## 6 Overcoming Barriers to Integration  
### Economic Challenges  
As deduced from the previous sections, the integration of secondary resources like cellulose waste, mining tailings, and metallurgy slags into the construction sector offers substantial environmental and economic benefits. However, significant barriers impede their widespread use, including economic challenges, technological limitations, restrictive regulations, and the need for innovative business models. Among them, economic challenges are a major obstacle to integrating secondary resources in construction [279]. The high costs associated with processing these materials, such as mining tailings and metallurgy slags, often involve specialized treatments, like grinding, chemical stabilization, or thermal activation, which require significant investments in technology and infrastructure. According to recent studies, despite the low cost or availability of these secondary materials, the processing expenses can be prohibitive, especially for small and medium-sized companies that lack access to the necessary capital and technological resources [280]. The inconsistent supply and \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**SRM** & **Application** & **Dosage** & **Effect on Properties** & **Reference** \\ \hline Cellulose fibers & Concrete & 0.9 kg/m\({}^{3}\) & \(\uparrow\) Compressive, tensile, and & [42] \\  & & & flexural strength & [42] \\ Waste paper & Concrete & 5–10\% & \(\uparrow\) Compressive strength, \(\downarrow\) & [96] \\  & & & beyond 10\% & \\ General cellulose use & Concrete & \(\leq\)1.0\% (typical) & \(\uparrow\) Tensile strength, \(\downarrow\) Brittleness, & [14, 98] \\  & & & \(\uparrow\) Durability (if treated) & \\ Iron tailings & Concrete & Up to 30\% aggregate & \(\uparrow\) Compressive strength, \(\uparrow\) & [154] \\  & & replacement & & Abrasion resistance & \\ Various tailings & Fine aggregate & 10–40\% & \(\uparrow\) Freeze–thaw resistance, \(\downarrow\) & [157] \\  & replacement & & Permeability & \\ Tailings as cement & Concrete & 5–20\% & \(\uparrow\) Durability, depends on SiO\({}_{2}\) + & \\ substitute & Concrete & 5–20\% & \(\downarrow\) Durability, depends on SiO\({}_{2}\) + & \\  & & & & \(\downarrow\) Al\({}_{2}\)O\({}_{3}\) + Fe\({}_{2}\)O\({}_{3}\) content \(\geq\)75\% & [157] \\  & & & & \(\uparrow\) Compressive and tensile & [242, 243] \\  & & & strength, \(\uparrow\) Sulfate resistance & [242, 243] \\  & & & \(\uparrow\) Density, \(\uparrow\) Mechanical strength & [247] \\  & & & \(\downarrow\) Abrasion resistance, \(\uparrow\) Density, & [251] \\  & & & & \(\uparrow\) Tensile strength & [256] \\  & & & & \(\uparrow\) Moisture resistance, \(\uparrow\) Fatigue & \\ Steel slag & Asphal mixtures & Various & & \(\downarrow\) Rutting & [257, 261] \\  & & & & \(\downarrow\) Rucrite & \\ Nickel slag & Concrete & 30\% & \(\uparrow\) Flexural and compressive & \\  & & & strength, \(\uparrow\) Durability & \\ Phosphorus slag & Concrete & 20–30\% & \(\uparrow\) Sulfate resistance, \(\uparrow\) Chemical & \\  & & & & durability & [256] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Performance of construction materials incorporating SRM (\(\uparrow\) increase; \(\downarrow\)decrease). variable quality of these materials further complicate cost-benefit analyses, making their integration less economically attractive [281]. Specific examples highlight the economic barriers associated with metallurgy slags, where steel slags need stabilization to reduce free lime content and prevent volumetric expansion, while copper slags must be rapidly cooled to retain their pozzolanic properties. The costs associated with these treatments can significantly impact the economic viability of using such materials. Similarly, cellulose derived from industrial processes, like paper manufacturing, requires extensive cleaning and refinement, which can outweigh the benefits if not optimized.