This project is part of the Summer 2013 Practivistas Dominicana project, led by Lonny Grafman in the Dominican Republic. Six students, three from Humboldt State University (HSU) in California and three from Universidad Iberoamericana (UNIBE) in Santo Domingo, will be collaborating with the community of Las Malvinas to construct two of four walls for a "Botica Popular" in the community. This team will be experimenting with cinder blocks, or concrete masonry units (CMUs) made of various upcycled materials such as sawdust, paper and rice hulls mixed with cement and pressed using an industrial cinder block maker. At the same time another team will be working on building the other two walls out of ecoladrillo, or upcycled plastic bottles.
Las Malvinas community members have identified and prioritized a list of needs. On that list are access to running water and medicine. To address the need for water a team of motivated community leaders are constructing a large cistern (approx. 50 cubic meters). An engineer from UNIBE assisted in the design. To address the need for medicine the two student teams mentioned above will work with community members to construct a Botica Popular.
Botica Popular
Boticas populares are neighborhood pharmacies that provide medications at cost price. They are part of government public health campaign called El Programa de Medicamentos Esenciales or "Essential Drugs Program" (PROMESE). Established in 1984 by presidential decree, PROMESE is the Dominican Republics central supplier of medications and medical supplies with a mission of ensuring quality, low-cost access to the nation's public health system, Sistema Publico Nacional de Salud. PROMESE has provided greater medical coverage to the population by optimizing public health spending with the implementation of an economy of scale and buying medications and medical supplies in larger volumes[1]. The "Essential Drugs Program" directly serves public and military hospitals, boticas populares, and rural clinics.
For boticas populares, the program fronts the medications and a accepts payment at cost price upon distribution to the patient. Las Malvinas does not have a local clinic or hospital. The nearest hospital is Moscosos Puello about 5 km away.
Objective
The community of Las Malvinas is seeking to construct a Botica Popular, or government-funded pharmacy, in their community. The objective of this project is to build two of the four walls of the Botica using alternative masonry and to erect the complete Botica by 5 July 2013. This student team will fabricate building blocks with sawdust, rice hulls or paper mixed with cement and pressed in an industrial block press. With the climate in the Dominican Republic, the blocks need to be able to withstand heat, rain and the test of time.
Part of the objective of this project is to find a building material, specifically a fiber-concrete mixture, that the community will be able to utilize in the future to make more blocks for other projects. As such, final product should be composed of locally purchased or acquired materials, and have a low cost, both monetary and environmental.
Entirely concrete cinderblocks have a high embedded energy, with an average of 0.67 MJ/kg and 0.073 kg Co2 per kg with a density of 1450 kg/m3[2].
Timeline
Friday June 7, 2013
Our group had an opportunity to meet Jacob, an Engineering student at UNIBE who showed us his experiments with sawdust-concrete and recycled styrofoam-concrete. He had been experimenting with different ratios of sawdust to concrete and testing the strength of different mixes. His experiments also included using wire to increase the tensile strength of the concrete slabs. He will likely be a useful contact while working on this project.
Saturday June 8
First day to work on mixes. We went to Las Malvinas in the morning and, with Ginger's help, secured a barrel of sawdust from the coffin manufacturer who will be providing our material and the block-making site next door where we and members of the community will be doing experiments and making blocks with sawdust and other materials. We also were given two bags of lime and loaned two barrels for mixing the sawdust, lime and water to soak. After an initial mix, the owner of the plant arrived and made some changes to the mixture we had put together, encouraging us to "go big" with our experiments. There was a high level of interest from the community members who came to work with us - they really ended up taking over much of the work, sifting, mixing and all the while peppering us with questions. A kid from the community spent most of the afternoon with us helping mix the sawdust, lime and water. We will be returning to the site on Wednesday to try more mixes and Thursday is the day to press blocks.
Literature Review
Components
Lime
For this project, we will be using lime in several stages. It is an ingredient in the upcycled cinder blocks and plaster because of its ability to prevent water damage. Mg and CaO are the active ingredients in lime. While other components in the lime can be present, they are considered impurities in the mixture. Hydrated lime is expressed as CaO+H2O>Ca(OH)2, which is the powdered dry material often used in plasters[3]. The hydrated lime then needs to be rehydrated in a process called "slaking". The action of slaking lime is a process of adding water to the powdered lime mixture until the powder can not absorb any more water. The CaO is responsible for this behavior of absorption and reaches a limit which becomes obvious due to a layer of excess water on top of the lime slurry.[4].
Lime can also be used as a component for mortars, plaster and a final lime wash. Plasters can be applied to moistened surfaces, upon which you can apply a scratch coat followed by a final smooth coat. Lime wash is typically used as a final coat for plasters and composed of water, slaked lime and pigment if desired.[5].
Important: Lime is very caustic, and therefore requires the use of protective gear when working with lime and water mixtures. The pH level can reach 12, which can damage the skin. Vinegar or lemon can be used to neutralize the lime if it comes in contact with the skin. As a precaution, it is suggested that you wear protective gear including rubber gloves, gogggles and appropriate clothing.[6].
Sawdust
Sawdust is considered a waste that is created during the manufacturing of coffins and many other things. It is a waste product that, if not added to the general waste stream is often burned. It often is not removed from the creation site, which allows it to become a hazard for fires and air quality.[7].
Rice Hulls
Rice hulls are the protective layer surrounding the rice grain that is composed of silica and lignin.[8]. Composting, open burning and livestock feed are some of the common ways to reduce waste of materials from the food industry.[9]. Rice hulls have been used in construction because of its potential low absorption, thermal resistance and insulative properties. These properties resist expansion and absorption and have allowed it to be used successfully as infill for houses.[10].
Fiber -Cretes
A fellow student and past Practivista at UNIBE shared some of his research into making blocks with sawdust and other materials. This research is currently underway, however in his experimentation, he was using sawdust for more than simply diluting the concrete, he was actually using it as a replacement for river sand. This is a potential area for experimentation in this project. His blocks were very durable, able to withstand approximately 2900 Newtons of force [11].
Paper-Crete
Papercrete is an alternative construction material that, in general, is made up of milled paper and an adhesion component like clay or cement. Since paper comes in many forms, i.e. junk mail, magazines, beer cartons, newspapers, etc., so does papercrete. While there is no definitive code for building with papercrete, various forms of papercrete masonry have been successfully employed.[12] Paper is a common waste product and can be sourced for free, making papercrete an affordable, green masonry alternative. In Santo Domingo, Republica Dominicana recycling services are not readily accessible and waste management is a visible environmental issue. The use of papercrete construction can be a paper-waste outlet for growing communities, while reducing the cost of building materials.
The papercrete blocks from 2012 In last year's Practavistas program, the Las Malvinas group worked on building a schoolroom out of papercrete and ecoladrillo. Their process involved pulping the paper with a blender in a mix of 4 parts paper to 1/8 part lime and 8 parts water, then letting the mixture dry. This was then mixed with concrete and water and the slurry was pressed into blocks [13]. In a visit to the site this summer, the papercrete wall in the schoolroom appeared to be in very good condition, better, in fact, than the ecoladrillo.
Properties
In terms of insulation, papercrete has an R-value between 2.0 and 3.0, making it a more suitable building material than concrete for the Dominican Republic's warm climate, (concrete's is about 0.08)[14].
Papercrete can have a compressive strength of about 150 lbs per square inch, much lower than concrete but enough to support a roof load[15]. Papercrete blocks tested at this amount of pressure squished, but did not crumble.
Recipes
Here is a starting formula provided by LivingInPaper.com for a 200-gallon batch[16]:
160 gallons (727 liters) of water
60 pounds (27 kilograms) of paper
1 bag or 94 pounds (43 kilograms) of Portland cement
15 shovelfuls or 65 pounds (29 kilograms) of sand
Here is a by volume mix provided by Papercrete.com[17]:
12 parts paper
4-6 parts soft clay
2-3 parts lime putty
Sawdust-Crete
BMP Association LTD is a company based out of Moscow that produces equipment for companies and experiments with different and new building materials, including sawdust concrete. They claim several benefits of using sawdust concrete:
Fireproof
Indoor humidity control
Frost-proof
Resistance to mold and fungi
Compatibility with various other materials and finishes
Much lower heat conduction than bricks: 0.08-0.17 Wt/m as opposed to 0.5-1.5 in brick.
According to their website, this means that it takes half as much energy to heat a home with 20cm sawdust-crete walls than with 50cm brick walls.
Much lower density: 400-850 kg/m3 as opposed to 1550-1950 [18]
Timbercrete is a company based out of Australia that specializes in bricks, pavers and finishes
Recipes
After World War II, a man named Friberg built his home in Idaho, USA with Sawdust concrete. Mother Earth News did a follow-up article on his home thirty years later. The home was found to be in excellent condition, with little sign of deterioration and excellent insulation. This mixture was found to only have one quarter to one third the strength of ordinary concrete and Friberg recommended it for indoor use.
By volume:
1 part cement
1 part diatomaceous earth
3 parts sawdust
3 parts shavings
1 part clay
Clay, diatomite and cement were mixed first, then sawdust and shavings were added.
This recipe was found on the Digest blog and is recommended for a durable concrete.
Sawdust is first mixed with minerals to resist decay, molding and rot. May somewhat mimic natural process of wood petrification.
85% wood
12% cement
3% fly ash
The resulting product weighs half as much as ordinary concrete, can be pressed into blocks skin to Concrete Masonry Units and has an r-value of 18. Buildings using these blocks, known as "Faswall Forms" do not use mortar, they are instead stacked, rebar is placed between the spaces in the form and then the form is filled with concrete. [21]
This recipe is used for making bat caves:
4 Quarts wood chips
1 Quart cement
Recommends only using CaCl in the water because sugars in the wood chips can keep the concrete from binding. [22]
The NSW Good Wood Guide offers this recipe for a sawdust-crete. This site reccomends use as a non-load bearing infill.
3 parts sawdust - hardwood used for best results
2 parts sand
1 part cement
Blend the dry ingredients, first sand and sawdust then concrete.
Add water, only enough to hold, but not produce excess when the mixture is squeezed. [23]
Rice Hull-crete
In the community presentation with Las Malvinas rice hulls were mentioned as a potential resource for the community. A study done in India analyzed the possibility of using rice hulls in concrete blocks. In the study rice hulls were added at 0.5, 1.0 and 1.5 percent as compared to the amount of concrete added to the mixture. Although workability of the concrete decreased, other factors such as tensile strength, impact strength, displacement and energy absorption were improved significantly. Also, the blocks with rice hulls added were found to tend to crack before failure as opposed to the plain concrete blocks, which would tend to fail without much warning.[24]
Recipes
One recipe for rice hull blocks from the book "Rice"
In visiting the schoolroom this year, some of the walls were cracking, which could have been partially from the mixture for the finish, so this year's project will likely want to revise this mixture if it is the one chosen.
↑Sivaraja, M., S. Kandasamy. Potential Reuse of Waste Rice husk as Fibre Components in Concrete. Vol 12. No 2. 211. Asian Journal of Civil Engineering. pp 205-217.
