# Effect of Cu, Cr, S Doped TiO\({}_{2}\) for Transparent Plastic Bar Reinforced Concrete
## 4 Discussion  
### Photocatalytic Reaction Mechanism of Transparent Plastic Bar Reinforced Concrete  
According to Figure 16, ordinary photocatalytic concrete can only experience the decontamination effect of photocatalysts on the incident side (\(S_{i}\)) of light. On the other hand, in the case of transparent plastic bar reinforced concrete, light can be transmitted through plastic bars so that light can be transmitted to the other side to maximize the photocatalyst reaction area [20]. The parameters and equations related to this are organized as shown in Figure 17 and Equations (1) and (2) below. The spacing of plastic bars is called \(I_{i}\) and the diameter is denoted by \(D_{i}\). The length of the concrete block incident cross section is \(L\) and the height is \(H\). The number of bars according to the diameter of the bars was called \(N_{Di}\), and the photocatalyst reaction area was indicated as \(P_{a}\). Since the plastics used in this study are PMMA (Poly methyl methacrylate) acrylics and generally have a light transmittance of 92%, the light transmittance of plastic bars, \(T_{acrylic}\), applied 0.92 [31; 32]. Taking 100 mm \(\times\) 300 mm concrete blocks as an example, as shown in Figure 18, the ordinary photocatalytic concrete can undergo photocatalyst reaction in all areas of the incident side, resulting in a 100% \(P_{a}\), but the transparent plastic bar reinforced concrete is inserted with 50 EA 10 mm bars, accounting for 13% of the concrete cross section, reducing \(P_{a}\) to 87%. However, light can reach the transmission side (\(S_{l}\)), indicating that 87% of the incident surface and 80% of the transmission surface have a total of 160% or more \(P_{a}\) when Equation (1) is applied. Transparent plastic bar reinforced concrete will be able to exert photocatalyst efficiency beyond ordinary photocatalytic concrete by the presence of light transmittance, which will be a good example of utilizing light diffusion indoors in a positive direction.  
\[P_{incident}^{a}=\frac{L\times H-N_{Di}\pi\left(\frac{D_{i}}{2}\right)^{2}}{ L\times H}\times 100 \tag{1}\]  
Figure 15: Doped TiO\({}_{2}\) concrete specimens and photocatalytic NO removal performance test of specimens.  
toluene and oleylamine are required, as well as a complicated manufacturing process. Since the photocatalytic cement has a similar ability to remove nitrogen oxides under visible light irradiation (approximately 15%) as the photocatalytic concrete in this study, it can be judged that the utilization of visible light photocatalytic concrete produced by an economical and simple method in this study is high [33]. Based on this, Figure 18 shows the effect of increasing the photocatalytic reaction area that occurs when 50 transparent plastic bars with a diameter of 10 mm are penetrated into a concrete block with a size of 100 mm \(\times\) 300 mm. As described in Section 4.1, the 100 mm \(\times\) 300 mm concrete block has a photocatalytic reaction area of 160%, so it is inferred that about 25.3% of NO can be removed. As a result of the NO removal test of the Cr-doped TiO\({}_{2}\) and S-doped TiO\({}_{2}\) concrete specimen, 1% of NO was removed. When plastic bars are penetrated into a concrete block having the same size as above, it is inferred that these specimens can remove about 1.6% of NO. It is considered that it is necessary to prove the theoretical value by conducting an NO removal test on the transparent plastic bar reinforced concrete specimen applied with a doped TiO\({}_{2}\) photocatalyst in the future.