There are lessons to learn

Experts from all over the world attended The International Inorganic Bonded Wood and Fiber Composite Materials Conference, held in Idaho in September.

They were there to learn about the latest production and marketing techniques and trends that make the composite panel industry so dynamic.

Chairman Dr Al Moslemi, University of Idaho, opened the session. He said that when the conference began in 1988 the building industry was wedded to wood, but now more than one billion ft² of fibre cement boards are produced annually.

He predicted a “tremendous growth trajectory” in siding business for fibre cement. US siding (cladding) is a US$7bn annual market. Roofing applications and tile backer boards are natural extensions of the current markets. He said that outside North America asbestos continues to have a good market.

It isn’t all roses. The spectre of over-production, at least in the short run, hangs over the industry, similar to the OSB situation.

The other ‘cousin’ of fibre cement is fibre gypsum. Slower in being adopted in the North American market, this technology has met success in some European markets, especially Germany. However USG has built a new fibre gypsum plant in Gypsum, Ohio.

George J Venta described glass fibre mesh reinforced cementitious boards. He said the product usually consists of an aggregated Portland cement-based core matrix reinforced with glass fibre scrims embedded on both sides. The scrims are coated with PVC plastisols to prevent alkali attack from the cement. He estimates its annual production capacity as approaching 75 million m² with 12 US producers and one each in Canada, the UK, Germany, and Brazil. He says the product retains its strength while wet.

Ryszard Koslowski, Institute of Natural Fibres, Poznan, Poland, described three-layer particleboard providing a fire barrier on both sides. The core would be of lignocellulosic particles while the faces would be exfoliated vermiculite. These are based on flax shive, waste wood particles and vermiculite. Amino resins reduce formaldehyde emission. Board properties are similar to those of conventional flax shive and wood chip shive boards.

Mr Kozlowski said the three layers are produced separately and then pressed. He said they are easy to finish, strong, durable, and ensure tough mechanical joints.

Dede Hermawan of the Wood Research Institute, Kyoto University, Japan, reported that mechanical and dimensional properties of conventional cold pressed cement-bonded particleboard could be improved significantly by post-press curing with either gaseous or super critical carbon dioxide. He said: “The curing was accelerated dramatically within a few minutes, rather than a week.”

He ventured that the high production of calcium silicate hydrate and calcium carbonate during the hydration of cement, and the interaction with wood surfaces, might be the main reason for the superior strength properties of the carbon dioxide-cured boards.

He said that when 10% or 20% of CO₂ was applied for 10 minutes, the properties were similar to those of two week curing.

He concluded: “Recycled CO₂ from boilers and engines of cement board industries is applicable to rapid production of high-strength cement-bonded particleboard.”

Shylesh Moras, Department of Civil Engineering and Applied Mechanics, McGill University, Montreal, Canada, touted the possibility of a new generation of lightweight cement based composites for residential construction.

He said: “Extrusion technology can incorporate large volumes of expanded polystyrene beads into a cementitious matrix. The characteristics of fibre cement, including superior durability in freeze-thaw conditions, fire resistance, insect and rot resistance, low maintenance and competitive cost, have already given it a share in the roofing and siding industry.” He said the low density and insulating characteristics of the beads brought the other attributes.

Mr Moras indicated that the beads could be used up to 80% in volume, although board strength and toughness decreased significantly as the bead content increased.

Scrim-faced cement board is the future in global lightweight construction technology, according to Kurt W Peterson, vice president sales and marketing, BMH Engineered Building Products Group, Dallas, Texas.

The product has two outer layers of PVC-coated fibreglass scrim with a core of Portland cement, lightweight aggregate, fly ash, high alumina cement, pulverised gypsum, water, plasticisers, foaming agents and other additives. Other aggregate options include volcanic ash, pumice, crushed blast furnace slag and polystyrene beads.

Mr Peterson said 11 North American plants produce the product with six more under construction. His organisation offers a licence technology. He said that US$11m investment would provide a 43 million ft² annual capacity plant. Based on current North American product selling price, he estimated payback at 26 months.

Chris Kliefoth, vice president, Certainteed Corp predicted that the fibre cement business will grow to a two billion ft² market.

Current capacity is 1.2bn ft². By the end of 2001 it will be about 1.8bn ft², including a small amount of imports. The industry is operating at about 80% of capacity now. Mr Kliefoth said production coming in could provide a challenge: some competing products will make markets tougher.

The biggest underlay product is still wood. The ultimate weapon of vinyl siding is that it’s prefinished and maintenance-free.

Earl T McCarthy, McCarthy Products Co, Seattle, Washington, said his dual parameter microwave systems can measure both moisture and dry mass of green and dry materials throughout a process. Systems vary from contact to one-sided non-contact. An on-board microprocessor acquires, processes, and stores data. His new QualScan on-line system measures area and length of 50,000 to 100,000 fibres or particles in a single test.

A study by D M Badger of Norske Skog-Tasman Ltd, Kawerau, New Zealand indicated that major influences are provided by fibre length and strength on cement board properties. However, he said, once refined length exceeds 2.6mm to 2.7mm there is little improvement in cement sheet strength.

John Jones, ARG division manager at Nippon Electric Glass America, Inc, described alkali resistant glass fibre that can be used to reinforce Portland cement composites. The material will not corrode in alkaline environments.

This has been used successfully to replace asbestos fibres, particularly in autoclaved calcium silicate products such as lightweight fire resistant insulation board. However, use in the Hatschek and Foudriani processes has been only partly successful.

Professor Parviz Soroushian, Michigan State University, East Lansing, Michigan, extolled the use of recycled fibres in reinforcing cement products. He said that studies showed that half the material in landfills is paper and its products.

He concluded waste paper fibres are smaller in average length and have a higher fine content than virgin softwood fibres. He said recycled fibre-reinforced cement composites require higher fibre contents for peak structural strength.

The same is true of fracture toughness where waste paper product is lower than virgin softwood fibre product, but it increases with fibre content.

There are plusses to the waste paper product which has higher densities and lower water absorption capacities than virgin softwood fibre. There are also smaller drying shrinkage movements.

Antony M Cooke, managing director Building Materials and Technology Pty Ltd, Carlingford, NSW, Australia, said: “Fifty-year durability for autoclaved cellulose fibre cement composite is a reasonable expectation providing that it is selected, installed, and maintained in a manner appropriate for its anticipated exposure.”

Michael Nisbet, principal, JAN Consultants, Montreal, Canada, said siding is the dominant North American use for fibre cement boards. Of the total US siding market of nine billion ft², fibre cement has 7% to 10% share.

He said there are six major US fibre cement producers: James Hardie Building Products, Certainteed Corp, MaxiTile Inc, FCP/Eternit, Fortra Fiber Cement Co, and Re-Con Building Products.

Michael Nisbet cited predictions that by 2005 fibre cement siding could gain as much as 25% to 30% of the total siding market. “However,” he said, “even if it fails to increase its market share, it can expect an average annual demand increase of 4% to 5% over the next 10 years. With the projection of solid growth in its major market and the prospect of larger market share, the outlook for fibre cement products is very positive.”

Dr Yasuo Kuroki, Nichiha Corp, Nagoya, Japan, said cement sidings in residential exterior walls exceeded 70% of the market in 1999 while the deluxe grade share was half. Finishing systems have been further developed using inkjet and photogravure printing. Sand and crushed stone can be used for multi-colour applications. This requires an ultraviolet ray-proof agent to be applied to the top layer.

Robert B Bruce, Innogyps Inc, Burlington, Ontario, Canada, said: “The gypsum industry will continue to outgrow the construction industry as access to gypsum board increases around the world. It continues to displace alternate materials, even in the more mature markets such as North America. The larger European players are continuing to expand their global businesses with their recent move into the US representing a significant milestone.”

Hans-Ulrich Hummel of Gebr Knauf Westdeutsche Gipswerke, Iphofen, Germany, described the Knauf system for producing high quality gypsum fibreboards. Gypsum, waste paper and water are processed using flow-on technology with a rotating forming cylinder. The board can be compressed by a flat press and then passed through a multi-layer dryer.

The main use of the Integral gypsum fibreboards is for double flooring construction.

Rolf Berkenkamp, project manager for Siempelkamp’s fibre cement board work, said Asia is still the main market for the products, but the Asian crisis decreased sales somewhat.

Japan still likes large, deeply structured, multi-coloured cladding boards which can be assembled almost without joints. In Europe, facade boards are used mostly as ventilated curtain cladding fixed to an insulated solid wall. He said markets are requesting more asbestos-free board. In Europe air-cooled slate is dominating that market, for small size roofing.

Mr Berkenkamp said North America has the highest increase ratio for fibre cement products and the strongest market movements will be in North and South America.

Dr Karsten Lempfer, responsible for Siempelkamp’s gypsum fibreboard, said its properties have been improved and market niches developed. He said North America has the highest per capita consumption of traditional wallboard. He expects more growth in gypsum fibreboard in the future.

Hans-Joachim Ferchland, who represents Siempelkamp’s market for sandwich panels, said these have a polyurethane or mineral wool core. Their design is flexible; they are quick to install; and have a superior thermal insulation. They have various sheet layer materials – metallic, rigid or flexible.

He said there are about 150 sandwich panel plants worldwide.

USG’s new Gypsum, Ohio operation is drawing plenty of interest. D Paul Miller, USG Research and Technology Center, Libertyville, Illinois described the new plant. The firm’s proprietary wet process has been scaled up to a 12ft wide line, the first such gypsum fibreboard line.

Gypsum is screened and conveyed to either a storage dome or to the Gypsum fibreboard wet building where it is screened and slurried with recycled process white water and fed to a gypsum slurry stock chest.

Bales of secondary fibre are pulped in recycled waste water and then pumped through primary and secondary screens to a fibre stock chest. For some products, the fibre stream is processed through a disc refiner.

Gypsum slurry, fibre slurry, slurried wet waste and dry waste are mixed and fed to a reactor feed tank where recycled steam is recovered to increase the gypsum/fibre slurry temperature. Reactors convert the slurry at elevated temperature and pressure to a mixture of paper fibre and calcium sulphate alpha-hemihydrate in a fibrous form.

The conversion is sensitive to contaminants. Recycled process water builds these up and an additive injected at the beginning of the calcine step prevents this.

A surge tank collects slurry flashed out of the reactor systems. The stream goes to the reactor feed tank for heat recovery.

Additives are injected into the calcined slurry stream ahead of the headbox which disburses the slurry across the 12ft width of the continuous former.

Water is removed by vacuum. Vacuum pump seal water is recycled through a cooling tower on top of the wet building, back through the closed loop of the system. This vacuum is applied to table boxes under the forming wire as well as to suction rolls in the primary press.

The white water is separated from the slurry, leaving a formed mat of calcium sulphate alpha-hemihydrate and paper fibres. It is then recycled to the process raw material make-up.

The former’s design speed is similar to that of wood insulation board or hardboard fourdrinier formers. It has a seamed bottom forming fabric and a continuous top primary press fabric.

Downstream of the primary press the 12ft wide continuous ribbon is cut to length. Both circular saw blades and water jet cutting have been used.

As the material is rehydrating, the Siempelkamp 12ft wide, 72ft long roller-type secondary press improves properties such as surface smoothness and strength and controls thickness variation. At this point, textures and edge tapers can be added.

Panels are conveyed for a distance to allow more hydration time before a right-angle transfer into the Dornier kiln. This is a belted 12ft wide multiple zone kiln, designed for paperless gypsum fibreboard panels.

From the kiln, panels pass through coating stations. Low VOC coatings are formulated by USG on site. Double-sided and single-sided dryers dry and harden them.

Mr Miller said this technology adds some significant strengths to the marketplace, and product flexibility. “We can create material that will fill market needs that are currently unmet. Strength is superior to those offered normally by gypsum panels.”