|Journal of the Network of African Countries on Local Building Materials and Technologies - Volume 1, Number 4 (HABITAT, 1991, 48 p.)|
* By S.N. Maugo, B.Sc., M. Eng., Department of Civil Engineering, University of Nairobi.
This paper was presented to the Third International Seminar on Structural Masonry for Developing Countries, held in Mauritius, July 1990.
This paper examines various constraints faced by developing countries in their efforts to develop a code of practice for structural masonry. It also outlines the steps the Kenyan Government has undertaken through the Kenya Bureau of Standards, a governmental statutory organization, to overcome some of the constraints in a move aimed at eventually the development of a national code of practice for structural masonry.
The task of developing a code of practice (for instance, for structural masonry in any country), is usually entrusted to a drafting committee. The committee sieves through all the available data and information on the subject and compiles a document which contains recommendations for dealing with various aspects of design based on what is generally considered to be of good practice at the time of preparing the code. The document is then revised regularly to incorporate recent developments on the subject.
In the developed countries, there is abundant research data and information which the drafting committees have used to prepare comprehensive codes of practice for structural masonry, and additional data are continuously being generated. However, in most developing countries very few research data are available. In addition, there are other constraints which most of the developing countries must resolve before formulating a national code of practice for structural masonry. These constraints include: low-level manufacturing technology, manufacture of non-standard masonry units, non-adherence to quality-control procedures during manufacture and construction, and lack of engineering education and training. These constraints are presented in this paper with particular reference to the situation prevailing in Kenya. Furthermore, remedial measures taken by the Kenyan Government through the Kenya Bureau of Standards are presented and some recommendations made.
Constraints facing the development of a code of practice for structural masonry for developing countries
Insufficient data on materials
As mentioned earlier, the code drafting committee has to have data on which to base its recommendations. Even though design principles are universal, data on materials for manufacture of bricks and blocks vary geographically. Further, design considerations involving environmental factors vary considerably from one area to another. Information on these factors is missing in most of the developing countries, because very little research work has been done.
Concrete hollow blocks produced in a modern plant
The limited research data or information available are not very well documented, and manufacturers have not been of assistance in this connection. They are unwilling to institute research work or provide funds to research institutions. They have actually inherited the manufacturing processes from their predecessors without making any changes so as to keep pace with recent developments. Manufacturers rarely provide technical information on their products and, if they do, only sizes and costs are indicated leaving out the pertinent information a designer requires, such as the strength of the masonry units.
Low-level manufacturing technology
Low-level manufacturing technology for the manufacture of masonry units exists in most developing countries. In Kenya, for example, there are only three manufacturers who produce wire-cut bricks. There are, however, numerous small-scale manufacturers and individuals who manufacture hand-made bricks. The green bricks in clamps are burned using coffee husks or firewood. Blocks are also manufactured by a few companies using old machinery, building contractors, small-scale manufacturers and individuals who use hand-operated machines. Such manufacturing methods under uncontrolled conditions are bound to produce masonry units of highly variable physical properties. It will, thus, be unrealistic to develop a code of practice for structural masonry using such masonry units.
Manufacturers of masonry units produce quite a number of products with varying shapes, sizes, and quality. In such a situation, an engineer designing a structure will be surprised to find that it is difficult to achieve the specified design strengths. Mostly, this has to do with manufacturers being willing to economize on labour costs and materials at the expense of quality. Thus, it is not surprising to find a whole batch of building blocks failing to meet the minimum specified strengths.
Non-adherence to quality-control procedures during manufacture and construction
Masonry units produced in factory conditions are expected to have minimum variations in their physical properties provided stringent quality-control procedures are adhered to. Testing of raw materials and finished products, mixing, pressing or extruding, compaction, curing and/or firing are important steps in the manufacture of masonry units. In each step, quality-control measures should be observed to ensure that the desired results are attained. Otherwise, products of varying properties will result. Incidentally, quality-control programmes are non-existent in most factories. Thus, the market is usually saturated with masonry units that are non-standard and of poor quality. Unless a complete overhaul of all the machinery and the existing manufacturing technologies is effected, such masonry units with highly variable physical properties will continue to be manufactured notwithstanding the existence of a national code of practice.
During construction, quality-control procedures should also be observed to ensure that good work is achieved as it significantly affects the strength of masonry. Whether there exists a code of practice or not, the final judgement as to whether a structure performs the intended functions depends, to a large extent, on the quality of the masonry units and the person who lays them. Factors, such as the construction factor of safety, mortar proportioning and mixing, and thickness of mortar joints, are greatly affected by the individuals who perform all these tasks. These individuals must, therefore, be knowledgeable enough in the material they are using in order to carry out the tasks correctly. However, many of the masons available are illiterate in so far as masonry education is concerned. Furthermore, most contractors use layfolk as masons, because well-trained masons are considered to be expensive and contractors tend to economize on labour costs.
Lack of engineering education and training in masonry
Masonry is considered by many as an old-fashioned, outdated material. Thus, it is rarely taught at university level even though many buildings are built and/or clad using masonry units. The present cadre of practicing engineers is, therefore, not prepared to design in masonry. A code-drafting committee comprised of such individuals will, thus, not contribute meaningfully to the formulation of the code. At lower cadre level, much work has to be done to educate and train enough personnel as masons or general overseers.
Remedial steps undertaken by the Kenyan Government through the Kenya Bureau of Standards
The Kenyan Government recognizes the fact that the development of a national code of practice on structural masonry requires substantial data and relevant information on which to base the document. Thus, the Kenya Bureau of Standards has been given the mandate to formulate compulsory standards on all masonry units. To date, specifications on bricks and precast concrete products (1), (2), (3) have been formulated. The specifications contain minimum requirements and manufacturers are expected to manufacture their products to higher specifications than the recommended minima. Failure of any manufacturer to meet the minimum requirements may result in prosecution in a court of law. It was found that deterrent measures were necessary since if the standards were voluntary, no meaningful progress in the quality of products could be achieved. Manufacturers who have difficulties in achieving the minimum requirements, because of machinery, are accorded a grace period within which to replace them.
The Bureau deploys a number of quality-control inspectors to help manufacturers set up quality-control programmes. The inspectors are well trained university graduates who have undertaken quality-control courses locally and/or abroad. The inspectors also monitor the quality of products, both at the manufacturers premises and in the market, through random sampling and testing for compliance to relevant Kenya Bureau of Standards specifications.
One of the Bureaus objectives is to educate the purchasers/sellers or manufacturers so that they become quality-conscious. In pursuit of this objective, the Bureau holds an annual standards and quality-control seminar, with participants drawn from industry and consumers. The Bureau gives regular lectures to both manufacturers and consumers on the importance of standardization and quality control.
Complaints from consumers are taken very seriously. Prompt investigations are instituted to establish the cause of the complaint and other related facts. The culprits are prosecuted in a court of law.
With these measures, the manufacturers have shown remarkable improvement in the quality of their products and are satisfied with the role played by the Kenya Bureau of Standards.
In addition to the role the Kenya Bureau of Standards is playing, three organizations, namely, the Kenya Building Research Centre (KBRC), the Housing Research and Development Unit (HRDU) of the University of Nairobi, and the Kenya Industrial Research and Development Institute (KIRDI), are currently carrying out research on building materials. The Government has also started the University Research Fund wherein funds have been set aside solely for use in carrying out research work. The Government has also introduced a new system of education in which practical subjects such as masonry and woodwork are taught at pre-university level. There are also several post-secondary education training institutions offering practical training courses such as masonry.
External wall made with fired clay-brick masonry
Conclusions and recommendations
Before developing a code of practice for structural masonry, developing countries must resolve the constraints outlined in this paper. In the case of Kenya, it is hoped that the remedial measures undertaken will, in the near future, provide adequate data on materials and masonry units which a drafting committee will use to formulate a national code of practice for structural masonry.
In view of the prevailing conditions in Kenya, and in most other developing countries, the following recommendations need to be considered:
(a) Research work is needed in order to generate adequate data on materials, masonry units, manufacturing and construction technologies, and environmental factors;
(b) Existing data and information need to be analysed and properly documented;
(c) Priority should be given to the introduction of a masonry course at university level;
(d) At the lower level of cadre, sufficient personnel should be trained in the use of masonry;
(e) There is a need for manufacturers of masonry units to form an association which will institute independent research work and provide technical information in the form of catalogues and design guidelines;
(f) Code-drafting committees should formulate reasonable standards wherein low-strength masonry units are allowed as such masonry units have performed successfully in the past;
(g) Adoption of mandatory specifications on materials and masonry units, as is the case in Kenya, or grading of manufacturers on the strength and the quality of their products;
(h) There is a need periodically to assess the performance of the standards institutions such as the Kenya Bureau of Standards.
1. Kenya Bureau of Standards, KS02-300: Specification for Burnt Clay Bricks.
2. Kenya Bureau of Standards, KS02-547: Specification for Clay Building Blocks.
3. Kenya Bureau of Standards, KS02-625: Specification for Concrete Masonry Units.
4. British Standards Institution, BS 5628 Parts 1, 2 and 3: Code of Practice for the Structural Use of Masonry.
5. Hendry, A.W., Sinha, B.P., and Davies, S.R., Load-bearing Brickwork Design (Ellis Horwood, 1987).
6. Curtin, W.G., Shaw. G., Beck, J.K., and Bray, W.A., Structural Masonry Designers Manual (BSP Professional Books, 1987).
7. Sahlin, S., Structural Masonry (Prentice-Hall, 1970).
8. Hendry, A.W., Structural Brickwork (Macmillan, 1981).