## 4 Conclusions  
With the growing concerns towards the adverse environmental impacts brought about by various forms of waste, the construction industry will have to alleviate its generation of construction waste. In this study, the application of alternative construction methods was \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Building Materials**} & \multicolumn{4}{c}{**Cost Reduction (USD)**} & \multicolumn{4}{c}{**Proportion (\%)**} \\ \cline{2-7}  & **VSS-SS** & **FPS180-SS** & **FPS210-SS** & **VSS-SS** & **FPS180-SS** & **FPS210-SS** \\ \hline \hline Ready-mixed concrete & \(-2109.02\) & \(-205.56\) & \(42.09\) & \(-12.93\) & \(-1.26\) & \(0.26\) \\ Rebars & \(-1919.78\) & \(-837.19\) & \(-1168.58\) & \(-10.87\) & \(-4.74\) & \(-6.62\) \\ Spacers & \(-326.29\) & \(-68.69\) & \(-34.35\) & \(-52.78\) & \(-11.11\) & \(-5.56\) \\ Forms & \(-29,558.19\) & \(-2656.82\) & \(-2041.10\) & \(-64.09\) & \(-5.76\) & \(-4.43\) \\ Void formers & \(598.65\) & \(0\) & \(0\) & \(1.95\) & \(0\) & \(0\) \\ Steel deciding & \(2581.69\) & \(0\) & \(0\) & \(8.42\) & \(0\) & \(0\) \\ Anchoring metals & \(77.28\) & \(0\) & \(0\) & \(0.25\) & \(0\) & \(0\) \\ Total & \(-30,655.65\) & \(-3768.27\) & \(-3207.93\) & \(-37.98\) & \(-4.67\) & \(-3.97\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Cost reduction from the different structural systems. assessed as one of the potential approaches to minimise the generation of waste during the construction phase. However, there is a lack of studies and methods to quantify and compare the amount of construction waste generation from different construction methods. This study, therefore, also assessed construction waste generation and its impacts on waste reduction involving the three different slab systems, namely, the solid slab system, the flat plate slab, and the void slab system. The results of the study show that:  
1. The total waste generation during the construction phase of the different slab systems shows that the solid slab system produces the largest amount of construction waste, which is 101,361.39 kg. On the other hand, the void slab system generates 87,603.96 kg of construction waste, which is the lowest amount among the four variables of this study. In addition, 98,657.41 kg and 99,335.16 kg of construction waste was generated for the flat plate slab with a thickness of 180 and 210 mm, respectively. 2. In this study, the building materials processed or manufactured in a factory would be one of the potential construction waste reduction factors. In particular, the conventional cast-in-place reinforce concrete requires formwork and reinforcement, which might be dependent upon the skill level of the workers. Since the different level of skill would be one of the factors for producing different amounts of construction waste on site, the application of manufactured products on site would be helpful to reduce the amount of construction waste. 3. Among the three different slab systems assessed in this study, the void slab system would be the most beneficial method to reduce the waste generation during the construction phase. The reduction of construction waste compared to the solid slab system was by 13,757.43 kg, 2703.98 kg, and 2026.22 kg for the void slab system and the flat plate slab system with 180 mm and 210 mm, respectively. The results indicate that the void slab system reduces total waste generation by about 13%, while the flat plate slab with a thickness of 180 mm and 210 mm reduces waste by approximately 2.7% and 2.0%, respectively. In particular, the waste reduction from plywood forms and ready-mixed concrete is about 64% and 13%, which are the highest reduction ratios amongst the building materials. 4. The additional purchasing costs due to the loss of construction materials were also investigated in this study. The results indicate that the solid slab system would require additional material purchasing costs of USD 80,709.76, which is the highest value out of the four variables in this study.