The world timber
demand is increasing at a rapid rate but the timber supply is depleting. It’s
been found through research that bamboo can suitably replace timber
and other materials in construction and other works. Industrially
treated bamboo has shown great potential for production of
composite materials and components which are cost-effective and can
be successfully utilized for structural and
non-structural applications in construction. Bamboo is one
of the oldest traditional building materials used by mankind.
The bamboo culm,
or stem, has been made into an extended diversity of products ranging from
domestic household products to
industrial applications. Examples of bamboo products are
food containers, handicrafts, toys, furniture, flooring, pulp and paper, boats,
charcoal, musical instruments and weapons. Bamboo is quite
common for bridges, scaffolding and housing, but it is usually used as a
temporary exterior structural material. In many overly populated regions of the
tropics, certain bamboos supply the one suitable material that is
sufficiently cheap and plentiful to meet the extensive need for economical
housing. It has been used in bicycles, windmills, scales etc. Its uses are
broad and plentiful.
With the
advancement of science and technology and the tight supply of timber, new
methods are needed for the processing of bamboo to make it more
durable and more usable in terms of building materials. Studies have been
carried out on the basic properties and on processing of bamboo into
various kinds of composite products. Bamboo has several unique
advantages like ability to grow fast with a high yield and also it matures
quickly. Additionally, bamboo can be grown abundantly and that too at
a lower cost which makes it more economical.
Processing
of Bamboo and Treatment of Bamboo:
It has been found
that bamboo panel composites have great potential due to their better
strength, dimensional stability and other characteristics.
Main characteristic features, which make bamboo as a
potential building material, are its high tensile strength and very good weight
to strength ratio. It can be easily worked upon by simple tools and machines.
The strength-weight ratio of bamboo also supports its use
as a highly resilient material against forces created by high velocity winds
and earthquakes. Above all bamboo is renewable raw material resource
from agro-forestry and if properly treated and industrially processed,
components made by bamboo can have a reasonable life of 30 to 40
years. Though natural durability of bamboo varies according to
species and the types of treatments, varied uses and applications in
building construction have established bamboo as an
environment-friendly, energy-efficient and cost-effective construction
material.
Through several technologies mat
based composites from bamboo have been developed like Bamboo Mat
Board (BMB), Bamboo Mat Veneer Composite (BMVC)
and Bamboo Mat Corrugated Sheets (BMCS).
The mat composites
are manufactured by hot pressing the woven strips of bamboo. Thin bamboo strips
called as “slivers” of width 0.6 to 1.0mm are manually woven into a mat of
different sizes and patterns of which herringbone is the most common pattern in
which the slivers are at an angle of 450 with respect to the
edges of the mat. Then the mats are dipped in Phenol formaldehyde resin which
is a chemical preservative to enhance resistance against decay and termites,
later they are dried and 2 to 5 mats are assembled and hot pressed to
the required thickness.
For BMVC mats wood
veneers are placed in-between the layers of bamboo mats. The property
of BMVC mainly depends on the properties of the inter-leaved wood
veneers.
Preservation and
Treatment
As bamboo has
less natural durability it requires chemical treatment for longer life.
Bamboos have low natural durability (1 to 3 years) against attacks by
fungi and insects. They are very difficult to be treated by normal preservative
methods in dry condition since their outer and to some extent inner membranes
are impermeable to liquids. The treatment of bamboo is, therefore,
best carried out in green conditions. The following are methods used
for bamboo preservation as per IS 401-2001- “code of practice for
timber preservation” and IS 9096-1979- “code for practice for preservation
of bamboo for structural purposes”:
Bamboo as
Construction Material:
Through research it
has been found that some species of bamboo have ultimate tensile
strength same as that of mild steel at yield point and this coupled with other
merits boosts the usage of bamboo as construction material.
Bamboo is a
versatile material because of its high strength-to-weight ratio, easy
workability and availability. Bamboo needs to be chemically treated
due to their low natural durability. It can be used in different ways for roof
structure as purlins, rafters and reapers, for flooring, doors and windows,
walling, ceiling, man-hole covers etc.
Bamboo Trusses:
The bamboo has strength
comparable to that of teak and sal. An experiment with the construction and
testing of a 4m span truss made of round bamboo and different
jointing techniques for web-chord connections gave results that were matching
with the strength of timber.
Bamboo Roofs
Skeleton:
It consists of bamboo truss
or rafters over which solid bamboo purlins are laid and lashed to the
rafter by means of G.I. wire. A mesh of halved bamboo is made and is
lashed to the purlins to cover the roof.
Bamboo walling/ceiling:
As the bamboo material is
light in weight it is more advantageous in earthquake prone areas as its
chances of falling are very less and even if it falls it can be re-erected
easily with less human and property loss with least efforts and minimum
cost. Bamboo walls can be constructed in different modes like
· Whole
stem, halved or strips of bamboo can nailed to one or both the sides
of the bamboo frame
· Split bamboo mats
can be fastened to the bamboo posts or mats can be woven, mud can
also be applied to both sides of such mats
· Bamboo strips
nailed to bamboo frame or posts for interior walling
· Cement
or lime plastering can be done on the mud covering for better appearance and
hygiene.
It has been found that the bamboo in
the vertical position is more durable than in horizontal direction. For
partition walls only single layer of bamboo strips are used.
Bamboo
Doors and Windows:
Bamboo frames can replace timber
frames appropriate to function. Bamboo mat shutters fixed to bamboo frame or a
panel of bamboo board fixed to the frame which is hinged to the wall can be
used as door. Small framed openings hinged to the top in the wall can serve as
windows.
Bamboo
Flooring:
Bamboo can be used as flooring
material due to its better wear and tear resistance and its resilience
properties. Whole culms act as frame work and the floor covering is done using
split bamboo, bamboo boards, mats etc by means of wire lashing these to the
frame.
Reed
Boards:
Reed boards are made by flat pressing
the reed at high temperatures. These reed boards are used in elements like
flooring, walls, ceiling and roofing. They can also be used for partitions,
doors, windows etc.
Scaffolding:
Bamboo poles lashed together have
been used as scaffolding in high rise structures due to their strength and
resilience. The timber planks can be replaced with bamboo culms and these can
be lashed to the vertical
Conclusion:
Scientific studies
have shown that Bamboo can satisfy the various structural requirements and also
due to its technical performance Bamboo can be used as a construction material
for various structural components. The important advantages which make Bamboo a
more suitable material are:
· It
is economical and helps achieve cost effective construction.
· Bamboo
is a fast growing species and it is a renewable resource which can be
cultivated in most types of soil.
· The
designs of the components being simple, there is no need of highly skilled
labour.
· The
dependency on the natural forests for wood will be reduced thus contributing to
the protection of the environment.
· As
it can grow in many types of soil, bamboo cultivation is suitable for
rehabilitation of degraded forests and other waste lands thus converting them
into fertile lands to some extent.
· Creation
of employment opportunities especially for the rural people as the Bamboo mats
have to be manually woven before making them into Bamboo Mat Boards, Bamboo Mat
Veneer Composites and Bamboo Mat Corrugated Sheets.
· Thus
due to all the above aspects there will be overall welfare of the society,
particularly of the economically weaker section.
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