## 3 Results and Discussion
### Potential Waste Reduction by Using Different Structural Systems  
Table 4 summarises the reduced amount of construction waste and the reduction ratio of the flat plate slab systems and the void slab system compared to the solid slab. Columns 5, 6, and 7 in Table 4 show the reduction ratio of each waste source to the reduction of the total construction waste generation by applying the flat plate slab and the void slab system. The test results showed that the application of alternative structural systems would achieve a total waste reduction of 13,757.426, 2703.976, and 2026.224 kg for the void slab system, the flat plate slab systems, and the solid slab system, respectively. It was indicated that approximately 8448.019 kg of construction waste was reduced from the ready-mixed concrete by the void slab system. In this study, the results also showed that applying to the void slab system would make it possible to decrease about 5054.780 kg of construction waste from plywood forms compared to the solid slab system. Furthermore, the estimation results of the flat plate slab indicate the reduced amount of construction waste over the solid slab system. While the reduction value of both flat plate slab systems was relatively smaller than the void slab system, the flat plate slabs with 180 and 210 mm of thickness showed about 2.7% and 2% reduction of total waste generation during the construction phase. For the flat plate slab system, the major reduction source of construction waste was reinforcing bars, which showed about 1264.371 kg and 1764.859 kg reductions for flat plate slab with 180 mm and 210 mm of thickness, respectively. The flat plate slab system is one of the more commonly used alternative systems for solid slab systems in recent years because of its simple formworks and longer spans for occupants. However, from the perspective of waste generation, the difference between the solid slab and the flat plate slab is relatively smaller due to the additional works \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Building Materials**} & \multicolumn{3}{c}{**Reduction of Construction Waste (kg)**} & \multicolumn{3}{c}{**Reduction Ratio (\%)**} \\ \cline{2-7}  & **VS–SS** & **FPS 180–SS** & **FPS 210–SS** & **VS–SS** & **FPS 180–SS** & **FPS 210–SS** \\ \hline \hline \begin{tabular}{c} Ready-mixed \\ concrete \\ \end{tabular} & \(-\)8448.019 & \(-\)823.420 & 168.605 & \(-\)12.93 & \(-\)1.26 & 0.26 \\ \hline \hline \begin{tabular}{c} Rebars \\ \end{tabular} & \(-\)2899.354 & \(-\)1264.371 & \(-\)1764.859 & \(-\)10.87 & \(-\)4.74 & \(-\)6.62 \\ \hline \hline \begin{tabular}{c} Spacer \\ \end{tabular} & \(-\)768.737 & \(-\)161.839 & \(-\)80.920 & \(-\)55.88 & \(-\)11.11 & \(-\)5.56 \\ \hline \hline \begin{tabular}{c} Forms \\ \end{tabular} & 5054.780 & \(-\)454.346 & \(-\)349.050 & \(-\)64.09 & \(-\)5.76 & \(-\)4.43 \\ \hline \hline \begin{tabular}{c} Void formers \\ \end{tabular} & 2014.901 & 0 & 0 & 59.03 & 0 & 0 \\ \hline \hline \begin{tabular}{c} Steel decking \\ \end{tabular} & 1216.493 & 0 & 0 & 35.63 & 0 & 0 \\ \hline \hline \
\begin{tabular}{c} Anchoring metals \\ \end{tabular} & 182.069 & 0 & 0 & 5.34 & 0 & 0 \\ \hline \hline
\begin{tabular}{c} Total \\ \end{tabular} & \(-\)13,757.426 & \(-\)2703.976 & \(-\)2026.224 & \(-\)13.57 & \(-\)2.67 & \(-\)2.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Waste reduction of the different structural systems. needed for enhancement around columns such as drop panels and an increased amount of reinforcement works. From the perspective of the waste reduction in each building material when replacing the solid slab with alternative structural systems, the void slab system would be the most beneficial method to reduce waste generation during the construction phase. In the case of waste generation from the void slab system, a reduction of 12.93% of the waste from the ready-mixed concrete, 64.09% of waste from forms, and 10.87% of waste from rebars could be seen.