Keramicalia

Tel: +27 (0)11 412 3261 or +27 074 587 2728 Fax: +27 (0)11 692 1232
We manufacture specialised refractories and ceramics.

Vermiculite

We have a wide range of vermiculite products, and we are expanding it as perlite becomes more expensive and difficult to obtain. Some of the more popular ones are;

Vermiculite Castable: Is a high strength pourable insulation with a very fine microstructure. It has a very neat appearance compared to conventional vermiculite refractory castables. Conventional ones are calcium aluminate (ciment fondu) bonded, and the vermiculite gets crushed and compacted during mixing. Ours has a huge water retention, so that you can mix it very wet in a bucket and pour it into place. Many customers buy Vermiculite Binder separately and add their own exfoliated vermiculite. For precasting, use Kerafire; see below.

Rapolite Vermiculite This is a cement free, chemically bonded, fast setting, material for rapid brick manufacture. It is hand mixed, poured into moulds and stripped after 20 minutes.


Ettringite Bonded Vermiculite: A variety of products are made with this superb binder. Pizzapour is for two sided pizza oven moulds and Pizzapack is a hand packing material for one sided moulds. Underfloor Grout is used as insulation below the wires of underfloor heating.


Vermiculite Board: These are pressed by a local abrasives manufacturer for us.


Kerafire: Originally perlite based, it has been converted to vermiculite to give improved performance with our patented endothermic heat dissipation technology. It is used for precasting of structural insulation shapes.



Rapolite Vermiculite

Vermiculite is a natural mineral related to the mica group.   It has layers of silicate plates with water molecules bonded between them.   On rapid heating the plates “exfoliate” into a long wormlike structure, from which the name vermiculite is derived. The expanded structure is quite weak and easily squashed.   Pressed insulation bricks have been made from vermiculite for generations, some good, some bad, but pressing vermiculite into bricks compacts the material and a lot of the insulation value is lost.

Conventional monolithic insulation based on vermiculite and mixed in a pan mixer, also squashes the particles to higher density.

In Rapolite technology the mixing is done in an ordinary concrete mixer and poured in a runny, watery consistency into the mould.   It looks like it could never set and it looks like it will segregate disastrously.   However, 20 minutes later the mould can be stripped to reveal a superb microstructure.   This super-gentle mixing does not compact the vermiculite at all.

The wet density is 1,0 kg/ litre and the dry density is 0,33kg/ litre.

In Rapolite technology the matrix between the expanded vermiculite particles is filled with a finer silicate, to further enhance the insulation value.   The thermal conductivity is approximately 0,2W/mK.   The microstructure is very much finer than that of vermiculite bricks or board.

Castings should be left to air dry naturally, as their permeability is low.

Vermiculite Board

Description; A backup insulation board made of potassium silicate bonded vermiculite. Eliminates the cracking and wedging problems experienced with calcium silicate board, and is easier to fit anchors through.

Maximum service temperature;   1100 oC

Chemical analysis;

Al2 O3       7%

Fe2 O       4%

SiO       47%

TiO       0,5%

ZrO     25,0%

CaO       2%

MgO     21%

Na O     0,5%

K O     11%

P O      0,0%

L.O.I.   7%

Total   100%

Thermal conductivity; 200 C 0,17 W/mK

                       400 C 0,20 W/mK

                       600 C 0,22 W/mK

Colour; Golden brown

Bulk density; 1000kg/m 

CCS; 4MPa

Size; 1,2m x 0,6m x 25mm

Vermiculite Bricks

 

Description :   Fired strength vermiculite based insulation brick

 Physical properties

Maximum service temperature  1200°C

Bulk density                0.80g/cubic cm

Cold crushing  crushing           3.0Mpa

Linear Change  -0.73% @1000 for 2hrs

Thermal expansion 0.75 @ 20°C – 1000 °C  

Thermal Conductivity     

 

Chemical Analysis                            %

Si O₂                                                       54.0

Al₂O₃                                                     29.1

Fe₂O₃                                                    4.5

TiO₂                                                        0.8

CaO                                                        0.5

MgO                                                      9.1

Na₂O                                                     1.1

K₂O                                                        0.9

 

APPLICATION

A high strength vermiculite insulating brick.    Its volume stability and thermal expansion levels make Culite H compatible with normal hot face firebricks.    Uses include  muffle kilns, pottery and enamelling furnaces backing brick in boilers annealing furnaces, soaking pits,  linings for ducts and flues, etc.

 

COMPATABLE MORTARS

40% alumina content mortars of most tradenames.