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*Secured the rice hull source for tests and block making, we should have rice hulls to use tomorrow.   
*Secured the rice hull source for tests and block making, we should have rice hulls to use tomorrow.   
*Joel found an admixture that we can use to accelerate the drying of the blocks. We will be experimenting with adding it when we make the test blocks.  
*Joel found an admixture that we can use to accelerate the drying of the blocks. We will be experimenting with adding it when we make the test blocks.  
'''Monday, June 24'''
*Acquired about 300 pounds of newspaper from Listin Diario.


===Proposed Timeline===
===Proposed Timeline===

Revision as of 16:02, 25 June 2013

Introduction

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 Republic's 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 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].

Criteria

This section was designed to assist in the determination of the different aspects of this project. The group chose these criteria based on the expectations of the client, the class and personal interest. Weighing the criteria allows for focus on certain elements of the project to ensure satisfaction with the final product.

Criteria Constraints Our Weight (0-10)
Aesthetics Must resemble local architecture 6
Production Cost Must cost less to produce than the common cinder block 10
Durability Must withstand elements, impact and pressure 9
Material Locality Must attain materials within or near Las Malvinas 7
Potential for Reproduction Ease of access to materials as well as documentation 8
Safety Must be safe both structurally and in the process of creation 10
Community Involvement Must include the local community members in the creation of this project 10

Timeline

Friday June 7, 2013

  • Summer 2013 sawdustcrete1.JPG
    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 that 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.

Wednesday, June 12

  • Our sawdust for blocks. We tested with both pre-soaked sawdust and dry sawdust.
    We returned to Las Malvinas and found our sawdust mixture in good shape. The coffin manufacturer next door gave us two more barrels of sawdust and we doubled the amount in our existing bucket, making a moist, but much drier, sawdust and lime mixture. The owner of the block making company will be allowing us to use his industrial cement mixer (if we have enough mix to fill it). We also discovered that there is not only ample rice hulls nearby, but ample ash from burnt rice hulls that is a waste product and the cement company already uses it. So we will be experimenting with using rice hull ash as well to reduce the amount of cement in our mixtures.

Thursday, June 13

  • First day of block making for our first tests! We ended up with four mixes, three of sawdust and one of rice hull. We totaled 113 blocks with three bags of cement, and that was good because at the site they usually make around 33 blocks per bag, so we are at least on par with their mixes in terms of cement used. The owner not only allowed us to use their machine, but also their industrial cement mixer. It was an excellent learning experience for all concerned, and testing the blocks begins on Saturday. We also obtained two barrels of very fine sawdust to experiment with in our next mixtures.
Ingredient Type of measurement Mix 1 Qty Mix 2 Qty Mix 3 Qty Mix 4 Qty
Sand 5 gallon bucket 2 2 1.5 1.5
Gravel 5 gallon bucket 0 2 0.5 0.5
Sawdust 5 gallon bucket 14 14 10 0
Rice Hull 5 gallon bucket 0 0 0 10
Cement Bag (90 lbs) 1 1 0.5 0.5
Rice Hull Ash (RHA) 5 gallon bucket 1/4 1/4 1/6 1/6
Lime Bag (approx. 1 5-gallon bucket) 1 1 2/3 2/3
Number Blocks 27 39 23 24
Compression Test Crumbled Crumbled Crumbled Held up


Saturday, June 15

  • Returned to Las Malvinas to test the blocks from Thursday. The rice hull blocks were nearly dry and the sawdust blocks were not dry yet. The rice hull blocks appeared the most structurally sound, although it is difficult to ascertain with the sawdust blocks still being so wet. Pulerimo, a community member, offered his advice that the blocks do not have enough cement, which is making them crumble. Our next mixtures will contain a greater amount of cement, and likely of RHA as well. It is possible that we will focus on rice hull blocks for the Botica, although we need to do more experimentation before that is certain. Work continues on the cistern, which will be part of the foundation of the Botica.

Sunday, June 16

  • Ricecrete blocks hold up in the compression test
    Work continues on the cistern, which will form the base for half the Botica.
  • Assessed the blocks again, sawdust blocks are still wet, rice hull blocks are closer to dry. The sawdust may not be used in the final round, testing will continue before this is a final determination. The rice hull blocks were found capable of supporting human weight, and general consensus is that they will work well with more cement. Papercrete is also going to be tested in the next round.
  • The very fine sawdust from the coffin manufacturers proved challenging to sift. It may not be used in blocks, it might be used in the finish for the Botica.

Monday, June 17

  • Sought sources for waste newspaper. Attempted several contacts.
  • Determined plan of action for block testing round 2.

Tuesday, June 18

  • A source for newspaper for making papercrete was secured.
  • We tore up and set paper to soak in water and lime for testing on Thursday or Friday.
  • Determined that using the 4 inch sized block forms will not make a significant difference for the tests: the forms in the machine will not be changed back to 6 inch blocks until Monday.
  • Seeking a paint mixer to pulp the paper for blocks.

Wednesday, June 19

  • Spent at least 3 hours tearing paper for block making several kids from the community came to help. We added more paper to the existing mixture and are hoping to find a paint mixer or similar for tomorrow. If one can't be found we may have to think of some other method to pulp the paper.
  • Secured the rice hull source for tests and block making, we should have rice hulls to use tomorrow.
  • Joel found an admixture that we can use to accelerate the drying of the blocks. We will be experimenting with adding it when we make the test blocks.

Monday, June 24

  • Acquired about 300 pounds of newspaper from Listin Diario.


Proposed Timeline

Date Task People involved
15-6-2013 Gather materials and stress test the 1st experimental blocks Group
18-6-2013 Make 2nd round of blocks Group
19-6-2013 Stress test 2nd round of blocks Group
21-6-2013 Gather materials for mass production Group
23-6-2013 Test mortar Group
24-6-2013 Building begins Group
27-6-2013 Finish brick construction Group
28-6-2013 Plaster, roof and/or floor Group
30-6-2013 Completed project Group
1-7-2013 Completed documentation Group
4-7-2013 Presentation Group

Literature Review

Climate

  • Being located between the geographical coordinates 17 ° 30 and 19 ° 56 north latitude and 68 ° 19 and 72 ° 31 W, Dominican Republic is located in the tropical region. It has a very rugged relief, about 50% of its territory is occupied by five mountain ranges and three great mountain ranges, among which are the highest peaks of the Antilles (Pico Duarte 3,187 m)[3].
  • The Dominican Republic, due to its geographical position, has a tropical climate that is regionally influenced by topography, trade winds, and atmospheric phenomena[4].

Temperature

The Dominican Republic has an average annual temperature of about 25 °C (77 °F) which is defined as a warm tropical climate. The higher temperature, about 34 °C (93 °F), recorded in the months from June to August, and the lowest, 19 °C (66 °F), recorded between December and February[5].

Precipitation

In the Dominican Republic there are three rainy seasons: Season Front (November-April), Convective Season (May-July) and hurricane season (August-October)[6].

Components

At the block-making site where we have been allowed to press our blocks, they use a mixture of sand, gravel, cement and water to make their blocks. For our blocks, we are replacing sand and gravel with other materials and in using rice hull ash and lime we hope to utilize less cement, making a cheaper and lighter block. The mixture used on-site that we are comparing to is 3 wheelbarrows of sand, 1 wheelbarrow of gravel, 1 bag of cement and 2 buckets of water, which makes around 33 blocks. [7]

Sand & Gravel

Cement is not enough to make a block by itself. Sand and gravel give blocks their structure, held together by cement "glue". In these experiments we are mostly replacing sand and gravel with our alternate materials.

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[8]. 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.[9]
  • 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.[10]
  • 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.[11]

Block Making

  • The raw materials used in the creation of concrete blocks typically include sand, gravel, and cement, but can vary depending on purpose and available materials. These materials are kept separate and dry until ready for pressing. They are then consolidated by using large mixing blades and adding water until the desired texture is reached. The mixture is then placed into a mold in a large machine that applies high levels of pressure to the mixture. Four blocks are produced at a time by the machine used in Las Malvinas. The curing process requires that the drying process is controlled so that the blocks do not dry too quickly, which would result in cracking. This is controlled through watering down the blocks several times depending on local climate.[12]

Fiber-Cretes

A fellow student and past Practivista at UNIBE shared some of his current research from making blocks with sawdust and other materials. In his experimentation he is using sawdust as a replacement for river sand. This is a potential area for experimentation in this project. His blocks were very durable and able to withstand approximately 2,900 Newtons of force.[13]

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 formula for building with papercrete, various forms of papercrete masonry have been successfully employed[14]. Paper is a common waste product and can be sourced for free, making papercrete an affordable, green masonry alternative. In Santo Domingo 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 the 2012 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. The ratios for these blocks were 1 part paper to 1 part sand and 1 part cement. [15]. 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. The R-value of concrete is about 0.08[16].
  • Papercrete can have a compressive strength of about 150 lbs per square inch, much lower than concrete but enough to support a roof load[17]. 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[18]:
    • 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[19]:
    • 12 parts paper
    • 4-6 parts soft clay
    • 2-3 parts lime putty

Sawdust-Crete

Sawdust

Sawdust is considered a waste that is created during the manufacturing of coffins and many other products. 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[20].

  • 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 [21]
  • Timbercrete is a company based out of Australia that specializes in bricks, pavers and finishes
Recipes
  • From an article on Scribd.com:
    • 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. [22]
  • 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.
    • 135 kg cement
    • 135 kg slaked lime
    • 600 kg sand
    • 200 kg sawdust
    • ~250 L water
    • This site claims 80 days for hardening time [23]
  • From an online book on building sauna floors:
    • 2 parts sand
    • 2 parts sawdust
    • 1 part cement
    • Cured for one month[24]
  • 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. [25]
  • 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. [26]

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.[27]

Rice Hulls

Rice hulls are the protective layer surrounding the rice grain that is composed of silica and lignin[28].‎ Composting, open burning and livestock feed are some of the common ways to reduce waste of materials from the food industry[29]. Rice hulls have been used in construction because of its potential low water absorption, thermal resistance and insulative properties. These properties resist expansion and absorption, which has allowed rice hulls to be used successfully as infill for houses.[30]. Rice hulls have a water absorption of 123.7% [31].

Recipes
  • One recipe for rice hull blocks from the book "Rice"
    • 1 part cement by weight
    • 0.25 parts rice hull by weight
    • 0.35 parts water by weight [32]
    • This translates from weight to volume to approximately:
      • 6 parts rice
      • 2 parts cement
      • 1 part water

Rice Husk Ash-Crete

A study published in India's NBM Media site suggested the use of 10% by mass rice hull ash (RHA) to enhance various properties of cement. Resistance to acidic environments, compressive strength and surface moisture of cement blocks were all found to have increased with the addition of approximately 10% RHA. This also counts for use in mortar. Concrete blocks fared best with 12.5% RHA[33]. A Brazilian study concurred, finding that 10% RHA decreased total water absorption by up to 38%. Compressive strength increased, with mixtures both of 5% and 10% RHA (5% having a greater compressive strength). These blocks were aged up to 28 days[34]. The Center for Vocational Building Technology suggests using 30% rice hull ash in a cement mixture, and that the quality of performance is on par with 100% cement [35].

Rice Husk Ash (RHA)

RHA is produced by the burning of rice husks and is a common by-product of rice production[36]. In Las Malvinas, there is a nearby producer of rice husk and also rice husk ash as a by-product of their activities. Rice husk ash is composed of 90-95% silicon dioxide and can improve the workability, stability, reduce cracking and reduce plastic shrinkage of cement[37]. It is also of interest for this project particularly for its ability to decrease the amount of cement needed.

Recipe
  • 10% rice hull ash by mass added to cement or mortar.
  • 12.5% by mass added for concrete.[38]

Mortar

Mortar can be made with cement, sand, and sawdust, although these mixes are known to be weaker than "traditional" mortars[39]. In a test of cement/sawdust mixtures, over 10% sawdust in a mortar decreased the compressive strength by more than half. Mixtures of 10% and less still had a significant effect upon the compressive strength of the mortar[40]. It is possible to utilize a lime-cement mortar, which consists of 1 part lime to 3 parts sand. Another option is to utilize compo-mortar which consists of 1 part cement, 1 part lime and 6 parts sand. [41]

Finishes

  • The finish used in the 2012 schoolroom project was composed of:
    • 4 parts water
    • 1/4 part lime
    • 4 parts sawdust
    • 3 parts sand
    • 2 parts cement.[42]
    • 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.

Roofing Materials

The roof of the Botica Popular will likely be of zinc sheets, similar to the 2012 schoolhouse project.

Flooring

References

Template:Reflist

Contributors

Holly Johnston, Elisabeth de Jong, Johnny Lococo, Judit Germán,

  1. http://www.presidencia.gob.do/comunicados/promesecal-aplicaci%C3%B3n-decreto-608-12-permite-ahorro-de-1320-millones-de-pesos
  2. http://www.greenspec.co.uk/embodied-energy.php
  3. http://www.dominicanaonline.org/portal/espanol/cpo_clima.asp
  4. http://www.dominicanaonline.org/portal/espanol/cpo_clima.asp
  5. http://www.dominicanaonline.org/portal/espanol/cpo_clima1.asp
  6. http://www.dominicanaonline.org/portal/espanol/cpo_clima3.asp
  7. Sr. Vasquez, owner of block-making company
  8. Uhler, Frank G. "Mortar and cement compositions." U.S. Patent No. 2,437,842. 16 Mar. 1948. http://www.google.com.do/patents/US2437842?printsec=abstract&dq=making+lime+plaster#v=onepage&q=making%20lime%20plaster&f=false
  9. Case, Gerald Otley. "Plaster and the like." U.S. Patent No. 2,016,986. 8 Oct. 1935. http://www.google.com.do/patents/US2016986?dq=making+lime+plaster
  10. http://www.traditionalandsustainable.com/TSB/Lime_Putty_files/Lime_Use_Guide-2.pdf
  11. http://www.traditionalandsustainable.com/TSB/Lime_Putty_files/Lime_Use_Guide-2.pdf
  12. Koski, John A. "How Concrete Block Are Made." Masonry Construction, October 1992, pp.374-377. http://www.madehow.com/Volume-3/Concrete-Block.html#ixzz2WDovZcR6
  13. interview with Jacob, 6/7/13, interviewed by: Holly Johnston, John Lococo, Elisabeth de Jong
  14. http://livinginpaper.com/
  15. http://www.appropedia.org/Las_Malvinas_ecoladrillo_schoolroom_2012#Papercrete
  16. http://www.masongreenstar.com/sites/default/files/Research_Report_Thermal_17p.pdf
  17. http://www.livinginpaper.com/tests.htm
  18. http://www.livinginpaper.com/mixes.htm
  19. http://www.papercrete.com/papercrete.html
  20. Davis, Gray, et al. "Feasibility Study on the Expanded Use of Agricultural and Forest Waste in Commercial Products."
  21. http://www.bmp.su/
  22. http://www.scribd.com/doc/40318020/New-Chips-on-the-Block . 1/1/00. Ken Roseboro.
  23. http://digest-1.blogspot.com/2011/05/how-to-make-wall-with-good.html
  24. Sauna: a Complete Guide to the Construction, Use and Benefits of the Finnish Bath by Rob Roy. 2004. Chelsea Group Publishing
  25. http://cms.zwergfledermaus.de/wp-content/uploads/2011/04/BatCaves-recipe.pdf
  26. http://www.rainforestinfo.org.au/good_wood/sawment.htm . Sawdust sand and Cement. By Russell Andrews. The NSW Good Wood Guide
  27. 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.
  28. Olivier, Paul A. "The rice hull house." The Last Straw 25 (2010). naturalhomes.org/img/ricehullhouse.pdf
  29. Davis, Gray, et al. "Feasibility Study on the Expanded Use of Agricultural and Forest Waste in Commercial Products."
  30. esrla.com/pdf/ricehullhouse.pdf
  31. 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.
  32. Rice, Vol 2: Utilization. Editor:Bor S. Luh
  33. Mishra, Sudisht. Dr. SV Deodhar. Effect of Rice Husk Ash on Cement Mortar and Concrete NBM Media. October, 2010. http://www.nbmcw.com/articles/concrete/18708-effect-of-rice-husk-ash-on-cement-mortar-and-concrete.html
  34. Tashima, Mauro M. Carlos A R Da Silva. Jorge L Akasaki. Michele Beniti Barbosa. The Possibility of Adding the Rice Husk Ash (RHA) to the Concrete. http://congress.cimne.upc.es/rilem04/admin/files/filepaper/p282.pdf
  35. http://cvbt-web.org/?q=Rice-Husk-Ash-Cement
  36. Tashima, Mauro M. Carlos A R Da Silva. Jorge L Akasaki. Michele Beniti Barbosa. The Possibility of Adding the Rice Husk Ash (RHA) to the Concrete. http://congress.cimne.upc.es/rilem04/admin/files/filepaper/p282.pdf
  37. Mishra, Sudisht. Dr. SV Deodhar. Effect of Rice Husk Ash on Cement Mortar and Concrete NBM Media. October, 2010. http://www.nbmcw.com/articles/concrete/18708-effect-of-rice-husk-ash-on-cement-mortar-and-concrete.html
  38. Mishra, Sudisht. Dr. SV Deodhar. Effect of Rice Husk Ash on Cement Mortar and Concrete NBM Media. October, 2010. http://www.nbmcw.com/articles/concrete/18708-effect-of-rice-husk-ash-on-cement-mortar-and-concrete.html
  39. Elpel, Thomas J. Living Homes, Integrated Design and Construction 5th ed. p 114. Google Books.
  40. Bdeir, Layla Muhsan Hasan. Study Some Mechanical Properties of Mortar with Sawdust as a Partially Replacement of Sand." Anbar Journal for Engineering Sciences. 3/4/12. http://www.iasj.net/iasj?func=fulltext&aId=41133
  41. http://www.fao.org/docrep/s1250e/s1250e09.htm
  42. http://www.appropedia.org/Las_Malvinas_ecoladrillo_schoolroom_2012
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