Chemistry:Sulfur concrete
Sulfur concrete 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.[1] Sulfur concrete is a thermoplastic material. After cooling and recrystallisation (time ~ 24 h) of the elemental sulfur in its crystalline phase stable at room temperature, the sulfur concrete reaches a high strength, not needing a prolonged curing period like normal concrete for achieving its setting and hardening.
A sulfur concrete patent was already registred in 1900 by McKay.[2][3] Sulfur concrete was studied in the 1920 and 1930 years and received renewed interest in the 1970 because of the accumulation of large quantities of sulfur as by-product of hydrodesulfurization process of oil and gas industries and its low cost.[3]
Characteristics
Sulfur concrete has a low porosity and is a poorly permeable material. Its low hydraulic conductivity slows down water ingress in its low porosity matrix and so decreases the transport of harmful chemical species, such as chloride (pitting corrosion), towards the steel reinforcements (physical protection of steel as long as no microcracks develop in the sulfur concrete matrix). It is resistant to some compounds like acids which attack normal concrete. However, unlike ordinary concrete, it cannot withstand prolonged high heat without adjusted mixture.[clarification needed]
Beside its impermeability, Loov et al. (1974) also consider amongst the beneficial characteristics of sulfur concrete its low thermal and electrical conductivities. Sulfur concrete does not cause adverse reaction with glass (no alkali–silica reaction), does not produce efflorescences, and also presents a smooth surface finish. 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. It also reacts with copper and produces a smell when melted.
Uses
Sulfur concrete was developed and promoted as a building material to get rid of large amounts of stored sulfur produced by hydrodesulfurization of gas and oil (Claus process). As of 2011, sulfur concrete has only been used in small quantities when fast curing or acid resistance is necessary.[4][3]The material has been suggested by researchers as a potential building material on Mars, where water and limestone are not easily available, but sulfur is.[5][6][7]
Advantages and benefits
More recently,[when?] it has been proposed as a near carbon neutral construction material. Its waterless, less energy intensive production in comparison with ordinary cement and regular concrete makes it a potential alternative for CO2 high emission portland cement based materials. Due to improvements in fabrication techniques, it can be produced in high quality and large quantities. Recyclable sulfur concrete sleepers are used in Belgium for the railways infrastructure, and are mass-produced locally.[8]
Disadvantages and limitations
Being based on the use of elemental sulfur (S0, or S8) as a binder, sulfur concrete applications are expected to suffer the same limitations as those of elemental sulfur which is not a really inert material, can burn, and is also known to be a potent corrosive agent.[9][10][11]
In case of fire, this concrete is flammable and will generate toxic and corrosive fumes of sulfur dioxide (SO2), and sulfur trioxide (SO3), ultimately leading to the formation of sulfuric acid (H2SO4).
According to Maldonado-Zagal and Boden (1982),[10] 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. Hydrogen sulfide (H2S) causes sulfide stress cracking (SSC) and in contact with air is also easily oxidized into thiosulfate (S2O2−3), responsible for pitting corrosion.
Like pyrite (FeS2, iron(II) disulfide), in the presence of moisture, sulfur is also sensitive to oxidation by atmospheric oxygen and could ultimately produce sulfuric acid (H2SO4), sulfate (SO2−4), and intermediate chemical species such as thiosulfates (S2O2−3), or tetrathionates (S4O2−6), which are also strongly corrosive substances (pitting corrosion), as all the reduced species of sulfur.[9][12][13] 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 formation of sulfuric acid could also attack and dissolve limestone (CaCO3) and concrete structures while also producing expansive gypsum (CaSO4·2H2O), aggravating the formation of cracks and fissures in these materials.
If the local physico-chemical conditions are conducive (sufficient space and water available for their growth), sulfur-oxidizing bacteria (microbial oxidation of sulfur) could also thrive at the expense of concrete sulfur and contribute to aggravate potential corrosion problems.[14]
The degradation rate of elemental sulfur depends on its specific surface area. The degradation reactions are the fastest with sulfur dust, or crushed powder of sulfur, while intact compact blocks of sulfur concrete are expected to react more slowly. 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. In other words, intact sulfur concrete does not chemically protect steel reinforcement bars (rebar) against corrosion. The corrosion of steel elements embedded into sulfur concrete will thus depends on water ingress through cracks and to their exposure to aggressive chemical species of sulfur dissolved in the seeping water. The presence of microorganisms fuelled by elemental sulfur could also play a role and accelerate the corrosion rate.
See also
- Asphalt concrete, similar aggregate material using 'bitumen' as a binder
- Lunarcrete: Sulfur based "Waterless Concrete", for proposals for its use as a lunar construction material
- Cenocell, a concrete material using fly ash cenospheres (hollow spheres) in place of cement
References
- ↑ Abdel-Mohsen Onsy Mohamed; Maisa El-Gamal (15 July 2010). Sulfur Concrete for the Construction Industry: A Sustainable Development Approach. J. Ross Publishing. p. 109. ISBN 978-1-60427-005-1. https://books.google.com/books?id=OYecyRmnTEkC&pg=PA109.
- ↑ McKay, G., U.S. Patent No. 643, February 13, 1900, p. 251.
- ↑ 3.0 3.1 3.2 Loov, Robert E.; Vroom, Alan H.; Ward, Michael A. (1974). "Sulfur concrete – A new construction material". PCI Journal (Prestressed Concrete Institute) 19 (1): 86–95. doi:10.15554/pcij.01011974.86.95. ISSN 08879672. https://www.pci.org/PCI_Docs/Publications/PCI%20Journal/1974/Jan-Feb/Sulfur%20Concrete%20-%20A%20New%20Construction%20Material.pdf. Retrieved 2022-09-20.
- ↑ Brandt, Andrzej Marek (1995). Cement-based composites: Materials, mechanical properties and performance. p. 52. ISBN 978-0-419-19110-0. https://books.google.com/books?id=DlQe8WAA8AEC&pg=PA52.
- ↑ Wan, Lin, Roman Wendner, and Gianluca Cusatis (2016). "A novel material for in situ construction on Mars: experiments and numerical simulations." Construction and Building Materials, 120: 222–231.
- ↑ "To build settlements on Mars, we'll need materials chemistry". 2017-12-27. https://cen.acs.org/articles/96/i1/build-settlements-Mars-ll-need.html.
- ↑ Nick Jones (2019). "Mixing it on Mars" (in English). sustainableconcrete.org.uk. The Concrete Centre. pp. 18-19. https://www.sustainableconcrete.org.uk/MPA-ACP/media/SustainableCon-Media-Library/Pdfs%20-%20Performance%20reports/TIC_innovation_Feb19.pdf. "Marscrete will be mission-critical to any future landing on the Red Planet, writes Nick Jones"
- ↑ "First recyclable sulfur concrete sleepers placed in Belgium". https://www.railtech.com/infrastructure/2021/03/08/first-recyclable-sulfur-concrete-sleepers-placed-in-belgium/.
- ↑ 9.0 9.1 MacDonald, Digby D.; Roberts, Bruce; Hyne, James B. (1978). "The corrosion of carbon steel by wet elemental sulphur". Corrosion Science 18 (5): 411–425. doi:10.1016/S0010-938X(78)80037-7. ISSN 0010-938X. https://www.sciencedirect.com/science/article/pii/S0010938X78800377. Retrieved 2022-09-19.
- ↑ 10.0 10.1 Maldonado-Zagal, S. B.; Boden, P. J. (1982). "Hydrolysis of elemental sulphur in water and its effect on the corrosion of mild steel". British Corrosion Journal 17 (3): 116–120. doi:10.1179/000705982798274336. ISSN 0007-0599. https://doi.org/10.1179/000705982798274336. Retrieved 2022-09-19.
- ↑ Smith, Liane; Craig, Bruce D. (2005-04-03). "Practical corrosion control measures for elemental sulfur containing environments". Corrosion 2005. OnePetro. https://onepetro.org/NACECORR/proceedings/CORR05/All-CORR05/NACE-05646/115569. Retrieved 2022-09-19.
- ↑ Fang, Haitao; Young, David; Nesic, Srdjan (2008). "Corrosion of mild steel in the presence of elemental sulfur". Corrosion 2008. OnePetro. https://onepetro.org/NACECORR/proceedings-abstract/CORR08/All-CORR08/NACE-08637/119135.
- ↑ Fang, Haitao; Brown, Bruce; Young, David; Nešic, Srdjan (2011-03-13). "Investigation of elemental sulfur corrosion mechanisms". Corrosion 2011. OnePetro. https://onepetro.org/NACECORR/proceedings-abstract/CORR11/All-CORR11/NACE-11398/119729. Retrieved 2022-09-19.
- ↑ Little, B.J.; Ray, R.I.; Pope, R.K. (2000-04-01). "Relationship between corrosion and the biological sulfur cycle: A review". Corrosion 56 (04). ISSN 0010-9312. https://onepetro.org/corrosion/article-abstract/111949/Relationship-Between-Corrosion-and-the-Biological.
Further reading
- Husam A. Omar; Mohsen Issa (1994). "Production of Lunar Concrete Using Molten Sulfur". 2. New York: American Society of Civil Engineers. pp. 952–959. ISBN 0872629376. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19980001900_1997093192.pdf.
- I. Casanova (1997). "Feasibility and Applications of Sulfur Concrete for Lunar Base Development: A Preliminary Study". pp. 209. http://www.lpi.usra.edu/meetings/lpsc97/pdf/1483.PDF.
- T. D. Lin; Steven B. Skaar; Joseph J. O'Gallagher (April 1997). "Proposed remote control solar powered concrete production experiment on the Moon". Aerospace Engineering 10 (2): 104–109. doi:10.1061/(ASCE)0893-1321(1997)10:2(104).
- Houssam Toutanji; Becca Glenn-Loper; Beth Schrayshuen (2005). "43rd AIAA Aerospace Sciences Meeting and Exhibit". American Institute of Aeronautics and Astronautics. doi:10.2514/6.2005-1436. ISBN 978-1-62410-064-2.
- R.N. Grugel; Houssam Toutanji (2006). "Viability of Sulfur "Concrete" on the Moon: Environmental Consideration". — also:
- R. Grugel; Houssam Toutanji (2006). "Viability of Sulfur Concrete on the Moon: Environmental Considerations". Journal of Advances in Space Research.
- Richard N. Grugela; Houssam Toutanji (2008). "Sulfur "concrete" for lunar applications — Sublimation concerns". Advances in Space Research 41 (1): 103–112. doi:10.1016/j.asr.2007.08.018. Bibcode: 2008AdSpR..41..103G. https://zenodo.org/record/1258768.
- Dugarte, Margareth; Martinez-Arguelles, Gilberto; Torres, Jaime (2019). "Experimental evaluation of modified sulfur concrete for achieving sustainability in industry applications". Sustainability 11 (1): 70. doi:10.3390/su11010070. ISSN 2071-1050. https://www.mdpi.com/2071-1050/11/1/70. Retrieved 2022-09-20.
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