Waste Mineral Fibre

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HISTORY OF DROPPED CEILING

Ceilings are classified according to their appearance or construction. A cathedral ceiling is any tall ceiling area similar to those in a church. A dropped ceiling is one in which the finished surface is constructed anywhere from a few inches or centimetres to several feet or a few metres below the structure above it. This may be done for aesthetic purposes, such as achieving a desirable ceiling height; or practical purposes such as acoustic damping or providing a space for HVAC or piping. An inverse of this would be a raised floor. A concave or barrel-shaped ceiling is curved or rounded upward, usually for visual or acoustical value, while a coffered ceiling is divided into a grid of recessed square or octagonal panels, also called a “lacunar ceiling”. A cove ceiling uses a curved plaster transition between wall and ceiling; it is named for cove molding, a molding with a concave curve. A stretched ceiling (or stretch ceiling) uses a number of individual panels using material such as PVC fixed to a permieter rail.

Ceilings have frequently been decorated with fresco painting, mosaic tiles and other surface treatments. While hard to execute (at least in place) a decorated ceiling has the advantage that it is largely protected from damage by fingers and dust. In the past, however, this was more than compensated for by the damage from smoke from candles or a fireplace. Many historic buildings have celebrated ceilings. Perhaps the most famous is the Sistine.

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INTRODUCING WASTE MINERAL FIBRE

Waste mineral fibre is generally “off-spec” mineral fibre products generated by the manufacturers of mineral or glass wool. Providing the waste material is a clean, consistent mineral fibre, it is generally suitable for use in the manufacture of ceiling tiles or in other applications.

The waste mineral wool/fibre is used as a direct substitute for other mineral fibres, and is dispersed in a solution of cold water, before being blended with the other fillers and binder ingredients. The mass is then formed into a continuous mat before being cut into sheets for drying. The dried sheets are then fabricated, “finish coated” and cut to final size.

Mineral fibre ceiling tiles contain up to 75% recycled content (6, 7). The content of recycled mineral fibre is not clear. However, levels of substitution of new fibre by waste fibre could be as high as 100% by weight, (the tile may be 25 to 75% mineral fibre). Ceiling tiles have a range of performance characteristics which can include resistance and reaction to fire properties, acoustical absorption and attenuation, light reflectance, basic physical strength and durability. The content and type of mineral wool used in these products will impact on these characteristics. The ceiling tile manufacturing industry has a history and willingness to utilise byproducts and has often replaced virgin raw materials with (usually) lower cost alternatives. The use of blastfurnace slag (from iron smelting) as the main mineral input into the melting and spinning process for mineral wool, as an alternative to quarried rock is one example. Starch recovered from the potato snack industry has been used as an alternative binder to virgin material in the manufacture of ceiling tiles.

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CHARACTERISATION AND BENEFITS

As fibre waste is inert, downstream processing will also usually not change that, but individual waste streams may differ. Results of basic waste analysis to assess waste mineral fibre for use in this product sector are as follows:

Mineral phases/oxide composition Glass SiO2, Al2O3, CaO and MgO
Visual description Grey/green/ yellow/pink fibres; yellow binder
Moisture content (%) 0.5%
Loss on ignition (%) < 1% by weight
Contamination (specify) < 5% by weight of non-fibrous material

Potential benefits:

  • Material related
    ii Local suppliers save both financial and environmental costs.
  • Legislation-related
  • Environmental-organisational-social
    ii. The use of waste fibre reduces the environmental impact caused by the production of virgin alternatives.
    iii. Avoidance of material going to landfill
  • Economic
    iv. Gate fee (benefit to manufacturer)
    v. The need to buy primary material is reduced (benefit to manufacturer)

SOURCES:

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