AbstractThe use of asbestos fibres in construction products has been banned in European countries for about two decades due to its effect on human health. At present, many developing countries use asbestos cement board as one of the most important construction products for roofing, cladding and partition walls. The Hatschek process is the most commonly used method to produce asbestos Fibre Cement Board (FCB).
There are two major problems for the asbestos FCB manufacturers in replacing their products with non-asbestos FCB. The first one is finding materials and fibres that are available and competitive in price compared to asbestos fibres, and the second is providing inexpensive machines and equipment to produce non-asbestos FCB.
In this research, an effort has been made to solve these two major problems. After the initial laboratory investigations on several natural and synthetic fibres some of the fibres with potential use in FCB were chosen for the further investigations. A slurry vacuum dewatering process was then designed and made for the laboratory use. The performance of material selections and mix designs selected from the laboratory studies were subsequently verified with factory Hatschek process in a factory site trial.
Many specimens with natural and synthetic fibres incorporating silica fume and limestone powder were made and tested in the laboratory. Silica fume and limestone powder were used for enhancing flexural strength and suppression of alkalinity to reduce breakdown of the cellulose fibres. The results of mechanical, physical and durability tests were analysed. The microstructure of the fibres and composites was also studied by SEM (Scanning Electron Microscopy).
At some stages, mix design optimization was carried out to gain the highest flexural strength. The most suitable mixes were chosen for the factory site trials. A number of full-scale non-asbestos trial boards were made successfully in an asbestos FCB factory and tested in accordance with the current national and international standards. The results indicated that the trial boards fulfilled the requirements of the relevant standards.
Based on the outcome of this research, a combination of acrylic fibres and waste cardboard in a mix incorporating silica fume and limestone powder in addition to Portland cement can be used to replace asbestos fibres. Although broadly compatible with the asbestos cement production process, this formulation change will necessitate some changes to the existing production lines in asbestos cement factories to produce non-asbestos FCB.
|Date of Award||2011|
|Supervisor||Essie Ganjian (Supervisor), Peter Claisse (Supervisor), Homayoon Sadeghi Pouya (Supervisor) & Messaoud Saidani (Supervisor)|
- Cement composite
- Properties of cement board
- Fibre cement board
- Natural fibres
- Synthetic fibres