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 () at ca.  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  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.