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Main » refractory-materials » Mortars » Heat-insulating expansion concretes

Heat-insulating expansion concretes

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Special heat-insulating expansion concretes (fireproof or refractory) provide for significant energy saving in the production process due to the high-grade heat insulation of the thermal generating units and their components. This material has a unique feature – it can expand swelling out by 25% - 100% (adjustable as needed) and forming a durable ceramic structure with following characteristics: thermal conductivity ~ 0.35 W /(m*K) at bending strength ~ 5 MPa (strength and conductivity are adjustable as needed within the certain limits.) The following characteristics contribute to a high quality of heat insulation of the material: upon expansion the concrete fills all pores and protects the masonry against heat losses, as well as increases its strength due to the additional reinforcing; heat-insulating layer is very strong mechanically that is extremely important for proper heat insulation as the latter does not shrink upon thermal expansion of the masonry, and the layer does not become thinner (heat losses are inversely proportional to the thickness of heat insulation layer, soft heat insulation shrinks, heat-insulating layer “disappears”, and heat losses increase.) This concrete is especially useful in hot repairs of the unit (while the unit is in service.) Concrete is injected into the local hot or overheated spots, expands and securely seals the hot (overheated) spot to further operate the unit safely.

Special concretes and heat-insulating paints are useful in heat insulating of thermal furnaces and burners, pipelines, gas fuels, etc. In addition, application of the expansion concrete as repair material provides for the energy saving. In such a case repairs may be done during operation of the unit that prevents any undesirable heat leakages. It should be noted that high heat-insulating properties of the concrete are complemented with its high strength that contributes to the stability of the heat-insulating layer (and, as a result, stability of the heat protection) upon high temperature stresses which may occur in the thermal generating unit masonry.

Lightweight porous fireproof multi-purpose solutions (refractory properties, heat and fire protection, heat insulation) play an important role here. Developing a wide range of materials with unique properties (low density and thermal resistance, corrosion resistance in chemically active environments, low thermal conductivity and others) through the rational use of individual properties of original components of blend compositions makes a breakthrough in the sphere of construction and industrial materials production and creates a new line in the series of ultra lightweight materials.

Operating temperature of the proposed heat-protective and heat-insulating materials ranges from -100 to +1600-1750оС, i.e. they are capable of protecting structures in both cooling and high temperature units. These materials modified by mineral fiber may be an effective means of fire and heat protection under fire conditions. High temperature expansion concretes shall be widely used in repair and renewal operations, including hot repairs of the thermal generating units, as well as in heat insulation of various high temperature units in metallurgy, machine building and many other industries.

Brief description of expansion concretes:

- after being mixed the concrete expands for 10-50 minutes (time may be adjusted as appropriate) and then sets in 10 minutes.

- actual operating temperature is up to 1,700оС.

- density of concrete may be adjusted from 650 to 1700 g/cm3.

- low thermal conductivity and high mechanical strength of the concrete ensure proper heat protection of the thermal generating units. Ordinary heat insulation is soft that is why it shrinks as the masonry expands, and heat insulation layer “disappears”; as a result, heat insulation of the thermal generating unit becomes poor. The concrete is very strong and has low thermal conductivity that provides for durable, stable and effective heat insulation.

Some applications of expansion concretes at metallurgical plants:

- repairs of thermal generating units (sometimes during their operation.) Concrete is being injected from the outside into the gap between masonry and enclosure. Concrete starts to expand, fills all pores, sets and reinforces the masonry. This may be useful in repairing the heating furnace enclosures in the course of the furnace’s operation, for example the hot spots, places of burner operation, etc. Repairs of blast furnace enclosures (injection of concrete between cooling unit and masonry), air heaters and hot-blast mains. Repair operations are to be performed in the same way as in case with the heating furnaces. Application of concretes in all above-mentioned units has shown positive results.

- heat insulating in the course of making the new linings of such units as heating furnaces, ladles, etc. In this case the concrete is being poured between enclosure and masonry, the concrete fills all pores and cracks.

Table of fireproof ultra lightweight VBF concretes



Operating temperature [°С]


Amount of blend per m3, kg

Amount of binding agent, kg/m3




ρ = 650 kg/m3


Heat insulation of any heating units, boilers, furnaces, baths, air heaters, blast furnaces, flaps, shutters, etc.

520 kg/m3



364 kg/m3


Binding agent for VBF


Filling technology

C exp. = 2.0



ρ = 850 kg/m3


Heat insulation of any thermal generating units: furnaces, boilers, baths, crowns, breeches, blast furnaces, air heaters, etc. As a repair material for partial repair to prevent capital repairs.

680 kg/m3




408 kg/m3


Binding agent for VBF


Filling technology

C exp. = 1.5



ρ = 1,000 kg/m3


Heat insulation of flaps, doors, covers, etc. Routine partial repair of the thermal generating units

800 kg/m3


320 kg/m3

Binding agent for VBF

Filling technology

C exp. = 1.25



ρ = 1,300 kg/m3


Repairs of heavy linings of thermal generating units

1,040 kg/m3


411 kg/m3

Binding agent for VBF

Filling technology

C exp. = 1.05



ρ = 1,500 kg/m3


Repairs of heavy linings of thermal generating units

1,200 kg/m3


420 kg/m3

Binding agent for VBF

Filling technology

C exp. =1.03



ρ = 1,700 kg/m3


Manufacture of burning blocks, deflectors, bars and other formed parts. Partial repair of thermal generating units

1,300 kg/m3

435 kg/m3


Binding agent for VBF

Filling technology

C exp. =1.0


Video: concrete expansion

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