Cellular Insulation

Cellular insulation is a new concept in refractories, developed by Keramicalia. The materials are based on cenospheres, tiny hollow ceramic balls, which give very good insulation properties, high strength and very good flow properties

Hollocast is a range of castables.
Keralite is the precast range.
Kerapour is self-levelling pourable insulation.
Insulmag is a basic cellular insulation material.
Kerapump is a range of pumpable or injectable materials.
Keratuff is a range of reinforced cellular insulation plasters.


Hollocast is the castable group of cellular insulation materials. They are strong insulation materials with largely sealed porosity .

Hollocast 1 is the general purpose castable, which is very user-friendly. It has an excellent track record in a very wide variety of applications.

Hollocast 2 is a low cement variety designed for pre-fired components, giving lower creep in load bearing kiln furniture.

Hollocast 3 contains barium, for aluminium furnaces.

Hollocast 4 is based on bubble alumina and Hollofill.

Hollocast 5 is based on bubble alumina and is totally silica free.

Hollocast 6 is based on a calcium aluminate foam with a composition of which is highly refractory. It is the best insulation material for 1500°C.



Maximum service temp

2023 Price/Kg excl vat.

Silica Content

Water Addition

Development No.











































Hollocast 1

Description: Hollocast is a refractory castable with a high insulation value yet high strength and resistance to thermal cycling.

Composition: Hollocast has a very fine microstructure and low permeability, yet the total porosity is 40%. The porosity is largely in the form of minute hollow alumino-silicate spheres of “Hollofill.”

Physical properties: Hollocast mixed with +18 to 21% water gives the following properties after firing to 1300°C.:

C.C.S: 20MPa.

Bulk density: 1.6g/cm³ (S.G. 2.75)

Total porosity: 40%

Permanent linear change: -0.8%

Thermal conductivity:

200°C 0.49W/mK
400°C 0.5 W/mK
600°C 0.52W/mK
800°C 0.55W/mK


Applications: Replaces all traditional “semi-insulation” materials, Hot face linings for ladles to reduce sculling. Soaking pit roofs, especially where Detrick bricks are used as anchors. Any roofs where a weight saving can reduce the structural support system. Brick kiln roofs. Insulation applications which are subjected to mild abrasion. Heat treatment bogeys. Intricate kiln furniture. Places where access is limited or difficult. High thermal shock applications. Aluminium launders, ladles and holding furnaces.

Installation: Mix with about +19% water to +23% water and place by pouring

DO NOT VIBRATE it will cause segregation and failure.

Pilot plant codes: OTO OZW and PGJ

Hollocast 1 Incinerator lining after 2 years of installation


Clean out the ladle completely. Fit well block and purge cone seating block with mortar. Cover sides of well block and seating block with cardboard and wrap with buff tape to leave gap for ramming. Cover top of well block and seating block with cardboard or a lid of some sort. Make mark on a trowel or stick to measure required floor thickness. Place a pan mixer next to the top of the ladle and make a discharge chute to pour directly into the ladle. Remove the ladder from the ladle. Weigh out or measure in buckets, 32 litres of water. Place 8 x 20kg bags of Hollocast in the mixer. Start the mixer and dump all of the water rapidly into it. Mix for about 20 seconds and then add a further 4 litres of water to

bring the mix to a very fluid consistency. (+22.5% water). Open mixer gate and discharge the whole mix directly into the ladle. Place the ladder back in the ladle, go down and check the thickness of Hollocast next to the purge plug seating block is approximately correct, using your prepared measure. Sweep material towards the edges of the ladle floor if it is flowing too slowly. Get out and remove the ladder. Clean out the residue from the mixer into an empty bag, to monitor setting time. The Hollocast will stop flowing after about 10 minutes. Once the setting sample in the bag is hard and warm, you may fit the former. (About an hour.) Repeat procedure for sidewalls.

Drying: Place ladle under the preheater and heat to 150°C for 3 hours. Raise temperature to 400°C and hold for 3 hours. Allow to cool and continue bricking the side up.

Hollocast 1 user references

* Armitage Shanks: 012 316 2571 Hennie van der Bank. Use it for sanitary ware kiln furniture, cycling through 1120°C daily. They find that its abrasion resistance is better than that of dense castable in their application.
* Aztek Furnace Services; 016 22 3414 Billy Wolmarans. Heat treatment furnace floors.
* Bohler Steel; 011 974 2781 Frank. Large heat treatment furnace floor.
* Custom Furnaces; 016 365 5723 John Lee Use it for all furnace floors, even forges.
* Fibreline; 016 54 020 John and Phillip Havenga. Used around 4 tons per month.
* Iscor Pilot Plant; 012 318 7785 Paul Hloben. Tested on project codes OTO, OXW, and PGJ.
* Pressure Die Casting; 0331 72327 Colin Belsham. Aluminium furnaces. Good resistance to thermite reaction.
* S.A.A.: 011 978 6298 Isaac van Rensburg Relined Wild-Barfield furnace with complex element bricks made from Hollocast. Also a large very flat heat treatment furnace floor.
* Darton: 011 432 0086 Darryl & Alan. Various furnaces.
* Microsteel: Insulation on floors of dolomite lined ladles.
* LTL Abrasives; 011 412 2920 Mike Reid. Furnace floors.
* Zimalco; Aluminium ladle linings. Kim Garner, 011 914 4300
* S.A. Metals; Ladle and tundish backlinings. Peter Lumley, 021 590 3943

Hollocast 4

Description: A bubble alumina castable for high temperature insulation. The bulk of the porosity is sealed in alumina bubbles.

Chemical analysis:

Al2 O3 85.0%
SiO2 8.0%
CaO 6.0%


Density: 1.25kg / litre.

Maximum service temperature: 1500°C

Cold crushing strength: ±8MPa.

Water addition for casting: +16%

Packaging: 10kg plastic bags.

Development no. 40330

Hollocast 5

Description: Bubble alumina castable, silica free. It has excellent flow properties and can be used for intricate shapes. The bulk of porosity is sealed in alumina bubbles.

Maximum services temperature: 1800°C

Chemical analysis:

Al2O3 95.0%
Fe2 O3 0.1%
Cr2O3 0.01%
SiO2 0.01%
TiO2 0.01%
Ca2O3 4.8%
MgO 0.2%
Na2O 0.2%
K2O 0.1%
P2O5 0.5%


Density: 2.1kg/litre

Cold crushing strength: ±20MPa

Water addition for casting: +18%

Packaging: 25kg Plastic bags

Development no. 40313

Hollocast 6

Description: A microporous calcium aluminate castable for high temperature insulation. The open porosity is 65-70% and the average pore size is ultra fine around 1 to 3 micron.

Maximum services temperature: 1500°C

Chemical Analysis:

Al2O3 82.1%
Fe2 O3 0.3%
CaO 16.4%
SiO2 0.5%
MgO 0.5%
Na2O 0.4%


Density: 1.2kg/litre

Cold crushing strength: 10MPa

Permanent linear change after firing to 1500°C -0.7%

Thermal conductivity:

500°C 0.6W/mK
1000°C 0.6W/mK
1500°C 0.6W/mK


Water addition for casting:

+45% for cohesive vibration castable, 1.22g/cm³

+50% for tapping, dry density. 1.2g/cm³

+55% for self leveling dry density 1.14g/cm³

Sets in 6 hours, high heat of hydration. Drying may start immediately, but take it slowly as with dense castables.

Packaging: 10kg plastic bags

Shelf life: 2years

Development no. 41646


Insulmag is a basic refractory insulation material.

Insulmag consists of magchrome and Hollofill aggregate, hydraulic bonded. It has a low density of 1.3g/cm³ and a high strength to density ratio.

If has a fine structure and even texture, giving good thermal shock resistance.

It is easily installed, being highly fluid and insensitive to temperature, contamination, and water quality. It mixes easily and can be poured into place.

Water addition is +30% by weight: 3 litres per bag.

Chemical analysis:

Al2 O3 28.0%
Fe2 O3 8.0%
Cr2 O3 12.0%
SiO2 8.0%
TiO2 0.2%
CaO 9.0%
MgO 33.0%
Na2 O 0.2%
K2 O 0.3%
P2 O5 0.2%


Packaging: 10kg plastic bags.


Keralite is a range of cellular insulation materials used mainly for precasting, to replace insulating firebricks.

Keralite 1: For high strength, fine finish and intricate castings. Also used for modelling, for its good machinability. Density 1.1 Water addition +35% castable with or without vibration. Used at up to 1250°C. Supplied in 15kg bags.

Keralite 2: General purpose replacement of IFB’s, because it has higher strength and can be moulded to required shape with no cutting or wastage. Has a density of 0.75. Add +45 to +50% water. They can be used at up to 1220°C. Supplied in 10kg bags.

Keralite 3: Differs from normal cellular insulation in that the matrix is hollow. It is not supplied in castable form, only precast parts. Used mainly for its high permeability, even structure and great machinability.

Keralite 4: Has a density of 0.5 and a maximum service temperature of 1230°C. It contains polystyrene balls which give off fumes during initial firing, which irritate ones eyes. Use with +40% water. Supplied in 10kg bags..

Keralite 5: A higher temperature material, mainly used in direct gas flame impingement areas. Has a density of 0.95. Develops high strength at 1200°C. Contains fine expanded polystyrene balls. Add plus 34% water. Supplied in 15kg bags.

Keralite 1

Description: A cellular insulation refractory for precasting of furnace components. It combines structural strength with good thermal insulation. It has a high porosity, in the form of sealed ceramic micro balloons, and a low permeability.

Maximum service temperature: 1280°C Density; 1.1g/cm³

Cold crushing strength: 8MPa.

Total porosity: <60%

Apparent porosity: <20%

Permanent linear change on firing to 1200°C: 0%  < 0.1%

Thermal conductivity at 800°C:

Approximately 0.4W/mK

Good thermal shock resistance.

Colour: Grey unfired, Beige after firing.

Applications: Element support bricks, furnace and kiln walls and roofs.

Installation: Mix with plus 30% water and vibration cast.

Packaging: 15kg clear plastic bags.

Chemical analysis:

Al2  O3 37.0%
Fe2 O3 1.0%
SiO2 47.0%
CaO 15.0%

Keralite 2

Description: A cellular insulation refractory for precasting of furnace components. It combines structural strength with good thermal insulation. It has a high porosity, in the form of sealed ceramic micro balloons, and a low permeability. It replaces insulation firebricks in kiln linings. Compared to the standard JM23, it has the same thermal conductivity, but much higher strength, and can be cast in any shape, whereas JM23 bricks are cut to shape. It is used as a high strength insulation in high temperature furnaces, e.g. DRH rotary kiln linings.

Maximum service temperature: 1250°C

Density: 0.8g/cm³

Cold crushing strength: 4MPa.

Total porosity: ±68%

Apparent porosity: ±22%

Permanent linear change on firing to 1200°C: 0% to -0.1%

Thermal conductivity at 800°C: Approximately 0.25W/mK

Colour: Grey unfired, Beige after firing.

Applications: Element support bricks, furnace and kiln walls and roofs. Backlinings of rotary kilns and high temperature furnaces.

Installation: Mix with plus 45% to +50% water and vibration cast.

Packaging: 10kg clear plastic bags.

Chemical analysis:

Al2 O3 40.0%
Fe2 O3 0.6%
SiO2 52 .0%
CaO 7.0%

Keralite 8

Description: A very fluid insulation pourable material for use up to 800°C. It flows self-levelling and gives a very fine and even texture. Most of the porosity is sealed pores. The permeability is relatively low. The cost per cubic metre is low.

Maximum service temperature: 800°C

Density: 0.75g/cm³

Cold crushing strength: 6MPa.

Thermal conductivity at 800°C 0.4W/mK.

Colour: Dark brown.

Installation: Mix with +40% water. (4 litres per 10kg bag). Place water in bucket, add powder on top and mix by hand from the bottom upwards. It flows immediately, then goes stiff and flows again. It is ready to pour after two minutes. Pour it directly into the mould. It takes 6 hours to set.

Applications: A self-levelling insulation for for bedding of aluminium launders, bogey decks, kiln cars etc. Any low temperature insulation.


Description: Kerapour is a cellular insulation material. It has an exceptionally high strength to density ratio and can be used as a structural member rather than just a filler. It has very low thermal conductivity due to its very fine structure. Kerapour has very low permeability due to its closed porosity. Kerapour is very easily mixed to a pourable consistency with +32% water, and flows right into the furthest corners, self-leveling.

Temperature C.C.S Density Porosity P.L.C
110oC 11.2MPa 1.1 50% 0%
400oC 11.9MPa 1.02 -0.38% 0.28Wmk
800oC 11.7MPa 0.99 -0.38% 0.34Wmk
1000oC 12.7Mpa 1.06 61% -0.90%
1300oC 18.0Mpa 1.07 58% -3%

Note: From the above data it is clear that Kerapour is exceptionally stable.

Particle size distribution: Very fine; 90% -0,85mm

Chemistry: Aluminosilicate.

Installation: Use 1.1tons per cubic metre. Mix with +32% water and pour it. Mixing can be done by hand in a bucket.

Applications: All insulation applications, especially where structural strength is an advantage, or installation is difficult or impermeability is desirable.

ISCOR pilot plant code: QJO



Mix 500g Kerapour with 160g water to give a highly viscous ball, which flows slowly but continuously, self-levelling. At this very viscous consistency the flow is most impressive. On a real installation, it can can be made wetter, to flow faster. After doing the demo. once, no need to weigh out the quantities.


Take two crucibles. Put one upside down on a clearing at least 4m diameter, with no combustible materials nearby. Place the other crucible on top of it, upright. The lower crucible is to keep the demo. one away from splashes, which could burn you or make it difficult to pick up the crucible after the reaction. The splashes also heat the outside of the crucible if it is on the ground. If you only have one crucible, substitute a brick or something. Pour thermite powder into the crucible, about half full. Make a depression in the thermite powder and place in it either about a teaspoonful of ignition powder or push in a starlighter. Over this, place about half a teaspoon of fuse powder. Light the fuse powder with a match and move up-wind of it. The fuse powder gives off a lot of smoke, and lights the ignition powder/starlighter. The ignition powder generates intense heat and ignites the thermite powder. The thermite powder splashes sparks up to 1m away. It reaches a temperature of over 2000°C. Once the sparks have stopped for at least 6 seconds, pick up the crucible in your hands. The outside will still be cold, and remain so for at least half a minute. You can now pour out some molten steel, if there is a completely dry surface available. Give the crucible to the customer to hold.

The purpose of the demonstration is:

1. To impress the hell out of the customer.
2. To show that Kerapour can withstand a thermal shock of ambient to 2000°C in seconds without cracking.
3. To show how good cellular insulation is.
4. To prove that Kerapour can withstand super hot molten metal in a breakout situation.

Kerapour demo. crucibles are prefired to 400°C.

In the event of a burn from a spark, apply Bactrazine Flammazine ointment to the burn. (It has never happened yet in about 50 demonstrations.)

The demonstration is very impressive and frequently misleads the customer into considering Kerapour for high continuous temperature applications. Most of the applications which the customer now thinks of can be satisfied by Kerapour, Hollocast castable, Keratuff/Keratuff 2 plaster, or Kerapump 1 to 5.

Now that you have the customer’s attention and interest, you will find him very communicative.


Pumpable materials can be installed into inaccessible places, or can be mixed far from the site of installation and pumped, usually a high vertical distance to their point of application.

All very fine materials can be pumped, but only carefully designed ones keep their volume after drying, without shrinking. Pumpable materials are not necessarily self-flowing materials.

The most versatile pumping materials are self levelling, insensitive to water addition, do not segregate, and do not shrink. They may be strong or soft, dense or insulating.

The Kerapump range contains a variety of materials, mostly cellular insulation.

Kerapump 1 is a high strength, very fast setting material.

Kerapump 2 is a very soft injectable material, mainly used in compensators, which can be poured.

Kerapump 4 is a medium strength cellular insulation material.

Kerapump 5 is a very light precision casting material for components traditionally made from Marinite or calcium silicate.

Kerapump 6  is a dense andalusite pourable material.

Kerapump 10  is a very user-friendly injectable insulation.

Kerapump 1

Description: A pumpable or pourable insulation refractory with a phenomenally high strength to density ratio.

Maximum service temperature: 1200°C

Physical properties:

Temperature C.C.S Density Porosity P.L.C
110oC 19MPa 1.23 50% -0.36%
400oC 27MPa 1.11 -0.38% 0.28Wmk
800oC 11MPa 1.04 -0.38% .034Wmk
1000oC 13Mpa 1.06 -0.62% 0.450W/mk
1200oC 17Mpa 1.08 -1.97%


Chemical analysis: 56% Al2O3

Applications: Ladle insulation: Most insulation materials become crushed in this application. Kerapump has a phenomenally high strength to density ratio and can therefore withstand the stresses of differential expansion better. Hot blast stoves: Kerapump may be pumped through the shell to repair hot spots. Furnace floors: Can easily be made by pouring Kerapump, especially kilns.

Water addition: 30% by weight.

Pilot plant code: MPU

Kerapump 10

Description: A pourable or pumpable insulation refractory. It is extremely fine and can be used for precision cast and detailed components. It can also be machined.

Maximum service temperature: 1150°C


110°C 7-12Mpa
400°C 10-15MPa
1000°C 6-10MPa
1200°C 15-25MPa


Density: 1.15g/cm³

Thermal conductivity: About 0,4W/mK at 600°C

Chemistry: Aluminosilicate cellular insulation.

Water addition: + 40% by weight.

Coke ovens pumping behind flashplates.
Blocking gas tracking.
Synthetic coals for gas fireplaces.

Chemical analysis:

Al2O3 34%
Fe2 O3 1.0%
Cr2O3 0.04%
SiO2 37%
TiO2 1.5%
Ca2O3 16%
MgO 0.5%
Na2O 0.6%
K2O 1.3%
MgO 0.5%
P2O5 1%


Packaging: 10kg plastic bags

Kerapump 5

The permanent linear change measurements on Kerapump 5 are as follows: (Taking air dried dimension as 100%) 110ºC -0.15% 400ºC -0.45% 1000ºC -1.7% 1200ºC -2.4%

Chemical Analysis:

Al2O3 48.0%
SiO2 36.0%
Fe2 O3 1.0%
CrO 0.09%
TiO2 0.7%
CaO 10.0%
Na2O 0.7%
K2O 0.8%
P2O5 1.1%
MgO 0.5%
L.O.I 1.5%
Total 100.39%

Kerapump 6

Description: A high density self flowing pumpable aluminosilicate. It flows well and de-airs itself down to 1mm bubbles at +10% water addition. It has almost no tendency to segregate.

Density: Wet 2.7g/cm³

Installation: Add plus 10% water, mix until self levelling and pump or pour into place. It penetrates well and de-airs itself.

Applications: Difficult access situations where a strong dense refractory is required.

Packaging: 25kg plastic bags on 1 ton pallets stretchwrapped.

Development no. 37706 Pilot Plant code;

Chemical analysis:

Al2O3 40.9%
Fe2 O3 1.1%
SiO2 54.4%
TiO2 1.61%
CaO 0.37%0.58
MgO 0.58%
Na2O 0.5%
K2 O 0.44%
P2O5 0.0%
L.O.I 0.90%
Total 100.35%


Cellular insulation plasters are called Keratuff, as they are reinforced with fine water dispersible drawn zirconia-ceramic fibres.

Keratuff 1is similar to asbestos cement in strength and resilience.

Keratuff 2 has high insulation properties.

Keratuff 1

Description: Keratuff is a structural refractory insulation. Insulation materials are normally only usable as a backing or with some kind of structural support. Keratuff has sufficient strength to be a free standing structure.

Applications: Precast pizza oven roofs, crucible furnace lids, heat shields, splash boards, aluminium launders, burner shields.

Thermal conductivity:

200°C 0.19W/mK
4000C 0.23W/mK
6000C 0.25W/mK
8000C 0.28W/mK
1000°C 0.31W/mK


Maximum service temperature: 1200°C. Keratuff melts between 1200°C and 1300°C. Shrinkage at 1200°C is 1.7%.

Density: 1.0 dry, 0.85 fired.

Strength: 23MPa at 110°C, 6MPa fired 1200°c.

Composition: Contains Litefill and Hollofill synthetic aggregates, and zirconia containing ceramic fibres. 53% alumina.

Preparation: Add +40 to +50% water to the powder, mix well and apply it. It can be vibration cast at +40% water, +50% is easier to apply by troweling. Water content is not critical and need not be measured. Extensive mixing and troweling improves the fibre dispersion and improves strength. All particles are less than 1mm diameter. Setting time is about one hour.

Packaging: 10Kg in thick polythene bags.

Pilot plant code: OEV.

Keratuff 2

Description: Keratuff 2 is a structural insulating refractory. Insulation materials are normally only usable as a backing or with some kind of structural support. Keratuff 2 has sufficient strength to be a free standing structure. It has low permeability and is easily machined or cut when dried or fired.

Applications: Electric kiln walls and element holders, crucible furnace lids, heat shields, masonry protection in charcoal ovens, aluminium launders, burner shields, machined components.

Thermal conductivity:

200°C 0.2W/ mK
4000C 0. 2W/’mK
6000C 0.231W/!mK
800°C 0.28mK


Maximum service temperature: 1230°C. Shrinkage at 1200°C is 1.91.

Density: 0.8 g/cm3 dry.

Strength: 6 MPa at 110°C, 6 MPa fired 1200°c.

Composition: Contains Litefill and Hollofill synthetic aggregates and zirconia containing ceramic fibres.

Preparation: Add +40-50% water to the powder, mix well and apply it. It can be vibration cast at +40% water. Water content is not critical and need not be measured.

Extensive mixing and trowelling improves the fibre dispersion and improves strength. All particles are less than 1mm diameter. Setting time is about one hour.

Colour: Grey. Yellow when fired 1200°C.

Packaging: 10Kg in thick polythene bags.

Pilot plant code: PGK.