## 5 Challenges and Future Prospects  
Modified sulfur cake concrete and bitumen technologies present promising advancements for sustainable infrastructure and road construction, while also accompanied by overlying limitations, challenges, and future perspectives that need to be studied to lead to effective usage in industries. A roadmap is presented in Figure 8, summarizing the major technological and environmental challenges in the utilization of modified sulfur cake for construction materials and their prospective solutions. Addressing these challenges through nanotechnology, process engineering, and regulatory frameworks will enable safer, scalable, and standardized applications of sulfur-based binders in sustainable infrastructure. The problem of stability and phase separation of the modified sulfur binders is a major restriction. Because of the complicated multi-phase nature sulfur cake is made up of, comprising elemental sulfur, calcium sulfate, calcium hydroxide, and other by-products, thermal processing tends to cause phases of separation as a result of higher temperatures (>135 \({}^{\circ}\)C). This deteriorates the uniformity of sulfur bitumen and sulfur-concrete composites, reduces their mechanical properties, and enhances the possibility of cracking or delamination of sulfur under cyclic loading [131]. For instance, SBS/sulfur-modified bitumen is found to be phase unstable in storage as an extreme result of sedimentation detectable after only 72 h of storage at elevated temperatures (160 \({}^{\circ}\)C) is observed unless compatibilizers are used [132]. This underlines the urgent need for more in-depth thermodynamic modeling of sulfur systems and molecular-level studies to better predict phase behavior. Future reviews and meta-analyses could comparatively assess compatibilizer effectiveness across formulations, which is currently lacking in the literature. Health and safety issues are also a significant problem when processing sulfur cake in hot conditions both in bitumen melting and in concrete production. The thermal decomposition of sulfur above 160 \({}^{\circ}\)C may release toxic hydrogen sulfide (H\({}_{2}\)S) and sulfur dioxide (SO\({}_{2}\)) gases, posing significant occupational hazards and requiring advanced ventilation and gas scrubbing systems for safe large-scale deployment [133]. To mitigate these emissions, several strategies have been proposed, such as incorporating metal oxides (e.g., ZnO, CaO) or industrial alkaline fillers that can chemically absorb H\({}_{2}\)S/SO\({}_{2}\) gases during processing. Additionally, pre-treatment of sulfur cake to remove ammonium salts and the use of multistage crystallization techniques, as described by [PERSON] et al. [133], can significantly reduce volatile emissions during thermal cycles. Moreover, the controlling of chemically modified residues especially those that contain ammonium salts or poly-sulfur species, requires strict temperature control and protective equipment, elevating high costs for industrial production [134]. Another limitation is the lack of standardization and scale-up mechanisms, which hinders the broader adoption of sulfur cake materials in infrastructure. Currently, no unified protocols exist for performance classification, long-term durability, or environmental impact assessment of sulfur-modified materials, which limits regulatory approval and cross-regional acceptance [135]. Furthermore, batch-to-batch variability in sulfur cake composition, especially in modified forms derived from flue gas desulfurization or coke  
Figure 8: Challenges and future prospects for modified sulfur cake utilization in construction materials. treatment, leads to inconsistent curing behavior and workability [136]. Critically, many studies fail to directly compare sulfur cake from different industrial sources or analyze its variability quantitatively, which weakens the reliability of performance claims.