## 3 Sulfur Cake
### Processing and Modification Technologies
#### 3.2.2 Blending with Additives  
The blending of sulfur cake with organic and inorganic additives has been shown to be very effective in improving the suitability of the cake for construction activities. Table 5 offers insights into the characteristics and performance improvements of sulfur cake with the addition of organic (e.g., dicyclopentadiene (DCPD), plasticizers) and inorganic (e.g., fly ash, silica fume, carbon materials) additives, with an indication of their particular roles, loading, and the obtained overall enhancement of mechanical, thermal, and chemical properties as construction material. Sulfur cake, normally made of elemental sulfur, calcium sulfate, and hydroxide, has a number of limitations including brittleness and resistance to cracking. Additional organic plasticizers, such as DCPD and other similar plasticizers, have been shown to contribute to major changes in the mechanical flexibility and long-term durability of sulfur-type composites. These additives also allow cyclisation and crosslinking reactions to occur in the heating process, forming sulfur polymers which do not recrystallize and thermally degrade. Experimental data have demonstrated that introducing sulfur-organic polymers into composites can enhance compressive strength by up to 30% and significantly improve protection against microbial and chemical corrosion in harsh conditions, including sewers and acidic soil [45]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Additive Type** & **Specific Additive** & **Loading (wt%)** & **Modified Property** & **Observed Effect** & **Ref.** \\ \hline Organic modifier & DCPD & 5–10 & Thermal stability, flexibility & Improved elasticity; suppression of sulfur recrystallization & [45] \\ \hline Organic modifier & Plasticizers & 2–8 & Workability, flexibility & Easier processing; reduced brittleness & [45] \\ \hline Inorganic stabilizer & Fly ash & 20–30 & Compressive strength, density, filler dispersion & \textgreater{}40\% increase in strength; lighter composite with uniform microstructure & [46] \\ \hline Inorganic stabilizer & Silica fume & 10–15 & Acid and sulfate resistance, microstructure refinement & \textgreater{}50\% enhancement in chemical resistance and long-term durability & [47] \\ \hline Inorganic filler & Carbon materials & 5–15 & Thermal conductivity, crack resistance & Reduced shrinkage; and stability under temperature changes & [48; 49] \\ \hline Combined additives & Fly ash + silica fume & 25–35 Total & Chemical durability, structural strength & Synergistic increase in strength and resistance to aggressive environments & [46; 47] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Characteristics of modified sulfur cake with organic and inorganic additives, corresponding the enhancements in mechanical and chemical properties. The FTIR spectra presented in (Figure 4a,b) offer valuable insight into the functional group compositions of the olefinic hydrocarbon and modified sulfur, respectively, which are critical for understanding their behavior and performance in infrastructure applications such as sulfur concrete and sulfur-modified bitumen. In both spectra, there are typical absorption bands of organic and inorganic functional groups to help explain the degree of chemical interaction and structural enhancement of modified sulfur. Figure 4a depicts the spectrum of the olefinic hydrocarbon presenting high peak intensities, which were at 2972, 2936, and 2894 cm\({}^{-1}\) and were attributed to C-H asymmetric and symmetric stretch vibrations. These indications can be considered as evidence of hydrocarbons remnants, probably belonging to organic binders or leftover bituminous matter. Moreover, carbonyl (C=O) and C=C groups were determined by the presence of absorption bands at 1730-1740 cm\({}^{-1}\) and 1597 cm\({}^{-1}\), which are usually found in oxidative degradation products or aromatic compounds [50]. By comparison, in Figure 4b, the FTIR spectrum of the modified sulfur reveals notable changes.