If you are looking for a strong, local, cheap and eco friendly building material then compressed earth blocks (CEBs) should be in your shopping list. A compressed earth block is nothing but moist earth mixed with a stabilizer (cement or lime) and pressed into a brick form. There are a variety of manual and motorized presses available for making the blocks that could be installed on site.
Compressed earth blocks are generally fine for load bearing construction upto 3 floors high.
Cement is normally used as a stabilizer (5%) but the choice of stabilizer depends on the type of soil. For sandy soil cement is preferred and for clayey soil, lime is the preferred stabilizer. If cement is used, the blocks must be cured for 4 weeks before use. Since there is no firing involved, the amount of CO2 emissions is about 8 times less compared to country fired bricks.
Its always a good idea to have the soil to be used for blocks tested. A good soil for CEB consist of 15% gravel, 50% sand, 15% silt & 20% clay. The ratio of these 4 components will vary based on the location but a simple analysis will help decide the ratio and type of recommended stabilizer.
Another variation of a stabilized compressed earth block is a compressed fly ash brick which consists of:
A simple manual press can produce about 1000 - 1500 blocks per day. For larger scale production and more consistent quality, motorized/hydraulic block machines are preferred.