The Pros and Cons of Refractory Bricks and Monolithic Refractories

Refractory materials can be generally divided into two kinds: refractories bricks (shaped refractories) and monolithic refractories (unshaped refractories). Both have its pros and cons and applications in the refractory lines.

Refractories bricks are shaped refractories which have fixed shapes. The shapes of refractories bricks maybe divided into two types: standard shapes and special shapes. Standard shapes have dimensions that are conformed to by most refractory manufacturers and are generally applicable to kilns and furnaces of the same type. Special shapes are specifically made for particular kilns and furnaces. This may not be applicable to another furnaces or kiln of the same type.

Shaped Refractory bricks are almost always machine-pressed, thus, high uniformity in properties are expected. Special shapes are most often hand-molded and are expected to exhibit slight variations in properties.

Refractory bricks possess high thermal strength at elevated temperatures. Combined with chemical resistance to alkali attack, the performance is improved for areas with mechanical and chemical impact. These performance characteristics are important in where archways and belly band areas are exposed to mechanical wear and chemical attack. One advantage of refractory bricks over monolithic refractories is that the structural properties are defined during the production process.

Unshaped refractories are without definite form and are only given shape when used. It forms joint less lining and are better known as monolithic refractories. These are categorized as plastic refractories, ramming mixes, castables, gunning mixes, fettling mixes and mortars.

Monolithic refractories exhibits properties that outperform traditional refractory bricks. They have better volume stability and better mechanical resistance to vibration and impact. Another advantage over fired bricks is that shrinkage and expansion of monolithic linings can be matched to the application. In some cases shrinkage can offset the thermal expansion resulting in a significantly different thermo-mechanical behavior compared to refractory bricks.

Use of Monolithic refractories eliminates difficult brick laying tasks and joints which may be accompanied with weakness in construction. Under certain conditions, monolithic linings of the same composition as firebrick provide better insulation, lower permeability and improved resistance to the spalling effects of thermal shock. With little or no preparation, monolithic refractories can be applied to form monolithic or joint free furnace linings in new constructions or to repair existing refractory lining.

Monolithic refractories are widely used in the construction of new kilns and furnaces and in the maintenance of older ones because substantial repairs can be made with a minimum loss of time and, in some cases, even during operations, and in a variety of other applications.