Porosity and permeability are crucial factors in insulating refractories as they directly impact the material's ability to resist heat transfer. Porosity refers to the presence of small interconnected pores within the refractory material, while permeability represents the ease with which gases or liquids can flow through these pores. High porosity allows for the trapping of air or gas within the refractory, creating an insulating barrier that minimizes heat conduction. This thermal insulation property is vital in applications where high temperatures are involved, such as in kilns, furnaces, or industrial processes. By reducing heat transfer, porosity helps to conserve energy, improve efficiency, and enhance the overall performance of the refractory material. Permeability, on the other hand, affects the material's ability to resist the ingress of unwanted substances, like molten metals or corrosive gases. Low permeability ensures that the refractory remains stable and durable by preventing the penetration of harmful agents, which can cause oxidation, erosion, or chemical reactions. This protection is crucial for maintaining the refractory's structural integrity and extending its lifespan. In summary, porosity and permeability play a vital role in insulating refractories as they provide thermal insulation and prevent the ingress of harmful substances. These properties are critical for achieving efficient heat management, ensuring operational safety, and prolonging the refractory's service life in high-temperature environments.

Strontium carbonate enhances the properties of refractory materials by acting as a fluxing agent, reducing the melting temperature and increasing the fluidity of the material during firing. This results in improved workability, increased density, and reduced porosity of the refractory material, leading to enhanced strength, thermal shock resistance, and overall performance.

Raw materials can have a significant impact on the resistance to oxidation of refractory products. Certain raw materials, such as high alumina content, can enhance the resistance to oxidation due to their high melting point and stable oxide formation. Other raw materials, like silica, may have lower resistance to oxidation as they can easily react with oxygen at high temperatures. The composition and selection of raw materials play a crucial role in determining the overall resistance to oxidation of refractory products.

The main sources of perlite in refractory raw materials are volcanic rocks and the subsequent processing of these rocks.