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View the documentIncreased cement choice in eastern and southern Africa - An alternative perspective
View the documentPromoting sound economic housing for Sudan and regionally

Increased cement choice in eastern and southern Africa - An alternative perspective

Why a Workshop on Alternative Binders?

Lime is one of the world’s most important industrial minerals and used in a large number of industries including paper making, leather tanning, sugar processing, paint making, steel making, pharmacuticals and fertilizers. Often the development of a lime industry in an area is a precursor to the development of other industries which depend on using it in their processes.

Lime is still also an important building material in some parts of the world, especially close to areas of production. However, there has been a steady decline in use of lime worldwide for building over the past decades in favour of Ordinary Portland Cement (OPC).

However, lime could still play an important role in building, especially in the renovation of older buildings and as an affordable binder for improved low cost building. OPC production is concentrated in few large and capital-intensive plants which take many years to set up, so supply inevitably lags behind demand leading to high prices and shortages in some areas. Increased lime production, based on plants which can be set up locally and quickly and at relatively low cost, could go some way towards easing local cement shortages. The low strength and slow hardening of lime - a benefit in certain applications but a drawback in others, can be overcome by mixing with a pozzolanic material such as rice husk ash or volcanic ash to produce a lime-pozzolana cement (LPC).

East Africa is one region where the cement shortage is becoming especially acute with rapidly growing towns and cities leading to unprecedented building demands. Although OPC production is set to expand, both at existing plants and, eventually at one or two new ones, the demand for cement is forecast to grow at an even faster rate and existing shortages will get worse.

Importation of cement is one option, and this is already being done, especially in Uganda which is importing nearly 80% of all cement consumed. This is not a satisfactory long-term option because it drains the country’s foreign reserves which could otherwise be more productively used.

Another option, which is already being implemented, especially in Kenya, is to extend the cement with certain relatively low cost additives such as volcanic ash pozzolana, diatomite, ground limestone and kaolin. With replacement rates of up to about 20% the cement properties are not significantly changed. However, some consumers still prefer unadulterated OPC and are willing to pay a higher price for it. Realistically by blending some of the cement produced with an extender, the total supply of cement could be increased by 5 to 10% at most.

The final option is the production of an alternative cement such as lime or LPC. It is, however, recognised that these binders would not have a large-scale impact on the demand and supply situation of binders globally or even nationally, but could have a significant impact locally, especially in areas where the necessary raw materials occur.

traditional lime kiln

new lime kiln using improved design

Finding a Possible Role for Alternative Cements

In December 1994 around 50 lime producers, researchers, policy makers, NGO representatives, architects builders and planners met in Tororo, Uganda, to discuss the cement supply situation in East Africa and to propose solutions for alleviating shortages, especially by looking at an increased role for alternative cements. The seminar was co-hosted by Intermediate Technology (IT) and the Ministry of Lands, Housing and Urban Development in Uganda.

Tororo is an important region of lime production in Uganda with a number of batch kilns in operation. Very recently a lime- producers co-operative has built a kiln to burn lime more efficiently and on a continuous basis. This kiln is yet to be fired. There is also an OPC plant in Tororo, but this is only working intermittently due to a shortage of working capital and obsolete equipment, some of which is more than 40 years old.

The seminar was principally based on the countries of Kenya, Tanzania and Uganda, but also considered neighbouring countries such as Sudan, Malawi and Zimbabwe where the problems and constraints on cements are similar.

Prior to the seminar a series of studies had been commissioned. Some looked at existing production and use of binders in particular countries whilst others looked at the difficulties faced by individual producers in these countries, means of overcoming these difficulties and the role individual producers could play in meeting demands for binders.

The findings of these studies were presented. The main aspects of these were considered to be:

(i) All the African countries represented, except Zimbabwe which currently has a surplus of cement, faced severe constraints in meeting demand for cement.

(ii) Except, possibly, in Tanzania lime is currently not making a significant contribution to the overall quantity of binders available on a national basis.

(iii) Lime and special earth are still being extensively used as binders in particular localised areas, especially for low cost building applications.

(iv) Hardly any production or use of LPC is taking place despite past support from funding, development and government agencies.

(v) The majority of lime is produced in small-scale batch kilns, which are inefficient. Access to improved but affordable production technologies is a problem for lime producers.

(vi) Alternative binders are seen as low status.

(vii) The existing standards, by-laws and codes do not favour the use of alternative binders.

(viii) Most small-scale lime producers face a number of constraints - depletion of fuelwood, lack of working and investment capital, lack of marketing and management skills, insecurity, interrupted power supplies for grinding, low quality products, poor access to road and rail facilities and poor health, safety and environmental practices.

After the presentation of papers the participants split up into working groups to come up with action plans to redress the above constraints. The discussions specifically concentrated on production, usage and policy aspects.

The Outcome

A series of resolutions were agreed proposing increased research and development on appropriate production technologies, advocacy work on amending codes, standards and regulations, increased and improved training and information dissemination, environmentally relevant actions and networking of producers and users.

The specific resolutions were:

(a) Energy efficient kilns be designed, developed and promoted to reduce the rate of fuel consumption.

(b) There should be mandatory re-afforestation to ensure sustainable use of fuel.

(c) Geological Survey Departments in collaboration with institutions promoting lime production should map out raw materials reserves.

(d) There should be provision in place for training of artisans, professionals and entrepreneurs in the use of binders.

(e) Standards and Codes of Practice for the quality and application of different binders be established.

(f) Relevant information on binders be disseminated e.g. through networking, exchange visits, etc.

(g) Further research be carried out on improved kilns, application of alternative binders, and more intensive use of waste as fuel and pozzolana.

From these resolutions a series of actions were proposed and organisations were identified which could take these actions forward. Organisations identified with possible leading roles included IT, to co-ordinate the plan of action as well as carrying out specific information and research tasks, UNIDO, UNCHS, research institutes in individual countries and government departments. Individual producers and users of alternative binders will also themselves have an important role to play if alternative binders are to impact significantly on the growing cement crisis in many countries in Eastern and Southern Africa.

The Follow-up

Both IT and UNIDO have been active in taking some of the proposed activities forward. A productive meeting between representatives of these organisations was held in April. By the end of July IT will prepare a detailed proposal outlining the role of a support service to lime producers and users in East Africa and how such a service, to be based in Kenya, could be implemented. UNIDO also intend to organise a similar workshop next year based on the West African region.

IT has received a grant from the Overseas Development Administration (ODA) of the British Government to carry out research on lime kiln efficiency based on the kiln it helped to develop in Malawi. Research will be co-ordinated by Energy Unlimited, a British-based group of energy specialists. The output of this work will be the preparation of design guidelines for small-continuously operated kilns which are efficient in terms of fuel use as well as a high quality product with low wastage rates. A spin-off from this work will be the development of an improved batch kiln, which would be less costly to build than a continuous one.

There is considerable interest in small-scale lime production in Zimbabwe. Although Zimbabwe currently produces a surplus of OPC it is still expensive in the more remote areas. IT has been giving technical assistance to an entrepreneur, based in the Eastern Highlands, who is now building a kiln based on the Malawi model which he visited. A parastatal NGO is also in the final stages of planning for a similar kiln.

In Uganda IT has been assisting the Nyalakoti Limemakers Co-operative in Tororo with technical information. They have a newly-built continuous kiln and hope to start producing soon. A visit by one or two representatives from this group to Malawi to study the lime plant at Chenkumbi Hills is also planned.