Which density of perlite concrete do you need? Grades by application
Updated: 4 days ago
The commonest question we are asked is which density to specify. The honest answer is that it is decided by the application, not by picking the best-looking number on a test report. This page maps the grades to the jobs they are actually for.
The tested grades
Thermal conductivity tested to ASTM C518-21 at a mean temperature of 0 degrees Celsius. The number in each grade name is its oven-dry density in kg per cubic metre.
Kelite 400: 0.0865 W/m.K
Kelite 500: 0.1025 W/m.K
Kelite 600: 0.1150 W/m.K
Kelite 700: 0.1254 W/m.K
Kelite 900: 0.1952 W/m.K
Kelite 1200: 0.3447 W/m.K
The pattern is consistent and it cuts both ways. Lower density insulates better and loads the slab less. Higher density is stronger and harder wearing, and insulates less. There is no grade that is best at everything.
Roof and terrace insulation: 400 to 700
This is where the light grades belong. The job is to cut heat gain through the roof slab and to form the fall at the same time, in one material rather than an insulation board plus a separate screed laid over it.
Which of 400, 500, 600 or 700 you choose depends on the thermal resistance your design calls for and on the traffic the finished surface has to take. Resistance is thickness divided by conductivity, so a lighter grade reaches the same resistance in less thickness, which matters when your parapet and door levels are already fixed.
One thing we will not tell you is that a light grade is cheaper than brickbat coba on installed cost. It is not. Compare it against insulation systems, which is what it replaces, not against coba on price.
Floor screeds: 1200
For a floor screed the priorities invert. You need a hard, flat, monolithic surface that takes a topping directly, and you need it to weigh less than what it replaces.
Kelite 1200 goes down at about 1,200 kg per cubic metre against roughly 2,400 for a conventional screed, which halves the dead load across the whole floor plate. It levels with an aluminium straight edge and sets to a smooth table-top finish. Tiles, vinyl, wood and carpet go on it directly, and drywall tracks screw straight into it, which most lightweight concretes will not hold. If a raceway has to be run later, it is cut and refilled.
This is also the grade where the commercial case is strongest, because it is replacing a conventional screed rather than an insulation board. It is best suited to commercial floors on post-tensioned slabs, where the weight saving is worth real money in the frame.
Terrace slope and coba replacement: 1200 to 1400
Where brickbat coba or AAC block coba is being replaced for weight and speed, the grade to compare at the same average thickness is 1200 or 1400. It goes down faster than coba, it does not settle, and it gives you some insulation alongside, which coba does not.
Sunken and podium fills: 1200 upward, and heavier for podiums
For a toilet or utility sunk, the job is a lighter filler in place of brickbat fill, at the density your structural consultant accepts. It does not settle.
Be clear about the limits of that claim. It is a filler. It is not a waterproofing layer and we do not offer it as one. Your waterproofing system stays exactly as specified, above and below.
Podium and terrace garden fills take the heavier end, usually above 1,600 and up to 2,000, because of the loads and the depth involved.
Two limits that apply to every grade
Minimum section thickness is about 25 mm. Thinner details are ruled out at any density.
The whole range is non-structural. It is not a structural lightweight concrete and should never be specified as one.
Not sure which one?
Send us the build-up you are working on, with the resistance you need or the load you are trying to come under, and we will work the grade and thickness back from it, with the specification wording and a BOQ format you can use directly.
Write to info@theperlite.in or call +91 98600 63626.
Kelite, a product by Keltech Energies. Specified, engineered and executed by Perlite India.
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