Las Malvinas ecoladrillo schoolroom

viernes, 8 de junio, 2012

Background

Las Malvinas es una comunidad cerca de Santo Domingo, en la República Dominicana. Hay más que 150 familias que se viven en esta escenario rural, al lado del un río. Por un voto de las manos, la comunidad ha decedido que el proyecto que se quieren más es que trabajemos juntos, con la cultura y deseos de ellos y con la tecnología inteligencia de nosotros, para construir una aula para la escuela, usando modos alternativos de construcción como "papercrete" y "ecoladrillo."

"Papercrete" es similar a bloques de concreto, pero estos bloques son de papel reciclado. "Ecoladrillo" se usa botellas plásticas y concreto para hacer paredes.

Hay un abundancia de ambos materiales (botellas y papel reciclados), y necesitan más espacio en la escuela. Entonces, váminos a trabajar con las materiales más locales y baratos para ayudar esta comunidad cumplir este objetivo mientras estámos apriendo a implementar modos de construcción sostenable.

Climate

The Dominican Republic is in a tropical climate zone, where rainfall varies seasonally but temperatures are relatively static, ^[1] ranging from 64-90 degrees F year round.^[2] The rainy season begins in early summer and last through mid fall, with the the most powerful tropical storms occurring during August and September.^[2] The average annual rainfall is 150cm^[3], much of which falls on the northern side of the island. This results in cooler temperatures and higher humidity in comparison to the south."^[4]

Problem Definition

Criteria

Criteria and constrains are needed to determine the success of a solution. Criteria are weighted with 10 being most important and 0 being least important.

Criteria	Constraint	Weight
Safety	The classroom meets or exceeds local building codes	10
Reproduction Costs	The total cost of construction is less than the cost of traditional construction.	8
Appropriate Materials	Building materials are local, alternatively resourced, and may be easily obtained by the community.	7
Aesthetics	The classroom looks good with the existing school structure while having a unique appearance that draws positive attention to its alternative construction.	8
Ease of Use	The classroom comfortably accommodates the most number of students possible for the given space, up to 35 students.	7
Community Interest	Maximize community involvement to develop their interest in the project, as well as their skills and knowledge necessary to replicate the project later.	10
Research and Development Costs	Spend no more than US$1000	5

Literature Review

Rammed Earth Floors

METHODS:

• At the Dancing Rabbit Ecovillage in Missouri, they made an adobe/rammed earth hybrid floor. On top of a plastic moisture barrier (protected on either side by a thin layer of sand), they laid 4-6 inches of compacted "road base mixture" which is comprised of clay, sand, and various sizes of gravel (allowing for more compactability). "We added a few inches at a time and tamped it in place by hand after spraying lightly with water." They then used their standard earth plaster mix of 6 parts sand, 2 parts clay, 1 part finely chopped straw, and applied a 1-inch thick layer to the floor. The plaster was troweled smooth, allowed to dry, and then applied 4 coats of linseed oil, each of which dried thoroughly before the next application. The last three coats of linseed oil were mixed with increasing ratios of citrus paint thinner. ^[5]
• Earthen floors refer to a layer of substrate dirt or sawdust that is laid down on top of a layer of fine gravel, which is then covered with a layer of clay or sand. The final step is sealing the newly laid floor with a layer of linseed and hemp oil. The result is a porous, supple and durable floor at less than a dollar per a square foot (including labor). ^[6]
• Though their specific ingredients and construction vary by location, the idea is the same everywhere: Take some dirt (with some clay content), add water, some stabilizing agents like sand and straw, and squish it until it's hard. Once dry, seal it with an oxidizing oil like linseed or hemp oil. ^[7]
• To get the right mix, experiment with a test area of at least 3x3 ft. The mix should be strong enough that it is not powdery when it dries, and it must contain enough fiber so that there are no cracks. Apply the mixture with a trowel in 1/2-3/4" layer. The material should come off cleanly and easily as you move the trowel across the sub-floor. If it sticks, there’s either too much clay or not enough moisture; if it won’t stick to the trowel, there’s either too much moisture or not enough clay. ^[8]
• Homeowners in a wet climate should put down several inches of gravel to enhance drainage. This can be a three- to four- inch layer of clay, sand, and gravel or crushed stone, on top of which lays the half-inch layer of finer mix. If you pour this supportive layer in a damp state—and even add lime to the mixture—it will dry and harden more quickly. ^[8]
• A typical earthen floor might include a 2.5-inch base layer of 70% sand, 30% clay, with handfuls of long straw for tensile strength. Once it is dry, the final layer will be installed and smoothed with a trowel, composed of a similar sand to clay ratio, but mixed with very short chopped straw. ^[9]
• "The floor area between posts must be higher than the outer area. The wall will be protected from rainwater that runs along the flat outer wall of the house. The mixture for the earth floor is earth, gravel and water/asphalt in a 10:2:1 proportion, respectively. Another way to build a good floor is to use pumice stone sand which provides a thermal insulation base for very cold or very hot regions." ^[10]

LINSEED OIL COATING:

• At the Dancing Rabbit Ecovillage, increasing amounts of paint thinner in the linseed coatings allow deep penetration of the oil into the floor:

1st coat - Only linseed oil 2nd coat - 3:1 linseed to paint thinner 3rd coat - 2:2 4th coat - 1:3

• Boiled linseed oil contains solvents and is highly toxic, while eco-friendly linseed oil can be expensive. “As a compromise, we take raw linseed oil and put it in the sun in shallow pans covered with a piece of glass, leaving a tiny air space. The oil pre-oxidizes and dries faster. It’s called sun-thickened oil.” ^[8]

STABILIZERS:

• The main categories of binders used for earth construction are Portland cement, lime, bitumen, natural fibre and chemical solutions such as silicates. Benefits of cement addition is improved structural integrity, while a downside is reduced permeability of earthen mixture and thus natural ability of earth to allow passage of moisture throughout the soil mass is reduced. ^[11]
• Tests have indicated that there is an optimum lime dosage for a soil beyond which compressive strength decreases. The likely dosages are between 6-12% lime by dry weight and will increase as clay content increases. ^[11]

Ecoladrillo

• “Eco-bricks” are a free and practical building material that can be used to construct almost anything from small planters and walls to schools and homes. Especially for rural communities the eco-brick represents the most ecological solution to manage household and plastic trash. ^[12] Any inorganic waste material can be used to fill the bricks, however ideal materials are those that cannot be recycled others. Examples include: food packaging, old socks, razor blades, used up pens and markers, clothing tags, cotton swabs, etc. The process of "up-cycling" such materials that would otherwise end up in the trash reduces waste and significantly cuts construction costs. ^[13] That being said, not all trash makes for good infill material. Anything organic such as food waste will not work. Trash must be clean and moisture free, as well as the bottles, and it is best to stay away from paper waste if at all possible. It is also important to stuff bottles as full as possible to increase insulation. Training of community members about these material requirements is important to ensure a stable and safe structure.^[14]

(Camille, I can't access the journal to gather the information needed to cite the source)

• A how-to slideshow on eco-brick bottle construction. ^[15]

(Not sure how to cite this, any way we can embed the slideshow on our page?)

Alternative Infill

Sawdust:

• When considering sawdust as a building material, there are functionally two different types wood: hardwood and softwood. The quality of the sawdust will vary depending on the species, but most hardwoods are relatively better than softwoods at absorbing water, which are typically harder and grainier. For this reason, sawdust gathered from hardwoods is more ideal. Sawdust can be used in mixes with clay to make adobe and cob or with cement to make concrete and plaster substitutes. It can provide insulation, protection against freezing. It can also be found for free.^[16]
• Cob and adobe are made from mixtures of clay, sand, lime, sawdust and/or green waste. The ratio's can vary greatly depending on availability and quality of materials, making cob and adobe very adaptable building materials. Because Las Malvinas has an abundance of sawdust, the ratio with the most potential requires 9 parts sawdust, 3 parts clay, 2 parts lime, and 1 part sand. The sawdust is soaked overnight and dried for a few hours, then mixed by hand or by hoe with the rest of the mixture and water.^[16] The amount of water need varies depending on the moisture content already present in the clay. The mixture can be made into adobe bricks or built up in monolith. Cob or adobe made with more sawdust rather than green waste will also dry faster.
• A mixture of sawdust, sand, and cement can also be used in infill. The mixture requires less cement than concrete or traditional cement plasters, however there is little information regarding its structural integrity. The common ratio is 3 parts sawdust, 2 parts sand, and 1 part cement, and the final mixture can be used as a plaster over another alternative infill material such as eco-brick.^[17]

Papercrete:

Structure

Exterior walls

• Lay out the wall location on the sub floor where the wall's bottom or sole plate will be positioned. Measure from the outside edge of the subfloor, the width of the sole plate plus the sheathing, if the sheathing extends to the sub floor; or the width of the bottom plate if the sheathing extends over the boxing joist to the concrete foundation wall. Snap a chalkline.

Select straight stock for the bottom and top plates, square of one end of each plate, and lay them side by side on the subfloor. If the plates have to be made out of more than one piece of lumber, make sure they join over a stud centre. Measure and mark the locations of the door and window opening centres, openings located from centres, partitions and studs. ^[18]

Marking Top & Bottom Plates

• Standard walls are 8' to 12' high. Older homes and warmer climates will have 2x4 wall studs.
• Wall studs are generally spaced 16" on center. The first stud will sit on the end of the plate. Measure and mark 15-1/4" from the end for the near edge of the second stud. From this mark make marks every 16" for the near edges of the remaining studs.
• Before starting the layout process, chalk line the locations of the walls and their window/door openings on the subfloor. These marks will enable you to visualize and check the project's layout before the walls are made. The chalklines also serve as guidelines when actually raising the walls into place. ^[19]

Assembling Walls & Corner Posts

• We usually assemble the wall on the floor, nail it together, then raise it into place. Working on a level surface is a major help in laying out the walls flush. Try to avoid assembling walls on the ground.
• Check- It's a good idea to check for squareness by measuring diagonally from the corners after nailing on each end and after each wall is assembled.
• Where two walls meet in a corner there needs to be some extra framing to make sure that there's something on each wall for the drywall on both walls to nail into. One wall at every corner needs a corner "post." Here are two ways to create one:

1) Add 2x4 spacer blocks between the end stud and then install an extra "corner stud."

2) Lay an extra corner stud sideways, flush with the inside edge of the bottom plate.

Once the corner post is secure, insulate the cavity before installing the sheathing. Once the sheathing is on and the wall goes up, the end of one wall section will cover the corner of the other making insulating impossible at that point. ^[19]

Plank and Beam Construction

• In the plank and beam framing method beams of adequate size and to support floor are spaced up to eight feet apart. Floors and roofs are covered with a two inch plank. These serve as sub-flooring and roof sheathing, and where tongue and grove is used provide a great finished look. ^[20]

Concrete Foundations

• With unstable soils, and it wet climate where re-enforced concrete is used with Masonry blocks walls typically have a 1/2 inch coat of portland cement applied to the exterior. Once set this is then covered with asphalt to resist water penetration of the walls by water. ^[20]

Corrugated Tin Roofing

• Corrugated tin roofing is commonly used in tropical areas because of its durability, sturdiness, and light weight design. The key attribute leading to the ability to remain useful for so long is due to the special corrugated shape the metal is formed to. ^[21]

• Main types of metals used are aluminum, galvanized steel, copper, aluzinc, and tin. ^[22]

• Integrated ventilation is very important since this style of material if often used in tropical, humid climates. It is meant to provide insulation from heat during most of the year, so to "provide generous wall openings, large doors and windows" is key during the construction of the roof. ^[23]

References

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