Unshaped Refractories definitions

Various terms such as mixes, refractory mixes, ramming mixes, and monolithics are included in the definition of unshaped refractory products. These products are distinguished from bricks, which have a definite shape, are prefired, and are laid. Unshaped refractories are placed in larger sections. For example, a furnace lining consists of unshaped refractories. They have few joints. 

The definition for an unshaped refractory is given in ISO 1927 (5) and EN 1402-1 It is a mixture, which consists of an aggregate and a bond or bonds, prepared ready for use either directly in the condition in which it is supplied or after the addition of a liquid that satisfies the requirements on refractoriness given in ISO R 836. They may contain metallic, organic, or ceramic fiber material. This mixture is either dense or insulating. An insulating mixture is one whose true porosity is not less than 45% when determined in accordance with EN 1094-4, using a test piece prefired to specified conditions. 

The maximum grain size is the mesh width through which at least 95% by weight of the material can pass. Another definition relevant to an unshaped refractory is the yield by volume, which is the mass of the material as delivered that is necessary to place 1 m [3] of the material, expressed in tons, to the nearest 1%. 

The definition of unshaped refractory products mentioned that these products may contain fibers. The addition of various fibers to these products will be discussed further in the following sections. 

In Europe much more time passed until the first tendencies for starting a standardization of unshaped refractories appeared. In February 1964, the PRE Bulletin No. 65 was published containing a first definition and classification of unshaped refractories and refractory mortars on a modest scale. 

The multitude of refractory aggregates (for example, calcined clay, flint clay, andalusite, mulhte, bauxite, fused white or brown alumina, sintered alumina, etc.) and the different grain sizes of these materials—in addition to the big variety of bonding agents, additives, and mixing liquids—enable endless combination possibihties in development work on unshaped refractory products. Therefore, a qualitative standardization is not really possible as it is the case for refractory bricks. As a result of the ENV 1402-1 standard, which now provides a more precise definition of the products, there will probably be adjustments on the market in the long run. If also considering economic aspects, suitable products will obviously be developed on the basis of all the available constituents. 

There are small differences in different classifications of refractory materials among ISO, DIN, and ASTM standards [1 ]. The most common definition is that refractories are shaped and unshaped materials that are durable at high temperature (>1,500 °C). Usually, heat refractory insulation materials have a service temperature of 800-1,100 °C. 

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