About 50 years ago castables were a bit of a novelty in refractories. Now they are consumed in higher tonnage than bricks.  The first castables were made from cement fondu which is 30% alumina.  Higher quality calcium aluminate cements were developed, with higher alumina content and lower iron content. It was sometime before castables reached the higher refractoriness of the best bricks. In the distant past away only a few large refractory manufacturers that you were making bricks. Now every Tom Dick and Harry can make castables because the capital outlay is very small.

The larger refractory manufacturers make batches of about 5 tons typically. Keramicalia makes batches of 25kg and less.  The large manufacturers do not make it to the wide variety of constables they like to make 1,300 1,400 1500, 1600, etc castable's for example. Keramicalia does not make these for 2 reasons. One is that our batch size makes it abnormally expensive.  The other is that we do not compete with the large manufacturers so that they don't mind sharing with us on more specialised products.

The large volumes of castables are normally used on very large castings. These also have much larger maximum particle sizes.  Since they are mixed in large batches on-site it's not necessary for every bag to be exactly correct. Since the quantities are very large the prices are competitive. A medium-sized refractory producer would turn out about 60 tons a day. We would struggle to do that in a month.

Since the 90s there's been an increased interest in low cement constables.  Lafarge patented Phlox technology, which involves low cement contents and the addition of silica fume.  These are cheap to make and more difficult to install. They require intensive high shear mixing to disperse the 2 micron silica fume particles. So-called conventional castables have high cement contents of around 15 to 20% and require little skill or experience to install.   Keramicalia insists on user friendly castables, because they still work if on site installation conditions are not ideal.

The large corporates have an increasing tendency to overstate the maximum service temperatures of their products. They have disclaimers at the bottom of their data sheets, because they are extensively false. There is also a tendency to downgrade their products but not change their data sheets. Only Keramicalia has a "claimer" at the bottom, saying that the above data had better be correct because Dave Onderstall stakes his reputation on it.". 

Oxide compositions have melting points. Before they melt they sinter and get harder and denser. One can therefore assume that a1400 castable used at 1400C will be stronger than a 1600 castable at 1400C. Not easy to prove though.

Castables are generally designed for the grading to follow the curve of highest density.  The majority are vibration castables.  They are installed on site with vibrating pokers or in factories on vibrating tables. Some castables are dilatant materials.  These will flow by themselves, but they go hard if pushed.  Beach sand sometimes exhibits this quality, when the majority of particles are of the same size. Our "dump mixes" are easily mixed. You can use a concrete mixer.  However you cannot use buckets to carry them.  They are highly cohesive and stick in the buckets, even though they are self leveling and self de-airing.  Civil Concrete technologists call these SCCs, "self compacting concretes".  We hope to convert Keraclase to one of these.  Reducing dump mix is our andalusite castable.  We tested it at 800C for CO attack resistance and found that it is stronger at 800C in a reducing atmosphere than in an oxidizing atmosphere.  Most castables are at the it weakest at around 800C.

Castables with low cement or no cement are weak after setting. The strength increases a lot after drying at 110C.  It increases a bit after drying at 450C and then drops around 800C. From 1000C a ceramic bond starts to form and the strength increases.  When it starts to melt if softens and becomes toffee-like.  If you cool it and do a cold crushing strength test on it you get a very high value.  This sometimes used to bamboozle non-technoligists. 

Some cement free castables are colloidal silica bonded.  A bit of MgO or calcium aluminate is added to make it set. (0,7%). These are very weak when stripped, strong after drying, and so hard after service that they are a huge problem to break out.

There are aluminium orthophosphate bonded castables.  Quick setting and non-brittle. We call them versimould.

Keramicalia does not manufacture standard castables, since there are a large number of companies already making them. We do make a few special castables

​Technicast is a very high density zircon-andalusite material for extreme environments.

Pipe mix is low cement andalusite castable for high integrity. Developed for the DRH process.Keracast is totally lime free.f-levelling tabular alumina castable for precasting.

Fibre Castable A hydraulic bonded castable based on ceramic fibres. Hollocast  is a range of cellular insulation castables.

Keralite  is a range of cellular insulation castable to replace IFB's.

Hardcast is a range of silicate bonded materials for various purposes, including castable for hot floors, acid resistance and shallow repairs.

High Temperature Kerasic A silicon carbide castable with particularly high thermal conductivity.

Kerachrome is a low cost, general purpose conventional castable.

Keracast 1600 a dense andalusite castable.

Keraflow 1900 is a High Temperature Kerasic  A silicon carbide castable with particularly high thermal conductivity.

Keratab dumping mix is a self-flowing alumina for installation in difficult areas without vibration.

Kerabrade C is a very string abrasive resistant castable.

Keratab is a range of tabular alumina castables.

Insulmag a basic insulation castable.

Coke Wharf Mix A high density castable for high heat retension.

Fused Silica Castable A vibration castable material for molten aluminium contact.

KERACLASE A periclase (MgO) castable, high purity magnesia castable for electric arc furnaces.

Keralcast A very resistant castable for contact with molten aluminium.

Keramag A dense, low prmeability high strength basic castable with hydration resistance. Slow setting, 2 days.

Sublimecast A coarse refractory concrete with extreme resistance to reduction.

Spinel Castable Fine Used in Kiln furniture for firing pure alumina ceramics.  See Pourable for self-flowing silicon carbide, zircon and tabular alumina materials.

Coke Wharf Mix​ This is a high density thermal shock resistant mix.

It was developed for lining coke wharves, where tons of burning coke are
pushed onto a sloping floor before quenching in water.

It can withstand repeated heating to 1000°C and quenching in water.
It is acid resistant and abrasion resistant.

The high density results in high thermal mass, and the material has found a number of applications for heat storage and others for heat dissipation.

Maximum service temperature; 1100°C.
Maximum particle size; 15mm. Also available in 6mm.
Water addition; +9%
Packaging; 25kg plastic bags, and 15kg plastic bags for -6mm.

Insulmag ​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;​​​​​​​​​​​​Packaging; 10kg plastic bags.

Kerabrade C​

Description: An abrasion resistant high strength castable for use up to 1200°C. The matrix is very hard, and fracture will occur right through the aggregate grains.​Physical properties:       Bulk density: 2,25g/cm³
                                          Cold crushing strength: 100 to 150MPa
                                          Permanent linear change: -0,2% after 800°C
                                          Thermal conductivity: 1,6W/mK

Installation; Place +7,5% water in a planetary (bakery type) mixer. Add half of the powder and mix until fluid. Add another quarter of the powder and mix until fluid. Slowly add the last quarter of powder, keeping the mix fluid. This will take about 5 minutes. The result is a self-levelling fluid.
Packing: 25kg plastic bags

Keracast 3

​Description; A cement free castable. It contains over 95% aluminosilicates and hardly any fluxes. Strength increases with temperature, but good thermal shock resistance is retained.

Maximum service temperature; Proven up to 1500ºC, probably in excess of 1600ºC.

Installation; Add plus 1-.5% Keracast binder to the powder, mix rapdily and vibration cast without delay.Pilot Plant Code; MPS.

Keracast 6

​Keracast 6 is a totally cement free, CaO free material. It is consequently highly refractory. The chemical analysis is approximately as follows;

 The mineral composition is about 87% alpha alumina, which is synthetic corundum, with a melting point of 2013ºC and 13% mullite,Al2 O3 .SiO2 , with a melting point of 1850ºC. The material therefore contains very little liquid phase below 1850ºC. Both mullite and corundum are chemically inert and immune to attack by sulphurous or acid gases. To develop good strength we pre-fire the castings to 1200ºC, so that the silica is all present in the mineral mullite. Mullite grows in needle-like crystals, which enhance the strength of the composite. Corundum is the second hardest natural mineral, with a hardness of 9 on the Moh scale. (Diamond is the hardest, at 10 on the scale.) The only refractory materials with higher melting points are lime, magnesia and zirconia. All three are prone to thermal shock.
Formulation no. 11484

Kerachrome

​Description; A dense chemically resistant castable for low temperature applications. It has a high thermal mass and high heat storage capacity. It is based on chromite and fused grain, with 16% calcium aluminate cement.

Maximum Service Temperature; 1200ºC
Quantity required to cast 1 cubic metre; 2750kg
Moisture addition for casting; 9 litres per 100kg
Permanent linear change; Fired to 1000ºCChemical analysis;

Packaging: Packed in 25kg bags, palletised and stretch wrapped.Storage life; 6 months under normal conditions.

Keraflow 1900​

Description; Keraflow 1900 is probably the highest temperature Tabular alumina castable developed to date. It contains no silica. Conventional castables containing tabular alumina are also silica free, but need high water contents. Keraflow 1900 can be vibration cast at only +3,8% water, and FLOWS SELF-LEVELLING @ +4,5% WATER. Consequently the strength is exceptionally high. Mix intensively for at least 4 minutes.

Physical properties; (5 hours soak)The variation in strength is due to different water contents.

Applications: Just about any application where the temperature is extremely high or the chemical or physical environment is too severe for normal materials. Packaging; 25kg clear polyethylene bags.

Keratab

​Keratab is range of refractory materials for electrical applications, where it is in contact with elements. Keratab can be supplied tailor made for the exact application, between an ultrafine creamy pourable material for delicate components and a coarse robust castable. A plasticised material, "Induction Coil Coating" is also part of the range.

All formulations are essentially based on aluminium oxide and contain over 90% Al2 O3. The iron content is less than 0.1% and sodium oxide less than 0.3%

The usual operating temperature is around 1300ºC to 1400ºC. but it could be used safely at 1700ºC.

The colour is white and the texture is fine with a smooth surface.

Thermal shock resistance; A slab can be heated with an oxyacetylene flame until it melts locally, without the slab cracking.

Applications; Element holding brick, kiln muffles, tubes, electrical connectors etc...

For small production runs of intricate components, a sample can be cloned in keratua by the multimould system.

Keratab dump mix​

Description; A dumping mix is a self-levelling castable for discharge directly into the installation. It flows rapidly without any assistance,and de-airs itself. It is based on tabular alumina. It can handle severe thermal shock.

Mixing; Mix with +9% water. It flows for about 20 minutes. It should be discharged directly into the mould, since its flow properties do not allow handling in buckets or wheelbarrows. No vibration is needed. Heat of hydration is high, but delayed. (About 7 hours) Drying should be slow and careful, as the material has very low permeability and a very fine pore size distribution.​Packaging; 25kg plastic bags.Shelf life; 12 months in unpunctured bags.Test results are based on single cubes.

Pipe mix​

Description; A high density, very low permeability aluminosilicate castable. It has excellent electrical insulation properties. Easy to cast, good flow, excellent microstructure.

Maximum service temperature; 1750ºC

Bulk density; 2,65g/cm³
Cold crushing strength; 75MPa.
Thermal conductivity; 1,2W/mK
Installation; Add plus 5.5% Water and vibration cast. If more water is added, the setting time will be long.Packaging; 25kg plastic bags.

Rubyflow​

Description; Rubycast is a cery string, highly refractory castable for extreme service environments. It flows well during vibration casting and has excellent thermal shock resistance and abrasion resistance.

Maximum service tenmperature; 17500°C.

* The chrome oxide is contined in the chrome-alumina agregate, and not as agreen chromic oxide addition.
Density; 2.6 to 2.65 (2.65 tons per cubic meter)
Water addition; 5.5 to 6.8 litres per 100kg.
Cold crushing strength; Dry 80Mpa, 1000°C 90Mpa.
P.L.C. -.18% fired at 1000°C.
Thermal conductivity; 1.5W/mK at 1000°C.
Packaging; 25kg transparent polythene bags.

Keraclase​

A periclase (magnesia, MgO) refractory of high purity and refractoriness.​Composition;  

Bulk density; 2,75 to 2,85g/cm3​Thermal conductivity;  Around 4,0W/mK

Cold crushing strength; 45 MPa plusMax particle size;  6mmMax service temperature, continuous;  1800C

Water addition; Nil for dry spiking,   +3-5% for ramming   +6-8% for casting, use vibration. 

Setting;  Note that it takes days to set.Curing;   After 2 days the former may be removed and heating may start immediately.   Do not leave Keraclase casting wet for too long in a hot damp climate, it will hydrate and crack.

Packaging;   25kg plastic bags.Development no;   115300

Technicast​

Description; A very high density zirconia-alumina-silicate castable with good workability and high strength. Very user friendly.

Installation; Add plus 3,8% water Applications; Difficult castings and precast.

Packaging; 25kg plastic bags on 1 ton pallets stretch wrapped.

Pilot Plant code; MPSDev. no. 36112

Hollocast​

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.

Keralite

​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 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. 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. 10kg bags, larger than our normal 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. 15kg bags.

Hardcast​

Hardcast is a range of silicate bonded materials.It is used in place of concrete where very low permeability is necessary, for acid resistance.It is also very quick setting, and can be used in thin applications where concrete would be sucked dry before it can set, for example repairs of factory floors. ​It can be used to repair acid damaged floors: Hardcast Acid Resistant Floor Screed.

Hardcast light is acid resistant insulation. Chloresist is the high temperature version, used in incinerators where chloride attack is the main problem. Hardcast Fine Acid Resistant Mortar is used as a glue where air setting is not possible, for example when bonding impervious sintered ceramic tubes.​The data sheets are all very similar, just read one and you know all the tricks. Once you have started using Hardcast, you will seldom use concrete again for small jobs.

Keralcast

​ Description:   Alumina based abrasion resistant castable. This is new technology, previous high abrasion resistant ceramics are based on high additions of silica fume. Keralcast has only 1% silica and can therefore be used at high temperatures, up to 1750ºC with virtually no molten phase present.

Density:     3.06 g/cm³Max particle size:   5mmThermal conductivity:  2W/mK

Water addition:   Extremely low:  +4.5%Mixing: 7 minutes in a bakery mixer or 20 minutes in a pan mixer. The consistency can be adjusted from putty to self-flowing, as preferred. The setting time can be adjusted from half an hour to 6 hours, as preferred.
Testing:       Try to grind it on a bench grinder.

Shelf life: 2 years

.Packaging:  25 kg plastic bags.

Project no.   1142

Claimer:   This data sheet had better be correct because Dave Onderstall stakes his reputation on it.

Keramag

​Description: a dense low permeability basic castable with excellent thermal shock resistance and hydration resistance.   Manufactured from fused grain.  Very slow setting, 2 days. Maximum service temperature:         1600°C​Chemical analysis: ​

Density:2.9g/cm³  

Installation: Add plus 7% water ± 1%.Applications: Contact with basic slags. Thermit  reaction vessels.

Packaging:  25kg plastic bags on 1 ton pallets stretch wrapped.

Pilot Plant code: KAN Development No. 12063

Sublimecast

​Description: A coarse refractory concrete with extreme resistance to reduction. Maximum service temperature: Not determined, will probably contain liquid from 1500°C. Not designed for free standing structures at high temperature. Density:   2.45 tons/m³Strength: 50 MPa Chemical analysis;​​

Installation:  Add  +8, 3% to  + 8, 8% water and vibration cast. Application: Apply 2m² at 250mm thick next to electrode on Aicheson furnace.

Development no: 73902Packaging;   Bulk bags

Spinel Castable Fine

​Description;​Spinel is the group of minerals with the composition R0R2O3.   It includes chromite and MgO.  This material is based on MgO Al2O3. It has a higher melting point than pure corundum; alpha Al2O3.   It is used in kiln furniture for firing pure alumina ceramics. There is no shrinkage; it expands and grows with progressive heat treatment at 1600°C.Vibration cast with +9,5% water.​Development no. 25709

Keracast 1600

​Description; A dense andalusite castable.
Maximum service temperature; 1600ºC
Bulk density; 2,6g/cm³
Cold crushing strength; 75MPa.
Thermal conductivity; 1,4W/mK
Chemical analysis;

Installation; Add plus 7% - 9% water and vibration cast. .
Packaging; 25kg plastic bags.Dev No: 151307

Fused Silica Castable

​A vibration castable material for molten aluminium contact. Mix 100 weight parts powder with 15 weight parts liquid binder. Mix for 2 minutes.Colour: Powder goes light brown when mixed with liquid, then white when fired.It casts nicely, and can go down to 8mm thick.It contains 95% SiO₂ and 2% Na₂O. Its main property is very low thermal expansion. It is non-wetting to aluminium. ​Packaging: A 25kg bag with powder, the liquid binder inside it in a bottle. Shelf life: Indefinite 

Development no. 51509 

Claimer: The above information had better be correct, since Dave Onderstall stakes his reputation on it.

Fibre Castable​

Description: A hydraulic boned castable based on ceramic fibre. Similar to vacuum formed ceramic, but quick and easy to mould.

​Maximum service temperature: 1300°C

Maximum particle size: about 3mm

Density:0,83kg/m3

Thermal conductivity; about 0,3W/mk

Colour: white to yellowish white.​

Chemical Analysis:                                       ​

Installation: Add plus +80% water and vibration cast.

Applications: insulation, element holding bricks.

Packing: 5kg plastic bags.

Shelf life: About 2 years store well.

Development no 55923

High Temperature Kerasic​

Description;  A silicon carbide castable with particularly high thermal conductivity.

Cold crushing strength; 40 MPa dried 110°C

Bulk density;   2,4g/cm³ dried 110°C

Maximum particle size; 3mm

Maximum service temperature; 1400°C​

Chemical analysis;

Packaging; 25kg plastic bags.

Water addition; +9,5%. Vibration cast

Development no: 76577

Claimer: This information had better be correct as Dave Onderstall stakes his reputation on it.