Production of fibre cement

Fibre cement has long been an excellent design material due to its malleability when wet and its exceptional strength when dry. The durability and reliability are based on a precise material composition, which is constantly being researched and further developed. The production process is a combination of many years of experience in traditional manufacturing and further innovative developments based on the latest findings.

Thanks to the long tradition of our group of companies, experienced employees are able to produce the fibre cement panels from the processed raw materials with specialized knowledge, precision, and craftsmanship. The interplay of tradition and innovation has delivered fibre-cement products to installations all over the world for over 100 years.

The main components of the fibre-cement recipe are cement, fillers, cellulose, synthetic fibres, colour pigments and water. In addition, depending on the intended application, some additional, functional raw materials are used. Within the research and development of Swisspearl, safety of health and environment are fundamental when developing the recipes and choosing raw materials. 

Even though all nine Swisspearl plants are asbestos-free for more than two decades now, also Swisspearl was one of the many fibre cement producers that used asbestos to produce fibre cement building materials due to its durable and hard-wearing properties. When studies proved the health risks of inhaling asbestos, Swisspearl initiated a successful research and development programme to find solutions to eliminate asbestos from the recipe. 

 Swisspearl was a forerunner in replacing asbestos when it started the phase-out already in the 80s – the time when stricter regulations on the use of asbestos only started being rolled out in Europe.

First, the cellulose bales are dissolved in water and ground to the desired fineness. The cellulose is added to a mixer with other raw materials and cement. The mixer agitation homogenises the slurry. As the cement bonding reactions start right away when mixed with water, the mixed slurry is pumped without delays to the production line.

In the production line the slurry is pumped to basins eqiupped with rotating cylindrical screens. Usually the so called Hatschek process has three to four rotating screens. 

On the surface of each of the rotating screens, supported with suction inside the drum a thin layer of the slurry is created, approximately 0.9 mm. From the screens the thin fibre-cement layers are transferred to a rotating felt on top of eachother. These multi-layers are then wrapped around the format roller until the desired thickness of the panel is achieved.

This process takes between 20–100 seconds, depending on the size and format of the panel. The diameter of the format roll determines the length of the panel, which is given its raw format by a corresponding cutting blade. In order to produce a different format, these units must be retooled. At this point, the fibre cement still contains a lot of water and the setting process is still in full swing.

In addition to Hatschek technology, Swisspearl uses flow-on technology. In the flow-on technology thin fibre-cement layer is formed on a felt, but by applying the thin layer on a felt from head box. From the felt this single layer is then wrapped around the format roller like in the Hatschek technology.

First, the panels are stacked in between layers of steel sheets and pressed under a pressure of up to 10,000 tons in order to extract excess water. Pressing reduces the water content of the panels from 28% to 15% and the panel density is increased. The remaining water in the panels continues to react with cement and hardening progresses. This, so called hydration process releases heat and takes place in a dedicated area, called curing hall. Usually after several weeks of curing, the water content is only 7–8%. However, curing can be significantly reduced by using autoclaving. In an autoclave panels are steam-cured in high temperature and pressure. Depending on the targeted characteristics, some panels are further processed after the curing. The additional stage includes further drying in a furnace to reduce and control the moisture content of the panels as well as adjust some durability properties.

Our wide range of colours covers most of our customers' needs. We colour the panels themselves by adjusting the colour of the slurry as well as can apply almost any colour to the panel surface upon request. The surface colours are poured or sprayed on the panels. Our range of colours vary from opaque to transparent, thereby allowing the aesthetic interplay of the panel surface and the colour. However, it is not only the colour itself that affects the appearance of the facade. Various surface treatments create visual effects, to which the shades of our colour lines are harmoniously and consistently coordinated with professional expertise.

Fibre cement allows many different surface treatment options - sanded, milled, iridescent, or left in its natural smooth state. We are constantly researching and developing additional special surface finishes. Our product families are targeted to various end uses. The maximum standard formats are aligned with them. On flat-boards the thickness range is from 3,2 mm to 12 mm, depending on the product family. We have in our portfolios standard formats targeted for direct installation as well as in many products maximum standard format 3050 x 1250 to be used for customization according to the customer specification. We also offer special productions on request, such as special cuts, milling, perforations, and ornaments.