What characteristic defines heat setting refractories during the curing process?

The characteristic that defines heat setting refractories during the curing process is that they must be protected from moisture. This is crucial because moisture can interfere with the curing process, potentially causing deterioration of the refractory material. Heat setting refractories typically undergo a chemical change or setting reaction when exposed to heat, and the presence of moisture can hinder this reaction, leading to improper hardening or performance issues.

Maintaining dryness ensures that the chemical processes necessary for setting and strengthening the refractory can occur effectively. If moisture is present, it can cause issues such as expansion, bubbling, or even cracking during the curing phase, as well as negatively affecting the final mechanical properties and thermal stability of the refractories.

In contrast, air curing is a method used for other types of refractories but is not suitable for heat setting types, while excess moisture during curing would be detrimental to the material's integrity. Low thermal conductivity is a specific property of some refractories but does not relate to the curing or setting process specifically. Hence, protecting heat-setting refractories from moisture is essential for their proper development and performance.