Refractory castables physical properties

In general the size of the pores depends, among other factors, on the particle size of the aggregate. Particle size is the most important parameter in the production of ceramic products it must be optimized to ensure that the desired mechanical and physical properties are achieved. The majority of ceramic products are manufactured by the process of slip casting in a mold. Maintenance of the desired PSD requires control of the dispersion stabUity of the ceramic shp. Like all ceramic materials and castables, in alumina refractories a proper PSD is of importance. 

As mentioned, refractory castables are combinations of refractory aggregates, matrix components, bonding agents, and admixtures. The proportions of each component used vary in each castable composition to achieve the desired physical and chemical properties and characteristics for the intended castable application. The general range of component quantities in a refractory castable is shown in Table 2. 

Because of the many types of advanced castables on the market today and due to the specialized development of many of these materials for specific uses, it is harder to characterize their strength development. The refractory manufacturer has less leeway in development of most dense conventional castables since they are viewed more or less as a commodity product (every manufacturer makes similar products) in the marketplace, and price dictates formulation constraints. This is sometimes true for low end (superduty, 50% alumina) advanced castable types in the low- and ultralow-cement classifications. However, application and performance criteria can and do call for the development and use of premium castables where the use of expensive formulations and exotic modifiers can modify physical properties and characteristics such as strength in specific temperature ranges that correspond to the anticipated service condition. 

For the past 30 years, refractory technologists have significantly improved refractory castable formulations, widening both the types of castables and the installation methods available. The improvement in their physical properties and characteristics have enabled castables to gain in market share and application at the expense of other types of refractories. In a recent report, an industrial market research firm predicted that castables would see the best sales growth in the refractory market over the next 5 years due to superior performance character-... 

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