Papercrete: An Introduction
What is papercrete?
Papercrete is a structural/ road building material recycling waste with properties that are a mix of wood and concrete.
Familiarity with paper, for most of us, obscures the fact that it is mostly wood fibre. Wood fibre and chips have significant strength, a fact that is daily attested by the wood board and particle board that we use and sit upon. To gain the strength, the wood fibres need to be bonded together by some adhesive. In case of papercrete that adhesive is cement. An alternative glue is lime but which not being considered in these phases as it is not a locally available material in the area of operation.
Look at concrete as an economical admixture of cement and stone aggregate. In concrete replace the stone aggregate with wood fibre (which are available from a wide variety of sources such as old newsprint, magazines, office waste paper, cardboard, corrugated sheets, straw, rice husk etc) and you have papercrete.
Papercrete is also known as fidobe, fibrecrete, padobe etc.It was first patented in USA in 1928 but for next 50 years did not move into mainstream usage. In 1980 two Americans Eric Patterson and Mike McCain independently invented mixers (tow mixers) that allowed papercrete to be made quite easily and started a revival of the material.
Today there are American sites that offer papercrete bricks that have strength equivalent to concrete (3000 psi) In USA old newspapers have no economic use and attract a cost to bury them in garbage disposal heaps. Recycling them as papercrete is a very attractive green option there. In India such newspapers have alternate economic uses and are sold by households at about Rs 7 to Rs 8 a kilogram. Using them in concrete to replace stone aggregate which costs up to Rs 2 per kilogram, prima facie does not appear to make any economic sense. However when stone aggregate is used in concrete, the volume of the final concrete produced is the same as the total volume of individual components of concrete. In papercrete, the wood fibre swells in volume on being soaked in water and it also traps tiny bubbles of air within itself in the process of mixing.
Use of papercrete
Housing, including housing for farm animals, civil construction items used within houses, industrial civil construction and roadswould be more affordable if their material and labour costs are reduced.
At present, costs of conventional materials are high, even though they usually do not include external costs and adverse ecological impact. Further, significant labour effort is involved in moving heavy conventional materials.
Papercrete has the potential to become an alternative, cheaper and superior industrial/structural construction material in multiple uses. Once fully developed, Papercrete would have an all-India scope and impact.
The benefits of papercrete over conventional civil construction material are summarised below:
| Category | Item | Bricks | Papercrete | Concrete |
|---|---|---|---|---|
| Costs | Price | 1 Unit | 70% to 80% of Brick | 150% to 200% of Brick |
| Mortar used | 1 Unit | 40% of Brick | 150% of Brick | |
| Labour effort | 1 Unit | 60% of Brick | 1 Unit | |
| Weight | 1 Unit | 40% to 50% of Brick | 200% to 300 % of Brick | |
| Usability | Plastering need | Rough surface requires plastering | Smooth surface, plastering avoidable | Minimal plastering |
| Size of foundation | 1 Unit | 70% of brick because of lower weight of structure | 150% of Brick | |
| Response to overloading | Cracks | No single point of failure. It compress under load and regains size when load is removed. | Ordinarily very difficult to overload. Cracks when that happens. | |
| Breathablility | Yes if unplastered | Breathable | No | |
| Can it be drilled into? | No | Yes | Very Difficult | |
| Can it be sawed to ensure perfect fit? | No | Yes | No | |
| Environmental | Emits carbon dioxide during manufacture? | Yes | No | No |
| Uses up firewood? | Yes | No | No | |
| Recycles Wood | No | Yes | No |
Recipes
The PDF Report of a Engineering College Students in Philippines on making and testing Papercrete tiles suggests various recipes for papercrete. Table 9 on page 50 and Table 10 on page 51 are worthy of study. Clearly, mixing 10% sand is very useful in achieving compressive strengths. I have extracted some details from Table 9 and sorted the samples according to decreasing compressive strengths.
| Sample | Paper | Cement | Sand | Compressive Strength (MPa) |
|---|---|---|---|---|
| Specimen #1 | 40% | 50% | 10% | 3.45 |
| Specimen #2 | 80% | 20% | 3.06 | |
| Specimen #3 | 50% | 50% | 2.99 | |
| Specimen #4 | 80% | 10% | 10% | 2.81 |
| Specimen #5 | 60% | 30% | 10% | 2.78 |
| Specimen #6 | 70% | 30% | 2.75 | |
| Specimen #7 | 70% | 20% | 10% | 2.25 |
| Specimen #8 | 50% | 40% | 10% | 2.18 |
| Specimen #9 | 60% | 40% | 2.11 |
As expected, the first sample with compressive strength of 3.45 has the highest cement in it. The second sample with very little cement in it and no sand in it is very close to the first sample with compressive strength of 3.06! Between the second and third sample there is very little to choose in terms of compressive strengths of 3.06 and 2.99; yet the second sample is very much cheaper to make! The fourth sample is the cheapest to make but still has very good compressive strength.
Sand can be obtained via rice straw or rice husk, further lowering the cost of papercrete.
| Constituent | Rice straw | Rice husk |
|---|---|---|
| Cellulose | 43% | 35% |
| Hemicellulose | 25% | 25% |
| Lignin | 12% | 20% |
| Crude protein (N x 6.25) | 3-4% | 3% |
| Ash | 16-17% (silica 83%) | 17% (silica 94%) |
Useful Links
- Wikipedia on Papercrete
- Another good introductory site with interviews with Tow mixers pioneers http://www.greenhomebuilding.com/papercrete.htm
- What can be built with Papercrete http://www.evesgarden.org/architecture
- Another look on what can be built with Papercrete. Has photo gallery. http://papercretenm.com/papercrete-structures.htm
- Educational videos and CDs on papercrete http://www.papercrete.com
- Images for papercrete houses
- Geodesic Dome built with papercrete panels http://www.starshipenterprises.net/Papercrete/Workshop/index.html
- How to Mix Papercrete: The Best Two Videos By Judith Williams http://www.youtube.com/watch?v=V3HmCV777cw and http://www.youtube.com/watch?v=rVtff0aZIY0
- PDF Report of a Engineering College Students in Philippines on making and testing Papercrete tiles; Has excellent and extensive bibliography and photos of testing machines. There are very good photographs at pages 67 to 69. Prior to that there is an excellent bibliography and web site listing. ASTM standards are also given. Unfortunately all formulas are given by volume in which paper volumes refer to pulped and drained papercrete volume. So to use the report formulas. We need to start with a given weight of paper, plup it and drain the plup. Then calculate the volume of the drained pulp.
- Very Active Yahoo Group on Papercrete with over 1,000 members http://groups.yahoo.com/group/papercreters/