With the addition of some modifying agents, elemental sulfur forms a copolymer (linear chains with styrene, cross-linking structure with DCPD[3]) and remains plastic.
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.
They also mention amongst its main limitations, its high coefficient of thermal expansion, the possible formation of acid under the action of water and sunlight.
Its waterless and less energy-intensive production (in comparison with ordinary cement and regular concrete) makes it a potential alternative for high-CO2-emission portland-cement-based materials.
[12] THIOTUBE is the brand name for certified acid-resistant DWF (dry weather flow) discharge pipes used in Belgium.
When the sulfur cycle is active in sewers and H2S emanations from the effluent waters are oxidized in H2SO4 by atmospheric oxygen at the moist surface of tunnel walls, sulfuric acid can attack the hydrated Portland cement paste of cementitious materials, especially in the non-totally immersed sections of sewers (non-completely water-filled vadose zone).
[14][15] Sulfur concrete, if proven resistant to long-term chemical and bacterial attacks, could provide an effective and long-lasting solution to this problem.
This could also depend on the progressive recrystallization of elemental sulfur over time, or on the rate of plastic deformation of its structure modified by the different types of organic admixtures.
According to Maldonado-Zagal and Boden (1982),[23] the hydrolysis of elemental sulfur (octa-atomic sulphur, S8) in water is driven by its disproportionation into oxidised and reduced forms in the ratio H2S/H2SO4 = 3/1.
[22][25][26] Therefore, long-term corrosion problems of steels and other metals (aluminium, copper...) need to be anticipated, and correctly addressed, before selecting sulfur concrete for specific applications.
The service life of components made of sulfur concrete depends thus on the degradation kinetics of elemental sulfur exposed to atmospheric oxygen, moisture and microorganisms, on the density/concentration of microcracks in the material, and on the accessibility of the carbon-steel surface to the corrosive degradation products present in aqueous solution in case of macrocracks or technical voids exposed to water ingress.
All these factors need to be taken into account when designing structures, systems and components (SSC) based on sulfur concrete, certainly if they are reinforced, or pre-stressed, with steel elements (rebar or tensioning cables respectively).
While the process of elemental sulfur oxidation will also lower the pH value, aggravating carbon steel corrosion, in contrast to ordinary Portland cement and classical concrete, fresh sulfur concrete does not contain alkali hydroxides (KOH, NaOH), nor calcium hydroxide (Ca(OH)2), and therefore does not provide any buffering capacity to maintain a high pH passivating the steel surface.