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Mineral Vermiculite

  • Mineral Mica's family, basically consist of  silicates of aluminium, magnesium and iron.

Mineral Vermiculite

  • Expanded vermiculite with thermic treatment with temperatures above 700 °C the mineral  expands increasing volume of 15 to 20 times


  • General-Mineral

Identification Colour

  • Bronze-Yellow


  • Pale yellow

Refractive index

  • Translucent


  • Vitreous

Mohs Scale hardness

  • 1.5-2

Specific gravity

  • 2.4-2.7

Crystal system

  • Monoclinic

Crystal habit

  • Clay, scaly, aggregate


  • Perfect


  • Uneven


  • None

Chemical formula

  • (MgFe,Al)3(Al,Si)4O10(OH)2·4H2O



The bulk densities of expanded vermiculite  ranging between 60 and 140 Kglm 3 as grain size


• Is insensitive to atmospheric agents
Is inert.

Insulation Data

Thermal insulation

  • The expanded vermiculite insulations   maintains its capacity from 200 "C and 1200 "C. Its thermal conductivity is of 0.053m Kcallhr. "C for an average temperature of 20 "C.Su calorffica capacity is very low (0.2)

  • The bright walls of the vermiculite mica flakes are a multitude of screens that reflect and disperse the heat energy transmitted by radiation, and make such the insulating material suitable for high temperatures.

  • Thermal Conductivity: k-value = 0.063 W/mK

  • Thermal Resistance: R Value: 16.1 m2K/W per metre of insulation.

  • Thermal Transmittance: U-Value: This is the overall rate of heat transfer.

  • To correctly calculate a U-value, all layers of insulation must be included and not the vermiculite layer alone.

  • The calculation requires the R-value for each layer (for R-value of vermiculite, see above) and also constants accounting for surface transmittance from the inner and outer surfaces (Rsi and Rso) and also for a small standard air gap (Ra).

  • This calculation is often performed with specialist software and is not elaborated upon here.

Fire resistance

  • Melting point 1370 "

  • Softening 1.250 "

  • stable at high temperatures

Mixture Ratios

Correct proportions for Roof Screed

  • 2 x 8kg bag medium vermiculite

  • 1 x 50kg bag Portland cement

  • Approx 40 l water

  • 10% V-Bond

  • Topping (6:1) sand: cement (10-15mm thick)

Quantities required per cubic meter

  • 15 x 8kg bags medium grade vermiculite

  • 7.5 x 50 kg bags Portland cement

  • Approx 280-300 l water

  • 30L V-Bond

To calculate volume

V = L x B x H
V= 20m (L) X 10m (B) x 50mm (H)
V= 20m x 10m x 0.05m
V= 10

Properties of the screed

  • Dry density 450 – 510 kg/m³

  • Thermal Conductivity K = 0,120 w/m °C

  • Compressive Strength Typically 0.5 MPa

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