Alker

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Alker is an earth-based stabilized building material produced by the addition of gypsum, lime, and water to earth with the appropriate granulometric structure and with a cohesive property. Unbaked and produced on-site either as adobe blocks or by pouring into mouldings (the rammed earth technique), it has significant economical and ecological advantages. [1] Its physical and mechanical properties are superior to traditional earth construction materials, and are comparable to other stabilized earthen materials. The ratios of the mixture are determined in accordance with the purpose of construction. Alker has primarily been used as a wall construction material; for this purpose, the addition of 8-10% gypsum, 2.5-5% lime, and 20% water to earth produces optimum results[ citation needed ]. These ratios may change according to the nature and content of clay in the soil.

Contents

Research

The initial research for Alker was completed in 1980 at the Faculty of Architecture of Istanbul Technical University. [2] The word Alker is an abbreviation combining the first syllables of the Turkish words for Gypsum (Alçı) and Adobe (Kerpiç). Alker was inspired by a traditional plaster material consisting of a mixture of earth, gypsum and lime, which has been in use in the earthen architecture of Anatolia since the neolithic era due to its high water resistance. [3] The initial project for Alker was based on the addition only of gypsum to earth with the appropriate qualities. The addition of lime was introduced later, and improved the material’s earthquake resistant properties. Research on the properties and application methods of Alker has continued, mainly at Istanbul Technical University. [4] [5] [6] [7] [8]

Alker has been used in numerous constructions in Turkey, where it was first developed, as well as in other countries. One of the earliest among these, constructed in 1995 in Istanbul Technical University’s Ayazağa Campus, has been in continuous use without needing significant repair. In this particular construction process, the material was poured into mouldings and rammed, with a view to exploring possibilities for mass construction with Alker.

Properties

Alker is characterized by its quick setting time (approximately 20 minutes), hence preventing clay shrinkage and eliminating the need for curing and drying processes. If needed, a retarding agent may also be added to the mixture. It is a porous material with a lower volumetric weight, and nearly four times more pressure resistance compared to traditional earthen wall materials. Structurally, Alker is comparable to concrete as a conglomerate material. It must be noted however that while properties of concrete improve in direct ratio to the amount of cement it contains, increased amounts of clay (the binding element) in the Alker mixture have negative effects on its physical properties, particularly in terms of pressure and erosion resistance. [9]

Alker exhibits high resistance to water-related erosion, in contrast to traditional unbaked earthen building materials which are characterized by poor resistance to water. In erosion tests pure earthen materials completely dissolve; the erosion rate in Alker is minimal. The material gains a rigidity of 0.375 MPa during the setting process, within the first twenty minutes after pouring. It gains rigidity while containing 20% moisture, which makes it possible to remove mouldings and stack blocks shortly after pouring the material. [10]

Its unit weight is lower than those of comparable building materials. Its shrinkage and expansion rates are low, and are comparable to those of concrete. As such, it can be poured continuously without necessitating a contraction joint. It is characterized by resistance to water and moisture. The ratio of lime in the mixture can be modified in order to completely eliminate water-related erosion. Experiments on capillary water absorption have shown that increased amounts of lime in the mixture results in an increase in quantity and in reduced width of capillary canals, proving the material’s erosion resistance. Compressive and shear strength and modules of elasticity and rigidity present advantages in terms of earthquake resistance. Once the mixture is poured into a mould, the production process is completed, and a significant degree of rigidity is reached. It does not require curing and drying, providing economy of time, labor, and energy. Resistance to pressure is 3,5 - 4 MPa. The lime in the mixture reduces resistance to pressure to a minimal degree, while increasing elasticity and resistance to impact. During pressure tests cube-shaped blocks fracture in pyramidal forms, comparable to concrete blocks, and do not disintegrate in the way unstabilized earthen blocks do. [11]

Alker is not a patented material. It has been developed with the aim of creating a widely used low-cost Ecological Building material available for self-building as well as for larger sustainable architecture projects. A number of projects have been developed that are based on Alker (gypsum- and lime-stabilized earth) technology. Among these is cast earth, which uses the Alker mixture with the addition of a retarding agent in order to lengthen the setting time. If Alker is to be produced on the construction site, addition of a retarding agent is not necessary.

Stabilization of earth only with gypsum addition does not produce material with the same physical and mechanical properties as that with lime and gypsum addition, and increased amounts of gypsum result in raised costs.

Related Research Articles

Adobe Building material made from earth and organic materials

Adobe is a building material made from earth and organic materials. Adobe is Spanish for 'mudbrick', but in some English-speaking regions of Spanish heritage the term is used to refer to any kind of earthen construction. Most adobe buildings are similar in appearance to cob and rammed earth buildings. Adobe is among the earliest building materials, and is used throughout the world.

Concrete Composite construction material

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement that hardens (cures) over time. In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, such as a calcium aluminate cement or with Portland cement to form Portland cement concrete. Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. Concrete is distinct from mortar. Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together.

Mudbrick Unbaked earth used as building material blocks

A mudbrick or mud-brick is an air-dried brick, made of a mixture of loam, mud, sand and water mixed with a binding material such as rice husks or straw. Mudbricks are known from 9000 BCE, though since 4000 BC, bricks have also been fired, to increase their strength and durability.

Mud

Mud is soil, loam, silt or clay mixed with water. It usually forms after rainfall or near water sources. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone. When geological deposits of mud are formed in estuaries, the resultant layers are termed bay muds.

Mortar (masonry)

Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as used between mud bricks. The word "mortar" comes from Latin mortarium, meaning crushed.

Plaster General term for a broad range of building and sculpture materials

Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications. Another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.

Building material Material which is used for construction purposes

Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, and wood, even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.

Rammed earth Technique for constructing foundations, floors, and walls by compacting a damp mixture of sub soil

Rammed earth, also known as taipa in Portuguese, tapial or tapia in Spanish, tàpia in Catalan, pisé in French, bijenica in Serbian, and hāngtǔ (夯土) in Mandarin Chinese, is a technique for constructing foundations, floors, and walls using natural raw materials such as earth, chalk, lime, or gravel. It is an ancient method that has been revived recently as a sustainable building method.

Earthbag construction is an inexpensive building method using mostly local soil to create structures which are both strong and can be quickly built.

Natural building

A natural building involves a range of building systems and materials that place major emphasis on sustainability. Ways of achieving sustainability through natural building focus on durability and the use of minimally processed, plentiful or renewable resources, as well as those that, while recycled or salvaged, produce healthy living environments and maintain indoor air quality. Natural building tends to rely on human labor, more than technology. As Michael G. Smith observes, it depends on "local ecology, geology and climate; on the character of the particular building site, and on the needs and personalities of the builders and users."

Cast Earth is a proprietary natural building material developed since the mid-1990s by Harris Lowenhaupt and Michael Frerking based on the earlier Turkish Alker, which is a concrete-like composite with soil of a suitable composition as its bulk component stabilized with about 15% calcined gypsum instead of Portland cement. It can be used to form solid walls that need not be reinforced with a steel frame or timber framing, unless extra seismic reinforcement is necessary. Forms are set up and filled with Cast Earth, which sets quickly and solidly. Once the forms are removed the wall stays sound.

Earth structure A building or other structure made largely from soil.

An earth structure is a building or other structure made largely from soil. Since soil is a widely available material, it has been used in construction since prehistoric times. It may be combined with other materials, compressed and/or baked to add strength. Soil is still an economical material for many applications, and may have low environmental impact both during and after construction.

Compressed earth block

A compressed earth block (CEB), also known as a pressed earth block or a compressed soil block, is a building material made primarily from damp soil compressed at high pressure to form blocks. Compressed earth blocks use a mechanical press to form blocks out of an appropriate mix of fairly dry inorganic subsoil, non-expansive clay and aggregate. If the blocks are stabilized with a chemical binder such as Portland cement they are called compressed stabilized earth block (CSEB) or stabilized earth block (SEB). Typically, around 3,000 psi (21 MPa) is applied in compression, and the original soil volume is reduced by about half.

Embankment dam Large artificial dam

An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay, or rock. It has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes the dam impervious to surface or seepage erosion. Such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance.

Earthen plaster is a blend of clay, fine aggregate, and fiber. Other common additives include pigments, lime, casein, prickly pear cactus juice (Opuntia), manure, and linseed oil. Earthen plaster is usually applied to masonry, cob, or straw bale interiors or exteriors as a wall finish. It provides protection to the structural and insulating building components as well as texture and color.

Hempcrete Biocomposite material used for construction and insulation

Hempcrete or hemplime is biocomposite material, a mixture of hemp hurds (shives) and lime, sand, or pozzolans, which is used as a material for construction and insulation. It is marketed under names like Hempcrete, Canobiote, Canosmose, Isochanvre and IsoHemp. Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and consequently does not need expansion joints. The result is a lightweight insulating material ideal for most climates as it combines insulation and thermal mass.

Alternative natural materials are natural materials like rock or adobe that are not as commonly in use as materials such as wood or iron. Alternative natural materials have many practical uses in areas such as sustainable architecture and engineering. The main purpose of using such materials is to minimize the negative effects that our built environment can have on the planet while increasing the efficiency and adaptability of the structures.

Wattle and daub

Wattle and daub is a composite building method used for making walls and buildings, in which a woven lattice of wooden strips called wattle is daubed with a sticky material usually made of some combination of wet soil, clay, sand, animal dung and straw. Wattle and daub has been used for at least 6,000 years and is still an important construction method in many parts of the world. Many historic buildings include wattle and daub construction, and the technique is becoming popular again in more developed areas as a low-impact sustainable building technique.

Lime-ash floors were an economic form of floor construction from the 15th century to the 19th century, for upper floors in parts of England where limestone or chalk were easily available. They were strong, flexible, and offered good heat and sound insulation.

Organosilicon water repellent:

References

  1. ↑ A Compendium of Information on Selected Low-cost Building Materials. United Nations Center for Human Settlements, 1986, p. 40; Sustainable Building Design Manual, vol. 2: Sustainable building design practices, (New Delhi: Energy and Resources Institute, 2004), pp. 121, 131; Horst Schroeder, Sustainable Building with Earth (Heidelberg, New York: Springer, 2016), pp. 320 ff.
  2. ↑ Ruhi Kafescioğlu, Nihat Toydemir, Erol Gürdal ve Bülent Özüer, “Yapı Malzemesi Olarak Kerpicin Alçı ile Stabilizasyonu”, TÜBİTAK Mühendislik Araştırma Grubu, Proje no: 505, 1980.
  3. ↑ Naumann, Rudolf, Architektur Kleinasiens von ihren Anfängen bis zum Ende der hethitischen Zeit (Tubingen: Wasmuth, 1971); Gourdin, W.H. and W.D. Kingery, “The Beginnings of Pyrotechnology: Neolithic and Egyptian Lime Plaster”, Journal of Field Archeology, v. 15 (1975):133-150.
  4. ↑ Ruhi Kafescioğlu, “Thermal Properties of Mudbricks: the Example of Gypsum Stabilized Adobe,” Proceedings of the Expert Group Meeting on Energy-Efficient Building Materials for Low-Cost Housing, United Nations Human Settlement Division, Amman, 1987
  5. ↑ Bilge Işık, Tugsad Tulbentci, Sustainable housing in island conditions using Alker-gypsum-stabilized earth: A case study from northern Cyprus, Building and Environment, Volume 43, Issue 9, September 2008, pp. 1426-1432
  6. ↑ Ruhi Kafescioğlu, ”Gypsum-stabilized Adobe (Alker) Structures: An Evaluation of Their Social, Economic, and Environmental Advantages,” 8th International Seminar on Structural Masonry: Proceedings; 05-07 November 2008, ed. Leyla Tanaçan (Istanbul: Istanbul Technical University, 2008)
  7. ↑ Bekir Pekmezci, Ruhi Kafescioğlu ve Ebrahim Aghazadeh, “Improved Performance of Earth Structures by Lime and Gypsum Addition,” METU Journal of the Faculty of Architecture, 29(2012): 205-221
  8. ↑ Burhan Çiçek, “Küreken 2013: Designing a New Village with Rammed Earthen Construction in Eastern Anatolia,” Vernacular Heritage and Earthen Architecture: Contributions for Sustainnable Development, ed. Correia and Rocha (London: Taylor and Francis, 2014), pp. 263-268.
  9. ↑ B. Pekmezci, R. Kafescioglu and I. Aghazadeh, "Improved Performance of Earth Structures by Lime and Gypsum Addition," METU Journal of the Faculty of Architecture, v. 29, 2012, pp. 215-217
  10. ↑ B. Pekmezci, R. Kafescioglu and I. Aghazadeh, "Improved Performance of Earth Structures by Lime and Gypsum Addition," METU Journal of the Faculty of Architecture, v. 29, 2012, pp. 206-209.
  11. ↑ Ruhi Kafescioglu, "Gypsum-stabilized Adobe (Alker) Structures: An Evaluation of Their Social, Economic, and Environmental Advantages," 8th International Seminar on Structural Masonry: Proceedings, 05-07 November 2008, ed. L. Tanacan, Istanbul: ITU, 2008, pp. 51-59

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