S GOPIKRISHNA WARRIER

IN 1976, the biogas lab of the Centre for the Application of Science and Technology to Rural Areas (ASTRA) was constructed on the Indian Institute of Science (IIS) campus in Bangalore with unique building blocks. They were not conventional kiln-fired bricks but stabilised mud blocks. Fourteen years and three machine-designs later, about 100 buildings had been completed, using mud blocks stabilised with a small quantity of cement.

Amulya Reddy, an ASTRA founding father seeking to develop a technology for rural areas, bought a Cinvaram, an early block-making machinedeveloped by a Latin American engineer in 1956. It was modified and renamed ASTRAM, but the model soon became obsolete. The present model is called Itge Voth (brick press, in Kannada).

The Itge Voth's operations are easy and can be mastered by semi-skilled and unskilled workers in only a few hours. As it weighs just 160 kg it can be transported easily to construction sites. Blocks moulded using a mixture of soil, cement and a small amount of water. The concentration of cement in the mixture can vary between 3.5 per cent and 7 per cent, depending on the quality of the soil. Just enough water is added to hold the mixture together. Two standard moulds are used in this process: one measuring 30.5 x 14.3 x 10 cm and the other 23 x 19 x 10 cm. But moulds can be made to size, as for example, the four used by Madras Fertilizers Ltd (MFL) in the construction of 90 houses in Manali.

After moulding the blocks are stacked and cured by sprinkling water on them for a week. They are then ready for use. In MFL projects which ASTRA K S Jagdish rates as the best example of a systematic large-scale operation using mud blocks, tests showed that seven days of curing is sufficient for the blocks to become strong enough for use in a two-storey building. At Manali, MFL is using a 7 per cent cement mix and the strength of the blocks is around 25 kg per sq cm, which is enough to construct a three-storey building.

Because the blocks are not kiln-fired there is an immediate saving of fuel energy of upto 70 per cent in the case of mud blocks. The total cost of a mud block is between Rs 1.65 and 1.95, depending on the construction site. As the mud block is 2.5 times the size of a conventional brick, its cost equivalent works out to 65 to 75 paise. The cost of a burnt brick is rarely less than one rupee. Says R Singaravely, MFL project manager, "We have saved over Rs 10 lakh in constructing these 90 houses."

The machine, which costs about Rs 9,000, also generates emplolment. On an average it can produce one lakh blocks before it needs refitting and during this period, seven labourers can get work.