Perlite is not a trade name but a generic term for naturally occurring siliceous volcanic rock. The distinguishing feature which sets perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands from four to twenty times its original volume.

This expansion process is due to the presence of two to six percent combined water in the crude perlite rock. When quickly heated to above 1600 ^o F (870^o C) the crude rock pops in a manner similar to popcorn as the combined water vaporizes and creates countless tiny bubbles in the softened glassy particles. It is these tiny glass-sealed bubbles which account for the amazing lightweight and other exceptional physical properties of expanded perlite.

The expansion process also creates one of perlite's most distinguishing characteristics: its white color. While the crude perlite rock may range from transparent to light gray to glossy black, the color of expanded perlite ranges from snowy white to grayish white.

Expanded perlite can be manufactured to weigh from 2 lbs/ft³ (32 kg/m³ ) to 15 lb/ft³ (240 kg/m³ ) making it adaptable for numerous applications in the construction, industrial, chemical, horticultural and petrochemical industries. A unique use for perlite is in cementing, oil, gas, water and geothermal wells.

BITUMIZED ROOFING BASE

A unique roofing base material that is produced and used extensively in Europe is bitumized perlite which offers several distinct advantages to the user. Among these advantages are:

• Provides roof insulation
• Can be sloped to drain
• Requires no curing or drying time
• Provides a monolithic base for roofing
• May be roofed immediately
• Is a lightweight, dry granular material
• Suitable for reroofing or new construction

A cold asphalt adhesive layer is applied to the roof base substrate and the dry granulated bitumized perlite is poured in place, spread and screeded to the desired thickness and slope. Following screeding, the bitumized perlite is compresssed by 40% by rolling. Initial rolling is over plywood sheets and the final rolling is directly on the surface of the material.

BITUMIZED PERLITE

Bitumized perlite is dry, granular material consisting of perlite particles coated with bitumen. The lightweight material is ready to use as poured from bags and requires no mixing; nor does it require the addition of any additives.

NEW CONSTRUCTION

Bitumized perlite can be applied directly over hard surfaces such as concrete that have been treated with a cold bituminous adhesive layer. When the bitumized perlite is to be applied over a wood base, an asphalt underlayment is nailed to the wood before the cold asphalt adhesive layer is applied. Built-up roofing may then be immediately applied by flood coating the surface with hot asphalt.

REROOFING

Bitumized perlite is an excellent material for repair of existing roofs as it can usually be applied over structurally sound roofs that have been swept clean of loose debris and coated with a cold asphalt adhesive layer. Not only does the new roofing base provide additional insulation but water ponding conditions may be corrected by sloping the new roofing base toward internal drains or to the perimeter of the roof.

APPLICATION

Roofs are prepared by applying a coat of cold asphalt that acts as an adhesive layer to bond the bitumized perlite to the structure of the building. Dry, granular bitumized perlite is poured from bags, spread and screeded to the desired slope and to a thickness 40% greater than the final desired thickness. Sheets of plywood are laid over the dry material and a 400 lb(180kg) roller is used to compact the material. Final compaction is achieved by rolling the bitumized perlite directly without benefit of the plywood sheets.

With bitumized perlite, roof grades can be easily established, low areas filled and a monolithic roofing base produced. As no curing or drying cycle is necessary, roofing material may be immediately applied. Built-up roofing is secured to the bitumized perlite base by flood coating the base with hot asphalt

If protection from ultraviolet radiation or mechanical damage is desired, ballast may be spread on top of the roofing material.

When bitumized perlite is used as a roofing base for rooftop parking areas, the parking surface may be applied directly on top of the built-up roofing.

The Schundler Company does not produce bitumized perlite and we don't know of any company in the United States which does. Until now it has been a product produced by and for the European market.

If you think your application would benefit from the properties of perlite please let us know by calling or contacting us at:

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