## 1 Introduction  
The global production of elemental sulfur has seen a steady rise over the past few decades, primarily due to its large recovery as a by-product in the refining processes of oil, gas, and metal. Every year, approximately more than 70 million metric tons of sulfur are produced globally, consumed in the volatile desulfurization processes in fossil fuel plants [1]. Sulfur has commonly been used in welding and the fertilizer industry, yet having too much of it has caused problems related to storage, getting rid of waste, and maintaining a healthy environment [2]. Storing a massive supply in open areas is one of the major challenges of surplus sulfur which harms the environment. Although sulfur is generally stable, it tends to oxidize and may result in sulfur dioxide under humid and acidic conditions. This compound can contaminate the soil and water if released into the environment [3]. A sulfur waste called sulfur cake is produced during the production of sulfuric acid and other hydrometallurgy processes and contains high levels of sulfur and inorganic material [4]. The disposal of sulfur cake poses both logistical and ecological problems due to its semi-solid nature and impurity content, limiting its industrial use and necessitating energy-intensive treatment methods [5]. Recently, researchers have shown interest in modified sulfur cake and other sulfur-rich industrial by-products to make construction materials such as sulfur concrete and sulfur-bitumen, resulting in a reduction in the huge amount (around 12 metric tons annually) of sulfur waste materials. The diversity of sulfur waste sources, their compositions, and the growing research interest in sulfur-based construction materials are summarized in Figure 1. Sulfur cake is usually treated with chemicals or heat to improve its composition, eliminate any toxic impurities, and increase its compatibility with cement or asphalt binders [6]. The use of modified sulfur in these materials has the advantages of both mitigating the environmental risks of sulfur disposal and supporting the development of sustainable and corrosion-resistant construction products. The motivation behind this innovation lies in the urgent need to close material loops and establish low-carbon pathways in the building and infrastructure sectors [7]. Many studies aimed at improving the composition and the functionality of the sulfur-based construction composites to make them more long-lasting and environmentally friendly. Sulfur-polymer composite materials have evolved to be more advanced, with enhanced acid-exposure-resistant performance and have also been modified with the aim of being applied in highly chemically hostile environments like wastewater treatment  
Figure 1: The left panel illustrates the production and treatment pathways of sulfur cake, the middle panel presents the composition of sulfur cake along with publication trends since 2015, and the right panel identifies various sources of waste sulfur. (Data retrieved from the Scopus database on 20 June 2025 using the search terms “Sulfur modified construction materials” within article title, abstract, and keywords). plants and chemical storage plants. Such composites not only withstand degradation at low pH environments but are also able to achieve compressive strengths of greater than 40 MPa, which is competitive when compared to conventional concrete compositions [8]. Researchers have also been able to make structural modifications by adding bitumen and stone flour to sulfur concrete, which results in improved structural cohesion and rheological properties and hence greater load-bearing capabilities [9]. Other notable developments include the incorporation of sulfur with foam-treated limestone and ferrous sulfate to fabricate non-odorous sulfur concrete which has the ability to extract nutrients in wastewater. The composite has a 90% efficiency in removing nitrogen and phosphorous, providing a two-dimensional use as well: replacing traditional methods of producing infrastructure and cleaning up the environment [10].