## 3 Sulfur Cake
### Processing and Modification Technologies
#### 3.2.2 Blending with Additives
The improved homogeneity and lower proportion of rigid crystalline impurities in sulfur concrete lead to improved thermal expansion compatibility and lower development of internal stresses,  
Figure 3: X-ray diffraction (XRD) patterns of the analyzed samples: (**a**) unmodified sulfur cake and (**b**) sulfur cake modified with oleic acid. This figure is reproduced from [PERSON] et al., 2024 [6], under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0). which is important to long-term durability in aggressive environments [55]. In the context of sulfur-modified bitumen, the inhibition of non-sulfur crystalline phases results in enhanced flexibility and adhesion, particularly when the modified sulfur is involved in crosslinking or co-polymerization during the mixing of the asphalt [56]. Moreover, the observed structural refinement is consistent with the wider endeavors in materials science to create polymeric or composite forms of sulfur with improved process ability and environmental performance [57]. Oleic acid modification is also a sustainable chemical approach to up-cycle sulfur waste, which complies with the principles of green chemistry, as it decreases the use of synthetic polymers and enhances the compatibility of sulfur binders in different infrastructure applications [58]. Inorganic stabilizers and fillers like fly ash, silica fume, and carbon-based materials further reinforce the structural integrity of sulfur composites. Fly ash, particularly at loading levels between 20 and 30 wt%, acts as a fine filler and pozzolanic agent, reducing the overall density while increasing compressive strength by more than 40%. The porous nature of fly ash particles also enhances the bonding and dispersion of sulfur, resulting in a more homogeneous and durable composite [46]. Silica fume, characterized by its high specific surface area and rich silicon dioxide content, refines the microstructure of sulfur binders and greatly improves their resistance to sulfate and sulfuric acid attack. Sulfur matrices blended with a combination of silica fume and fly ash have demonstrated a 50% increase in resistance to chemical degradation, making them particularly valuable in aggressive industrial and marine environments [47]. To further substantiate these advantages, a quantified performance comparison between modified sulfur cake (MSC)-based composites and traditional concretes is provided in Table 6. The data demonstrate that MSC-based systems incorporating fly ash and silica fume exhibit up to 45-60% higher acid resistance than ordinary Portland cement (OPC), and tensile strength improvements of approximately 25-30% compared to conventional asphalt binders [59; 60]. Freeze-thaw stability is significantly enhanced in bitumen-modified sulfur concretes, with less than 5% mass loss after 100 cycles, as compared to 12-15% in standard concrete [61]. These improvements align with the findings of [PERSON] et al. [62] and [PERSON] et al. [63], confirming the mechanical and chemical durability of the modified sulfur composites under aggressive environmental stressors. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Property**} & **MSC-Based Composites** & **Conventional OPC** & **Improvement (\%)** & **Ref.** \\ \hline Compressive & & & & \\ strength (MPa) & & & & \\ \hline Tensile/flexural & & & & \\ strength (MPa) & & & & \\ \hline Acid resistance & 45–60\% less & Moderate to high surface & & \\ (H\({}_{2}\)SO\({}_{4}\), HCl) & degradation & degradation & & \\ \hline Freeze-Thaw & \textless{5\% mass loss} & & & \\ stability & after 100 cycles & 12–15\% mass loss & +60–70 & [61] \\ \hline Thermal & 0.8–1.2 (carbon & & & \\ conductivity & fillers & 0.5–0.6 & +40–60 & [63] \\ (W/m\(\cdot\)K) & enhanced) & & & \\ \hline Water & Significantly & & & Improved impermeability & [64] \\ permeability & reduced & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparative performance of MSC-based composites and conventional materials.