JOURNAL OF THE

Volume1 Number 1 April 1989 ISSN 1012-9812 of African Countries on local building materials and technologies

CONTENTS

Foreword 3 Background 4 How to overcome the high cost and scarcity of ordinary Portland Cement 5 Ghana Blended cements from bauxite waste 8 Low-cost binder using lateritic soils and limestone 10 Kenya Standards and specifications for fibre-concrete roofing tiles 11 Promotion of wide-scale adoption of fibre-concrete roofing tiles 11 Cost comparison between fibre-concrete roofing tiles and other roofing materials 11 Malawi Fired-clay bricks 13 Sand-cement tiles 13 Performance standard specifications for sand-cement roofing tiles 13 Cementitious materials from rice-husk ash 14 Performance tests on rice-husk-ash/ lime binder 14 Mauritius Lime production 15 Pozzolanas from bagasse ash 15 United Nations Centre for Nigeria Human Settlements (Habitat) Use of agricultural residues for production of building materials 16 Uganda Lime production .14\' Limestone deposits ~~~ Fired clay bricks 18 ~J United Republic of Tanzania Low-cost binder from natural Commonwealth Science pozzolanas 19 Council (CSC) Events 21 NETWORK JOURNAL

Foreword

The economic recovery of Africa must remain at the forefront of international agendas as it is of the efforts of African governments themselves. Despite economic conditions which continue to deteriorate, and the continu­ ing inadequacy of the external financial flows which Africa needs for recovery, economic recovery programmes are being undertaken or planned by most African governments. And they are fInding that, to build their economics anew, they have literally to build. The rehabililation or creation of infrastructure, the development of new industries, the promotion of exports and the provision of shelter and public amenities are key elements in such recovery programmes, and all require construction and building materials. The adequate supply ofbuilding materials is thus critical to Africa's efforts at economic recovery. Without this, recovery is even more uncertain. Over the years, the United Nations Centre for Human Settlements (Habitat) has treated this issue as a priority, in view of the precarious situation ofthe building materials industry in most developing countrie and its central importance to national development. Through its Research Division, the Centre has assisted developing-country governments in remedying the situation of the building materials industry, while its Technical Cooperation Division has conducted field projects amply demonstrating possible improvements. There is now a vast weight of experience from which to argue that the building materials sector offers opportunities for lessening import dependency or even for attaining national self-sufficiency by increased indigenous production. Yet a serio~s lack of technology and know-how for commercialisation of local production has meant that such opportunities have rarely been taken. While the limitations of technology transfer from industrialised to developing countries may be substantially the cause, there is much that developing countries can do to transfer technology among themselves. The establishment of effective mechanisms for technology collaboration at regional and sub-regional level and between neighbouring countries would bring the achievement of basic targets in indigenous production capacity, particularly in the building materials sector, within grasp. The Commonwealth Science Council (CSC), like UNCHS (Habitat), has long realised the significance of the building materials sector and the need to promote local capacity through sustained support to national insti­ tutions in several areas of technology development. In this connection, a workshop was organised by the esc, in collaboration with UNCHS (Habitat), in Kampala, Uganda, in June 1985, aimed at establishing collaboration among African countries in research and development for the promotion of local building materials. The subsequent efforts of the CSC and UNCHS (Habitat) to sustain that aim have resulted in the existence of an active and continuously expanding network of African countries collaborating over local building materials technology. This Journal marks an important milestone in the activities ofthe network which gives it its name. By promoting the development of indigenous technological capacity through the flow of information among participating countries, we feel sure that Network Journal will make a real contribution to building a new Africa, and that it will be relevant also to other interested countries and institutions worldwide. We wish it every success.

Dr ArCot Ramachandran Shridath S Ramphal Executive Director Secretary-General UNCHS (Habitat) Commonwealth Secretariat.

3 JOURNAL OF THE NETWORK OF AFRICAN COUNTRIES

Background

Local raw materials for construction is an area of human survey oflocal raw materials for housing construction, commissione'd endeavour that relates to the socio-economic and socio-cultural by the Commonwealth Science Council as Phase I of the African settings ofa country. particularly in the area ofshelter construction. Regional Project on Local Building Materials. and national case It is in the area of shelter that a dichotomy appears to exist studies on manufacturing technologies, standards and specifications between sheller as a basic neccssity for mankind, on thc onc hand, on local building materials, commissioned by UNCHS (Habitat) and shclter as an area in thc devcloping countries which is as part ofthe inputs to a workshop on standards and specifications encumbcrcd by problems of affordability, availability, durability. on local building materials which was organized jointly by the habitability, reliability and vulnerability in relation to the pertinent African Regional Organization for Standardization(ARSO).the materials of construction or the buiJt-fonns. Commonwealth Science Council (esC) and the United Nations In pursuancc of its objcctive tocnhancc indigenous capability of Centre for Human Settlements (Habitat), in Nairobi, Kenya, individual nations to gcnerate and usc science and technology for March 1987. Information from both the CSC-sponsored surveys thcir economic, social and environmental developmcnt, the and the UNCHs...sponsored reports were to form the nucleus of Commonwealth Science Council, in collaboration with the United the Journal of the Network of African Countries 0/1 Local Nations Centre for Human Settlements (Habitat), established in Building Materials and Technologies, of which the present Kampala. Uganda, in lune 1985. an African Regional Project on edition is the first issue. Local Building Materials and Technologies. To date the African Broadly, the Journal will, interalia, disseminate infonnation on Project comprises II collaborative research network. the Network the activities of the Network, particularly aimed at low-cost ofAfrican Countries on Local Building Materials and Technologies. innovations in local building materials and technologies. Infonnation consisting of Cyprus. Ghana. Kenya. Malawi. Malta, Mauritius, in the fonn of technical papers, illustrations, news items and Sicrrll Leone. Uganda. the United Republic of Tanzania and announcements of activities on local building matcrials and Zimbabwe. which are represented country-wise by national co· associated areas, from the private or public sector, from within and ordinators. Activities of the network have so far altraeled the outside the African region, will also be welcome. participation of various international and regional agencies and The Local Building Materials Project, the Network and the organizations with special interest in the field of local building lournal. are envisaged as playing thc vital role of a link in co­ materials and. also. the participation of a substantial number of operative techno-scientific endeavour between a number of non-Commonwealth countries of the African region. international and regional agencies and organizations and various The Jounlal for the Network ofAfrican Counlries on Loca' national institutions and individuals in the area of local building Building Maleria's and Technologies, as a possible medium of materials and technologies in theAfrican region both now and for communication and infonnation exchange for the Network. several years to come. originated in two recent activities of the Network, namely, a Rogers W'O Okot-Uma

Contributions to the Journal Department of Civil Engineering This journal welcomes infonnation or articles on low~cost The Polytechnic innovations in building materials technology. Infonnation in the UniverSity of Malawi fonn oftechnical papers, i11ustrations, news items and announce­ Malawi ments ofevents can be sent from individuals or institutions in the Department of Architecture and Civil Engineering private or public sector, from within and outside the Africa University of Malta region. All correspondence on the loumal should be addressed Malta to the editors: Mr. Frank Tackie. Research and Development School of Industrial Technology Division. UNCHS (Habitat). PO Box 30030. Nairobi. Kenya. University of Mauritius or Mr. Rogers W'O Okot-Uma, Conunonwealth Science Counci~ Mauritius Marlborough House, Pall Mall, London. SWlY 5HX, UK. Nigerian Building and Road Research Institute (NBRRJ) The views expresscd in this journal do not necessarily refleci Lagos either those of the United Nations or the Commonwealth Nigeria SecretariaL The reprinting of any of the material in this publication is welcome, provided that the source is mentioned Faculty of Engineering and one copy sent to each of the addresses mentioned above. Fourah Bay College Nalional Network Institutions University of Sierra Leone Sierra Leone Cyprus Organization of Standards and Control of Quality Geological Survey Mines Department Ministry of Commerce and Industry Ministry of Lands and Mines Cyprus Entebbe Building and Road Research Institute (BRRI) Uganda Kumasi University Building Research Unit (BRU) Ghana Dar es Salaam Housing Research Development Unit United Republic ofTanzania School of Architecture Ministry of Public Construction and National Housing University of Nairobi Harare Kenya Zimbabwe

4 - •

ON LOCAL BUILDING MATERIALS AND TECHNOI.OGIES. I (I) AI'KII. 19H9

How to overcome the high cost and scarcity of ordinary Portland cement In developing countries, the trends of consumption of Portland explained below. indigenous cemcntitious materials can be cement have shown a rapid increase over the pasI20 years. and produced and used in a variety of ways. thus offering individual the rate of imporl has been equally significant. For example, developing countries a vast range of options to improve the imports of cement rose from 54 per cent of total consumption availability of binders to suit their panicular conditions. in 19701080 per cent in 1979. In monetary terms, the negative Before the advent of Portland cement. lime was the main trade balance for the cement industry alone grew from SUS 900 binding agent used for construction and. despite its decline in million in 1970 to ovcr SUS 1.7 billion in 1979. Domestic popularity, its use as a binder is still appropriate. Portland production of Portland cement, for the same period, increased cement and lime have one basic common property when mixed in all developing regions, notably showing a 64 per cent in­ with water, they have the tendency to set and harden so that crease in Africa and a 13.6 per cent increase in Asia. In some they are subsequently strong and impervious to water. Lime particular cases, developing countries have become net export­ has a slower setting rate than cement, and the final strength is ers ofcement. lower, but lime is perfectly adequate for most low-strength Despite the trends of rising imports and the eJCpansion of applications, such as mortars, plasters. foundation concrete domestic production, Portland cement is still not available in and building blocks. In addition. lime has other qualities. such sufficient quantities and, in any case, is only available at costs as good workability, ability to accept movement without crack­ which are prohibitive for the bulk of the population. The main ing, water retentivity resistance to water penetration, thus reason for this situation is that foreign-exchange constraints have making it more suitable than Portland cement for masonry limited quantities and kept costs high for imported products, and. work. because domestic production is generally dependent on imported In general, pozzolanas are classified into two groups: natural and artificial. A pozzolana is a material which. on its own. is not inputs. the same limitations apply to local production. Unfor­ cementitious but which, with the addition of lime, reacts to form a tunately. in most dev:e1oping countries the only binder used in material which sets and hardens. Thus. for the purpose of the construction sector is Portland cement so that its limited construction, a pozzolana is not an end in itself. but rather a means supply and high cost have meant that investments in construc­ of achieving the ultimate product - lime-pozzolana Lime­ tion are either withheld, diverted or abandoned. pozzolana is a low-strength binder used in the same manner as Portland cement has a clearly defined role as a binder in lime for blocks and for soil stabilization. Normally, a mixture of fulfilling the functional requirements for high-strength applications. one part of lime to two parts of pozzolana is adeQuate for lime­ However, in actual construction practice. Portland cement has pozzolana binders and, even if a ratio of I: I is applied, savings become a ubiquitous material, largely as a result of its wrong of about 50 per cent of the available supply of lime is achieved. application in construction. Portland cement is predominantly In this way. where pozzolana is obtained at a lower cost than used in low-strength applications, for foundation concrete, plasters. lime, lime-pozzolana becomes an attractive material for low­ mortars and soil stabilization. This wrong application of Port­ cost construction. land cement is not only unnecessarily costly but, more import­ Blended cements are produced by mixing ordinary Portland ant, technically defective. cement with a low-cost cementitious material, notably blast­ The degree to which Portland cement is wrongly applied in furnace slag, lime or any of the popularly adopted pozzolanas. construction has reached alanningproportions, and it is estimated The principle behind blended cements is to obtain a binder which that only 20 per cent of the worldwide use ofcement requires the is nearly equal in strength to Portland cement but. at the same strength of Portland cement In most African countries, there is time, is cheap. Examples of blended cements are Portland­ hardly any alternative binder to Portland cement However, in pozzolana, Portland-slag or Portland-lime-pozzolana. There almost every developing country, there are ample opportuni­ are cases where blended cements have been produced by re­ ties for the use of other binders, based on known cementitious placing about 25 per cent of the volume of Portland cement materials Which, even though not exact substitutes for Portland with a pozzolana, and the resulting binder is recorded to have cement, can serve the same function in construction and, most satisfied the same 28-day strength test as for normal Portland or all, can be produced within the resource limitations of devel­ cement. Blended cements have an advantage over Portland oping countries, using indigenous factors of production. As cement in terms of workability and water resistance.

, JOURNAL OF THE NETWORK OF AFRICAN COUNTRIES

Pozzalanas In selected countries

Pozzolanas Pozzolanas Pozzolanas of natural 01 plant of artificial origin origin origin

GHANA Natural pozzolanic materials such as Rice husk ash, groundnut husk ash, Ctays. shales, baullite and bauxite-waste pumice, scoria, or diatomaceous earth coffee husk-ash and sugarcane bagasse occur in deposits some investigations are not readily available. are potential sources. already carried oul

Some volcanic rocks in the Birrimian Fairly well distributed in all the regions system have potentials for use as and of suitablequanlities lorencouraging pouolana. establishment of small-scare industry. MALAWI Volcanic ash and post-karoo volcanic Macadamia shell, tung shell, cotton seed materials such as pumice and line-grained shell, and groundnul shell ash. tuffs.

Available in Karapa districts and Chitipa Grown in estate larms(macademla, tung) area and by larmers and small-scale holders (cotton, groundnut).

Quantities estimated as lollows: macadamia: 600 tons p.a lung: 150 tons p.a. cotton seed: 4000-6000 tons p.&. groundnut: 120 tons p.a MAURITIUS Soils with active substances such as Bagasse ash (estimated at 2.8% dry Coal ash from use of imported pulverized kaolinite, hal1uysite, gibbsite. particularly weight of bagasse) in the form of the coal as fuel In sugar factories during lateritic salls which form the bulk of following: Inter-crop season. MaurlUan soils, and volcanic ash which - Grate ash. with lairly high silica content covers most of Rodrigues Island. of 70-75%.

Most of Mauritius, apart from some con­ - Hopper ash, with fairly high slUca con' solidated coral and shell debris around lent 0170-75%. the coast. - Fly ash. basically carbonaceous matter. No test has ever been performed to determine the pozzolanic reactivity of local lateritic salls. Mineralogical test results have shown that the highest contents 01 amorphous silica and alumina were only 3% and 10% respectively. UGANDA Volcanic ash. scoria and pumice occur Include calfee husk ash, rice husk ash, Include soft fired clay from the following: very extensively in Kisoro-Kabale area 01 groundnut husk ash, bagasse ash and west Uganda and to a lesser extent"in legume husk ash and otheragricultural - reject bricks Ihe Bunyaruguru-Kazinga channel area wasle ash. - agroindustrial ashes and Fort Portal area - fly ash

Mine tailing of Wolfram mines of Mutolere, Estimated annual ash outputs are as Klrwa, Bjordal and Nyamulilo (west follows: Uganda,j contain a good quality of volcanic ash andscoriaActual reserves - coffee husk 650 Ions not known Estimated reserves enormous. - groundnut husk: not available Shales and diatomaceous earths occur - bagasse: 850,000 tons (UNIDO) extensively in various areas: (estimate) -saw dust 20.oooml - others: not available • ON L.oCAL BUILDING MATERIAL.S AND TECHNOLOGIES. I (I) APRIL 1989

Pozzolanas Pozzolanas Pozzolanas of natural of plant of artificial origin origin origin

(~ Toro-Ankole area, as light grey sedI­ ments, mainlyashyshales and mudstones derived from normal stream and volcanic action. Actual reserves not available.

(II) Ml Elgon area, mainly as a group of sandstones and arkoses and also as fine grained black/dark grey ashy shales and mudstones.

(ii~ Pakwach area Estimated reserves about 100,000 tons. UNITED REPUBLIC OF TANZANIA Volcanic ash, pumice and tuffs Rice husk ash. Pulverized fired clay bricks (Surkhi) Abundant in areas of previous volcanic Abound in rice-growing areas around Flourishes where brick production is on eruptions such as: Kilimanjaro area: Mbeya, Iringa, the coast and in the west a reasonable scale as in the Ruaha Valley Arusha with large Quantities In the and North-west around the lakes. and Iringa, Dodoma and Kisarowe. form of volcanic dust around slopes of Ml. Meru; Iringa, around Sao HIli area; and Mbeya, aroynd Mgozi area, Kyejo and Suma, and Songwe.

Source: Local Raw Materials for Housing Construction - Africa Phase 1: Surveys -A Synthesis Summary Report (CSC Technical Publication Series No. 240 CSC (87) ISP-31j Natural pozzolana deposits in African Countries

Known occurrences/ Suitability Current use location/Quantity

BURUNDI Pozzolana{trass) deposits in Bujumbura Decomposed lava from Cibitoke tested Plant for production of pozzolana cement area estimated atl million tons. Deposits and found to be active. VolcaniC rock at Bujumbura also found around Cibiloke and from Musongati area also found to be EMACCI considering setting up lime Moaaongatl. active. pozzotana.

CAMEROON Pozzolana found in volcanic mountains About 18,000 tons pozzolana are prO'" nedr Douala duced annually.

CAPE VERDE Large deposits of pozzolana found in Islands

ETHIOPIA Owin~ to earlyvolcanic action, pozzolana Investigations on sample of scoria show Pumice used in manufacture of pozzolana materials are fOund in abundance all it can be used as partial replacement of at Addis Ababa cement factory. over the Country. Portland cement up to 25 per cent. POZZOlana, Identified as pumice, scoria, volcanic ash.

RWANDA large quantities of pozzolana are found A pilot plant for pozzolana cement is in around Glseny and Ruhengeri. operation at Ruhengeri. 7 JOURNAL OFTHI=: NETWORK OF AFRICAN COUNTRIES

Known occurrenceS/ Suitability Current use location/quantity

UNITED REPUBLIC OF TANZANIA Owing 10 early volcanic activity, pozz~ Little work done on chemical analyses of Lime pozzolana plant at Oldonyo.Sambu, lanas are found in many regions. There pozzolana Arusha are about 40 known occurrences. Large Laboratory tests on samples from ones are Mbeya-Rukwa area(18 occur­ Otdony~Sambu show that 20 per eel'll rences) and Arusha region (13 occur­ replacement can be made in Portland rences). cement without violating strength require­ Pozzotana identified as pumice, yellow ments. line-grained tuff, volcanic ash.

Source: ECA. DevelOpment of lhe production 01 lime, pozzolana and lime-pozzolana products in the African Region (Addis Ababa, May 1983).

Rice husk availability in Africa (1980)

Countries with 10,000 Estimated quantity Countries with 10,000 Estimated quantity tonS/year (or more) (1,000 tons) tonS/year (or more) (1,000 tons)

Egypt 470 Zaire 49 Madagascar 422 United Republic of Tanzania 43 Nigeria 2'. Mali 2. Sierra Leone 103 Mozambique '4 Cote d'ivoire 102 Senegal '2 Guinea 70 Ghana '2 liberia 49 Malawi • Source: ECA, Op.cit.

Ghana Blended cements rrom bauxite waste by waste material, so that potential agricultural land is being Bauxite mining is an important export activity and so is of wasted. significance to national economic development. The process of The pozzolanic properties of bauxite waste have long been bauxite extraction generates substantial quantities of mining established in experiments conducted at the building and Road tailings in the form of bauxite sludge which currently is a waste Research Institute. Kumasi. Table I provides asummary of the product. About three million tons of bauxite sludge have so far chemical composition of bauxite wastes from Awaso. accumulated at Awaso. On average, about 300 tons of sludge is From the data in table 2, it is evident that Ihe chemical discharged daily as waste material at the bauxite mines. In this characteristics of the bauxite wastes from Awaso are compara­ process, about 80 hectares of land have already been covered ble with those of other typical pozzolanas.

Table 1. Chemical composition of bauxite and bauxlt.waate from Awaso

Bauxite Percentage bauxite waste

SiD, 0.64 7.42 AJ,O, 60.68 45.94 Fe,O, 4.20 20.45 roo, 1.11 ZS9 cao 0.25 MgO H,o+ 32.32 H,o­ 1.05 v,O, 0.02 Loss on ignition 23.44

8 ON LOCAL BUILDING MATERIALS AND TECHNOL.OGIES, I (1) APRIL. 1989

The laboratory process ofproducingpozzolana from the Awaso ties. This is confirmed by the fact that when ordinary Portland bauxite was"te involved the following: excavation of the sludge cement is replaced with 40 per cent of bauxite waste from from thedump; sun-drying ofthe waste for two weeks; calcination; Awaso, the resulting binder portrays the basic characteristics of and arinding. Basically, the excavated mud is sUJ}->dried and ordinary Portland cement. caJciMd at around 600"C to 800"C, after which it is ground to the One of the most desirable qualities of a pozzolana is its fineness of ordinary Portland cemenl contribution to developing strength in concrete or similar ce­ Ultimately, the perfonnanee ofa pozzalana is detennined when ment-composite materials. This can be determined by measur­ used as a composite material, i.e. as a blended cement or as a lime­ ing the compressive and flexural strengths of concrete products pozzolana binder. An analysis of the chemical characteristics of using pozzolana-cement binders. Results of experiments to various blends of bauxite-waste/cement mixtures indicates that determine the engineering properties of concrete produced such blended cements are similar 10 ordinary Portland from a blend of ordinary Portland cement and bauxite wastes cemenl. This phenomenon is demonstrated in table 3. from Awaso proved satisfactory. Table 4 gives the results of From the above analysis, there is every indication that the three mixes of concrete in ratio of I: 1:2. using Portland-pozzo­ bauxite wastes from Awaso have acceptable pozzolanic proper- lana cement as the binder.

Table 2. Typical pattern of chemical composition of selected pozzolan•• (percentage)

810, ",0, F.,o, CaD MgO Na20& so, Ig01lion ."""'.... <,0 ....

Burntda' 62.8 17.2 7.S 2.3 2.5 4.5 2.7 1.7 Spent oil shaJe 52.0 22.2 11.2 4A 1.2 3.S 2.3 3.0 Diatomite (burnt) 72.0 14.5 8.2 1.5 2.2 3.2 7.8 Fly"'" 44.8 18.4 11.2 11.6 1.1 3.1 2.0 8.0 Rice husk ash 85.S 2.5 0.3 1.0 1.0 2.5 1.5 RIoeIbeuxite waste 14.4 48.9 30.0 0.2 0.1 1.2 3.8 Son1orin ....""'" 85.2 13.0 5. 3.• 2.0 S.' 4.0 _ 54.7 16.8 4.1 2.' 1.4 9.0 0.3 9.0 _. 72.3 13.3 lA 0.5 0.• 7.• 4.2

Table 3. Comlaratlve chemical analysis of bauxlte--waste pozzolana, ordinary Portland cement and cement bien ed with various mixes of bauxite waste (percentage)

Portland cement Bauxite-waste 80% cement 70%cemeot 60% cement """"'"' """"'" pozzolana 20llbpozzolana 30% pozzolana 40% pozzolana

SIO, 20.80 7.42 19.42 18.34 18.22 6.14 45.94 14.28 19.04 22,75 Fo,o, 2.52 20.46 7.18 9.12 11.27 """CaO 65.07 0.18 51.37 45.14 38.81 MoO N.,o 1.94 0.13 2.48 2.10 1.57 <,0 0.01 710, 0.11 MoO 2.69 .,0, 0.03 so, 0.31 1.93 Nil 2.54 1.88 1.54 Lou 00 ~"l/tion 1.19 lnaolu~ 22.73 2.88 3.14 3.68 residue 0.41 TOTAL Om 1.26 2.16 100.00 100.00 100.00 100.00 100.00 '.88 88.39 21.46 28.16 34.02 CaOiSIb,~""" 3.38 0.16 1.36 0.96 0.80 3.13 0.02 2.85 2.13 2AS , JO RNAL Of THE ETWORK OF AFRIC Oll TRIES

The commercial possibility of producing pozzolanas from the ually raised to 1100" in eight hours. The temperature in th. Awaso bauxite waste seems obvious. For as long as bauxite kiln is maintained at a con tant 1100· for a period of .1:. production remains an importantexport activity in Ghana, there is ?o~rs, and .a soft clinker is formed. After allowing it to c~~~ likely to be sufficient waste material to support a lOO-ton-per-day Ide the kiln to room temperature, the clinker i ground to an a output of pozzolana for eventual blending with ordinary Portland fine powder with about 90 per cent f it pa sing BS ieve No cement It is estimated that a bauxite-cement binder would cost 200. There is no addition of any material dunng and after th . about 50 per cent less than the price ofordinary Portland cement grinding of the clinker. C 2 Low-cost binder using lateritic soils and Iimestone In order to test the strength of the I w-cost binder, a Laterite soils are commonly found in Africa. nOl111ally with particle mortar mix was prepared by adding standard sand and water to sizes greater than 60mm or in the size range of gravels or as fine­ the binder in a ratio of one part binder. three part sand and grained soils with a gravel fraction Ie s than 10 per cenl The relevant one part water, all measured by weight. Specimens of the chemical composition oftypical limestones and laterites wnich have mortar were cast in 50mmJ teel moulds and t red under moi t found to be satisfactory for use in the production oflow-cost binders conditions in the shade. is shown in table 5. The specimens were remov d from tho; moulds after 24 The experimental procedure for producing a binder from hours. The strengths of three cubes tested at 14 to 28 days were limestone and laetrile is as follows: Lime tone and laterite are 2.35 MPa and 2.35 MPa and 4.74 MPa respectively. It wa ground separately to the required fineness in a ball mill. Fine­ observed that the mortar became stand hardened after 24 ness aimed at is about 80 per cenl passing BS sieve No. 200. A hours. Re ults 0 far btained at the Civil Engineering Labora­ slurry of five parts limestone to one part laterite is prepared, tories at the University of iellce and Technology, Kumasi, indicate that the low-co t limestone-laterite c ment produced is vigorously stirred and allowed 10 eule for 24 hours. Water is drained off, and the wet limestone and laterite meal is allowed suitable for making mortars for building brickwork and for to dry in the shade until it is pia tic. The plastic meal is further rendering and plastering. The range of firing temperatures i blended by kneading, made into balls and allowed to dry for such that the limestone-laterite clinker can be produced in a three days. The dried meal is fired in an electric kiln. The rate potter's kiln. Such a technology, no doubt, would be appro­ priate in rural Africa. of firing is gradual, the initial temperature of 23°C being grad-

Table 4. Compressive strength of concretes produced with bauxite ponolana cements (percent- age)

Mix Age Mean compressive strength (M Pal (days) Control 80% cement 70% cement 60% cement 10% cement 20% pozzolana 30% pozzotana 40% pozzolana

1:1 :2 7 35.8 34.2 28.2 23.4 28 SO.5 46.0 42.2 33.0 60 57.2 52.9 48.4 34.8 90 63.7 60.8 SO.3 36.5 180 65.1 64.0 53.6 39.1 365 69.0 66.5 57.0 42.2 1:2:4 7 21.0 22.5 20.7 12.8 28 30.0 31.0 29.4 22.1 60 34.9 32.2 31.6 24.0 90 38.7 33.8 32.9 27.8 180 42.5 35.3 33.6 30.4 365 44.6 37.9 36.2 32.8 1:3:6 7 20.6 17.8 17.2 14.5 28 24.2 22.0 20.7 17.5 60 26.6 23.8 21.7 20.3 90 28.7 26.5 24.9 23.5 180 30.1 28.0 26.6 25.6 365 31.3 29.4 28.7 27.3

Table 5. chemical composition of typical limestones and laterites (percentage)

MgO CaO Si02 AJ20 3 Fe203 Limestone (%) 53.84 14.20 0.80 0.02 4.03 Laterite (%) 0.50 21.60 36.50 0.37

10 LOCAL BUILDING MATERIALS AD TECHNOLOGIES. I (I) APRil. 1989

Kenya

Standards and specifications for fibre-concrete For roof-cladding materials. permeability is easily the single 3 most important indicator f an acceptable product. In the KBS roofing tiles ., . Effort are being made to promote the Wide adoptIOn of flbre- draft standard. fibre-concrete roofing tiles are required to be tested concrete roofing material. Part of this overall effort ha con­ for pemleability in the same manner as that required for concrete centrated on the formulation of standards and specifications for tiles, namely, when a vertical tube is sealed to the top side ofa tile locally produced fibre-concrete roofing tiles. The Kenya Bu­ and filled with water to a depth of250mm, the level ofthe water in reau of Standard' (KBS) has prepared draft standards which the tube shall not drop by more than 13mm in 24 hours, and no ar currently under review. In the formulation of the draft drops of water shall form on the underside of the tile. tandards for fibre-concrete roofing tile , reference was made Water absorption is another important indicator of acceptable t the KS02-444. the Kenya standard specification for inter­ tile . In the KBS draft standard fibre-concrete roofing tiles must locking concrete roofing tiles and $.1.21, I rael standard for have an average percentage of water absorption of not more than interlocking concrete roofing tiles. 20 per cent. Finally, the nominal length, width and thickness oftiles must be While the specification for unreinforced concrete tiles allows 490mm 250mm and 6mm respectively, with tolerances of for a man to walk on the roof and rest his entire weight on a single ± 10mm on length. ± 5mm on width and ± 2mm on thickness. tile. an assumption wa made that this requirement was excessive The minimum thickness of the ridge must be at least IOmm, with for fibre-concrete tiles. The requirement for asbestos-cement equivalent tolerances. roofing sheets does not allow for a man's weight to be supported, Durability of building materials is normally determined for which rea on, walkways or roof boards are required to carry after several years of service life. Galvanised steel sheets have out any repai rs over the roof. Since a broken fibre-concrete roofing a durability expectancy of 5 to 15 years, clay tiles of 10 to 50 tile can be easily removed and replaced from below the roof years, and 20mm-thick concrete tiles of 30 to 80 years. 1t is too without climbing on to the roof, especially where no ceiling is early yet to specify the durability of fibre-concrete tiles. How­ provided, there is hardly any reason to expect the tiles to be ever, fibre-concrete tile installed in 1978 have a. yet shown no strong enough to withstand the weight of a human. sign of deterioration or decrease in trength and permeability. The strength requirements of fibre-concrete tile • as stipu­ lated in the Kenya draft standards. are in re ponse to three Promotion of wide adoption offibre-concrete types of loads: roofing tiles 4 The promotion of local building materials is a demanding task, a. The self-load of the tile, which is marginal; requiring efforts in several related activities. Standards formulation b. The impact load that may result from branches of tree, or is one of the key activities required to promote local building fruit from trees, or hailstones dropping n the roof; materials. However, standards formulation is only meaningful ifit c. Imposed load due to uplift wind pressure. is backed by activities leading to the actual adoption of the The most demanding of these loads is the wind load. Kisumu is standards in the production and use of the materials. In Kenya, typical of a windy location where. once in every 50 year, the efforts are being made to promote the wide adoption of fibre­ gu -t wind speed can be expected to exceed 160kmh. This give concrete tiles through several interrelated activities, beyond a cOrre ponding uplift pre sure of about 1400 Pa. There are 13 standards formulation. There is a training workshop in Nairobi, tiles ~er quare metre of ro f area thus making the wind load where on-the-job training is offered for a fee ofabout K Sh 2.000. per tile I09N. The draft standard pecifie that each tile hall There is also information dissemination targeted at a cross­ upp rt a minimum load of 25 kg and the average tile hall section of the construction sector. For instance, a seminar was upport a maximum of 35 kg when loaded at it mid- pan, half held in March 1987, coupled with site demonstration visits way b tween two battens. However, in actual tests, orne tiles focusing on production. The seminar brought together, among have been found to support as much as 80 kg. Unlike the others contractors, building materials manufacturers, finance standards for asbesto -cement heets concrete tiles and fired­ institutions, architects housing development agencies standards clay ~ricks, the draft tandard for fib~e-concrete tile specifies institutions and researchers. As a follow-up to the seminar, the requirement for impact load namely, that the tile must not Housing Research and Development Unit, University ofNairobi, crack wh:n a 250g steel ball i' dropped on it from a height of in collab ration with Action Aid (Kenya) and the Intermediate ~.5m. Thl ~ould be sufficient to guarantee against breakage Technology Development Group (Rugby, England), has embarked In case of failing branches, fruit or hail-stone. on a programme to prepare simplified field manuals to guide local artisans in the production and use of fibre-concrete roofing tiles. b In fibre-.concrete roofing technology, lugs playa key role, y Upporllng the tiles on the roof battens. Therefore, the Cost comparison between fibre-concrete roofing trcngth of the lugs is an important determinant of ali factory tiles and other selected roofing material perf~rmance of a tile. The lugs must with tand the self-load of The cost in the market place for fibre-concrete tiles varies between the tile as weli a the wm. d ad. In a few tests they were found KShs3.00 and KShs4.00 for plain tiles and KShs3.50 and t be r !)able of supporting as much as a 35 kg load which is KShs4.50 for red tiles depending on the location of the aho':: 20 f h . ' . 1m s t e load f the tile and more than twice the production facility. A typical costing analysis for tiles made in the maximum uplift load expected in a hurricane-force wind. How­ Nairobi area is shown in Table 6. ~v~r. the draft tandard stipulates that the lug mu t have uf­ On an averag -'ize house with a nom \ f 50m2 (72m2 roof ICI nt strength t uppnn at least 15 kg. area) the IOlal roofing cost~ can l~<, slIlllmariz<,u (IS shown in lahlc 7. 11 r

JOURNAL OF THE NETWORK OF AFRICAN COUNTRIES

Table 6. Costs required to produce 1 m2 of roofing (13 tiles)

Item KShs

6.5kg cement 11.44 19.5kg sand 2.60 39101 sisal fibre 0.65 Subtotal 14.69 Depreciation on equipment and structure 4.21 labour 6.50 Subtotal 25.40 Overheads at 50 per cent 12.70 Total 52.79

Table 7. Summary of roofing coats of a 72m roof-are. house comparing alternative cladding materials (KSho)

Coslilems Fctile5 Other concrete Of day Galvanized tiles COlTUQ8ted-30 gauge

Cia

A..umpllona Fibre-concrete tiles: o CoSl 01 one tile - KSh 3.52 (13 tiles per m'l o Roof structure baaed on 150 • 50mm trulsed ralters at 2m cts, 100 x 50mm Intermediate ratters at O.5m cis, 50 x 25mm battens at 0.33 cia. o labour. 0.6 man days per m' of roof. o Transport - hire 01 pick up. Concrele or elay Illes; o Cosl 01 one lIle _ K.Sh 4.90 plus 17% sales hu (1 e tiles per mf 21. o Rool slructure based on 150 I( 50mm lrussed rafters al 2m ets, tOO I( 50mm IntermedIate railers at 0.5m cis, 50 I( 25mm ballens It 0.33 CiS. o Labour:z 0.6 man-dlYS per m' 01 roof. o Transport - hire of lorry. Gel sheets; o Stlndard price oI2m sheels. o Roof strueture based on 100 I( 50mm trussed rafters at 2m cts and 75 I( 50mm purllns It 0.93 cls. o 0.4 man-daya per rn".

The""'aweight of fibre

d 01'1 LOC'AL BUILDING MATERIALS ANDTECHNOL(X;IES. I (I) APRil 1989

Malawi

Ssnd--<:ement tiles Fired--<:lay bricks . Fired-clay bricks are easily the single most popular walhng A survey of 10woCOSi houses in Malawi indicaled that. for a terial. Typically, (hey are used for most govemment-fi­ house of floor area between 5Om~ and 90m 2, the COSI of roof ::nced projects and for most buildings which require appro~al cladding was about 25 per cenl of the total cost of the building. as permanent structures, by the Town and Country ~Iannmg excluding cost of services, glazing and fillings. The reason for Departmenl. Most of the prevailing technologi~s fo~ f1red-clay this is that the predominant roofing material. galvanized-steel bricks are rudimentary, such as hand mouldmg m wooden sheets. is produced mainly from imported components. In an moulds using wood-fired clamps with an average output of erfort to overcome this limitation, a project has been started on 2 000-2 SOO bricks per day and a labour force of 17 people. the production of unreinforced concrete roofing tiles. This Normally most of the bricks are of poor quality with a high technology is based on small-scale manual-production tech· incidence of breakage. Energy has emerged as a factor ham­ niques. Apart from basic masonry tools used for ordin

1 1.18 1.1 0.45 ...., 630 430 630 730 1.1'h 0.45 71. Cracked I 12 O.SO 500 500 430 500 580 12'h 0.62 560 490 430 490 530 1~ 0.70 293 270 130 VO 330 2.00 1.1 0.'" 7SO 760 630 710 630 1.1 'h 0.42 490 710 630 710 630 1.2 O.SO 520 550 530 550 680 1.2 'h 0.56 426 410 380 410 430 1.3 0.65 260 260 230 290 360 2.36 1.1 0.36 786 840 780 630 680 1.1 'f.! 0.40 560 .90 630 .90 760 1.2 O,SO 52. 560 530 560 630 1.2 '12 0.52 364 360 3SO 760 400 1.3 SAMPlES ACCIDENTALLY BROKEN

13 JOURNAL OFTHE NETWORK OF AFRICAN COUNTRIES

Table 9. Chemical composition of rice husk ash in Malawi (percentage)

Type 01 incinerator Chemical composition of ash Wire basket Open brick-joint Closed-brick jOint

~(Silica) 90.7 663 66.' PA(Phosphate) 1.7 2.' 3.1 K:zO (Potash) 2." 3.4 3." CaO (Calcium) 0." 0.' 0.' Total C (Carbon) 1.1 0.' 0.7 loss 01 ignition '.0 2.' 2.4 (includes lotal C)

The transverse strength test was based on British Standards improvization of pestle and mortar with subsequent sieving ofthe as 473 and as 550. Part I (1971). The tiles also passed the ground ash. first in a 300 micron sieve and finally in a 150 micron penneability test stipulated in the South ATrican Bureau of sieve. The lime for blending the rice-husk ash was locally Standards for concrete tiles. produced, having the following properties. Cementitious materials rrom rice-husk ash Rice production ranks fourth 10 tobacco. lea and COllon. Be­ Ca(OH)2{Ca1cium hydroxide) 55.6 cause of the I3rgc number of small-scale growers who do not Mg(OH)I(Magnesium hydroxide) 27.2 record their output. the exact quantity of rice production is not CaCOJ(Ca1cium carbonate) 11.7 known. It is. however. estimated that, in 1980. Malawi ranked SOJ(Sulphate) Nil fourteenth in rice production in Africa, with a rice-husk gener­ Ponion not soluble in dilute acid 6.7 ation of about 8.000 tons. There arc three plants, one located in each of the three regions of Malawi. and evidently there arc Two different methods were adopted for mixing the rice· large quantities of rice husks as ':Vaste product at all the pro­ husk ash with lime in proportions of 1: I. 1:2 and 1:3, measured duction siles. A project is currently under way to experiment by weight. In method 1. the two ingredients were mixed in a with production of rice-husk-ashflime as ;1 low-cost binder. The ball mill for about five minutes and. in method 2. the mixing project is based at the Polytechnic of Malawi, with technical was done manually in a mixing bay using shovels and, there­ assistance from the British Research Establishment. Walford. after, the mixture was ground with a pestle and mortar. England. A cylindrical wire basked was designed in the form of an Performance tests on rice-husk-ashllime binder incinerator in which a sample of the rice husk was fired at In order to determine the initial and final setting times ofthe rice­ controlled temperatures, the maximum being 8ooG e. Because of husk-ash/lime binder. the test method stipulated in British the high COSt of the metal frame and wire mesh. the project Standard BS4550( 1978) was used. With a 1:2 mixture oflime 10 switched to the use of a clay-brick incinerator. leading to a cost rice-husk ash and a water ratio as high as 82 per cent, a mortarwas saving of about 90 per cenl. An open-brick and a closed-brick fonned achieving a standard-consistency paste. The initial and design were adopted for two types of incinerator and. in both final setting times were determined as four and seven hours cases. temperatures were controlled at around a maximum of?50­ respectively. The compressive strength of the binder was deter­ 8ooG e. Table 9 gives a chemical analysis of the samples of ash mined for dilTerent mix proportions of lime and rice-husk ash. i.e. from the three incinerators. A further analysis. using X-ray I:!. 1:2 and 1:3. by forming cylindrical cubes of size 50mm x diffraction. showed th;tt. in all threc cases. the ash was amor­ 45 mm which were left under damp conditions for two days. Upon phous. demoulding, the cubes were stored under water at 2O"C for 7 and 28 days. respectively. The results in table 10 were Grinding of the rice-husk ash was done in twodilTerent ways­ obtained. using a standard five-litre capacity ball mill and then using a local Table 10. Compressive strength test of rlce--husk~ash!llmebinder

Mix: proportions Water content Compressive strength lime:ash (percentage of solids) (MPa) (by weight) 7 days 28 days

1:3 100 0.3 0.3 60 0." 0." 60 2.2 2." 1:2 100 2." 3.4 60 ".0 6.2 60 7.1 7.3 1:1 100 2.0 •., '0 3.2 7.0 60 7.4 12.3

14 ON LOCAL BUILDING MATERIALS AND TECHNOLOGIES. I (I) Af'RII. 19H9

Based on this in.itial finding. the 1:2 mix was selected as the most When the results of the tests on the limelrkc-husk-ash feasible for a low.cost cemenlitious material and was thus adopted binder wen.' comp,lTcd with those specified in other national for subsequent tests to detennine the strength of monars made standards. such as Indian Standards. it was found that the from such a hinder. Sand of diameter 1.18mm or less was miKel' material was susitable for use in masonry mOrt,lrs or founda· with the rice-husk·ash/lime binder in proponions of I:2:3 (lime: tion concrete. Surprisingly. the ",shes prnduced hy using the rice-husk·ash:sand) and with the ash from the three different locally improvizcd pestle ;Ind mortar for grinding proved just as incinerators and using a ball mill and pestle/monaro respectively. satisfactory as others. the results shown in table II were obtained.

Table 11. Tests of compressive strength of mortars using different samples of ash in a mix of 1:2:3 (IIme:rtee-husk-ash:sand)

IllCinerator type Ballmilling period Water content Compressive strength Remarks (mins) (percentage 01 total solids) (MPa) 7days 28 days

Wire basket 30 20 3.4 Open brick 24<) 22 2.0 3.4 120 20 2.5 37 30 20 2.4 3.7 5 25 0 0 Crumbled belore test Closed brick 120 20 3. 4.5 30 20 2.3 35 5 25 0 0 Crumbled Wire basket Pestle & mortar 150 p..m sieve 25 12 1.7 75 p..m sieve 40 1.3 1.9

Mauritius 6

Lime production lime, are recycled and ground into an inferior-grade lime used Sugar·cane production is the main source of foreign exchange by the building industry. On the whole, lime is marginally used earning. Lime is a key chemical in the manufacturing process in in construction - for whitewashing and. negligibly, in mortars thc sugar industry. For this reason. Mauritius produces lime for plasters or block-making. primarily to meet the demands of the sugar industry. Out of an Pozzolanas from bagasse ash estimated 4,000 tons o( lime produced per year. about 3,500 The average annual production of sugar-cane over the past 10 tons go the sugar industry and only 5UO tons arc used by years has been 5.6 million tons. Bagasse, which is the fibrous the construction industry. However. Mauritius i~ in the residue of sugar

b. Hopper ash which is the residual collected on hoppers by produced. Approximately 1.2 million tons of leaves are gener4 blowing se<:ondary air through the combustion chambers; ated per annum. When crushed, cane leaves yield about 50 per c. Fly-ash which is the fine ash normally blown out of the cent bagasse. Cane leaves have no direct value to the sugar furnace with nue ga~es. industry, other than as a rt:sidual waste product, so that, when An analysis of the chemical composition of the various they are converted into bagasse, there is every opportunity to ashes, to determine their pClzzolanic characteristics, indicated exploit their pozzollanic value. Cane leaves generate a higher that grate ash and hopper ash have very similar chemical com­ rate of ash than the stem itself, i.e. 5.4 per ceO! of the dry positions, with high silica contents and, therefore, promising weight of the bagasse compared with 2.8 per cent in the case of pozzolanic values. This is illustrated in table 12. the cane stem. However, as indicated in table 13, the ash obtained from cane leaves has less silica than the ash from the Table 12. Typical chemical composition of gl1lt8 aah cane stem. Table 13. Chemical composition of bagasse Percentage compositioo Constituent ash from cane leaves Si02 73.07 Constituent Percentage composition (range) AIA+FeA 12.00 CaO 4.30 MgO 2.66 SiOl 45 - 60 K,o 2.65 CaO Na,o 0.16 4· 7 p,o, 2.57 MgO so, 0.23 K,O CI, 0.01 15·21 loss 00 ignition 1.30 "'0, 2· 4 The third category ofbagasse ash, ny-ash, has rather uninteresting So far, the experiments todetermine the viability ofbagasse ash as characteristics, with a loss on ignition ofabout 70 t080 percent It a pozzolana have been limited to research work on chemical is basically a carbonaceous maUer, containing high levels of properties ofthe basic raw material. A big gap remains to determine unbumt or partially burnt bagasse particles, and is thus unsuitable the physical properties ofbagasse ash as a pozzolana. The granular as a pozzolana. formation ofthe ash is coarse, so that with the present condition of Another type of bagasse is obtained from cane leaves. For not having access to a ball mill at the research laboratory, very little every ton of cane harvested, about 0.3 ton of cane leaves is progress can be made on this project

Nigeria 7 Use of agricultural resides for production of building materials properly utilized. Likewise, some non-agricultural plants, such as There are a number ofnon-wood, fibrous, agricultural materials in eupatorium odorata and Pennisetum purpareum, i.e. elephant the country which can be used to supplement products for which grass, are abundant As a result of the availability of such large wood and wood-based materials are employed in the housing amounts ofagricultural residues, the Forest Products Laboratory industry. Bagasse, a major by-product of sugar production, was directed its engineering section to explore the possibilities is one such material being successfully used in Cote d'ivoire, of using these materials for building purposes. Cuba, Egypt and Greece (FAO, 1976). Bagasse was the first material to be investigated. The process Nigeria has two sugar-processing plants: at Bacita and Numan, used, which is similar to the Cort Technology of Nnabuife and in Kwara and Googola States respectively. The Numan plant is Bryant, involves the pounding of agricultural waste, such as expected to produce about 105 million kg of bagasse, while the bagasse, coconut husk, rice straw, groundnut shell and elephant Bacita plant produces over 35 million ~g of bagasse annually grass, using a pestle and mortar. The flakes produced are sieved (Dada and Badejo 1981). Both plants bum olTbagasse to generate in a 2 nun wire mesh to remove the dust and pith, and the fine energy and reduce the handling costs of waste. particles are separated from the coarse particles by sieving. The The country has now established nine river basin authorities. boards are made from a ratio of4: I of coarse to fine particles of These agencies are expected to take a lead in producing large each material used. Cascamite is used as the resin, while other quantities of rice, maize, millet and groundnulS. Wastes from additives include ammonium chloride, paraffin wax and hexamine. these crops run into thousands of tons per year. The nUrrferous Each panel produced has a final volume of 0.001 m\ after an agricultural development plans launched by the Federal Government initial cold-pressing with a pressure of 1.23 MPa for 10 minutes over the past few years (the Green Revolution, Operation Feed and a later hot-pressing for 20 minutes at a temperature of 150Q C the Nation, and Back to Land programmes of the present and pressure ofO.63MPa. A final thickness of 13mm is obtained administration) have generated harvests with huge agricultural for each board after pressing. residues. Coconut is an agricultural fruit whose husk is not In al~ twosetsofproductsofdensities600kglm', 700kg/ml and

16 ON LOCAL BUILDING MATERIALS AND TECHNOLOGIES, I (I) APRIL 1989

800kg/m' and additive concentrations at levels ofS, 10 and 12 per Some basic advantages in the production of boards from cent were used to produce the boards. Bending properties of the agricultural residues are: boards as well as the water absorption and thickness were all a. Minimal quantities of adhesives arc consumed; determined within 24 hours of production. b. The boards end up with smooth and even surfaces: c. All tools to be used in the manufacturing process can be The basic properties ofbagasse boards are shown in table 14. hand-operated and require minimum capital. while the expansion properties of the boards. produced using The properties of these fibre-reinforced composites 8rc maize stalk. elephant grass, groundnut shell and rice straw, are fairly comparable with those ofconventional hardboards. They are shown In table IS. From the results obtained, it was found that easy to saw and nail. On prcxluclion costs. it is envisaged that it the two variables used were highly significant at the 0.01 level will be cheaper and more durable than thatch which is now being and that there was also interaction between the variables. An used in most rural areas of developing countries. The boards are increased use of resin content resulted in increased bending light and would be safer than tile roofs during an earthquake. strength and reduced water·absorption capacity. The water­ Finally, the prcxluction of these building components in rural absorption capacities of the various boards. after soaking for 24 areas would encourage farmers to plant food crops. since they hours, decreased, as the resin content was increased for all could sell both their grains and agricultural residues (so giving materials except rice straw. additional income per unit area of land cultivated).

Table 14, Properties of bagasse-based particle board

Resin content Specific gravity Bending strength Water absorption Thickness swell' (24 hours) Percentage (MPa) Percentage Percentage

9 0.60 34.53 59 11 0,20 44.74 4' 11 12 0.60 41.20 55 9 0.70 SO.62 43 7

15 0.60 44.54 39 9 0.70 - 63.96 38 5

•Atl8l' 24 hours soak.

Table 15. Mean expansion percentage of thickness In water of fabricated boards from agricultural wastes

Maize Elephant grass Rice stalk Grounctnut shelt

24 48 2 24 48 2 24 48 2 24 48

D1/Rl 82.9 84.8 60,63 65.18 28.30 37.27 62.87 81.00 O'IR2 59.8 84,3 48.84 55.32 25.70 2950 41.71 59.20 DlIR3 35.1 42.4 37.50 4386 16.04 19.55 28.64 37.91

02lRl 49.5 54.3 58,60 62.00 24.09 37.08 38,54 49.15 D2IR2 50.3 55.2 52.07 55.98 17.05 20.03 30.53 44.42 D2IR3 44.8 52.5 49.12 53.55 16.17 18.35 33.13 43.92

03JRl 59.9 86.4 41.14 46.73 26.29 30.81 50.08 59.85 03lR2 48.2 54.9 28.84 34.32 16.49 19.42 25.95 47.63 03103 51.3 57.9 20.95 25.58 11.00 13.37 31.69 51.24

·01,02 and 03 represent board density at levels of 600 kg m3,700 kg,m3 and 800 kg mJ,while Al. R2 and R3 represent the resin corHenl at levels of 8. 10 and 12 per cent respectively. 17 - JOURNAL OF TH E NETWORK OF AFRICAN COUNTRIES

Uganda 8

Lime production to be a source of limestone in Eastern Uganda. They contain a Uganda, like most African cQunlries, is heavily dependent on high percentage of magnesium which may be as high as 8 per cent Portland cement as the only binder for construction. There are in areas around the north-east Karamoja (Napak). They have a two factories producing cement and they both use local lime­ high calcium content and a PiOs content of less than 0.5 per cent stone deposits. The factory at Hima has an installed capacity of Total reservcs of limestone are 56 million tons as indicated 300,000 tons of cement per year, while the Toraro works has an ore and 16 million tons as inferred ore Total limestone outpul capacity of 120,000 tons per year. The known limeslOne deposits are in the range of 10 million to 17.5 million tons. rese ..... es suitable for cement production do not exceed 10 mil­ The foUowing is the chemical analysis of hydrated lime lion tons and al the rate of exploitation, they arc estimated to produced from one of the limestone reserves in Uganda. be running out. The search for alternative cemcntitious materials has thus become a pressing and important issue for 8i02 1.00% Uganda. Opportunities to promote the production and use of Ah03 1.30% low-cost cementitious materials exist but, as yet, these have not Fe.0 3 3.20% been exploited. Lime is currently being produced at Tororo, C,O 63.69% where there are 10 small kilns each with a capacity of 10 tons of quicklime per day. The average monthly output for the first MOO 2.80% three months of 1986 was about 35 tons. Typically, 40 per cent loss on ignition 21.40% of the output goes as reject lime, while the remaining 60 per Others 4.41% cent is used for road conslruction and the whitewashing of Average real value of lime is 57'" buildings. while only a marginal proportion is used as a binder in building construction. In the case of Tororo. the lime pro­ Apan from lime production at Tororo cement works, there are a duced has a chemical composition of 62 per cent CaO for number of unorganized traditional producers of lime around the building purposes and 56 per cent for road construction. Cao Tororo area who exploit the same deposits oflimestone as for the In general, the lime is produced 10 conform 10 British Standard parent factory. After the blasting operation at the deposit by the Specifications 8S89O. A review of selected unexploited lime· Tororo cement factory, the small-scale producers undenake SlOne deposits follows. selective han

the clays are derived from gneissose and granitoid rocks of the sit, mainly because most of the clay deposits arc sedimentary in Buganda-Toro series. Clays derived from gneissose and granitoid origin. having undergone various levels of leaching leading to rocks are usually highly leached and essentially acid-washed, large constituent variations. i.e. v,lriations in particle size. enriched in quartz. Owing to the leaching and washing within variations in content of kaolin. iron. alkali and clay in compari­ these clays, there are usually abrupt changes within the deposits in son with sand and grit. a downward dire<:tion. In Kampala, the largest fired-clay production At the Kapnsi clay works in Kampala. which is semi-auto­ unit is at Kasan;ii. where leaching has produced a 2 m layer of mated. an interesting innovation is the usc of coffee husk as quartz and ochre-free clay down to a distinct horizon level where fuel for firing the Hoffman kiln. The bricks arc fired at ilround this clay is quite dark in colour. It then changes to a very pale, 8500c-I()()()OC.Apart from solid and hollow bricks. the f,lctory sandy clay containingactive stains and then develops slowly into a produces fioor tiles, roof tiles and l.!ecor'ltive clay bricks. Typi­ very ochreous sandy clay just after I m. The most interesting cally the f,lctOry experiences about 8 per cent rate of reject features of these clays are: products. The following i~ a profile of properties of Kajansi clay products: a. Low wet-to-dry shrinkage level; o crushing strength of bricks: 500 psi b. Extreme plasticity; o water absorption of Mangalore tiles: 17.1 per ccnl on 24 c. High vitrification range, up to 16OO"C. thus making it a high­ houTS. energy consuming clay. o transverse strenglh of Mangalore tiles: 310 psi. Compared with imported roof tiles which have strenglh However, the clays derived from amphibolites and basic of 200 psi and water absorption of 20 per cent in 24 rocks, even though possessing a high wet-t()-dry shrinkage level, tend hours). to have a vitrification range of 1200"C to I 400°C so that good o apparent porosity of clay: 210/0. strong bricks and tiles can be produced at fairly low temperatures. o ignilion shrinkage in 24 hours at 200"C = I per cent. On the whole, clays in Uganda have distinct features that o cone of refractoriness = cone 29 giving a temperature of are rather unfavourat:>le for brick and tile production. They 1610"C. require extensive pretreatment before they are suitable for o bulk density of the clay = 132Ib/cu.rt. production. Often, the clays contain a large fraction of quartz o comparative thermal conductivity (k) of small particle size, so that the clays will not easily settle Kajansi bricks k = 2 which causes problems at the drying stage of brick and tile Stone blocks k = 10 manufacture. besides, there is little uniformity within a depo- Concrete blocks k = 8 United Republic of Tanzania 9 Low-cost binder from natural pozzolanas addition leads to a strength of 45 MPa. The low strength attain­ Natural pozzolanas can be found in areas of previous volcanic ment in the Tanzanian experiment could be attributed to the eruption, such as Kilimanjaro. Arusha and Mbeya. The chemi­ fact that the pozzolana was ground separately before mixing cal composition varies from one deposit to another as well as with the cement rather than the two materials being ground (rom one layer to another. Studies carried out so far have simultaneously. Table 18 indicates that the results of the pre­ shown that the natural pozzolana of Mbeya region is more vious table are similar to those from samples of pozzolana calcareous than the pozzolanas of Arusha and Kilimanjaro. obtained from Lengijawe, Arusha region. Here, pozzolana of The chemical test results of pozzolana materials collected from density 2-44 kg/cm) and ground to a fineness of 6300 cm~/g, was Arusha and Mbeya Regions have been compared with ASTM used to prepare ash mortar of pozzolana-cement:sand in the C618-73 as shown in table 16. ratio of 1:3 by weight. Table 17 gives results of laboratory tests on the strength of In general, the test results show that by adding up to 40 per cent concrete prepared with different mixes of pozzolana-cement, pozzolana to ordinary Portland cement, mortars or concrete can using the pozznlana deposits of the Oldonyo Sambu, Arusha be proolleed with adequate strength for basic functions in region.The pozzolana was obtained from 2 to 3 m below ground construction and with additional qualities, such as water level, crushed and. after drying, sieved through 0.25 mOl mesh. A impermeability or water resistance. The Mbeya cement fac­ moisture content of 12-13 per cent was recorded. Concrete was tory, with a targeted production output of 250,000 tons of prepared consisting of pozzolana-cement, sand and aggregate in cement per year. is potentially suitable for production of poz­ the ratio of I: I:2. Concrete cubes of IOcm were cured under zolana-cement. There are deposits of pozzolana about 50km water. away from the cement factory and it is estimated that an The above results are comparable with strength require­ investment in the pozzolana-cement project could lead to sav­ ments of pozzolana-eement in, for instance, Spain, where an ings of about TSh30-60 million a year and an increase of about addition of up to 20 per cent pozzolana to cement produces 25 to 50 per cent in the supply of binders. concrete of 55MPa strength. while a 20-40 per cent pozzolana 19 =

JOURNAL. OFTHE NETWORK OF AfRICAN COUNTRIES

Table 16. Basic properties of pezzals"a. from Arusha and Mbeya regions

Place collected Constituents (percentage results) AI,o, SiD, F.,o, GaO "00 Loss on ignition

Leogijawe 18.38 45.24 7.80 6.68 2.35 3.5 Kandaslkirt 19.00 53.00 10.00 '.0 '.0 Ngozi 1 17.28 61.52 5.48 0.46 0.04 Ngozl2 22.68 34.68 5.00 14.00 12.34 Kyenjo 30.23 41.78 12.70 2.29 2.42 Suma2 18.43 41.78 13.03 1.04 0.51 ASTMC618-73 Al203 + SiCI2 + Fe203. Maximum 70 Maximum - 5 Maximwn= '0

Table 17. Tests on compressive strength of concrete using pozzolanlH;8ment

T". Percentage Percentage Compressive strength MPa Series cement pOZlolana 7days 28 days 3monlhs 6 months

II. 100 0 27.1 40.7 47.7 55.7 1111 80 20 21.3 31.2 31.2 33.' "' 60 40 20.' 24.8 26.' 29.2 Compaction with wooden tamper, 25 strokes for each of three layers.

Table 18. Tests on compressive strength 01 mortars prepared from pozzolana-eement using pozzolana depositsof Lengljawa. Percentage Percentage Number 01 Waterlbinder Slumpcm cement pozzolana Compressive strength MPa ratio '""" 3 days 7 days 28 days SOda,. 12 0.5 15 100 o 28.1 35.7 46.7 SO.2 28.2 35,8 26.6 35.2 46.' SO.5 25.6 34.'

Average 27.1 35.3 46.' SO.6

12 0.5 10 75 25 25.6 31.1 40.' 43.7 26.2 31.4 40.0 41,9 24.6 33.' Too stiff 23.' 31.7

Average 24.6 32,5 40.' 42.9

12 0.6 13 75 25 16.5 2>.7 31.1 33.2 16.9 23.' 30.' 32.' 16.8 21,4 16,2 21.4

Average 16.6 22.5 30.7 33.1

Rderenc~ I Hammond, A.A., 'Mining and quarrying W.tSle$ ulilit;lli{)n in Ghana', 6 Mohamedbhai. G.T.G., 'Case sTudy of MauriTius on local prodUCTion of unpublished doctor of technical seiences thcsis, Eindhoven, Holland. block., lime and pouolana' unpublished report prepared (or UNCHS 1986. (Habital). Mal"<'h 1986. 2 Ben·George, M.• 'o.:velopment of low-rosl Clement using lateriTic $Oils 7 Ademiluyi, E,O•• and Badego, 5.0., 'The role of forestry Re~ardl and limestone'. PrrxuditTgs ofCIB-RIL£M Symposi~m OtT AppfUl"'Ur Institute, lbadan, in Tbe use of indigenous raw materials for low

Events

Expert aroup meetlna on enef'J)' emdent-buildina materials codes of practice in usc of the material. In addition other for low-cost bQuslna. Amman., Jordan. 14-19 November 1987. inlernational agencies. notably UNIOO. G17.. ITDG. The meeting was organized by lite Economic and Social Commission Shelter-Afrique. ECA. and Appropriate Technology Inter­ for Western Asia (ESCWA) for countries or Ihe region_ The national, participaled in the meeting. meeting had four le<:hnical sessions dealing wiih: ECA meetina on formulation of project for local buildina a. An overview oflhe building materials sector; materials production in Africa, Addis Ababa. 19-29 April b. Energy-efficient building materials; 1988. c. Architectural design. and The Economic Corr.mission for Africa.(ECA)is in the process of d. Usc and properties of concrete. implementing a project on the promotion of the local building materials industry in selected African countries. So far. ECA. At the invitation and request of ESCWA. UNCHS (Habitat) with the technical support of UNCHS (Habitat).has completed prepared a speeiallheme paper on soil as an energy-efficient low­ the preparatory phase ofthis project which is in the fonn ofa draft cost building material. project document to be submitted to UNDP. New York. Upon The meeting was aUended by about 11 professionals from approval, this document will form the basis for the implementation building research-related institutions in Ihe region as well as phase ofthe projecl In this connection a two-tier meeting was representatives ofselected international organizations. At Ihe end held firsl a meeting of experts to review and finalize the of the deliberatens. several recommendations were adopted. project document from 19-22 April followed by another top-level mainly addressed to ESCWA tostrengthen and suppOrt activities meetmg from 26-29 April for Ministers of Housing from Ihe aimed. at promoting low-cosl energy-efficient building materials in respective African countries covered in the preparatory phase of the region. the projeel UNCHS - CSC worksbop on formulation of standards and CSCIDRC project Identlficatlnn meetlna on promntlnn of specifications for the production and utilisation ofstabilind local buildlna materials in Africa. Nairob~ 8-11 December soil blocks and lime in Ghana, Accra, 18 - 22 July 1988 1987. The United Nations Centre for Human Seulement (Habitat) The Commonwealth Science Council(CSC) and the International and the Commonwealth Science Council sponsored a workshop Development Research Centre (IORC) sponsored a meeting on on standards and specifications for the production and utilization local building materials. which was held in Nairobi, 8-11 ofstabilized soil blocks and lime in Ghana.Theworkshop reviewed December 1987. The purpose ofthe meeting was to review project and adopted technical recommendations which would form the proposals from participating countries 10 Ihe African region basis for a draft Ghana standards and specifications on soil blocks and to establish modalities for funding a few projects on a and lime for low cost construction. It also formulated strategies for pilol-demonstration basis. The participating countries in­ the wide adoption of soil blocks and lime masonry on the basis of c1uaed Burundi, Ethiopia, Ghana, Kenya, Malawi, Mauri­ standards and specifications. tius, Nigeria, Rwanda, Sierra Leone, Somalia. Uganda, United Republic of Tanzania, Zaire and Zimbabwe. The UNCHS-CSC Workshop on formulation of standards and project proposals covered materials such as stone, lime, spedncaUons for the production of fibre concrete roofing pozzolanas, soil blocks and timber. UNCHS (Habitat) pro­ (FCR) In Malawi, Blantyre, 12 -16 September 1988. vided technil:al assistance, including guidance for specific This is similar to thc An'ra workshop abcne in both format and topics- notably, quality control in production processes and scope.

" t - ~------~ SOME AI'I'ROI'RIATE BOOKS ON I3UILDI0JG from Intermediate Technology Publications

Appropriate Building Materials Rowland Stutz Standards and Specifications for Local Building and Kiran Mukerji NEW EDITION Materials: The Report of the ARSOICSClUNCHS Workshop, Nairobi, A substantially updated and enlarged description of 16 - 24 March 1987 low-cost building materials and methods. With emphasis on locally available materials it covers Lack of appropriate standards for indigenous building foundations, noors, walls, ceilings and roof materials has been one of the major constraints in the construction, and brickmaking. wide adoption of local' building in Africa. The workshop addressed this problem and made proposals 424pp. 1/1115. October 1988. (SKAT/IT Pubs GATE). ISBN 0 94668821 1. £9.95 for the future, reviewing standards and specifications for soil blocks, burnt day bricks, lime, pozzolana and Stone: An Introduction Asher Shadrnon fibre concrete roofing. One of the oldest and most widespread of buiJding 60pp. 1987 ISBN 0 946688 79 6. £7.95. materials can provide livelihoods for craftsmen and Building Mainlenance: A management manual entrepreneurs. This book describes the vari.eties and Derek Miles & Paul Syagga uses of stone as a building material - whether This revised edition comprises in one volume the dimensional' ('cut') or 'field stone', how to extract, management and administration of building work and use it. maintenance and the methods of basic technologies. f 128pp. Fully Illus. Forthcoming 1988. Aimed at Managers of small building units it describes ISBN 0 946688 08 7. £9.95 some common causes of the deterioration of building Building with Bamboo Jules J.A. Janssen fabric and suggests some solutions. With line drawings. photographs and text the author T60pp. Illlls. 1987. ISBN 0 946688 92 3. £7.95 shows how bamboo can be harvested, seasoned and Understanding Natural Fibre Concrete: lis uses jointed to form walls, doors and windows, roofs, floors, and value in building Barrie Evans ceilings and roof trusses, and bridges, and how to weave bamboo. Bllilding with Bamboo is designed for field A technical rationale of how and why natural fibres workers in developing countries. 'reinforce' cement concrete, with chapters on the strength, properties, durability, manufacture and 72pp. 1IIu5. 1988. ISBN 1 85339 OlD O. £5.95 installation of natural fibre products. Building with Earth: A handbook 44pp. I//us. 1986. John Norton ISBN 0 946688 77 X. £4.95 A basic handbook giving practical help with choosing Small-scale Lime-burning: A practical whether, and how to build with earth. Gives guidance introduction on the selection of soil through to construction and Michael Wingate & others maintenance. A practical guide to the selection, design and operation 72pp. 1IIu5. 1986. ISBN 0 946688 338. £4.95 of lime-burning plant for small-scale operations. The book contains sections on fuels and raw materials, as Thatching: A handbook well as on the physical and chemical background, and Nick Hall guidance on the methods appropriate to a small scale. Thatch uses renewable natural resources whose 144pp. II/u,. 1985. ISBN 0 946688 01 X. £6.95. production and processing can be a source of valuable rural income. Thatching is labour· rather than Homes for the poor capital-intensive work. Appropriate Technology Journal: December 1984 This handbook is a guide to good quality thatching, Articles on new approaches to large-scale low-cost describing in words and pictures hqw to achieve the housing provision, rice husk ash cement, earth, maximum possible roof life using either cultivated or community architecture in developing countries, stone, naturally occurring materials. and much more. 40pp. 1IIu5. 1988. ISBN 185339 06Q 7. £4.95. 36pp. £2.50

All these books can be ordered from IT Publications Ltd. Please send a cheque, IMO or International Postal Order to the value of the order PLUS 20% p.,?stage and packing in the UK, 25% for posta~e and packing overseas except in the Far East, Australia and the PaCific (ai:id 40%). Overseas deliveries are sent alr-speei:ied post. Intermediate Technology Publications. Dept. N], 103/105 Southampton Row, London, WCl B4HH L T~: ~ 4~-92:61______.J

r------,This Network Journal was prepared for tile U"ited Nations Centre for Human Settlements (Habitat) I and The Commonwealth Science Council by Intermediate Technology Pilblications in associatio" with J L ~ Whiting and Birch. Ltd. .J OBITUARY

The Network (Africa) deeply bewails the untimely demise of Dr John Kamwanja in Blantyre Malawi, on 9 February 1986 after a short illnes . Dr Kamwanja was an active member of the Network and a founder member of the Network Journal.

He is sadly mis ed by u all. -Editors.