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Autoclaved aerated concrete

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(Redirected from Aerated autoclave concrete)

"Aerated concrete" redirects here. For cellular concrete (foamed concrete), see Types of concrete § Cellular concrete. For lightweight blocks, see Expanded clay aggregate.

Sectional view of AAC.
Palette stacked AAC blocks.

Autoclaved Aerated Concrete (AAC), also known as autoclaved cellular concrete or autoclaved concrete, is a lightweight, prefabricated concrete building material. Developed in the mid-1920s, AAC offers a modern alternative to traditional concrete blocks and clay bricks.[1] Unlike cellular concrete, which is mixed and poured on-site, AAC products are prefabricated in a factory.[2]

The composition of AAC includes a mixture of quartz sand, gypsum, lime, Portland cement, water, fly ash, and aluminum powder.[3] Following partial curing in a mold, the AAC mixture undergoes additional curing under heat and pressure in an autoclave.[4] AAC is versatile and can be manufactured into various forms, including blocks, wall panels, floor and roof panels, cladding panels, and lintels.[5]

Cutting AAC typically requires standard power tools fitted with durable carbon steel cutters.[6][7] Similar to cellular concrete, AAC products can be used in a wide range of construction projects. When used externally, AAC products often require a protective finish to shield against weathering. A polymer-modified stucco or plaster compound can be used for this purpose, as well as a covering of siding materials such as natural or manufactured stone, veneer brick, metal, or vinyl siding.[8]

History

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House construction site using AAC (Ytong) blocks in Ablis, France.
Residential house constructed of AAC (Siporex) blocks in Kuopio, Finland.

AAC was first created in the mid-1920s by the Swedish architect and inventor Dr. Johan Axel Eriksson (1888–1961),[9][10] along with Professor Henrik Kreüger at the Royal Institute of Technology.[9][10] The process was patented in 1924.[11] In 1929, production started in Sweden in the city of Yxhult. "Yxhults Ånghärdade Gasbetong" later became the first registered building materials brand in the world: Ytong.[12] Another brand, "Siporex", was established in Sweden in 1939.[citation needed] Following World War II, demand for the product declined, leading to a significant reduction in production, with no new plants constructed after the 1990s.[13] Josef Hebel of Memmingen established another cellular concrete brand, Hebel, which opened their first plant in Germany in 1943.[14]

Ytong AAC was originally produced in Sweden using alum shale, which contained combustible carbon beneficial to the production process.[citation needed] However, these deposits were found to contain natural uranium that decays over time to radon gas, which then accumulates in structures where the AAC was used. This problem was addressed in 1972 by the Swedish Radiation Safety Authority, and by 1975, Ytong abandoned alum shale in favor of a formulation made from quartz sand, calcined gypsum, lime (mineral), cement, water, and aluminium powder.[citation needed][14]

In 1978, Siporex Sweden opened the Siporex Factory in Saudi Arabia, establishing the Lightweight Construction Company (LCC), supplying Gulf Cooperation Council countries with aerated blocks and panels. Since 1980, there has been a worldwide increase in the use of AAC materials.[15][16] New production plants are being built in Australia, Bahrain, China, Eastern Europe, India, and the United States. The use of AAC has expanded globally, particularly in regions experiencing rapid urban development.[17] Currently, LCC has three branches in Saudi Arabia.[18]

Today, the manufacturing of autoclaved aerated concrete (AAC) is most prevalent in Europe and Asia, with limited production facilities in the Americas and one known plant in Egypt.[citation needed] While growth in the European market has slowed, AAC production in parts of Asia has expanded, particularly in response to urban development demands. As of 2025, China remains the world's largest autoclaved aerated concrete market, hosting over 2,000 manufacturing plants and producing approximately 190 million cubic meters of AAC annually.[19][20] The most significant AAC production and consumption occurs in China, Central Asia, India, and the Middle East, reflecting the dynamic growth and demand in these regions.[21]

Residential house constructed at the Finnish Seinäjoki Housing Fair in 2016 using AAC blocks.[22]
AAC blocks on a residential house construction site in Russia.

Uses

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AAC is used for both exterior and interior construction.[23] It has been applied in high-rise construction projects and areas with frequent temperature fluctuation.[24] Due to its lower density, AAC can reduce the structural load, potentially decreasing the required amounts of steel reinforcement and conventional concrete in certain building applications. The mortar needed for laying AAC blocks is reduced due to the lower number of joints. Similarly, less material is required for rendering because AAC can be shaped precisely before installation. Although regular cement mortar is compatible with AAC, many buildings employing its components utilize thin bed mortar, typically around 3.2 millimetres (1⁄8 in) thick, in accordance with specific national building codes.[citation needed]

Manufacturing

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Uncured AAC blocks (on the right) ready to be fed into an autoclave to be rapidly cured into a finished product under heat and pressure; AAC production site in China.

The aggregate used in AAC is usually smaller than sand.[25] Binding agents include quartz sand, lime, calcined gypsum, cement, and water. Aluminium powder constitutes 0.05–0.08% by volume. Some countries (such as India and China) use fly ash from coal-fired power plants (50-65% silica) as the aggregate.[26]

When AAC is mixed and cast in forms, aluminium powder reacts with calcium hydroxide and water to form hydrogen. The hydrogen gas foams, doubling the volume of the raw mix and creating gas bubbles up to 3 millimetres (1⁄8 in) in diameter.[27] At the end of the foaming process, the hydrogen escapes into the atmosphere and is replaced by air, resulting in a product weighing approximately 20% of conventional concrete.[citation needed]

Once the forms are removed, the material is solidified but remains soft. It is then cut into either blocks or panels, if necessary, and placed in an autoclave chamber for 12 hours.[citation needed] During this steam pressure hardening process, when the temperature reaches 190 °C (374 °F) and the pressure reaches 800 to 1,200 kPa (8.0 to 12.0 bar; 120 to 170 psi), quartz sand reacts with calcium hydroxide to form calcium silicate hydrate, which gives AAC its high strength and other unique properties. Because of the relatively low temperature used, AAC blocks are not considered to be fired bricks but lightweight concrete masonry units. After the autoclaving process, the material is stored and shipped to construction sites for use. Depending on its density, up to 80% of the volume of an AAC block is air.[citation needed] AAC's low density also accounts for its low structural compression strength. It can carry loads of up to 8,000 kPa (1,200 psi), approximately 50% of the compressive strength of regular concrete.[citation needed]

Reinforced autoclaved aerated concrete

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See also: 2023 United Kingdom reinforced autoclaved aerated concrete crisis

Reinforced autoclaved aerated concrete (RAAC) is a reinforced version of autoclaved aerated concrete, commonly used in roofing and wall construction. The first structural reinforced roof and floor panels were manufactured in Sweden. Soon after, the first autoclaved aerated concrete block plant started there in 1929. However, Belgian and German technologies became market leaders for RAAC elements after the Second World War. In Europe, it gained popularity in the mid-1950s as a cheaper and more lightweight alternative to conventional reinforced concrete, with documented widespread use in a number of European countries as well as Japan and former territories of the British Empire.[28][29]

RAAC was used in roof, floor, and wall construction due to its lighter weight and lower cost compared to traditional concrete,[30] and its fire resistance properties; it does not require plastering to achieve fire resistance and fire does not cause spalls.[31] RAAC was used in construction in Europe, in buildings constructed after the mid-1950s.[32][33] RAAC elements have also been used in Japan as walling units, owing to their good behavior in seismic conditions.

RAAC has been shown to have limited structural reinforcement bar (rebar) integrity in 40 to 50 year-old roof panels, which began to be observed in the 1990s.[33][34][35][36][37] The material is liable to fail without visible deterioration or warning.[33][37] This is often caused by RAAC's high susceptibility to water infiltration due to its porous nature, which causes corrosion of internal reinforcements in ways that are hard to detect. This places increased tensile stress on the bond between the reinforcement and concrete, lowering the material's service life. Detailed risk analyses are required on a structure-by-structure basis to identify areas in need of maintenance and lower the chance of catastrophic failure.[38]

Professional engineering concern about the structural performance of RAAC was first publicly raised in the United Kingdom in 1995 following inspections of cracked units in British school roofs,[39] and was subsequently reinforced in 2022 when the Government Property Agency declared the material to be life-expired,[40] and in 2023 when, following the partial or total closure of 174 schools at risk of a roofing collapse,[41][42] other buildings were found to have issues with their RAAC construction,[43][44][45] with some of these only being discovered to have been made from RAAC during the crisis.[46][47][48] During the 2023 crisis, it was observed that it was likely for RAAC in other countries to exhibit problems similar to those found in the United Kingdom.[29]

On June 21, 2024, the Ontario Science Centre, a major museum in Toronto, Canada, permanently closed its original site due to the severely deteriorated roof panels from its 1969 opening. Despite the proposed repair options, the provincial government of Ontario, the center's ultimate owner, had already announced plans to relocate the center and therefore requested immediate closure of the facility instead of funding repairs. Approximately 400 other public buildings in Ontario are understood to contain the material and are under review, but no other closures were anticipated at the time of the Science Centre closure.[49]

Sustainability

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The high resource efficiency of autoclaved aerated concrete contributes to a lower environmental impact than conventional concrete, from raw material processing to the disposal of aerated concrete waste. Due to continuous improvements in efficiency, the production of aerated concrete blocks requires relatively little raw materials per cubic meter of product and is five times less than the production of other building materials.[50] There is little loss of raw materials in the production process, and all production waste is returned to the production cycle. Production of aerated concrete requires less energy than for all other masonry products, thereby reducing the use of fossil fuels and associated carbon dioxide (CO2) emissions.[51] The curing process also saves energy. Steam curing occurs at relatively low temperatures, and the hot steam generated in the autoclaves is reused for subsequent batches.[52][53]

Advantages

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Closeup of structure

Autoclaved aerated concrete (AAC) has been used in construction since the early 20th century and is valued for its lightweight and insulating properties.

AAC possesses several characteristics that make it suitable for specific construction applications:

  • Thermal efficiency: Due to its cellular structure, AAC offers thermal resistance that may help reduce heating and cooling loads in buildings. [54]
  • Fire resistance: AAC exhibits good fire resistance; its mineral composition and porous structure can provide extended fire ratings under standard testing conditions. [55]
  • Workability: AAC can be cut and shaped using standard tools, allowing for precise fitting and reducing material waste on construction sites.
  • Environmental profile: AAC generally has a lower embodied energy and environmental footprint compared to traditional concrete. In some contexts, it may contribute to achieving points in green building certification systems such as LEED.[56]
  • Low density: The material is significantly lighter than conventional concrete, which can simplify manual handling, reduce transportation demands, and may lower structural loads in seismic design scenarios.[57]
  • Construction efficiency: AAC blocks and panels are often available in larger dimensions than traditional masonry units, potentially reducing installation time and labor. However, the overall impact on construction schedules depends on site-specific logistics and integration with other systems. [58]
  • Moisture regulation: The vapor-permeable nature of AAC allows for limited water vapor diffusion, which can help moderate indoor humidity and mitigate moisture accumulation or condensation-related issues. [59]
  • Dimensional accuracy: Factory production techniques yield blocks and panels with tight tolerances, which can reduce the need for on-site trimming and minimize the use of finishing materials such as mortar or plaster.
  • Durability: AAC is resistant to pests, mold, and typical climate variations. It maintains its structural and thermal performance over time under normal conditions, although its long-term durability may depend on design detailing and exposure environments. [60]

Disadvantages

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While autoclaved aerated concrete (AAC) has several advantages, it also presents limitations, particularly in regions with construction practices that differ from monolithic masonry, such as the United Kingdom, where cavity wall systems are common.

  • Specialized training: Installation of AAC requires construction techniques that may differ from those used with traditional masonry. As a result, builders may need targeted training to handle, cut, and assemble AAC components effectively[61]
  • Shrinkage cracks: Non-structural shrinkage cracks may develop in AAC installations, particularly under humid conditions or after rainfall. This phenomenon is more frequently observed in low-quality blocks or those that have not undergone adequate steam-curing during production.[62]
  • Brittleness: AAC is more brittle than conventional clay bricks or dense concrete blocks. This characteristic necessitates careful handling during transport and installation to minimize breakage.
  • Fixings and fasteners: Due to its porous and brittle composition, AAC requires specialized fasteners for securing fixtures such as cabinets or shelves. Long screws and wall anchors designed for AAC, gypsum board, or lightweight masonry are typically used. Conventional plastic wall plugs and masonry drill bits are generally unsuitable. [63] In high-load applications, certified anchors may be required,[64][65][66] and drilling should be performed using high-speed steel (HSS) drill bits without hammer action to avoid cracking.[64][65]
  • Insulation limitations: AAC blocks manufactured at lower densities (e.g., 400 kg/m³ under European Standard B2.5) may require substantial wall thicknesses—often exceeding 500 mm—to meet thermal insulation standards in colder climates such as Northern Europe. This can offset space and cost benefits in some applications.[61]
  • Water sensitivity: The aerated structure of AAC contains fine air voids, which can absorb moisture. In freeze–thaw environments, absorbed water may expand upon freezing and cause damage to the block structure. Protective finishes and proper detailing are typically recommended in such conditions.[67]

References

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  1. ^ "Climate Action Network International Briefing, Copenhagen March Ministerial March 2023". Climate Change and Law Collection. doi:10.1163/9789004322714_cclc_2023-0001-0004. Retrieved 1 January 2025.
  2. ^ "Advantages of Using AAC Blocks | Blocktec". Blocktec AAC Wall System. Retrieved 9 April 2025.
  3. ^ "Autoclaved Aerated Concrete". Mumbai: Bennett & Coleman Ltd. Retrieved 12 July 2023.
  4. ^ "Autoclaved aerated concrete (AAC)". Victoria: Connection Magazines. Retrieved 11 July 2023.
  5. ^ "Products specifications - AIRCRETE". aircrete-europe.com. Archived from the original on 2 April 2015. Retrieved 16 July 2014.
  6. ^ "AAC can bring down construction cost by up to 20 percent". Indian Cement Review. 31 October 2015.
  7. ^ "Using Autoclaved Aerated Concrete Correctly". Masonry Magazine. 1 June 2008. Retrieved 28 November 2018.
  8. ^ "Autoclaved Aerated Concrete". Washington: Portland Cement Association. Retrieved 12 July 2023.
  9. ^ a b "Hebel: The History of AAC". Archived from the original on 4 November 2010.
  10. ^ a b Berg, Samuel A (2004). "Pionjärinsatser i betongens barndom - Konstruktionsbetongens historia 1890-1950" [Swedish Association of Historical Buildings: Pioneering work in the early days of concrete - history 1890–1950]. Byggnadskultur (in Swedish) (4/2004). Archived from the original on 25 May 2012. Retrieved 9 February 2021.
  11. ^ "History of AAC". European Autoclaved Aerated Concrete Association. Retrieved 18 June 2025.
  12. ^ "BIM objects - Free download! Ytong | BIMobject". BIMobject. Retrieved 27 December 2024.
  13. ^ "History of Autoclaved Aerated Concrete - Aircrete Europe". www.aircrete.com. 26 September 2018. Retrieved 10 January 2025.
  14. ^ a b "Autoclaved Aerated Concrete (AAC)". Material Testing Expert. Retrieved 27 December 2024.
  15. ^ Minerals Yearbook. The Bureau. 1998. p. 120.
  16. ^ "Autoclaved aerated concrete in vietnam" (in Vietnamese). Retrieved 11 August 2024.
  17. ^ Gyurkó, Zoltán; Jankus, Bence; Fenyvesi, Olivér; Nemes, Rita (1 September 2019). "Sustainable applications for utilization the construction waste of aerated concrete". Journal of Cleaner Production. 230: 430–444. Bibcode:2019JCPro.230..430G. doi:10.1016/j.jclepro.2019.04.357. ISSN 0959-6526.
  18. ^ "LCC Siporex". www.lccsiporex.com. Retrieved 10 January 2025.
  19. ^ "Turnkey services for autoclaved aerated concrete projects". Retrieved 13 May 2025.
  20. ^ "AAC China digital". Retrieved 13 May 2025.
  21. ^ "AAC India". Archived from the original on 24 March 2013. Retrieved 11 March 2013.
  22. ^ "Jämerä Sämsö Seinäjoki 2016" (in Finnish). Espoo: Jämerä Kivitalot Oy. 2016. Retrieved 26 July 2023.
  23. ^ Hornbostel, Caleb (16 January 1991). Construction Materials: Types, Uses and Applications. John Wiley & Sons. p. 959. ISBN 978-0-471-85145-5.
  24. ^ Gangurde, Abhimanyu Savliram (16 November 2019). AAC block manufacturing and its application in building construction.: Complete solution for AAC block manufacturing and use in building construction. Abhimanyu Savliram Gangurde. p. 8.
  25. ^ Gangurde, Abhimanyu Savliram (16 November 2019). AAC block manufacturing and its application in building construction.: Complete solution for AAC block manufacturing and use in building construction. Abhimanyu Savliram Gangurde. p. 12.
  26. ^ Muñoz-Pérez, Sócrates Pedro; Lozano-Sánchez, Jaime Jamill; Ramírez-Silva, Diana Mareline; Vallejos-Madianero, Joicie Elizabeth (9 October 2023). "Use and effect of fly ash in concrete: A literature review". Revista Facultad de Ingeniería Universidad de Antioquia. doi:10.17533/udea.redin.20230927. ISSN 2422-2844.
  27. ^ Triggle, Nick (25 May 2023). "Five hospitals at risk of collapse to be rebuilt". BBC News. Retrieved 25 May 2023.
  28. ^ "Expert reaction to situation with RAAC in school buildings". Science Media Centre. Retrieved 6 September 2023.
  29. ^ a b "Industry experts speak on RAAC". International Construction. 5 September 2023. Retrieved 6 September 2023.
  30. ^ "What is RAAC concrete and how many schools are affected?". BBC News. 31 August 2023. Retrieved 1 September 2023.
  31. ^ Buekett, J; Jennings, B. M. (1966). Reinforced Autoclaved Aerated Concrete. London: The Concrete Society. pp. 1–23.
  32. ^ Goodier, Chris; Cavalaro, Sergio; Lee, Kelvin; Casselden, Rebe (30 June 2022). "Durability variations in reinforced autoclaved aerated concrete (RAAC) – extended abstract". EDP Sciences. 361. MATEC Web of Conferences: 06005. doi:10.1051/matecconf/202236106005. S2CID 250201723. Retrieved 11 July 2023.
  33. ^ a b c Goodier, Chris (17 March 2023). "Expert explainer: What is Reinforced Autoclaved Aerated Concrete (RAAC) and why are people concerned about it?". Loughborough: Loughborough University. Retrieved 11 July 2023.
  34. ^ "Children At Risk In Schools Where Concrete Could Collapse". Itv.com. 16 March 2023.
  35. ^ "Reinforced autoclaved aerated concrete: estates guidance". GOV.UK. 31 August 2023.
  36. ^ "What is the problem with Reinforced Autoclaved Aerated Concrete (RAAC)?". Surveyors to Education. 8 April 2021. Retrieved 16 March 2023.
  37. ^ a b "Information on Reinforced Autoclaved Aerated Concrete (RAAC)". Local Government Association (UK). Retrieved 1 September 2023. The LGA is advising its members to check as a matter of urgency whether any buildings in their estates have roofs, floors, cladding or walls made of Reinforced Autoclaved Aerated Concrete (RAAC)
  38. ^ Tagg, Adrian; Purnell, Phil (1 September 2023). "Expert reaction to situation with RAAC in school buildings". SMC. London: The Science Media Centre. Retrieved 3 September 2023.
  39. ^ Victor Whitworth (21 February 1995). "Verulam column: Relying on British Standards". The Structural Engineer. 73 (4): 68.
  40. ^ Booth, Robert; Walker, Peter; Adams, Richard (31 August 2023). "Thousands of pupils may have to start term online as over 100 schools affected by crumble-risk concrete". The Guardian. Retrieved 31 August 2023.
  41. ^ "School buildings in England to shut over concrete safety fears". BBC News. 31 August 2023. Retrieved 31 August 2023.
  42. ^ Standley, Nathan (19 September 2023). "Raac: Number of English schools with unsafe concrete rises to 174". BBC News. BBC. Retrieved 19 September 2023.
  43. ^ Ghosh, Pallab (6 September 2023). "Experts warn RAAC concrete affects thousands of UK buildings". BBC News. Retrieved 6 September 2023.
  44. ^ Youngs, Ian (7 September 2023). "Several theatres shut doors over fears about Raac concrete". BBC News. Retrieved 7 September 2023.
  45. ^ Doherty, Aisha; Clarke, Vanessa (7 September 2023). "Student unions and lecture halls shut at Raac unis". BBC News. Retrieved 7 September 2023.
  46. ^ "Heathrow and Gatwick airports have Raac on sites". BBC News. 8 September 2023. Retrieved 8 September 2023.
  47. ^ "Preston Guild Hall: Crumbling Raac concrete fears at venue". BBC News. BBC. 11 September 2023. Retrieved 11 September 2023.
  48. ^ Leonard, Eben; Grey, Jack (20 September 2023). "Bridgend Indoor Market shuts immediately over concrete concern". BBC News. BBC. Retrieved 20 September 2023.
  49. ^ Crawley, Mike (26 June 2024). "Hundreds of buildings with Science Centre roof panels remain open". CBCNews.ca. Retrieved 26 June 2024.
  50. ^ Hertwich, Edgar G.; Ali, Saleem; Ciacci, Luca; Fishman, Tomer; Heeren, Niko; Masanet, Eric; Asghari, Farnaz Nojavan; Olivetti, Elsa; Pauliuk, Stefan; Tu, Qingshi; Wolfram, Paul (16 April 2019). "Material efficiency strategies to reducing greenhouse gas emissions associated with buildings, vehicles, and electronics". Environmental Research Letters. 14 (4): 043004. doi:10.1088/1748-9326/ab0fe3. hdl:1721.1/134640. S2CID 159348076. Retrieved 10 October 2022.
  51. ^ "Autoclaved Aerated Concrete (AAC) A Sustainable Building Material". globenewswire.com (Press release). 11 January 2018. Retrieved 10 October 2022.
  52. ^ "Production of environmentally friendly aerated concrete with required construction and operational properties" (PDF). matec-conferences.org. Retrieved 10 October 2022.
  53. ^ Decorative Concrete Guide
  54. ^ Zade, Nikhil P.; Sarkar, Pradip; Davis, Robin (25 January 2024). "Life cycle energy of AAC masonry infilled residential building in India". Energy Efficiency. 17 (1): 9. doi:10.1007/s12053-024-10188-y. ISSN 1570-6478.
  55. ^ "Fire Resistance". EAACA S (in German). Retrieved 15 July 2025.
  56. ^ "AAC Blocks". Copenhagen: UN Climate Technology Centre and Network. 8 October 2018. Retrieved 12 July 2023.
  57. ^ "AAC India - Advantages of using AAC". Archived from the original on 4 October 2013. Retrieved 3 October 2013.
  58. ^ Thakur, Abhishek; Kumar, Saurav (1 January 2022). "Evaluation of cost Effectiveness of using autoclave aerated concrete (ACC) blocks in building construction". Materials Today: Proceedings. CMAE'21. 51: 1063–1068. doi:10.1016/j.matpr.2021.07.095. ISSN 2214-7853.
  59. ^ Kočí, Jan; Korecký, Tomáš; Černý, Robert (1 October 2017). "Identification of Moisture Diffusivity of Autoclaved Aerated Concrete in the Form of Smooth Two-Variable Function". Energy Procedia. 11th Nordic Symposium on Building Physics, NSB2017, 11-14 June 2017, Trondheim, Norway. 132: 219–224. doi:10.1016/j.egypro.2017.09.758. ISSN 1876-6102.
  60. ^ Jerman, Miloš; Keppert, Martin; Výborný, Jaroslav; Černý, Robert (1 April 2013). "Hygric, thermal and durability properties of autoclaved aerated concrete". Construction and Building Materials. 41: 352–359. doi:10.1016/j.conbuildmat.2012.12.036. ISSN 0950-0618.
  61. ^ a b Princy, A.J. (3 May 2021). "India AAC blocks and Non-Reinforced Panels: A Concise Guide". Pune: Research Dive. Retrieved 12 July 2023.
  62. ^ "Cracks in AAC Blocks Wall – Causes and Repair". Navsari: Gharpedia. 28 February 2022. Retrieved 28 July 2023.
  63. ^ "Technical Guidance | Aerated and Concrete Block Fixings | Thomas Armstrong (Concrete Blocks) Ltd". www.thomasarmstrongconcreteblocks.co.uk. Archived from the original on 1 December 2023. Retrieved 15 July 2025.
  64. ^ a b "Fixing Guide for greencon AAC Blockwalls". Shah Alam: RFM Construction Products. Retrieved 16 July 2023.
  65. ^ a b "Concrete Blocks Technical Guidance: Fixings". Flimby: Thomas Armstrong (Concrete Blocks). Retrieved 16 July 2023.
  66. ^ "Aircrete Booklet" (PDF). January 2012. Archived from the original (PDF) on 4 June 2016.
  67. ^ "3 Problems with Autoclaved Aerated Concrete Blocks". Fox Blocks. Retrieved 26 May 2025.
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