Appropriate Technology: Tufa as a building material
August 31, 2007 at 2:00 am (Systems Design, rice husk)
The Romans in the early years of the Republic used a stone called Tufa for building. It’s volcanic in origin being basically limestone bubbled out of hot springs which then set. It is easy to cut and shape; the romans did so with bronze tools. Tufa hardens on contact with air and is lightweight. It’s vulnerable to frost damage since it’s porous.
Nowadays if you talk about building anything in the tropics or subtropics all you hear about is concrete, which is less than ideal if you are poor. Also if you’ve ever seen how concrete is made it’s incredibly energy intensive. In my previous post I wrote about the possibility of partly replacing expensive portland cement with rice husk ash generated by the rice husk furnace, since there will be occasions when you would not wish to use a rock which is not waterproof.
In some situations, such as building a sand filter for cleaning water you would need concrete for the interior surface, but you could have tufa as the primary support material. I came up with this idea while looking at geological maps of East Timor, the eastern half of a volcanic island (the other half belongs to Indonesia) which lies just north of Australia.
They’re dirt poor and are having to rebuild their country from the ground up since the Indonesians levelled the place as they were getting pushed out. In situations like that the ability to build cheaply but well is of real importance. Rice is a major crop in East Timor so there is an abundance of rice husk ash, after the husks are burned twice, in the Belonio Gasifier Stove.
(http://www.crest.org/discussiongroups/resources/stoves/Belonio/Belonio_gasifier.pdf)
The East Timorese have an abundance of Tufa as well. Combine both of these with bamboo and you a high strength low cost construction industry that all but the poorest people can afford to build with in East Timor, Indonesia, Papua New Guinea and The Philippines.
