What Is Perlite Concrete? Densities, Uses and Thermal Values Explained
Perlite concrete is a lightweight, heat-insulating concrete made with expanded perlite in place of normal sand and stone. It is used for roof insulation, floor screeds, sunk fills and podium fills, where the job is to fill, slope or insulate without adding heavy dead load.
What perlite is
Perlite is a natural volcanic glass. When crushed perlite ore is heated quickly in a furnace, the water locked inside turns to steam and the grains expand many times, like popcorn. The result is a light, white, glassy granule made of countless tiny cells. That expanded perlite is the aggregate.
At Perlite India we use Kelite, a construction-grade expanded perlite made by Keltech Energies Ltd. It comes in two grades, fine (about 65 kg/m³ loose) and coarse (about 125 kg/m³ loose).
How the concrete is made
Kelite is mixed with cement, or cement and sand, and an admixture. Changing the proportions changes the dry density of the finished concrete from about 300 kg/m³ to 2,000 kg/m³.
Density band | Typical use |
Lightest grades, e.g. 400 kg/m³ | Roof and terrace heat insulation |
1,200 to 1,400 kg/m³ | Direct replacement of brickbat coba |
1,600 to 2,000 kg/m³ | Podium fills that carry traffic |
Chosen per project | Floor screeds and sunk fills, to suit the load and the finish |
Key properties
Heat insulation: the lower the density, the better it insulates. Thermal conductivity goes as low as 0.08 W/m·K in insulating grades.
Light weight: a fraction of the weight of brickbat coba or sand-cement screed.
Non-combustible: perlite is an inorganic mineral that fuses above about 1,260 °C. Source: Perlite Institute (USA); Keltech Energies Ltd is a member.
Hard, monolithic finish: a smooth, table-top surface that takes tiles, vinyl, carpet, wood or waterproofing directly.
Holds a screw: drywall tracks can be screwed straight into the screed.
Zero settlement once cured.
Chemically inert and does not rot or decay.
How it is delivered
Mixed on site
Pre-mixed bags, just add water
Ready-mix (RMC), pumped to the floor or terrace
Where it is used
Terrace slope and insulation screeds
Floor screeds over RCC, PT and deck slabs
Sunken toilet, bath and kitchen fills
Podium fills for pedestrian and vehicle traffic
Insulating plaster for walls
Loose-fill insulation in cavity walls
Where it is not used
Perlite concrete is not a structural concrete. It does not replace the RCC slab, beam or column; it sits on the structure as a fill, screed or insulation layer. The minimum practical section is about 25 mm.
Frequently asked questions
Is perlite concrete the same as foam concrete?
No. Foam concrete gets its lightness from air bubbles; perlite concrete gets it from the expanded perlite aggregate. See foam concrete vs perlite concrete.
What is the thermal conductivity of perlite concrete?
It depends on the density. Insulating grades go as low as 0.08 W/m·K; denser grades conduct more heat but are harder.
Can I buy perlite concrete in bags?
Yes. It is available in pre-mixed bags, as well as site-mixed and RMC supply.
About Perlite India. Perlite India designs and lays perlite lightweight insulating concrete for roofs, floors, sunk fills and podiums, with 3M+ sq.ft laid across India. Supported by the Perlite Construction Division of Keltech Energies Ltd, a member of the Perlite Institute (USA).
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