## 4 Technological Developments of Sulfur in Construction
### Modified Sulfur Cake Concrete
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Concrete Type** & **Additive(s)** & **Additive Content** & **Compressive Strength MPa** & **Tensile/Flexural Strength MPs** & **Durability** & **Ref.** \\ \hline \hline \multirow{4}{*}{\begin{tabular}{c} Sulfur \\ concrete \\ \end{tabular} } & Sulfur binder (100\% replacement) & 100\% of binder & 40–60 (24 h cure) & 3–8 flexural & (\(<\)0.05\%), high acid/alkali resistance, excellent freeze–thaw stability \\ \hline \hline \multirow{4}{*}{\begin{tabular}{c} Fiber- \\ reinforced \\ \end{tabular} } & Steel/glass/ polypropylene fibers & 0.5–2.5\% vol & 35–70 & 5–12 tensile; up to 15 flexural & \begin{tabular}{c} Enhanced toughness, \\ crack control, impact \\ and fatigue \\ resistance \\ \end{tabular} & [74; 75] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Polymer- \\ modified \\ \end{tabular} } & SBR, acrylics, epoxy, silanes & 5–20\% by cement weight & 45–70 & 4–7 tensile; 7–12 flexural & \begin{tabular}{c} Improved \\ permeability, early \\ strength gain, \\ chemical/weather \\ resistance \\ \end{tabular} & [76; 77] \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} Fly ash \\ concrete \\ \end{tabular} } & Class F/C fly & 15–40\% cement & 35–60 (28–90 d) & 2.5–4.5 tensile &
\begin{tabular}{c} Long-term strength \\ gain, Improved \\ sulfate/chloride \\ resistance; lower \\ heat of hydration \\ \end{tabular} & [78; 79] \\ \hline \end{tabular}
\end{table} 
Table 7: Comparative analysis of sulfur concrete with other advance modified concrete types, detailing additive composition, properties, and durability. Modified sulfur cake, containing elemental sulfur mixed with calcium hydroxide, calcium sulfate, and stabilizers, is a significant contributor to improving the structural matrix. Its formation will enhance a stronger bonding between aggregates and sulfur, decrease shrinking, and enhance chemical attack resistance of the matrix. Compressive strength gains of up to 25% have been recorded when conventional sulfur is substituted by modified sulfur cake at a ratio of 10-20 wt% of the binder because of a denser, more cohesive binder matrix [62]. In addition, the incorporation of fly ash and bitumen-modified sulfur along with the sulfur cake makes the pore structure more refined and increases the mechanical properties as well as thermal stability. The process of sulfur modification is not merely a physical dispersion of additives but involves chemical transformations, particularly when sulfur is heated with hydrocarbon-based stabilizers or additives like bitumen. These reactions include the formation of polysulfide chains, crosslinking networks, and sulfur-carbon bonding, which enhance the rheological behavior and stability of the final matrix. Recent studies confirm that sulfur-extended binders undergo significant chemical changes that affect curing behavior and long-term performance [83,84]. Moreover, the nano-structural evolution of aged and rejuvenated sulfur-modified binders demonstrates molecular interactions beyond simple blending, further proving the chemical nature of the modification process [85]. A response surface methodology (RSM) is used to optimize concrete of sulfur using micro- and macro-steel fiber-similar formulations. Findings indicate a 30-40% increase in tensile strength and up to a 45% increase in flexural strength when fiber was at optimum levels, between 1.0 and 1.5 vol% [86]. Additionally, sulfur concrete offers rapid setting times (less than one hour at ambient temperature) and can be fully cured within 24 h, enabling faster construction cycles [87]. Durability studies demonstrate that sulfur concrete exhibits excellent resistance to acids, salts, and freeze-thaw cycles, outperforming conventional concrete in long-term exposure tests [88]. In structural applications, sulfur concrete reinforced with rebar showed comparable load-bearing capacity and better corrosion resistance than ordinary concrete [89].