Research and development activities plays vital roles in the development on a nation. The application of the results of such effort leads to the development of new materials, machineries and equipment for the production of various facilities, goods and services to enhance the quality of life of the people. No where is this more notable and significant than in the provision of housing.
Before the impact of Western technology that came with colonial rules, housing was undertaking with traditional building materials and technology.
Most of the technologies were based on sound building science and are still being used in various rural areas today. The main building materials then was the soil available in locality. In most parts of northern Nigeria the soil consist of well kneaded clay nixed with straw. Clay balls which had been allowed to mature for two or three months are laid as brick and fresh clay is used as mortar.
The roof consist of clay reinforce with stick and required Skilled Craftsmen for its execution.In most parts of southern Nigeria, building was also consisted of well kneaded clay mixed with straw. The building is constructed in stages. At each stage, the clay wall was allowed to dry to minimise subsequent shrinkage.
The roof consisted of timber from coconut trunk. The roofing sheet material was made from palm leaves. In many areas bordering the coastal strip, the available soil is low in clay content. As a result the wattle and daub system was evolved. It consists of sticks in two rows which define the wall thickness. The two rows of sticks are kept together with lateralties made also of sticks. This arrangement of sticks is used to retainthe soil and provide reinforcement.
As a result of the influence of
western technology, those who could afford it, replaced the thatch with corugated iron sheets and the earth walls with fired clay bricks. Fired clays bricks were subsequently superseded by sandcrete blocks. As prosperity of the nation increased, especially during the oil boom economy of the nineteen seventies, Nigerian developed a strong taste for high quality goods and services.
The effect in the housing sector in urban centres was the regular use of asbestos and aluminium sheets for roofing, steel and aluminium for windows and doors and marbles and terrazo for floors. With the collapse of the oil boom economy and the consequent fall of the value of the naira against foreign hard currencies by mid nineteen eighties, all imported conventional building materials.
were beyond the reach of most Nigerians. The costs of materials sinçe then have continued to increasė at a high inflationary rate. The unfortunate consequence is that the ownership of a house is now beyond the reach of most Nigerians.
STRATEGIES FOR LOW COST HOUSING
In the light of ever increasing
cost of building a house, various methods of reducing costs have been considered by all who are involved in housing delivery. Some of the most important factors which adversely affect costs are high cost of building materials;
(i) inappropriate technology;
Ciii) high cost of labour;
(iv) inefficient use of building
(v) ineffective supervision of
labour resulting in low productivity;
In the light of the current economic climate, the main source of high cost is directly linked with the inflationary high prices of conventional building materials. These are sandcrete blocks,asbestos and aluminium roofing sheets, steel and aluminium windows and doors and reinforcing rods and cement. It is in these areas, that building materials research and development can have a significant impact in reducing Costs.
Indeed research and development over the past decade or so have produced dramatic and quantifiable results. Hereafter some or the research and development Work done to produce cheaper altermative building materials are presented. The potentialities of pozzolana, as a substitute for cement in appropriate situations, and of plastics, a versatile material of the petrochemical age, are discussed. The main thesis is that research and development work on building materials is very beneficial to the housing sector and should be sustained on a continuous basis by generous funding
In the introduction, reference was made to the use of clay as a
traditional building material. When it is formed into bricks and suniried, it is known as adobe. Lateritic soils which become hard on air drying were particularly suitable for making adobe. The traditional method involves kneading the clay with foot and the clay is made workable by adding water.
The wooden mould is filled with clay without compaction. The brick is removed out of the mould and sun-dried. Bricks made by this method are of low strength and have low resistance to water. The compressive strength is low, usually less than 1 N/mm?, but adequate for bungalows and hence suitable for most rural housing.
Research has shown that the properties of the adobe brick can be improved by controlling the water content and increasing the compaction pressure. Its appear ance can be enhanced by using a
rigid mould. These improvements can be achieved if the bricks are made under pressure in a block making machine. Various brick making machines have been developed. The first major break through was the Cinva Ram developed in Colombia, which is currently marketed in Nigeria. Other presses include Tek-Block Press (Ghana) Brepak (Ghana) Ceneema Cameroun) Supertor (Brazil) Testaram (Mali) Ellson Block master. (South Africa), Latorex (Belglum) Cerratec (France). The Nigeria Building and Road Research Institute has also produced a press of improved performance.
The original version had three moulds and three blocks could be produced in one operation. This press has been replaced by a new version with two moulds of a better performance with compaction pressure of 3 N/mm’. These presses are labricated locally. Sun-dried blocks produced by the NBRRI machines have been used in rural housing and for farm houses.
CEMENT STABILISED BLOCKS
The properties of soils for building can be improved by
stabilisation. The most common
agents are cement, lime and bitu-
men, depending on what is avail-
able locally. Portland cement has
been found to be the most effective
of all the agents, especially for
tropical lateritic soils available in Nigeria. Stabilisation increases the resistance of the soil to water absorption and increases the compressive strength. The potential stabilised soil became a reality when, through research and development, presses of high compactive effort were produced. One of the first and most famous is the Cinva Ram.
In the light of local conditions in
Nigeria, cement stabilised blocks
cannot be a viable alternative to
sandcrete block unless its cement
content is less than that in sandcrete block. In the research and development work in the Nigerian Building and Road Research Institute (NBRRD, the maximum cement content was fixed at 5%. The goal was then to develop a press with adequate compaction today produce a table stabilised block. After various laboratory and field trials, a press was fabricated that was a pable of producing a block whose compressive strength was adequate for building a bungalow.
Typical properties of a cemen
stabilised block based on NBRRI
research are as follows:
-Bulk density 1810 Kg/m
-Water absorption 12.5%
-Compressive strength 1.65 N/mm’
Cement stabilised blocks are
successfully used in a full scale
house construction in Festac Town,
Lagos in a joint project by the Federal Housing Authority and Nigerian Building and Road Research Institute. As a result of using these blocks and other local building materials for the ceiling, the cost of the building was reduced by 50%
FIRST CLAY BRICKS AND
Another method of using local
clay for building is by firing. The technology for fired day bricks is
well known. In the nineteen seventies a good number of fired clay brick industries were built by Federal and State Govemments. Initially, the fired clay bricks could not provide a viable altemative to sandcrete blocks because they were in most cases not cheaper than sandcrete blocks, Madedor and Omange 1985. Curently, fired clay bricks are considerably cheaper than sandcrete blocks and are receiving a well deserved and increasing patronage. This change is not due to any development in the technology; it is rather the result of the astronomical rises in cement and sand prices, the two main conıponents of sandcrete blocks.
The only difficulty now is that most of the brick industries are
unableto meet the denmand becuse
ney are operating under hali capacity. This draw-back is due to the high technology enyployed in these industries. As a result the cost of maintenance is high. The spare parts for maintenane have to be Imported, and given the low value the Nigerian currerncy, the spare pafts are exhorbitantly higb.
Consequently, curent eftorts are going on in NBRRI to develop a much simpler technology that is more efective n the current economic climate. To this end, the International Development Research
Center (1DRC) of Canada and NBRRI
engaged in a joint project to development scale draughi kiln.
The kiln be fired by diesel or coal available locally. Owing to the current ditficulty in obtaining coal locally, the finał design of the kiln is to employ used engine oil from vehicles or diesel oil.
The green (wet) clay blocks will be made manually with the second version of NBRRI block making machines. The resulting production process will be more economical and very easy to maintain. It is gratifying to report that the draught kiln has been consructed and firing rials wall started in July, 1992. This development was concluded possible for small scale brick making factories were able to constnuct in various construction
catchment areas of the country.
Its enable the country to transfer reliance on production of building
materials from large companies to small ones, resulting in flexibility in production and reduction in transportation costs as more small units are sited in all States.
FIBRE CONCRETE ROOFING
Apart from the walling material, roofing sheet is the most expensive
component of a housing unit. Due
to the curent very low value of the Nigerian currency, conventional
roofing sheets of asbestos and auminiun are beyond the reach of
the average Nigerian.
Fortunately, research and development has produced cheaper and equally efective altematives which have received wide acceptance for low cost housing. These are fibre concrete roofing sheets and tilees. The technology of fibre concrete rooling sheet is simple. In its crudest form, it consists of a simple table on which a wet screed of cement of specified proportions of cement, sand and natural fibre is prepared within a timber frame.
The thickness of the screed is controlled by a perimeter timberedge. The screed is levelled and all air bubbles are renoved. The screed is then transferred from the timber by a combined action of tilting the timber frame and gentle pulling of the polythene sheet on which the screed lies on to a corrugated mould.
As asbestos sheet can be used as such a mould. Any slight imperfections especially on the ridges during the sliding action are remedied by simple manual touches. The screed is left to set for about twenty-four hours before curring in the conventional manner. Aiwo-man team can produce a square metlre fibre concrete rooting sheet in filteen minutes.
NBRRI has investigated this technology with local fibres. Coconut coir fibre in the south and ramma in the north of the country are found to be suitable for making fibre concrete roofing sheets. Fibre concrete roofing sheets like asbestoss sheets are britle and should be handled with care during transportation. Breakage can be virtually eliminated if production of the sheets is done at the constructiorn site.
In this regard, fibre concrete roofing tiles have a greater advantage and have displaced the roofing sheets in popularity. Since they are smaller units, they are less reliable to breakage during transportation Typical composition and properties of one square metre of corrugated fibre concrete roofing sheets are given below:
PIBRE CONCIRTE ROOFING TILES
Pibre concrete roofing ties are made of the same materials as fibre
concrete roofing sheets, that is cement, sand and natural fibre.
The tiles are produced with the help of a vibrator ensuring better qualty control. Since the fibre is mainly used for shaping tile while it is wet, vitualy any fibre can be used for its productlon.
Currently, fibre concrete tiles are commercially available in lagos,
Oyo, Enugu and Abia States with imported vibrators. Consequently
the initial investment can be high, NBRRI is developing a vibrator that can be fabricated locally. Two prototypes with improved vibration have been perfected and should be available for commercial use. Fibre concrete roofing tiles have become popular in housing in new housing estates in Enugu State. They are planned to be used in new ones planned in Lagos State.
From this subject and limited review of research and development effort in Nigeria in the past ten years, it is self evidence that research and development in the building sector has had a tremendous beneficial impact on housing in Nigeria.
The impact would have been much greater if more funding has been made available. The limited resources allocated to research at the moment is understandable in the current economically difficult situation. It is hoped that as the economic circumstances improve,more resources will be allocated to research to enable new materials
and systems to be investigated to
meet the dynamic changes that must
occur in the society.