Natural Fibre Composites - a new application in bamboo technology
 

Bamboo has a long and well established tradition as a building material

Structural frames for shelters made
out of Bamboo based NFC elements

throughout the world’s tropical and sub tropical world. It is widely used for many forms of construction , specially for housing in rural areas. It is a fast growing, renewable and versatile resource, characterized by high strength and low weight, and is easily worked upon using simple tools. Bamboo constructions are easy to build and with correct details are resilient to wind and earthquake forces with correct details. Yet, the use of bamboo has been largely restricted to temporary structures and lower grade buildings due to limited natural durability, difficulties in jointing, flammability and lack of structural design data.
 

Moulded in different shapes….

Perhaps, one of the biggest advantages of bamboo is the versatility in the forms and the composites it can be used in. It can be used in conjunction with other materials while offering excellent structural properties. One such application is the use of bamboo in Natural Fibre Composites (NFC). Bamboo forms the core material which is encased within resin to give monolithic structural elements. The intermeshing of fibre to resin combination gives a dense matrix of high strength and a relatively light composite material. The bamboo core can be customized to different applications- small bamboo culms, split bamboo, flattened bamboo, bamboo mats,etc. After cutting the bamoo in the required shape and size, it is placed in the mould, similar to laying a reinforcement cage and the resin is poured into the forms to encase it. The resin is mixed with accelerators and hardeners according to specifications to make it ready for use.The demoulding time varies from 40 minutes to 2 hours.


Many applications

By using moulds of different geometries, a series of shapes and sizes for different applications can be achieved. NFC materials can be moulded into sheets, boards, gratings, pellets, frames, trench covers, stair treads etc. Many structural sections can also be fabricated like beams, columns, trusses, purlins and rafters. This makes it possible to use them in prefab housing, cubicles, kiosks, sheds and even geodesic domes and pyramids. They can also be used as a substitute for wood, metal or masonry for partitions, false ceilings, fences, railings and even as flooring roofing and walling tiles.


The use of resin

The use of resin imparts resistance to chemicals like acids and solvents, thermal and electrical resistance and makes the composite water proof, termite proof, rot proof . This makes the product ideal for use in wet environments and other extreme conditions like industries.

A truss of 7 ntre span weighting
around 55 kg.

The material can be potentially very cost effective since a large proportion of the end product comprises of bamboo or other natural fibres or agro based biomass of different varieties. The use of resin is the influencing factor in determining the cost of the material. The percentage of resin in the finished product depends on its shape and size. In smaller and thinner products like gratings and tiles, the proportion of resin can be 50- 60 %, whereas in structural elements like trusses and beams, it can be 25- 30 %. Since, resin is the only industrial product used in the technology, the rationalized use of resin in the elements will not only further bring down the cost of the technology but also make it more environment friendly. q    

Reported by Pankaj Khanna

For more information on the technology

contact Mr. Khare
Shree Bhargav Fibres, Pune
E-mail : sparkonix@vsnl.net

FC Roof Channels manufacturing and marketing
- Experiences in Himachal Pradesh

Subodh Abbhi farmfood@sancharnet.in

We run a precast concrete products unit located in the village Batamandi of Sirmur District in Himachal Pradesh on the banks of the river, 7 km from Paonta Sahib.

Four years ago we started manufacturing ferrocement roof channels with technology and machines sourced from Development Alternatives New Delhi. We used these channels in a roof of our office and have never looked back. Several asbestos cement roofs in our unit were replaced with ferrocement channel roofs. All roofs in our campus are now of ferrocement and cover approximately 5000 sq. ft. area. Several industrial units in the neighbourhood too adopted these ferro roofs in their buildings.

These buildings invite interest from far and near. An army veteran used these for a school he was running in Uttranchal near Dehradun. An industrialist of Yamunanagar adopted the roof channels for a ramp drive leading to the first floor of his house where he installed another ferrocement channel roof for a lawn and the area below for living quarters and storage. A farmer of a village near Nahan constructed his two storied house with roof channels, and walls of interlocking earth bricks. He is a very happy customer who firmly believes that the ferrocement technology made possible a shelter at almost 50 percent of the cost.

Problems

Leakage of water from the joints has been a major factor against the use. Our experience shows that this can be corrected by forming and curing the joint with a layer of Ferro cement and then putting concrete for making the slope. Handling of the roof channels has been a major problem but it need not be so when a person is convinced that the channels are the right option for his roof. It has been convenient to lift the channels from the truck directly on to the roof with the assistance of a crane or chain pulley block fixed on to a vertical steel mast. The farmer from Nahan carried the roof channels by head load for a distance of 2 km for his double storied house as there was no road to his village.

The technology is acceptable to people here but the shape deters most of them. The poor do not adopt it as they probably do not want something which is not approved by the Block office and therefore not subsidised through a government scheme. The block people do not recommend the construction method as they loose on the commissions for the building material used in the subsidized houses.

However, our experience has established this technology as a viable option for economical shelters, without any shortfall, in strength and aesthetics when compared to the conventional RCC slab. q

 

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