Re-Roofing Base

Perlite concrete insulation is ideally suited for re-roofing applications. It provides permanent, cost effective, slope to drain designs with high R- values over flat and often- irregular substrates found in re-roofing projects. Using a perlite concrete slurry coat, the polystyrene insulation board is positively attached to the substrate and covered with a uniform layer of perlite concrete insulation. If the existing substrate is sound and capable of the additional loading required, then the perlite concrete insulation can be applied to the existing roof thereby eliminating costly tear offs.

3- PERLITE AND SAND LIGHTWEIGHT INSULATING CONCRETE

One of the most effective ways to reduce the dead load in multi- storing building is to lighten the weight of the floors. Perlite / Sand insulation concrete is suitable for use over structural concrete and varies types of light structural forms such as corrugated steel, rib steel or cellular steel floor units and plywood sub floors.

Proposed Mix Design

Mix designs E to I table 5 specifically for dead load in multi- story building.

	Cement m3	Perlite m3	Sand m3	Water m3	Entrainment Liters
E	1	3	2.2	1.51	3.2
F	1	3	2.0	1.08	3.2
G	1	1.6	2.5	1.24	3.2
H	1	1.1	2.1	1.05	3.2
I	1	3	1.75	1.13	3.2

Expected Physical Properties Of Proposed Mix Designs

Physical properties of perlite/ sand insulating concrete vary according to mix design table 6.

	Typical air dry density kg/m3	Compressive strength kg/cm2	Wet density when  placed Kg/m3
E	1040	55.2-62.1	1312±80
F	1200	62.1-82.8	1280±80
G	1312	75.9-89.7	1568±80
H	1408	158.7-172.5	1680±80
I	1584	138.6-151.8	1760±80

4- PLASTER

Perlite has been used as lightweight aggregates for plaster too. When mixed with either gypsum or Portland cement (with or without sand). The final plasters are lightweight, fir-proof, insulating and weigh approximately 60 % less than conventional cement sand plaster. The addition of alkali resistance glass, polypropylene or acrylic fibers makes possible the manufacture of prefabricated steel stud, lath and plaster exterior wall panels for high rise structures. Perlite also is basic ingredients in a number of commercials available premixes of both plaster and plaster patching compounds designed for professional and amateur plaster when produced for these applications.

Mixing

LIMITATIONS

• Portland cement plaster is recommended on exterior surfaces regularly exposed to water.
• Plaster application on any surfaces that have been coated with bituminous compounds is not recommended.
• Long continues runs of plaster should be broken appropriately to relieve stress and strain cased by thermal or structural movement.

In batch mixing all required water is placed in the mixer and cement is added and mixed for approximately one minute until the slurry is uniformed Perlite aggregate and chopped fiber is added as the mixer is rotated. Mixing should continue until the mix is thoroughly blended but should not exceed 4 minutes.

• For machine application, 13-mm long fibers are preferred.
• On vertical application, plastering should consist of separate scratch and brown coats.
• Brown coats should be flat and even but be sufficiently rough to receive finishes.
• The base coat plaster should be kept damp for at least 48 hours.
• Finish materials may be applied after at least 5 days.