Refractory Gunning Mixes (a Type of Unshaped Refractory Material)

Unshaped refractory materials applied via a spraying process to repair the linings of thermal equipment are known as "refractory gunning mixes." These materials consist of refractory aggregates with a specific particle-size distribution, chemical binders, and various additives; they are generally classified as either heat-setting or air-setting materials. Unlike refractory spray coatings (which are often used for initial lining application), refractory gunning mixes are primarily employed for the repair of existing linings in thermal equipment.

The selection of the primary material for a refractory gunning mix is ​​based on factors such as the maximum temperature the furnace or kiln may reach, the range of temperature fluctuations, the nature of the slag, and the composition of the existing furnace lining. Common base materials include magnesia, dolomite, magnesia-chrome, aluminosilicate, zircon, and silicon carbide. Binders used may include silicates, phosphoric acid or phosphates, polyphosphates, chromates, sulfates, chlorides, pitch, resins, or cement.

To ensure good application characteristics—such as ease of transport, proper wetting, plasticity, adhesion, and sinterability—various additives must be incorporated, including wetting agents, coagulants, plasticizers, and sintering aids. Commonly used plasticizers include clay and carboxymethyl cellulose (CMC), while sintering aids include iron oxide, serpentine, and olivine.