Monday, February 08, 2010

1 Chron 12:32 Report, no 58: On the possibilities of Bahareque construction technologies for Haitian reconstruction and for the wider region

An old optimist's saying is that every cloud has a silver lining, and it is now a commonplace that the Chinese character for "crisis" is built up from the components: danger PLUS opportunity. (Never mind the usual hair-splitting academic debate . . . !)

So it is no surprise that the horror of the recent Haiti Earthquake disaster opens up opportunities for a new and more sustainable approach to construction, especially for housing, agricultural buildings, and light commercial, industrial and institutional buildings in the Caribbean (and beyond).

To some extent, this blog has already remarked on this, in an earlier post of Jan 18 [at point no 40] wherein we may see that, first and foremost, we need to change the way buildings are being built. Thus, the first step is to look seriously at the breakthrough Moladi cast foamed concrete plastic former house building system, which is capable of delivering one hurricane and earthquake resistant house per day per mould, with the moulds rated at fifty house- castings apiece:

Going beyond that, I noted:

Possibilities -- in addition to the Moladi-type approach [cast, reinforced foamed concrete housing using prefabricated plastic moulds that can cast one house per day per mould, the mould having a working life of fifty castings] -- include:

a] The Classic CINVA Ram-type compressed earth brick or block presses (including the soil-cement block or brick variation, for which cement stabilises the blocks against moisture), with The Liberator being a faster production development. [The original is rather labour intensive, producing 50 bricks per hour per machine, with several thousand bricks being a typical requirement for a small house. But, we are dealing with a low labour cost environment in looking at Haiti's rural villages.]
b] The Auram modern development that can make a considerable variety of bricks and blocks, including Lego-style interlocking blocks
c] Modern clay, sand, and straw asphalted bricks (going all the way back to the Babylonians!)
d] Use of bamboo canes as a reinforcement medium for adobe type construction (as in "grow your own rebars").
e] The online World Housing Encyclopedia (and other sources) has many more ideas and even training manuals, e.g. this one on proper use of reinforced concrete.
But also, an updated form of the traditional Bamboo Hollow Bahareque construction technology from Columbia and Ecuador and related techniques (e.g. here and here) also offer significant potential, especially for situations where lower capital costs and use of indigenous materials and techniques accessible to ordinary relatively unskilled labour are important factors:

1 --> Traditional Bahareque construction took advantage of the fast-growing [ = "sustainable timber"], strong bamboo Guadua angustifolia (also known as "vegetable steel") and a development of wattle and daub construction, using bamboo strips as the wattles and a mud-horse dung [second use straw!] mortar as the daub.

2 --> Such buildings have proved to be surprisingly durable (lasting upwards of a century) and have also proved resilient in earthquakes; providing the structural bamboo is in good condition.

3 --> In recent years, Jorge Gutierrez, Engineer Professor and Chair, Structural Engineering Department, School of Civil Engineering, University of Costa Rica, has led an effort to develop this technology through application of engineering analysis, experiment and design techniques.

4 --> While aiming to do an ultimately all-bamboo timber design, initial housing was built using an interim timber framed version of the technique. These were at the epicentre of a Mag. 7.5 quake in Costa Rica, and survived without significant damage.

5 --> Similarly, as the modified technique creates an outer wall thickness of 5 cm [~ 2 inches] of bamboo strip reinforced concrete, it is credible that the walls will also be resistant to hurricane winds and most hurricane-carried projectiles.

6 --> Durability of bamboo is an issue in the tropics, with insect and fungus attack as significant challenges. The traditional treatment is to use borax solution to coat laths and creosote oil to coat bamboo columns and beams. Also, more modern treatment techniques now exist, for a prospective commercial trade in plantation-grown sustainable bamboo timber.

7 --> Such sustainable bamboo timber can also be made into bamboo composites
such as a bamboo matting version of the traditional corrugated steel roofing sheet, into plywoods and laminated woods [which can in some cases be harder than oak].

8 --> Bamboo trusses can then support the roof, which can be of various types. (We should look at the use of stabilised compressed earth tiles, and at foamed cement tiles.)

9 --> A similar technique as tested in India is to use bamboo framing, and a network of laths, with attached chicken wire used as a basis for ferrocement construction of the same 2 inch thickness. Inthsi case, a timber ring beam was used to support the roof, and attachments were based on concrete infilling of up to 18" of the bamboo columns, then casting in rebars [to tie into a reinforced concrete foundation] or bolts that were passed through the timber ring beam serving as the base for the roof.

10 --> Plainly, the blending of bamboo lath and/or chicken wire concrete wattle and daub -- this last being a version of thin shell ferrocement construction used for sculptures, boats and buildings -- with bamboo, timber or steel framing holds many possibilities for creating an alternative, more sustainable, more affordable and yet disaster resistant construction technology for both Haiti and the wider region.
(Similarly, compressed earth bricks, blocks and tiles and adobe with bamboo cane reinforcement can be blended in.)

11 --> However, resistance to novel and often perceived "inferior" technologies and materials is a challenge.

12 --> This is where churches, church-based aid and development groups, other non-government and/or community-based organisations and the like can step up to the plate and demonstrate through key pilot demonstration projects, the utility, aesthetics, sustainability, affordability and potential acceptable quality of such new approaches.


So, again, let us ask: why not now, why not here, why not us? END

No comments: