Green Materials for Low Cost Construction
There are a variety of components required in building construction such as bricks, cement, aggregates, steel, aluminium, coatings, wood, cladding materials among many others. The demand for building materials for construction is continuously rising with the increasing need of houses both in rural and urban areas. In the rural areas, the problem is worse due to decreasing access to traditional materials such as timber, bamboo and thatch which mostly form part of bio-mass.
One of the ways to overcome the problem is to use agro-industrial by-products and wastes for the production of reconstituted wood products. Efforts have been made in India and abroad in this direction, which have resulted into setting up of some commercial units for the production of particle and fibre boards. However, looking at the quantum of by-products and wastes produced in the country (due to revolution in the agriculture sector), their utilization for making value-added products remains insignificant.
However, there is a renewed interest in products that are biodegradable, recyclable, and cost effective with a long-term guaranteed supply of resources. In the case of agro-based composites, these resources include fibre, labour, water, energy, and processing equipment. Some of the new alternative materials are manufactured using wastes such as fly ash, agricultural and industrial wastes and down streams of process industries. The resultant building material is also sustainable as it has minimal impact on the natural resources. For example, reconstituted wood, fibre composites in inorganic and polymer matrices, MDF boards and polymer sheets are increasingly being used in buildings.
Likewise, cement bonded fibre reinforced boards are gaining momentum in the area of doors, windows, cladding, partitioning, false ceiling applications in buildings. The new materials have many advantages like better functional efficiency, cost effectiveness, better durability and ease of construction. Moreover, these less energy intensive materials have minimum defects, produce minimum waste and need less maintenance.
Alternative Eco-Friendly Materials
Coir – CNSL (Cashew Nut Shell Liquid) Board
Coir-CNSL Board is a wood alternative which can be used for surfacing, door and window shutters, partitioning, false ceiling, panelling, furniture, cabinets and packaging. It is a single layer flat pressed class Medium Density Fiber (MDF) Board. It has low water absorption, negligible change in dimensions due to water absorption, workable with normal wood working tools, paintable, pre-laminable, nailable and screwable. The board can replace wood or re-constituted wood by 100%. Salient features of Coir-CNSL Board are:
- Both the constituent materials i.e. coconut fibre and cashew nut shell liquid are available substantially in coastal areas and are renewable agro-wastes
- Technology is developed at pilot level and ready for transfer
- Technology is techno-economically viable as per pre-estimates
- The estimated cost of the board is around 30% cheaper in comparison to commercially available similar products such as MDF board, plywood, and block board
Bagasse-Cement Boards and Panels
The developed product and process utilizes sugar cane bagasse and ordinary Portland cement. The physico-mechanical behaviour of the developed board passes most of the requirements of general purposes high density board and is cost effective too.
Arhar-stalk-Cement Boards and Panels
Composite panels developed using fibrous biomass such as Arhar Stalks meet the requirements of ISO (International Organization for Standardization) and BIS (Bureau of Indian Standards) specifications. The product helps in conserving wood in construction industry and can easily be made in rural regions which can facilitate low cost housing in these areas.
Lightweight Sandwich Panels
The cellulosic refuse of paper industries are rich in small fibres. These can be used to make value added product that can be utilized for acoustics and thermal insulation purposes in buildings. These developed panels have their end applications in partitioning, panelling and false ceiling with its unique aesthetics. The estimated economic viable capacity is two tones per day and most suitable for paper industries as a downstream process. Panels with different surface textures can be produced.
Rigid PVC Foamed and Un-foamed Boards
Variety of products made up of PVC are available commercially for use in building construction such as pipe, sanitary wares, tiles, electric switches, and wires. Another product made out of PVC is board, which is a wood alternative. The product and technology have been developed using PVC scrap. Work emphasis has been given to keep the dependency on imported equipment and chemicals to minimum, resulting in lower product cost.
The sugar cane bagasse is used to make the building boards using PVC as the binder. PVC is the most widely used resin in different building products like door shutters, pipes and cables due to its inherent self extinguishing characteristic and lowest cost.
Coir-CNSL Thermal Insulation Board
The board is a composite material which utilises coconut fibres as re-enforcing material and CNSL as the natural binder. The density of the board is kept low around 350-450 kg/m3. The product can be given suitable shape to be fitted with the surface to be insulated. The thermal conductivity is 0.0745 kcal/hr.m2.°C. The developed material is suitable for moderate temperature insulation purposes such as ceiling insulation, insulation of air-conditioned built spaces, industrial instruments like heat exchangers, water coolers and fluid supply systems.
The product is cost effective and eco-friendly and its commercial use in construction can help in green building construction.
Causes of poor acceptability of innovative materials
- Lack of knowledge about new materials
- Non-inclusion in various National codes and Specifications
- In-appropriate environment for research and development
- Non-availability of proper forum for promoting new materials
- Ineffective and improper publicity
- Unawareness among users
- Poor competition among new material manufacturers
- Higher price structure of new materials
- Lower emphasis on research on eco-friendly materials
- Negative attitude of engineers/ architects toward non-scheduled items
- Lower confidence on quality
- Negligible technological thrust for wider acceptance and adoption
However, a positive role by government agencies, leading engineers and technologists, end users and entrepreneurs can bring sustainable development process in the construction industry. There is a strong need to put in organised efforts in the direction of developing newer eco-friendly materials to replace conventional materials. As building materials account for 65-75% of the total cost of construction, alternative materials will help reduce the cost of building structure.S.P Agrawal Chief Scientist & Coordinator Organic Building Materials Central Building Research Institute, Roorkee
Source: Science Tech Entrepreneur – Magazine of National Science and Technology Entrepreneurship Development Board (NSTEDB)