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RESEARCH ON BUILDING TECHNIQUES AND MATERIALS IN INDIA

P. L. DE Q)

A survey of recent achievements at the Central Building Research Institute, Roorkee, India.

In India there is an urgent need for research for the development of new and improved building materials and construction techniques which aim at increasing productivity and reducing cost in the building indus- try. The Central Building Research Institute (C.B. R.I.) of India is doing pioneering work in this direction and the results of researches carried out there have great potentialities in reducing cost and improving efficiency and productivity of buildings. Some of these researches are highlighted in this article.

BUILDING TECHNIQUES

An economic and efficient foundation design depends on a proper knowledge of the site conditions and soil properties. The C.B.R.I. has developed several improved and economical techniques of site investi- gation which have been successfully applied in solving a number of foundation problems. Special mention may be made of deep subsoil exploration and sampling by use of bentonite slurry. The process is simple and fast and the equipment required is inexpensive. The method avoids use of casing pipes and is speedy. For obtaining undisturbed soil samples a simple device has been used which ensures continuous pene- tration. The sampler opens by rotating the drill rod only at the desired depth. I t has been successfully used for recovering undisturbed soil samples from depths upto 80 metres from sandy river bed at a bridge site.

(1) Scientist-Coordinator, Central Building Research Institute, Roorkee, India.

Another foundation problem solved through the efforts of research is foundation in black cotton soil which was hitherto posing a serious problem due to the expansive nature of the soil. Structures built on such soils often crack due to differential movement caused by alternate swelling and shrinkage of the soil. Conventional trench foundations are costly besides being inefficient in preventing such cracks. The technique of under-reamed pile foundations developed by the Institute has proved both economical and efficient. These are short bored concrete piles having a large bulb at the bottom. More than 20,000 buil- dings have been constructed uptodate on such foun- dations and an economy of 25 to 40 per cent in the foundation cost has been reported. The scope of under-reamed piles has been extended to sandy soils and filledup grounds. For heavier loads the use of multi-under-reamed piles has been advocated. The increase in bearing capacity of such piles is mostly due to the increased friction and it has been indicated that their load settlement behaviour is considerably improved as compared to uniform large diameter piles. Suitable techniques have also been developed for the construction of under-reamed piles under water table.

Prefabricated Components

Precast concrete door and window frames have been developed which are economical compared to timber frames besides being resistant to decay and white ant attack. Several low cost precast roofing units such as doubly curved tiles, precast cellular

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units, cored concrete, etc., have been developed and successfully used in buildings.

Prefabrication in building effects increase in pro- ductivity and may ultimately lead to economy. Joints offer special problem in prefabrication and as such special attention has been given to the deve- lopment of suitable joints. Work is also in progress on battery casting of prefabricated components and the problems associated with them. A prototype two-roomed house has been constructed with such battery-cast prefabricated components.

Building Services

The normal drainage system for a house as per existing practice in India involves the use of two main waste pipes, the soil stack taking the discharge from the W. C. and another pipe taking the waste from the bath and the wash basins. In this system, vent pipes are fitted to prevent the unsealing of the traps of various appliances. I t has been shown that these vent pipes are often unnecessary and a single stack system where all appliances inclusive of W.C. dis- charge into one stack and the traps are unventilated, can be safely used. This single stack system has been successfully tried in several muhistoreyed buil- dings and recommendations have been made to the Indian Standards Institution for revision of code in this respect. Improved " Dual acting " flushing systems have been developed for the conservation of water which is a problem in big cities in India.

Mechanization

At present most of the building operations in India are manual whereas application of simple mecha- nization in some selected operations could lead to economy in addition to increased productivity. A tamping machine, developed at the C.B.R.I., has been found to be efficient and economical for tamping lime concrete on roof. A double deck metal scaffolding developed at the Institute finds use in single storey buildings and leads to saving both in time and cost of construction of walling. A power trowel has been developed for efficient and economic finishing of large floors.

Functional Efficiency in Buildings

Studies on " Functional Efficiency " in buildings, which have provided data for thermal design, venti- lation, climatological effects on buildings, economic daylighting of factories and muhistorey buildings, acoustic design of auditoria and economic design of noise reduction have helped the Indian building industry in developing indigenous materials and techniques for achieving functional efficiency.

BUILDING MATERIALS

Bricks and Tiles

Bricks being the most widely used building material in India, any economy in the production of bricks will have considerable impact on the building industry. There are two direct approaches towards cost reduc- tion in brick production, viz. mechanization of the

brick making process and improvement of the effi- ciency of brick kilns. Since complete mechanization involves considerable capital investment and foreign exchange, a semi-mechanized process of brick making using indigenously available machineries with suitable modifications should be preferable for small and medium scale brick industries in India. With this in view a brick making machine having a capacity of producing 3,000 bricks per hour has been developed. Improved designs for brick kilns have also been developed.

One big problem with the brick industry in India is the non-availability of suitable soil in many regions of the country. Hence intensive research is being carried out to find ways and means of rendering naturally unsuitable soils suitable for brick making without incurring appreciable extra expenses. An improved technique of production of good bricks from black cotton soils (montmorillonitic clay) deserves special mention. By utilizing the process, which mainly consists of blending the clay with 20 to 30 per cent powdered ' grog ' (clay lumps burnt at about 600 ~ it has been possible to produce better quality of bricks.

Another interesting type of brick is the sand- lime brick which is expected to have good prospects in certain locations, such as Rajasthan, where clays are generally not available and sands or sandy soils are widely distributed. Researches carried out at C.B.R.I. have shown that suitable sand-lime bricks could be produced from the desert sand of Rajasthan.

Results of research could bring benefit to the tile industry also. Cracking and warping of green tiles during drying is one of the major problems facing the tile industry in India. A process developed at the Institute, which consists in mixing raw clay with a small amount of ammonium chloride, has been found to be effective in reducing the losses to a considerable extent.

Cement

The increased demand for cement against limited supply prompted the Institute to investigate the possibilities of increasing the productivity of cement by pozzolanie substitution or by use of substitute raw materials. Investigations have shown that fly ash produced as an industrial waste from thermal power stations can safely replace upto 20 per cent by weight of normal portland cement.

Portland blast furnace cement is another ma- terial whose production has already started in India. Investigations carried out at C.B.R.L have shown that even slag containing high alumina, low CaO/SiO~ ratio and high manganese oxide can be used upto 33 per cent by weight in making portland blast furnace cement.

Lightweight concrete

The Institute has successfully produced light- weight aggregates from industrial wastes like flyash, blast furnace slag, silt deposit of water works and certain suitable natural clay deposits. These can be used for in situ construction, making masonry blocks and precast structural members. Extensive surveys have been conducted for the location of suitable clay deposits from which lightweight bloated clay aggregate could be produced.

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Asbestos- Cement

The asbestos-cement industry in India, at present, uses most ly imported chrysotile asbestos. The Indian deposit of amphibole variety, though available in plenty, could not be used in a - c products on account of certain deficiencies in their property. A new process for improving the s trength of asbestos-cement products has been developed which aims at using Ind ian amphibole asbestos as a par t replacement of the imported chrysotile variety. The process is adaptable to the existing industrial installations and will effect economy and saving in foreign exchange through replacement of imported chrysotites by cheaper indigenous amphiboles.

Magnesium oxyehloride cement

Magnesium oxychloride cement is used in India as i n s i t u flooring material mainly for rai lway carriage floors and also hospitals, offices, factories, etc. The chief source of magnesium oxide required for the manufac ture of oxychloride cement is magnesite mineral which is ra ther costly. C.B.R.I. has deve- loped a method of subst i tut ing for magnesite the cheaper raw material dolomite. A process for making terrazzo flooring tiles f rom magnesium oxychloride cement using magnesite or do]omite as the raw materials has also been developed.

Gypsum-based building materials

One of the ways of effecting economy in the use of Cement in building is to use low grade gypsum for making plaster, plaster boards and building blocks at such places where gypsum is available in large quan- tities at low cost. C.B.R.I. has used Bikaner gypsum of 70 to 75 per cent pur i ty in investigations for deve- loping plaster boards, hollow blocks and foamed blocks for par t i t ion walls.

Building lime from sugar press mud

Sugar press mud (lime sludge), a waste material, can be a good source for making building lime. The mud, part icular ly from carbonation process sugar mills, is 90 to 95 per cent calcium carbonate. About one million ton of it is thrown out every year as a waste material around various sugar mills in India. Work done at C.B.R.I. has shown tha t this press mud, after calcination in the form of briquettes, makes good building lime conforming to Indian Standard Specifications.

Building materials f rom coconut wastes

Wood and other types of particle boards are finding increasing use in the building materials industry. Coconut husk is one of the materials which could find use for this purpose. Work at C.B.R.I. has shown tha t coconut husk board can be prepared from mature husks using only 0.5 per cent paraformaldehyde resin as against 6 to 9 per cent adhesive used for boards made from wood or bagasse. Since the major port ion of the cost of a particle board is the cost of the adhe- sive, the cost of coconut husk particle board is expected

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to be low. The boards produced in the laboratory have been tested and found to have adequate strength, stability, thermal insulation and fire resistance.

C.B.R.I. has developed an expansion joint filler based on cashewnut shell liquid, aldehyde resin and coconut pith, a waste product of the coir industry. A fire-resistant lightweight building board, suitable for insulation as well as for use as an expansion joint filler has also been produced from unret ted coconut husk pith by a simple process of felting it with a fibrous material like wood fibre or banana stem fibre.

Coconut pith can also be used to produce light- weight concrete for thermal insulation of roof. The process is simple requiring only the intermixing of pi th and cement with requisite quant i ty of water and laying it on the roof. They may be mixed in various proport ion to produce lightweight concrete for thermal insulation of various degrees.

Cement Paint

The incidence of organic growth such as algae, mould and lichen on external walls finished with cement paints is very common in India. To over- come this drawback, a project was taken up on the development of paint formulations suitable for tro- pical climates. Based on these investigations a new cement paint formulation has been developed which has given sat isfactory service in preventing such organic growth on external walls. The process has been licensed to the industry for commercial manu- facture.

Technical Aid to Industry

Besides developmental works on new materials and techniques the Inst i tute is rendering considerable aid to the building industry by way of consultation services, training, testing of materials, site investi- gation works and information and advice on various building problems. The Ins t i tu te prepares short notes summarizing information on selected building techniques and materials f rom the results of research carried out for the use of practising engineers and architects. These are widely distributed under the titles " Building Digests " and "' BuUding Material Notes ". So far some 90 topics have been covered. These have created considerable interest amongst engineers, architects and the builders. The Ins t i tu te maintains a close liaison with the indust ry and renders technical assistance in utilization of new materials and techniques developed by it.

CONCLUDING REMARKS

Short notes on some selected new building techni- ques and materials recently developed at the Central Building Research Inst i tute have been presented in this article. Besides these, several other techniques and materials have been developed or are in the process of development. Technical information on these materials can be had from various publications of the Insti tute. The technical know-how for the product ion of several of these materials has been licensed to the industry for commercial production.

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