Term: Sulfur concrete
**Characteristics and Properties of Sulfur Concrete**:
– Low porosity and permeability
– Resistance to acids
– Low thermal and electrical conductivities
– Compatibility with glass
– Smooth surface finish
– Waterless production
– Near-carbon-neutral construction material
– Utilization of excess sulfur
– Acid resistance
– Recyclable applications
– Resistance to some compounds
– Potential as a building material for Mars
– Acid-resistant discharge pipes
– Durability testing against bacteria
– Long-term challenges and considerations
**Advantages, Benefits, and Applications**:
– Waterless production process
– Recyclable applications
– Acid-resistant discharge pipes
– Large-scale production capabilities
– Potential for sustainable development
– Proposed applications in space exploration
– Utilization in lunar construction materials
– Fast curing properties
– Energy-efficient production
– High-quality fabrication techniques
**Corrosion and Durability Factors**:
– Stability and durability issues with steel reinforcement
– Strength loss in wet environments
– Corrosion of steel reinforcements
– Elemental sulfur’s reactivity
– Generation of toxic fumes in case of fire
– Corrosion factors and mechanisms
– Degradation influenced by exposure to oxygen and moisture
– Impact of microorganisms on corrosion
– Lack of chemical protection for steel
– Factors affecting service life and degradation kinetics
**Production and Composition of Sulfur Concrete**:
– Elemental sulfur hydrolysis
– Formation of sulfuric acid
– Sensitivity to oxidation
– Corrosion issues with metals
– Production methods and techniques
– Use of organic liquids for stabilization
– Cross-linking reactions
– Historical background and patents
– Research on properties and applications
– Design considerations and applications
**Studies, Research, and Further Reading**:
– Performance of cement-based materials in aggressive environments
– Corrosion in elemental sulfur environments
– Isolation and identification of sulfur-oxidizing bacteria
– Applications of sulfur concrete in various settings
– Viability in space environments
– Lunar concrete production
– Environmental considerations
– Recyclable applications in railways
– Scientific studies and publications
– Aerospace and space exploration conferences and proceedings
Sulfur concrete, sometimes named thioconcrete or sulfurcrete, is a composite construction material, composed mainly of sulfur and aggregate (generally a coarse aggregate made of gravel or crushed rocks and a fine aggregate such as sand). Cement and water, important compounds in normal concrete, are not part of sulfur concrete. The concrete is heated above the melting point of elemental sulfur (115.21 °C (239.38 °F)) at ca. 140 °C (284 °F) in a ratio of between 12% and 25% sulfur, the rest being aggregate.
Low-volatility (i.e., with a high boiling point) organic admixtures (sulfur modifiers), such as dicyclopentadiene (DCPD), styrene, turpentine, or furfural, are also added to the molten sulfur to inhibit its crystallization and to stabilize its polymeric structure after solidification.
In the absence of modifying agents, elemental sulfur crystallizes in its most stable allotropic (polymorphic) crystal phase at room temperature. With the addition of some modifying agents, elemental sulfur forms a copolymer (linear chains with styrene, cross-linking structure with DCPD) and remains plastic.
Sulfur concrete then achieves high mechanical strength within ~ 24 hours of cooling. It does not require a prolonged curing period like conventional cement concrete, which after setting (a few hours) must still harden to reach its expected nominal strength at 28 days. The rate of hardening of sulfur concrete depends on its cooling rate and also on the nature and concentration of modifying agents (cross-linking process). Its hardening is governed by the fairly rapid liquid/solid state change and associated phase transition processes (the added modifiers maintaining the plastic state while avoiding its recrystallization). It is a thermoplastic material whose physical state depends on temperature. It can be recycled and reshaped in a reversible way, simply by remelting it at high temperature.
A sulfur concrete patent was already registered in 1900 by McKay. Sulfur concrete was studied in the 1920s and 1930s and received renewed interest in the 1970s because of the accumulation of large quantities of sulfur as a by-product of the hydrodesulfurization process of oil and gas production and its low cost.