NGO Another Way (Stichting
Bakens Verzet), 1018 AM
SELF-FINANCING, ECOLOGICAL,
SUSTAINABLE, LOCAL INTEGRATED DEVELOPMENT PROJECTS FOR THE WORLD’S POOR
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FREE E-COURSE FOR DIPLOMA IN INTEGRATED DEVELOPMENT |
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Edition 07: 11 October, 2007.
Edition 08 : 31 August, 2011.
PREPARATION OF PRODUCTS MADE FROM GYSPUM COMPOSITES
There
is no single form, shape, appearance, colour, hardness, resistance, or surface
for gypsum composite products. A sample of à gypsum composite
product is therefore meaningless
unless it is a given product, designed for a specific purpose, for use in a
specific area, using cheap gypsum or anhydrite from a specific deposit.
Each product has to be individually developed, and its
development typically requires about six months of research. Some important
aspects are:
THE PRODUCT(S) REQUIRED
Description
of the products needed?
What are they needed for?
How users are accustomed to meeting the needs
Physical conditions in which they will be used
Drawings
Specifications : size and volume, preferred shape, resistances, type of finish,
colour, weight limits
THE MARKET
Clear
list of priorities : which items are to be first
Quantities required
Rate of production required
Territorial distribution of the consumers
The degree of automation (if any) required.
(WASTE) MATERIALS LOCALLY AVAILABLE
Which
waste materials are usually available locally? Examples : discarded coconut
fibres; flax fibres.
THE LOCAL CHEAP GYPSUM AND/OR ANHYDRITE DEPOSITS
Where
the deposits are situated.
The project coordinator or his appointees will be led through a series of tests
to check the specific characteristics of the locally available cheap gypsum or
anhydrite deposits to be used to make the products. This work must be done
scientifically and the instructions exactly followed.
PREPARATION OF TEST RECIPES
On
the basis of the raw material test results, the product specifications, and the
local waste materials available, a number of different recipes are developed.
These are used to make product samples for testing and approval by the users.
PREPARATION OF MOULDS
The
moulds to be used are finalised, preferably in the gypsum composite production
units which in the meantime will have been designed and built. The first moulds
can be quite expensive to make, which is why the number of products each
production unit can make to start with may be rather limited. Successive copies
of the moulds are, however, easy and cheap to make.
METHOD OF MANUFACTURE
This
varies according to the nature of the product. A water container (=jug) will
normally be made in two halves, joined together, the internal pores first
filled, and an epoxy coating given to the inner surface to make it impermeable
and hygienic. Tanks will normally be made in hexagonal segments.
2.0 EXAMPLE OF A MORE ADVANCED APPLICATION
Here
are the procedures to be followed for the development of "more or less
waterproof" material with transpiration for the external covering (not
strengthening) of mud houses. To reach a solution efficiently it is important
that all work be extremely systematically executed. Every development has to be
"scientifically" recorded. Every sample must always be carefully
coded and labelled. Failure to do so will just cause extra work for everyone,
especially for the local partner, as there is quite a lot of paper work to be
done. For the same reason systematic cross-checking of data is of vital
importance, as will be seen from the following description.
PROJECT FOR EXTERNAL PROTECTION FOR MUD HOUSES
Phase One
a)
Collect samples of the following basic raw materials from various sites in the
project area. Each sample must be carefully coded dated and labelled. As a
general rule, the less the water in the chemical structure the longer the
hardening time.
The two basic types of interest are:
Anhydrite : CaSO4 + 1/2 H2O. Has a lower water
content, hardens in 1 1/2 hours. For your guidance, this costs between 2 1/2 -
3 US cents per kg in
"Cheap" gypsum : CaSO4 + H2O. Has higher water content, hardens in
less than 30 minutes. This is what is discarded during gypsum production. It
costs between 4 and 5 1/2 US cents per kg in
Conserve three sets of the carefully coded dated and
labelled samples in sealed plastic bags. Keep the bags in darkness at about 18
degrees C.
b) Collect two samples each of about
c) Send one set of the samples under b) to the
Consultant.
d) Test one set of the samples under a) for their
hardening time. Record the date and hardening time on the labels OF THE
HARDENED SAMPLES ONLY.
e) Collect samples of fine milled sand and/or desert
sand (the sand on the leeward side of hills is finer than that on the windward
side). You may use several types of sand, in which case the procedure under
phase two is to be conducted with each type of sand.
Phase two
Prepare
b) following before proceeding with a)
a) For each raw anhydrite or cheap gypsum collected
under a) above make sample blends each blend containing 50% of sand and 50% of
the raw material concerned. Each such blend must be carefully coded, dated and
labelled. Use EXACTLY the same quantity for every such mixture.
b) The following must be conducted exactly. Hold in
reserve before proceeding with point a) a reserve container with EXACTLY one
third of the amount of water used in a), and a second reserve container with
EXACTLY one third of the amount of anhydrite or cheap gypsum used in a)
The blend in a) must be just pourable, so that the
mixture is just able to flow. If it is too liquid add some more
anhydrite/gypsum, if it is too thick add some more water.
c) Carefully record hardening time, the EXACT
percentage of extra water or raw material added, and code, label, and store the
new composite products.
d) Copy to us all a full documentation on everything
done on raw materials, sand and material mixtures, wall samples to date.
Phase 3
a)
An analysis is now made of the materials most suitable for the application in
question and a set of 5-7 recipes will be formulated according to the wall
materials to be protected.
b) You then prepare two sets of each mixture according
to the recipes given, and carefully code and label them. One set is tested for
ageing. The second set is to be kept in a labelled plastic bag in a dark place
at a temperature of around 18 degrees Centigrade, preferably without air.
c) From your own recorded observations and from your
paper-work, we can then assume which material(s) are likely to give the best
results.
d) The UNTESTED examples of the best material(s) are
then sent to us so that we can conduct mirror tests for counterchecking
purposes.
Phase 4
a)
This is the most important phase. We discuss the final (presumable) recipes and
the financial consequences of choosing various possible additives.
b) A simulation project is then set up with, say, 5
houses in each of say 5 regions, each house with 5-10 check points. Ideally the
houses should be the ones the samples under 1 b) come from. If other houses are
involved, then collect samples for them as set out in 1 b) above, code them,
label them and pack them well.
c) Apply the recommended mixtures to the walls of the
chosen houses, carefully recording:
-code of mixture and code of wall sample
-date and time of day
-weather conditions
-humidity at the moment of application
-details of mixing
-size of mix
-number of people working
-ease (feel) of application
-comments of workers (seems too thick, seems too thin)
-hardening time
-ALWAYS with exact measurements of quantities etc
c)Every week thereafter at exactly the same time,
check the control points:
- is the material still strong
- description of climatic events over the week
- tears or signs of tears with description of length and width of tears
indicating whether they are on the North, South, East or West side of the house
- if the moisture feels uniform to the touch at the top and at the bottom of
the walls and around the doors
- check uniformity of colour
- check if little black spots appear, especially towards the bottom of the wall
- check carefully what happens at the bottom of the wall in contact with the
soil, by tapping the wall with a stick and listening for "empty"
sounds.
Phase five
After
about six months a decision will be taken on what the final recipe will be from
the point of view of cost, storage, handling, preferred colour etc.
BACK:
Information
on gypsum composites technology.
Some recommended technologies.
“Poverty is created scarcity”
Wahu
Kaara, point 8 of the Global Call to Action Against Poverty, 58th
annual NGO Conference, United Nations,
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