The technical indicators of refractory castables are the main reference for the procurement process, determining the quality of refractory castables. There are seven main technical indicators of refractory castables, namely A2O3 content, bulk density, apparent porosity, compressive strength at room temperature, refractoriness under load, and thermal shock resistance. Taking high-alumina refractory castables as an example, their technical indicators are analyzed below.
The A2O3 content, in layman’s terms, refers to the content of aluminum oxide in high-alumina castable, which determines the level of various other properties. Therefore, it is the main performance indicator of highalumina castable refractory.
bulk density
Bulk density is the ratio of the dry mass of high-alumina castable to its total volume, with the unit being g/cm3. It primarily indicates the compactness of high-alumina castable refractory. Generally, the bulk density of high-alumina castable is closely related to its porosity and mineral composition.
Flexural strength at room temperature
Ambient temperature flexural strength refers to the maximum bending stress that a strip-shaped test block made of high-alumina castable can withstand during testing. The chemical composition, mineral composition, microstructure, production process, etc., of the material have a decisive impact on its flexural strength, especially its high-temperature flexural strength. Generally, selecting high-purity raw materials, controlling the reasonable particle size distribution of the material, increasing the forming pressure, using high-quality binders, and improving the sintering degree of the product can enhance the flexural strength of the material.
Ambient temperature compressive strength
Compressive strength refers to the ultimate load that a high-alumina castable construction body can withstand per unit area without being damaged at a certain temperature. The compressive strength at room temperature can indicate the sintering condition of the material and its properties related to its organizational structure. Additionally, other properties such as wear resistance and impact resistance can be indirectly evaluated through the compressive strength at room temperature.
Load softening temperature
The refractoriness under load of high-alumina castable refers to the temperature at which deformation occurs during use. It indicates the ability of refractory materials to resist both high temperature and load simultaneously. To a certain extent, it reflects the structural strength of the product under similar usage conditions.
alkali resistance
High-alumina castables used in cement kilns are often eroded by alkaline gases inside the kiln. Therefore, it is necessary to test the alkali resistance of the materials. Alkali resistance refers to the ability of refractory castables to resist alkaline erosion at high temperatures.
The above are the key technical performance indicators of high-alumina castable. When purchasing and using high alumina castable refractory, it must be selected strictly according to the actual kiln requirements, in order to extend the service life of the high-alumina castable, prolong the usage cycle, and save maintenance costs.
