Physical, Thermal and Chemical Properties of Refractory Materials -->

Physical, Thermal and Chemical Properties of Refractory Materials

Properties Of Refractory Materials
Refractory materials are essential in various high-temperature applications, such as furnace linings, kiln linings, and incinerators. The quality and suitability of refractory materials for these applications depend on their physical, thermal, and chemical properties. The most common properties of the refractory material are listed below.

Physical properties

The refractory materials commonly characterized by their physical properties.

Bulk density

The bulk density of a refractory material is a general indication of its quality and is calculated as the ratio of its weight to its volume, measured in g/cm3. A higher bulk density indicates a more dense and compact material, which is typically stronger and has a better stability.


It is defined as the ratio of its pores volume to its total volume. A low porosity is desirable in refractory materials as it affects several other properties, such as resistance to abrasion and thermal conductivity. In general, a good refractory must have low porosity. Here are some advantages and disadvantages of high porosity

Advantages of high porosity
(i) Highly porous refractory have lower thermal conductivity. This is due to the presence of more air voids, which act as insulation and therefore, be used for lining furnaces.
(ii) High resistance to the thermal shock and heat spalling.
(iii) Pores act as a crack inhibitor.

Disadvantages of high porosity
(i) Reduces the strength.
(ii) Reduces the resistance to abrasion and corrosion.
(iii) Lower load bearing capacity.

Cold compressive strength

This indicates how refractory material can handle the load of installation or ability to withstand rigours transport, whereas the hot compressive strength shows how they will perform at high temperature. It is measured by a compression test. It is used to ensure that there is no crushing of refractory brick where it is subjected to high pressures. 

Flexural strength

Flexural strength; credit:wikimedia

Also known as the “bend strength.” The test consists of subjecting a concentrated central load on a specimen resting on two edges. The specimen is bent until it rapture and  highest stress obtained during the test represents the flexural strength of the material.

Wear resistance

The refractory walls in furnaces and kilns are subjected to shock from hot gases and abrasive raw solids, so it is important that they have good wear resistance. Hence, they must have good wear resistance to withstand these conditions, ensuring their longevity and effectiveness.

Thermal properties

Melting point

A good refractory material should have a very high melting point. The melting point of a refractory material is an essential factor in determining its suitability for high-temperature applications.

Thermal expansion

It is the measurement of the linear stability of material when exposed to high temperature. All bodies undergo a reversible change in dimension under the influence of temperature. If refractory material undergoes higher expansion; it will suffer flaking of the surface.

Dimensional stability

Dimensional stability refers to a refractory's resistance to changes in volume when exposed to high temperatures for an extended period. A good refractory should have excellent dimensional stability to maintain its shape and structure under extreme conditions.

Thermal Shock

Fluctuations in temperature can significantly reduce the strength of refractory surface, causing the breakdown or peeling of layers if it is exposed to no. of thermal cycles. It is important because most process experiences alternative heating and cooling. A good refractory should show a very good resistance to thermal shock.

Thermal conductivity

Thermal conductivity refers to the ability of a material to conduct heat from the hot face to the cold face. This property is important for thermal insulation and determines how well a refractory material can maintain a consistent temperature.

Pyrometric cone equivalent (PCE)

The Pyrometric Cone Equivalent (PCE) is a measurement of the heatwork of a refractory material, which is the combined effect of temperature and time.

Chemical properties

Corrosion resistance

The refractory material should have high corrosion resistance since these directly contact with hot gases and slag.
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