10 junho 2014

Mud House Design 2014 Competition

Nka Foundation invites entries for Mud House Design 2014, an international architecture competition open to recent graduates and students of architecture, design and others from around the world who think earth architecture can be beautiful. The challenge is to design a single-family unit of about 30 x 40 feet on a plot of 60 x 60 feet to be built by maximum use of earth and local labor in the Ashanti Region of Ghana.
This is the design problem: In Ghana, as in other countries in West Africa, stereotypes about buildings made of earth persist because of poor construction. From the cities to the low-income villages, use of concrete - despite its dependence on imported resources - is considered indispensable for building. Yet an excellent, cheap and local alternative called laterite, red earth, is available everywhere in Ghana. The long-term goal is to enable the Ghanaian population and lots of other places, to overcome the stigma that mud architecture is architecture for the very poor.
Registration and submission of entries runs from March 15, 2014 until August 31, 2014. For additional information, see the competition

09 junho 2014

Additives to Clay_Aditivos orgânicos à terra argilosa para construção

Earth has been used for thousands of years for building throughout the world spanning a diverse range of climates and cultures. 
Earth itself is a multi-component system usually consisting of stones, sand, silt, clay, water and, near the ground surface, organic humus. Structural stability of earth buildings is maintained by the structural integrity of the sand and stone framework, by the pore filling capacity of the silt and, most importantly, by the binding qualities of the clay, which are in turn influenced by the moisture content of the soil. 
Compared with some building materials earth can be considered to have some disadvantages – it has relatively low compressive strength, tensile strength and abrasion resistance. It may also lose a lot of its rigidity in the presence of water. Nevertheless it is very cheap, very widely available, environmentally friendly, strongly linked to local cultures and traditions and, with skilful construction, can contribute significantly to the aesthetic appeal and user comfort of buildings. 
Good and durable earth buildings can be built provided certain precautions are taken. These precautions will depend on local conditions and structural requirements, but can broadly be classified into four categories: 
Soil selection 
Different soils can have very different characteristics. The quality of a soil for building is strongly dependant on grain size distribution and on excluding humus. 
Soil preparation and construction methods 
Builders should be familiar with soil pulverising, proportioning, mixing, maturing and curing as well as masonry techniques. 
Building design 
The design should take account of the properties of the raw material by appropriate load distribution and structural dimensions, and by incorporating protective elements against damp, rain, impact and abrasion. Protection can be achieved by adding more durable but complimentary materials at places such as the wall base, roof overhang and the copings, and by using plasters and renders on the walls. 
Improving the material quality 
Different treatments or additives, collectively known as stabilisation, can modify the properties of soils to control their shrinkage and swelling characteristics and so improve the binding ability of the clay in the soil. 
These stabilisation methods are described below. 
Compaction increases the soil’s density and hence its strength and resistance to mechanical damage. It also reduces water absorption but, with the associated reduction in porosity, durability may be reduced. 
Compaction is done in a mould or form: 
• statically (i.e. in a single pressing), with cylindrical rollers, wheeled rollers or presses; 
• dynamically (i.e. repeated), with tampers or rammers, vibrating rammers or pick 
• surface, with a beater – mainly for floors or roofs, although sometimes used on rammed 
earth walls before they dry. 
Effectiveness of compaction depends on applied pressure or energy, soil type and water 
Vegetable additives 
Fibres are widely used when building with earth. Generally fibres can be most easily mixed in with the soil if it is in a plastic or liquid state; that is not too dry. The fibres act to increase the tensile strength, reduce density, accelerate drying and reduce cracking by dispersing stresses. 
Fibres vary in shape, size, strength, elasticity and their bond strength with earth, so possible improvements with different types of fibre will vary, as will the amount of a particular fibre required. Usual proportions range between 1 and 4% by weight, representing in bulk a volume which can be as high as the volume of soil. 
The most common fibres used include straw, for example from wheat, rice or barley. The chaffs or husks of these crops can also be used. Other suitable vegetable fibres include hay, hemp, millet, sisal, filao needles, and elephant grass. Cow dung and, less frequently, horse and camel dung have also been used as additives because they contain short fibres which make the soil workable for plastering and rendering. Synthetic fibres such as colophane, steel or glass wool have found very limited application. Best results are obtained with fibre reinforcement if the wet mix is prepared several days before use. 
One drawback of vegetable fibre is variable durability. Dry fibres will generally last a very long time but when wet they are liable to rot. Also some are attacked by insects, especially termites, but others are not and often local knowledge exists to identify the most resistant types. 
Vegetable Oils and Fats 
The best additives of this type are those which dry, thereby harden, quickly and are insoluble in water. Such additives include coconut, cotton and linseed oil as well as castor oil – which is very expensive. Kapok, palmitic oil and shea butter have also been tried, but with variable results, so local trials are recommended. Shea butter can repel termites, and an addition of around 3% is recommended, although it can also be painted or sprayed on surfaces. 
Tannins are constituents of many plants, fruit and seeds. Chemically they are polyphenols and produce the dry bitter taste found in some fruit, teas and alcoholic drinks. A common use is in the tanning of animal skins and hides; hence the name. 
When added to soils, tannins often act to disperse clay particles so that they coat sand grains in the soil more evenly and, also help to break up clay lumps during compaction as well as reducing permeability of the soil and improving water resistance. 
The amount of tannin required varies from a small percentage of the mixing water for the most active types to completely replacing the mixing water in the case of decoctions – solutions obtained by boiling the natural products. In some regions of West Africa a decoction of the bark of the “Néré” tree (parkia biglobosa) is used for surface protection and it can also be used to stabilise gravelly soils with good results. Other tannins are prepared from the bark of oak, chestnut and scorpioid acacia. 
Gum arabic 
This is a product obtained from the acacia tree. It acts primarily as a flocculant: that is it helps to form flocs of clay particles within the soil which help to increase dry compressive strength and slow down water absorption, hence reducing shrinkage. However, it is soluble in water and so offers little protection to long-term moisture exposure. It is best used inside a building, added at 5 to 10% proportions. 
Palmo copal 
Copal is a resin obtained from certain tropical trees. It is usually added at 3 to 8% concentration to sandy soils. One variety, manilla copal, has waterproofing qualities. 
Sap and latexes 
The latex of certain trees, such as euphorbia, hevea rubber and concentrated sisal juice, reduces permeability slightly and improves cohesion. Proportions between 3 and 15% are normally used and best results are achieved with neutral rather than acidic soils. The juice squeezed from banana leaves, which is subsequently precipitated by mixing with lime to clean it, is another material which has similar properties. 
Dehydrated sugar molasses contain aldehydes which can be converted into polymers at high temperatures with the aid of phenolic catalysts. The resinous material obtained is similar to asphalt and other resins in its effects. It improves the strength and reduces permeability.
Normally a proportion of about 5% is used. 
Animal additives 
Care must be taken with animal products. In particular it is important that the animal has not suffered from a contagious disease for humans, such as anthrax. 
Hair and fur from animals are used with plasters and renders to reduce shrinkage and improve adhesion and impact resistance. 
These can contain chemicals such as phosphoric acid and potassium minerals which have beneficial effects. In addition excrements contain fibres. Additions of up to a third are possible, or even half for a finishing mix. Cow, horse or camel dungs are normally used. 
Goat dung can be used to lighten the soil. It is normal practice to leave a soil and dung mix to ferment for several days before use. 
Horse urine, added to a soil, reduces its shrinkage and makes it more resistant to erosion. It can replace the mixing water and is sometimes mixed in with straw before adding to soil. The strong smell disappears on drying. 
Proteinic casein, in the form of whey – a product formed by the souring of milk, sometimes mixed with animal blood, can be used for stabilisation. Milk powder has also been used. One proprietary mix is known as Poulh’s soup and is a mixture of diluted casein and brick dust beaten to a paste. 
Animal glues 
These improve strength and water resistance. They are made by boiling the skins and bones of animals in water. 
Termite mounds 
Termite mound material can be mixed with soil for a stabilising effect. Termite mounds are cemented with a cellulosic binder produced by the insects. 
Oils and fats 
Fish oil and animal fats can serve as waterproofing agents with stearates being the active component. Proportions from 5% are used but the effect can be variable. 

The need for additives 
It should be noted that there is not always a need to add stabilisers. Soil properties will dictate need and there are many examples across the world of the effective use of unstabilised soil. Stabilisers also add significantly to cost. 
If a stabiliser is deemed necessary the choice of which one to use will depend on a number of factors including: 
• the part of the building on which the soil is used and its exposure to the elements 
• the property of the soil which needs improving; e.g. dry strength, wet strength, water erosion, abrasion resistance, surface protection, etc. 
• the level of improvement required 
• the quantity of stabiliser required 
• the cost and availability of the stabiliser 
• whether production of the stabiliser is carried out locally or whether it needs to be imported. 

The precise quantities of additives often need to be determined empirically by trial and error for each particular situation. 
The results of laboratory tests often cannot be transferred directly to field practice, although they do provide useful guidance and a starting point for field tests. In the field, relatively simple and inexpensive tests such as observation of block durability on soaking in water and the use of a simple press to assess the load a block can carry in flexure can provide information on stabiliser requirements. As preparation of soil mixes and their use for building is often carried out under less rigorous conditions in the field than for testing, a reasonable increase in stabiliser dosage to compensate for this is recommended.

The original articule Technical Brief from Pratical Action can be found here.

Publicación online_X CIATTI-2013

Publicación online libro con las ponencias del X CIATTI-2013
El GrupoTierra ha publicado en su sitio de la web el libro en formato digital del Congreso del año 2013: "La arquitectura construida en tierra, Patrimonio y Vivienda" - X CIATTI. Congreso de Arquitectura de Tierra en Cuenca de Campos 2013.

El enlace donde lo podéis consultar es el siguiente:

"La arquitectura construida en tierra, Patrimonio y Vivienda" - Congreso de Arquitectura de Tierra en Cuenca de Campos 2013
Coordinadores: José Luis Sáinz Guerra. Félix Jové Sandoval.
ISBN: 978-84-617-0473-6
D.L.: VA 470-2014
Impreso en España
Junio de 2014
Publicación online.
Se accede a cada artículo a través de los enlaces de esta web:

Arquitectura vernácula básica. El refugio en el municipio de Bocairent (Valencia) 
Alesandra Insa Calabuig, Pablo Rodríguez-Navarro.

The Rammed Earth Building In Nigeria 
David C. Okoronkwo, Dr Jamal K. Khatib, Dr Nwabueze Emekwuru, Prof Richard F. Hall.

La vivienda tradicional de adobe en los Altos de Chiapas, México: un patrimonio vivo 
Nancy Jaqueline Jiménez Zomá, Luis Fernando Guerrero.

Casas de adobe mexicanas, una visión contemporánea. 
Leonardo Meraz Quintana, Diego Rescalvo Grajales y Luis Fernando Medina Esquivel.

Re-habitar a terra. Reflexão sobre a questão habitacional nos países em desenvolvimento 
Ana Luisa Leite.

Principios de la arquitectura popular griega 
Katerina Maleka, Atenas, Grecia

Change of 'Yaotong' which is one of Rammed Earth architecture in China 
Toshiei Tsukidate.

Construcción en tierra y calicanto en Madrigal de las Altas Torres (Ávila): Estado de conservación de la arquitectura vernácula y monumental 
Verónica Coca Zancajo, Guillermo Quiroga Pérez, Valladolid, España

Proyecto de un edificio rural en 1934: pervivencia de la tradición constructiva del adobe y la tapia en España. 
F. Javier Carbayo, Félix Jové, Fernando Sánchez

Dos caras de una misma técnica constructiva. Registro y trasmisión de la construcción en tapia. 
Àngels Castellarnau Visús y Félix A. Rivas.

Las murallas de Mascarell (Castellón). Estudio gráfico y constructivo Víctor Gamero Bernal, Pablo Rodríguez-Navarro.
Caracterización de la tapia del S XII en la torre de la iglesia de San Pedro. Becerril de Campos, Palencia 
Mónica del Río Muñoz, Jesús San José Alonso, Félix Jové Sandoval.

Técnicas medievales de construcción en tapial de tierra y de cal y canto: los castillos de Soria 
Ignacio Javier Gil Crespo.

Torres de Tierra en Castilla y León: Evolución desde la torre maciza al recubrimiento cerámico. 
Sánchez Rivera, J. I., Fernández Martín, J.J, San José Alonso, J. I.

Creación de un espacio intercultural inspirado en el temazcal tradicional oaxaqueño 
Boris Aparicio, Alfonso J. Aparicio

Del barro a la piedra en la arquitectura rural auxiliar. Chozos y casetas en tierra de campos y Montes Torozos. 
Óscar Abril Revuelta, Félix Lasheras Merino.

El destino de las kasbahs del Alto Atlas en Marruecos. Tres ejemplos en el valle del M'Goun 
Pablo Rodríguez-Navarro, Teresa Gil Piqueras.

Estudios previos para la restauración de la Torre Muza de Benifaió (Valencia): Un planteamiento multidisciplinar en el ámbito universitario. 
Vicente López Mateu, Teresa M. Pellicer Armiñana, Pablo Rodríguez Navarro, Santiago Tormo Esteve

Recuperación del patrimonio arquitectónico del oasis de M'Hamid. Una oportunidad para el desarrollo 
Oriol Domínguez Martínez, Emilio Roldán Zamarrón, Alejandro García Hermida.

Con los pies en la tierra. Experiencia en el sur de Marruecos 
Andrea Lamas Domingo, Anna Rico Llopis.
Diversas intervenciones en una torre de tapia de tierra en el Castillo de Oropesa del Mar. 
Fermin Font Mezquita. 

Consecuencias de intervenciones erróneas en la arquitectura de tapia. Ignacio Matoses Ortells, Javier Hidalgo Mora. Generalitat Valenciana, Consellería, 
Valencia, España. 

Revestimientos con fibras vegetales: metodología de estudio 
Diego García, Laura Milla, Antonia Navarro, María Palumbo 

Revitalización de la Tradición constructiva en Tierra y Bambu en comunidades rurales y urbanas en Oaxaca, México 
Joao G. Boto M. Caeiro.

Casa S-low. Sistema Innovador de bioconstrucción modular con entramado de madera y tapial 
Àngel Estévez, Sandra Martinlara. Casa S-low, Barcelona, España

Proyecto Casa S-Low: construcción del prototipo y experiencia docente 
Montserrat Bosch, Antonia Navarro, Luis Allepuz, Cristian Poza.

Accessing the Initial rate of sorption for rammed earth made with palm kernel shell 
David C. Okoronkwo, Dr. NwabuezeEmekwuru, Prof. Jamal M. Khatib, Prof. Richard Hall.

Evaluación del comportamiento geométrico-estructural del Prototipo de las Ánimas 
Juan Ricardo Alarcón Martínez, Juan Manuel Everardo Carballo Cruz, Noemí Bravo Reyna

Apuntes sobre lo estereotómico en la arquitectura contemporánea y sistemas naturales para su configuración 
Fco. Javier Blanco Martín, Javier Arias Madero.

Iniciación al análisis del cumplimiento del Código Técnico de la edificación mediante el empleo del BT como material de construcción 
Ana Romero Girón, Reyes Rodríguez García, Jacinto Canivell García de Paredes, Ana González Serrano.

Construcción con muros de carga monocapa con BTC ligero Cannabric en el clima del sur de Europa 
Monika Brümmer.

Telheiro da Encosta do Castelo - Um Espaço de Tradição e Inovação 
Nuno Grenha.

"DSA Architecture de Terre" de la Escuela de Arquitectura de Grenoble (ENSAG), Laboratorio CRATerre Teoría y práctica en una formación pos-máster en Arquitectura de Tierra 
Bakonirina Rakotomamonjy, Enrique Sevillano.

Analysis of the earth construction's thermal behavior - in situ measurement and evaluation of thermal performance of three rammed earth case studies 
Sofía Sampaio, M. Gloria Gomes, António Borges Abel.

Construcción de un módulo de adobe reforzado con mallas de junco en cañete, Ica-Perú 
María Teresa Méndez, Jimmy Onofre, Gabriela Prado, Kattia Barreto, Cristina Arias, José García. 

Cómo puede ayudar el conocimiento de la construcción sostenible en el desarrollo de las ciudades. El ejemplo de Manta. Proyecto de Cooperación Internacional de la Universidad de Valladolid, España, y la Universidad Laica Eloy Alfaro de Manabí, Ecuador. 
José Luis Sáinz Guerra, Félix Jové, Rosario del Caz, Pedro Olmos, Miguel Camino

Viviendas de adobe en Camerún 
Sandra Bestraten Castells, Emilio Hormias Laperal.

El horno de ESTEPA: Calor sin leña 
María Brown Birabén, Raquel Martínez Fernández, Mariana Mas Gómez.

La tierra en la construcción de cerramientos con materiales de reciclaje 
Javier Arias Madero, Javier Blanco Martín.

Fogones mejorados de adobe 
Elena Carrillo Palacios, Jon de la Rica Extremiana. 
Ver índice e introduccion

Para más info:
E.T.S. de Arquitectura.   
Universidad de Valladolid - Av. de Salamanca s/n.  47014-Valladolid. España
T: +34  983 184 940  <tierra@arq.uva.es