Development Alternatives (DA) has developed two options of compressed soil blocks to replace the use of kiln-fired bricks and roofing tiles to finish houses. Both have been used in the DA building in the Capital's Qutab Institutional Area, which was built a decade ago. ``Most people are afraid that such technology will not be strong but we have proved that they can be used with little maintenance costs,'' says Aprajita Gogoi, spokesperson of DA.

One of the first alternate technologies developed by DA was the TARA Balram, a manual press for production of compressed soil blocks, marketed by DA's sister organisation, Technology and Action Rural Advancement (TARA). Thecompressed soil blocks are made using the simple, hand-operated Balram machine, which can be used for a variety of applications in walls and roofs.

A team of six persons can easily make 1,200 blocks a day. With inputs of human and sunlight energy and ordinary soil, the compressed blocks provide a cost-effective option for construction.

The production of these blocks is based on the simple principle of densification of raw earth mixed with a stabiliser (cement or lime, in small quantities ranging from 5 to 10 per cent). The production process has three stages: mix preparation, compacting and post-production treatment for wet curing. And of the six persons needed to operate the Balram machine, only one skilled worker is needed, the remaining five are semi-skilled.

The workers can be trained to operate the machine in 10 to 12 days. The block making machine also has the options of different standard sizes and can also be fitted with special moulds to make conduit blocks. DA experts suggest that soil samplesshould be taken from 3 to 4 points of the plot with a minimum of 15 m apart from every acre of the construction site. A minimum of six kgs of sample is required for conducting the tests and if sample blocks are also needed then 16 kgs of soil have to be sent to TARA. TARA charges Rs 750 per sample as testing charges.

The TARA tile maker, DA's other eco-friendly building product, can be used to produce micro-concrete roofing tiles. The micro concrete mix consists of one part cement, two parts graded sand and one part stone grits smaller than 6 mm in size. This mix needs a water cement ratio between 0.45 and 0.5.Using this mix and the TARA tile maker, a labour force of four persons can produced up to 200 tiles per day.

The tile maker uses consistent vibro-compaction at controlled frequencies to make the tiles. The production process is principally the same as for all screeding machines: clamping down a plastic sheet with a screeding frame, placing measured amount of mortar on the screeding surface,spreading it out under vibration, smoothening the surface, lifting the screeding frame, removing the plastic sheet with the screeding mortar and placing it on a high impact polystrene mould for setting.

TARA already has an impressive list of clients for its environment systems branch including multinational agencies, international institutions, government agencies, academic insti- tutions and corporate clients. The corporate clients include Confederation of Indian Industry, Tata Chemicals, Shriram Industrial Enterprises Limited, Vam Organics, Tata Iron and Steel, Power Grid Corporation of Indian and Met-Chem Canada Inc.

For details contact: TARA, B32 Tara Crescent, Qutab Institutional Area, New Delhi 110 016, Ph: 011-6967938, 6851185. Fax: 011-6866031, E-mail: tara@sdalt.ernet.in