the diffractogram of ternary (glass/silica fume) blended paste (SGC), blended silica-fume (SC) paste and hydrated cement paste (CMT). The SGC paste was more amorphous compared to the SC and CMT. The inclusion of glass induced the formation of larnite (L-hydrated calcium silicate compound, 2 CaOSiO\({}_{2}\) PDF#96-200-0096) around the 2-theta angle of 39.5\({}^{\circ}\) (Region 2) while calcite (CaCO\({}_{3}\)-CC-PDF#99-200-0080) formation was noticed to reduce in the SGC compared to SC. This was due to the additional pozzolanic effects that caused the conversion of portlandite (P- PDF# 96-900-8367) to additional CSH via a secondary hydration, as shown in Equations (2) and (3) (Figure 11). The presence of amorphous silica interferes with tricalcium aluminate (C\({}_{3}\)A) in the process of the formation of early ettringite and the hydration of C\({}_{4}\)AF (CF PDF#96-200-0015) to form calcium aluminosilicate silicate hydrate (CA(S)H--Region 2, Figure 11) or an octahedral form of hydrogarnet [33; 34; 35]. The absence of the peak of C\({}_{4}\)AF (CF PDF#96-200-0015--Region 1) suggested the possibility of such a reaction. The ettringite formed in glass-infused silica-fume concrete was seen to be less ordered in comparison with the OPC concrete (Figure 11).