**4. Scanning Electron Microscope (SEM) Analysis**

SEM investigation was achieved with samples taken from some samples of this experimental study. The images are magnified 500 times to show the interaction among binder materials and aggregates. In SEM analysis, there are images of two different mixtures. The first four are images of concrete samples containing only CGW, and the last four are images of samples containing both CGW and glass powder. Figure 7a shows the situation where CGW is swapped by aggregate. It is seen that the glass pieces, in the range of 4–9 mm, are homogeneously dispersed in the homogeneous concrete by providing good compatibility with the cement binder. Figure 7b shows the slightly larger and closer state glass particles dispersed in the concrete and their harmonious positions. In Figure 7c, it can be said that the interface among the glass piece and the binding cement remains in a discrete form. Figure 7d shows that gaps and holes are formed in some regions. This problem can be eliminated with better compression and vibration. Glass powder makes a good pozzolanic effect because it has a higher specific surface area than cement [30,50]. It can be seen in Figure 7e that the binding property of the CWG powder cement and the pozzolanic property of the glass powder results in good bonding. Etringite formation is an important issue in Portland cement concretes due to early phase hydration [51,52]. Although the hydration of glass powder and cement show similarities, some ettringite formation is seen in Figure 7e. While the samples were being prepared, a good mixing in the mixer ensured the homogeneous distribution of the additional powder particles. Although a very small part was examined in the SEM analysis, the compressive and FS consequences show a homogeneous distribution among homogeneous binders with an increasing productivity in the range of 10–40%. Figure 7f shows the standing of small and large CGWs in concrete. While there is a line among the large particle and the cement, it is seen that the smaller piece of glass has a better bonding with the cement. It is stated that the use of glass particles as aggregate can increase cracks and voids, and this will cause a decrease in strength [53]. Figure 7g shows the distribution of glass powders and small glass particles in the concrete. It can be said that the use of both CWG together for concrete is a good match. In Figure 7h, it is seen that there are gaps and holes in places. These can be considered as mini problems. It is stated in some studies that glass powder with finer particles has a high pozzolanic effect and provides better strength in concrete. The consequences obtained confirm the statements in the literature [53–56].

**Figure 7.** *Cont*.

**Figure 7.** Consequences of SEM analysis.
