• Researchers in Gibson's lab have collected bamboo samples of various thicknesses to analyze bamboo's microstructure. 

    Researchers in Gibson's lab have collected bamboo samples of various thicknesses to analyze bamboo's microstructure. 

    Photo: Jennifer Chu/MIT

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  • This images shows a vascular bundle. You can see it is made up of the vessels (large dark holes, empty looking) and supporting fibers (somewhat dark very solid looking regions). The parenchyma (light circular cells) surround the vascular bundle (vascular bundle refers to the overall clover shaped structure).

    This images shows a vascular bundle. You can see it is made up of the vessels (large dark holes, empty looking) and supporting fibers (somewhat dark very solid looking regions). The parenchyma (light circular cells) surround the vascular bundle (vascular bundle refers to the overall clover shaped structure).

    Courtesy of the researchers

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Building up bamboo

MIT researchers study bamboo for engineered building material, similar to plywood. Watch Video


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Bamboo construction has traditionally been rather straightforward: Entire stalks are used to create latticed edifices, or woven in strips to form wall-sized screens. The effect can be stunning, and also practical in parts of the world where bamboo thrives.

But there are limitations to building with bamboo. The hardy grass is vulnerable to insects, and building with stalks — essentially hollow cylinders — limits the shape of individual building components, as well as the durability of the building itself.

MIT scientists, along with architects and wood processors from England and Canada, are looking for ways to turn bamboo into a construction material more akin to wood composites, like plywood. The idea is that a stalk, or culm, can be sliced into smaller pieces, which can then be bonded together to form sturdy blocks — much like conventional wood composites. A structural product of this sort could be used to construct more resilient buildings — particularly in places like China, India, and Brazil, where bamboo is abundant.

Such bamboo products are currently being developed by several companies. The MIT project intends to gain a better understanding of these materials, so that bamboo can be more effectively used structurally. To that end, MIT researchers have now analyzed the microstructure of bamboo and found that the plant is stronger and denser than North American softwoods like pine, fir, and spruce, making the grass a promising resource for composite materials.

“Bamboo grows extensively in regions where there are rapidly developing economies, so it’s an alternative building material to concrete and steel,” says Lorna Gibson, the Matoula S. Salapatas Professor of Materials Science and Engineering at MIT. “You probably wouldn’t make a skyscraper out of bamboo, but certainly smaller structures like houses and low-rise buildings.” 

Gibson and her colleagues analyzed sections of bamboo from the inside out, measuring the stiffness of each section at the microscale. As it turns out, bamboo is densest near its outer walls. The researchers used their data to develop a model that predicts the strength of a given section of bamboo.

The model may help wood processors determine how to assemble a particular bamboo product. As Gibson explains it, one section of bamboo may be more suitable for a given product than another: “If you wanted a bamboo beam that bends, maybe you’d want to put the denser material at the top and bottom and the less dense bits toward the middle, as the stresses in the beam are larger at the top and bottom and smaller in the middle. We’re looking at how we might optimize the selection of bamboo materials in the structure that you make.”

Gibson and her colleagues have published their results in the Journal of the Royal Society: Interface. 

Lorna Gibson, an MIT professor of materials science and engineering, explains her group's research into using bamboo as a building material.

Video: Melanie Gonick/MIT

A look at bamboo, from the inside out

For their experiments, the researchers analyzed specimens of moso, the main species of bamboo used in China. Like most types of bamboo, moso grows as hollow, cylindrical stalks, or culms, segmented by nodes along the length of a stalk. Bamboo can reach heights of 20 meters — as tall as a six-story building — in just a few months. The stalks then take another few years to mature — but still much faster than a pine tree’s statelier, decades-long growth.

“One of the impressive things is how fast bamboo grows,” Gibson notes. “If you planted a pine forest versus a bamboo forest, you would find you can grow far more bamboo, and faster.”

Researchers used electron microscopy to obtain images of the bamboo microstructure and create complete, microscale cross-sections of the entire culm wall at different heights along the stalk.

The resulting images showed density gradients of vascular bundles — hollow vessels — that carry fluid up and down the stalk, surrounded by solid fibrous cells. The density of these bundles increases radially outward — a gradient that seems to grow more pronounced at higher positions along a stalk.

The researchers cut sections of bamboo from the inside out, noting each sample’s radial and longitudinal position along a culm, then gauged the stiffness and strength of the samples by performing bending and compression tests. In particular, they performed nanoindentation, which uses a tiny mechanical tip to push down on a sample, to gain an understanding of bamboo’s material properties at a finer scale. From the results of these mechanical tests, Gibson and her colleagues found that in general, bamboo is stiffer and stronger than most North American softwoods commonly used in construction, and also denser.

The researchers then used the stiffness and density data to create a model that accurately predicts the mechanical properties of bamboo as a function of position in the stalk. Gibson says wood processors that she works with in Canada may use the model as a guide to assemble durable bamboo blocks of various shapes and sizes.

Going forward, the processors, in turn, will send the MIT team composite samples of bamboo to characterize. For example, a product may be processed to contain bamboo along with other materials to reduce the density of the product and make it resistant to insects. Such composite materials, Gibson says, will have to be understood at the microscale.

“We want to look at the original mechanical properties of the bamboo culm, as well as how processing affects the product,” Gibson says. “Maybe there’s a way to minimize any effects, and use bamboo in a more versatile way.”

Oliver Frith, acting director of programme for the International Network for Bamboo and Rattan, headquartered in Beijing, says that very few species of bamboo have been classified, and the lack of knowledge of the material’s microstructure has impaired efforts to design efficient, optimal structural products.

“MIT’s work is very timely and has great potential to support development of the sector,” says Frith, who was not involved in the research. “While bamboo has similarities to wood, as this study shows, the material also has very distinct properties. Although current approaches to developing structural engineered bamboo have tended to focus on mimicking engineered wood products, the future will probably lie in innovating new approaches that can better enhance the natural advantages of this unique material.”


Topics: Sustainability, Materials science, Biology, Plants, Architecture, Research, Materials Science and Engineering, School of Engineering

Comments

bamboo products have already been invented.usa needs to start using.I grow Moso.

Excellent.

Bamboo has a long and well-established tradition as a building
material throughout the world’s tropical and sub-tropical regions. It is widely
used for many forms of construction, in particular for housing in rural areas.
Bamboo is a renewable and versatile resource, characterized by high strength
and low weight, and is easily worked using simple tools. It is widely
recognized as one of the most important non-timber forest resources due to the
high socio-economic benefits from bamboo based products. It is estimated that
there are 1200 species growing in about 14.5 million hectares area. Most of
them grow in Asia, Africa and Latin America.

Bamboo is the world’s fastest growing woody plant. It grows approximately 7.5
to 40cm a day, with world record being 1.2m in 24 hours in Japan. Bamboo
grows three times faster than most other species. Commercially important
species of bamboo usually mature in four or five years time, after which
multiple harvests are possible every second year, for upto 120 years in some
species and indefinitely in others. Bamboo also excels in biomass production,
giving 40 tons or more per hectare annually in managed stands. It accounts for
around one-quarter of biomass produced in tropical regions and one-fifth in
subtropical regions.

It has been used successfully to rehabilitate
soil ravage by brick making in India, and abandoned tin-mine sites in Malaysia.
It shelters top soil from the onslaught of tropical downpours, preserves many
exposed areas, providing micro-climate for forest regeneration and watershed
protection It is often introduced into the banks or streams or in other
vulnerable areas, for rapid control of soil erosion; one bamboo plants closely
matted roots can bind upto six cubic meters of soil.

GENERAL
USES

a) Soil stabilization, wind break, urban waste water treatment
and reduction of nitrates contamination

b) Creating a fire line in traditional forests-due to the high
content of silica.

c) Removing atmospheric carbon- bamboo can capture 17 metric
tons of carbon per hectare per year, i.e., effectively than any other species.

d) The shoots are edible.

e) Building and construction.

f) Small scale and cottage industries, for handicrafts and other
products.

g) New generation products as wood substitutes

h) Industrial products

i) Transportation industry- truck bodies, railway carriages etc.

j) Boards and furniture

k) Medicine

l) Paper and pulp industry

m) Long time source of biomass for industry

n) Fuel source- capable of generating 1000-6000 cal/g- for
households and small industries is an age-old, continuing practice.

PROPERTIES

TENSILE STRENGTH

Bamboo is able to resist more tension than compression. The
fibres of bamboo run axial. In the outer zone are highly elastic vascular
bundle, that have a high tensile strenght. The tensile strenght of these fibres
is higher than that of steel, but it’s not possible to construct connections
that can transfer this tensile strength. Slimmer tubes are superior
in this aspect too. Inside the silicated outer skin, axial parallel elastical
fibers with a tensile strength upto 400 N/mm2 can be found. As
a comparison, extremely strong wood fibers can resist a tension upto 50 N /mm2.

COMPRESSIVE STRENGTH

Compared to the bigger tubes, slimmer ones have got, in relation
to their cross-section, a higher compressive strength value. The slimmer tubes
possess better material properties due to the fact that bigger tubes have got a
minor part of the outer skin, which is very resistant in tension. The portion
of lignin inside the culms affects compressive strength, whereas the high
portion of cellulose influences the buckling and the tensile strength as it
represents the building substance of the bamboo fibers.

ELASTIC MODULUS.

The accumulation of highly strong fibers in the outer parts of
the tube wall also work positive in connection with the elastic modulus like it
does for the tension, shear and bending strength. The higher the elastic
modulus, the higher is the quality of the bamboo. Enormous elasticity makes it
a very useful building material in areas with very high risks of earthquakes.

ANISOTROPIC PROPERTIES.

Bamboo is an anisotropic material. Properties in the
longitudinal direction are completely different from those in the transversal
direction. There are cellulose fibers in the longitudinal direction, which is
strong and stiff and in the transverse direction there is lignin, which is soft
and brittle.

SHRINKAGE.

Bamboo shrinks more than wood when it loses water. The canes can
tear apart at the nodes. Bamboo shrinks in a cross section of 10-16 % and a
wall thickness of 15-17 %. Therefore it is necessary to take necessary measures
to prevent water loss when used as a building material.

FIRE RESISTANCE.

The fire resistance is
very good because of the high content of silicate acid. Filled up with water,
it can stand a temperature of 400° C while the water cooks inside.

In some cases Bamboo is used as pipes to run water. In West
Godavari District of Andhra Pradesh, India Bamboo frame just like iron rod
frame is used inside the almirah and plastered on both sides.

Indeed Bamboo is versatile.

Dr.A.Jagadeesh Nellore(AP),India

Very exciting stuff!

They state that it is vulnerable to attack from insects in the article, but then never address how this might be addressed in the future. Would this be less prevalent in a dense ply-wood like (ply-grass... I guess?) product? Or would some sort of treatment have to be applied?

Several pests take advantage of bamboo's hollow tube-like structure, so one would think block of "ply-grass" would be more resistant. However, bamboo (some species more than others) often has a good bit of extractives (organic minor constituents), which can attract and feed bugs.

People says the time of the month in relation with the phase of the moon is very important. Some people burn the outside of any wood this increases the density, seals the exterior faces, and it makes termite and boring insects "believe" the wood is burnt and there is no use going inside.

I don't want to report names of private companies, but -in Japan- people are working on drying processes of bamboo. They want to modify the radial dependency of mechanical properties of bamboo using different cycles of drying. Evolution of humidity in time is a crucial aspect of many "delicate artifacts", e.g. musical instruments. This article reminds me the work of Joseph Nagyvary at Texas A&M University on the construction of the violin.

I am an M.tech student and doing my thesis on the topic "bamboo as soil reinforcement". I find this article really interesting and glad to see people are utilising bamboo in all means. I would like to hear any suggestions or advice one can give on my topic

From the publication:
Bamboo as a Building Material - by F. A. McClure - May 1953
Foreign Agricultural Service - United States Department of Agriculture

In the section:

Bamboo Reinforcement of Concrete - Pg 7 - 11

Published references to the use of bamboo in reinforcing cement concrete structures or parts thereof indicate that the practice has been followed for some decades at least, in the Far East (China, Japan, and the Philippine Islands).
During the 1930's several experiments were carried out in Europe, particularly in Germany and Italy, to test the performance of cement concrete beams reinforced with bamboo.
The most recent, comprehensive, and readily available information on the subject is to be found in the report of a series of experiments carried out by and under the direction of Professor H. E. Glenn.
-------------------------
GLENN H. E. 1950. Bamboo Reinforcement in Portland Cement Concrete. Eng. Expt. Sta., Clemson College, Clemson, South Carolina, Eng. Bull. No. 4.
--------------------------

Two important sections are quoted here in entirety. - F. A. McClure

Summary of Conclusions From Results of Tests on Bamboo Reinforced Concrete Beams

Below is given a summary of the conclusions as indicated from results of tests on the various beams included in this study.

1. Bamboo reinforcement in concrete beams does not prevent the failure of the concrete by cracking at loads materially in excess of those to be expected from an unreinforced member having the same dimensions.

2. Bamboo reinforcement in concrete beams does increase the load capacity of the member at ultimate failure considerably above that to be expected from an unreinforced member having the same dimensions.

3. The load capacity of bamboo reinforced concrete beams increased with increasing percentages of the bamboo reinforcement up to an optimum value.

4. This optimum value occurs when the cross-sectional area of the longitudinal bamboo reinforcement was from three to four percent of the cross-sectional area of the concrete in the member.

5. The load required to cause the failure of concrete beams reinforced with bamboo was from four to five times greater than that required for concrete members having equal dimensions and with no reinforcement.

6. Concrete beams with longitudinal bamboo reinforcement may be designed to carry safely loads from two to three times greater than that expected from concrete members having equal dimensions with no reinforcement.

7. Concrete beams reinforced with unseasoned bamboo show slightly greater load capacities than do equal sections reinforced with seasoned untreated bamboo. This statement was valid so long as the unseasoned bamboo had not dried out and seasoned while encased in the concrete when the load was applied.

8. When unseasoned untreated bamboo was used as the longitudinal reinforcement in concrete members, the dry bamboo swelled due to the absorption of moisture from the wet concrete, and this swelling action often caused longitudinal cracks in the concrete, thereby lowering the load capacity of the members. These swell cracks were more likely to occur in members where the percentage of bamboo reinforcement was high. This tendency was reduced by the use of high early strength concrete.

9. The load capacity of the concrete members reinforced with bamboo vary with the dimensions of the members.

10. The unit stress in the longitudinal bamboo reinforcement in concrete members decreased with increasing percentage of reinforcement.

11. The ultimate tensile strength of the bamboo in bamboo reinforced concrete members was not affected by changes in the cross-sectional area of the members so long as the ratio of breadth to depth was constant but was dependent on the amount of bamboo used for reinforcement.

12. Members having optimum percentage of bamboo reinforcement (between three and four percent) are capable of producing tensile stresses in the bamboo of from 8,000 to 10,000 pounds per square inch.

13. In designing concrete members reinforced with bamboo, a safe tensile stress for the bamboo of from 5,000 to 6,000 pounds per square inch may be used.

14. Concrete members reinforced with seasoned bamboo treated with a brush coat of asphalt emulsion developed greater load capacities than did equal sections in which the bamboo reinforcement was seasoned untreated or unseasoned bamboo.

15. When seasoned bamboo treated with a brush coat of asphalt emulsion was used as the longitudinal reinforcement in concrete members, there was some tendency for the concrete to develop swell cracks, especially when the percentage of bamboo reinforcement was high.

16. Care should be exercised when using asphalt emulsion as a waterproofing agent on seasoned bamboo as an excess of the emulsion on the outer perimeter of the culm might act as a lubricant to materially lesson the bond between the concrete and bamboo.

17. Concrete members reinforced with unseasoned sections of bamboo culms, which had been split along their horizontal axes, appeared to develop greater load capacities than did equal sections in which the reinforcement consisted of unseasoned whole culms.

18. Concrete members reinforced with seasoned sections of bamboo culms, which had been split along their horizontal axes and treated with a brush coat of asphalt emulsion, developed considerably higher load capacities that did equal sections in which the reinforcement was split sections of seasoned untreated bamboo.

19. When split sections of seasoned untreated large diameter culms were used as the reinforcement in a concrete beam, longitudinal cracks appeared in the concrete due to the swelling action of the bamboo. This cracking of the concrete was of sufficient intensity as to virtually destroy the load capacities of the members.

20. When unseasoned bamboo was used as the reinforcement in a concrete member, the bamboo seasoned and shrank over a period of time while encased in the concrete. This seasoning action of the bamboo materially lowered the effective bond between the bamboo and concrete with a lessening of the load capacities of the members.

21. Increasing the strength of the concrete increases the load capacities of concrete members reinforced with bamboo.

22. Concrete members reinforced with seasoned bamboo treated with methylolurea did not develop greater load capacities than did equal sections in which the bamboo reinforcement was seasoned culms treated with a brush coat of asphalt emulsion.

23. The load capacities for concrete members reinforced with unseasoned, seasoned or seasoned and treated bamboo culms, were increased by using split bamboo dowels as the diagonal tension reinforcement along the sections of the beams where the vertical shear was high.

24. The load capacities for concrete members reinforced with unseasoned, seasoned or seasoned and treated split sections of bamboo were increased by the use of a combination of split dowels and the bending up of the upper rows of the split bamboo from the bottom of the beam into the top and covering sections of the beams where the vertical shear is high.

25. Ultimate failure of bamboo reinforced concrete members usually was caused by
diagonal tension failures even though diagonal tension reinforcement was provided.

26. A study on the deflection data for all the beam specimens tested indicated:

(a) That the deflections of the beams when tested followed a fairly accurate straight line variation until the appearance of the first crack in the concrete.

(b) Immediately following the first crack, there was a pronounced flattening of the deflection curve (probably due to local bond slippage) followed by another period of fairly accurate straight line variation, but at a lesser slope, until ultimate failure of the member occurred. This flattening of the deflection curve was more pronounced in the members where the amount of longitudinal bamboo reinforcement was small.

(c) In all cases noted, the deflection curve had a lesser slope after the appearance of the first crack in the concrete, even though high percentages of bamboo reinforcement were used.

27 No pronounced variations were observed when the behavior of bamboo reinforced concrete members under flexure and having "tee" sections was compared with that of equal members having rectangular sections.

28 Bamboo reinforced concrete members under flexure and consisting of "tee" sections were no more effective than were equal rectangular sections, provided the breadth of the stem of the "tee" section was equal to that of the rectangular section and the effective depth of both were the same.

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