|FCR: Fibre Concrete Roofing (SKAT, 1987, 185 p.)|
Limits of application and acceptance
- The future users of FCR have to make a conscious decision to adopt FCR, in order to ensure their identification with the material and to prevent subsequent rejection which may happen for social reasons.
- Emphasis is needed on good training of the workteam and on quality control.
- A basic management organization is essential to undertake production, transport and use of the FCR elements.
- FC roofing can be cheaper than any comparable material, but only if it is manufactured fulfilling accepted quality standards. Otherwise limited lifespan will destroy the economic advantage.
- The following points can be considered as the limits of application:
· Insufficient standard of
craftmanship in manufacture and installation
· Deficient roof structure
· Lack of good management
· Extreme weather conditions like hailstorms and hurricanes
· Vandalism, certain ballgames and fruit trees dropping heavy fruits
· Deficient raw materials
· Deficient tools and equipment
· Uncertain social prestige
· Public does not trust the new material
It has to be noted however, that the same limits apply to other materials to a varying degree, particularly in the case of hurricanes.
- Economics are not purely valued in profit but in socio-economic benefits such as
· Job creation
· Import savings
· Use of local materials
· Improvement of roofing technology
- If the producer and user are the same organization, the
problems are more production orientated. Acceptance of the product Is easier In
such cases, because the users are involved
In the production process.
- In the case where the producer and user are separate, marketing becomes the first problem; quality standards and costs will be judged by the market.
- The buyer will ask for guarantees from the producer. But the quality of the roof depends also on the appropriateness of the substructure as well as on how the roofing elements are mounted on the roof. In cases where the producer sells directly to the user he might be In position to provide assistance and advice on these aspects. The producer should be able to give guarantees for the product; but in many cases he has no Influence on how the roofing elements are Installed on the roof substructure.
- The chopped fibre plays Its main role In giving the fresh mix a better cohesion and It enables the moulding of corrugated products.
- All types of natural fibres are possible to use in FC as long as they are clean.
- Concrete with chopped natural fibres is a material with properties more like burnt clay than asbestos cement and it has to be looked upon as an unreinforced material.
- The durability of natural fibre concrete is good if the batching, mixing, compaction and curing are done properly.
- The stresses within the roofing element are dependent on its dimensions and how it is fixed. In this respect the roofing tile seems to have an advantage compared with the roofing sheet.
- The production of FCR is a sound technique and much practical experience is available.
- Failures are identified and are usually due to production errors.
- Tilemaking can be started in most places with fair chance of success, if professional training is provided and if the appropriate method is chosen.
- Future experiments should take into account the history and the state-of-the-art and not simply be in the spirit of appropriate technology enthusiasm.
- The design of the roof structure should be simple.
- The minimum pitch should be 20°, but up to 30° is required in areas where torrential driving rains occur.
- Wind suction may produce higher forces than self weight.
- Good quality timber is desirable for the roof substructure though wood is getting scarce and expensive.
- FC tiles need approximately the same quantity of timber as FC sheets.
- Carpenters who traditionally build roofs for C.I. sheeting will need special training to achieve the more demanding quality execution required for FC roofing.
- Prior to installation on the roof, check FC elements for good quality.
- The laying of the sheets should be done by a team of carpenters and sheetmakers.
- FCR elements should be handled with great care.
- The driving of nails through the elements must be discouraged. If screws or J-hook bolts or nails through predrilled holes are used they must not be overtightened. Cast-in wire-loops which allow fixing from underneath seem to be a good solution as well.
- Treat FC products like clay tiles!
- Never go on a roof without crawling boards!
Costs and economics
- In most countries FC sheets or tiles can be produced at a cost of 2 to 4 US$ per square metre.
- A square metre of FC roof including cost for the roof structure varies between 4 and 8 US$, depending on the local situation.
- A FC roof Including roof structure can be built at 2/3 to 3/4 of the cost of a similar roof covered with asbestos-cement or galvanized corrugated Iron (GCI) sheets.
- The roof structure will consume half of the investment, the FC roofing material the other half.
- The economics of FC products depend largely on the life span of the sheets or tiles.
- From the technical point of view the life-span of FC pro ducts can be ten years or more.
- Both the manufacturer of FC products and the roof builder influence the lifespan of the products by their actions.
- Economics of FC are not only valued In costs but in other benefits to a local economy such as
· Use of local
· Low Initial Investment
· Job creation for men and women
· Less foreign currency necessary
· Low transport costs.
- The import component In a FC product - if any - is in the cement and the plastic for the moulds. It Is typically between 30% and 50% of the costs of the FC product.
- Knowhow for proper production and application of FCR elements Is ready and available. But there exists a lack of provision of knowhow and technical rationale representing the actual state-of-the-art to the practitioners.
- Most failures in FCR production and application so far were due to no or bad knowhow transfer and insufficient professional training.
- Since the technical rationale of FCR is still in a process of development, the decision-makers and practitioners should be kept up-to-date with the provision of the most up-to-date data and facts.
- No continued professional education seems to exist. Continued knowhow transfer Is essential for the FCR producer.
- The dissemination of knowhow and continued support of the producer, adapted to the local demands, should be done through several regional FCR centres.
- A good FCR hardware kit must be accompanied by a well adapted knowhow transfer package.
- The decision makers need better Instruments to make their decision based on objective criterias.
- A complete decision making package should be prepared within the FCR follow-up study.
- The most efficient training seems to be possible at regional training centers or on the job, but there appears to be a lack of qualified teachers and money available for knowhow transfer and professional training.
- In many cases of the introduction of new products into new markets it is the dynamic (acceptance) of the market, which decides whether a product is appropriate for a given situation.
The producer has to Improve the product It the market refuses it. Our analysis shows that the FCR technology does not (yet) fit into this self-control by the market, because: FCR is not yet a well understood common technology. Therefore failures because of inappropriate production or application may discredit the technology Itself for the future. FCR is a roofing method which should not only serve the interest of a single manufacturer, but create additional jobs and save foreign exchange.