Mortars, Refractory

finely divided refractory mixtures used (usually after the addition of water) to bind refractory articles and to fill seams. Refractory mortars consist of a filler and a binder; their composition usually must be compatible with the properties of the refractory articles. A distinction is made among ordinary refractory mortars, which harden at high temperatures as a result of the formation of a ceramic bond; hydraulically hardening mortars, which contain a hydraulic cement; and mortars with chemical bonding, which harden at room temperature or upon heating. Mixtures to which a nonceramic binder has been added are called refractory cements.

The degree of fineness of a refractory mortar is determined by its purpose. The grain size of fine-grained mortars does not exceed 1 mm (for some special mortars, 0.5 and even 0.1–0.2 mm); that of the coarse-grained mortars is up to 2 mm. Refractory mortars are used for linings of industrial furnaces and other equipment—for example, firebrick and high-alumina mortars in blast furnaces, air heaters, and steel-casting ladles; Dinas mortars in coke ovens; and magnesia mortars in open-hearth furnaces. A solution of the required consistency, consisting of mortar and water (or, less frequently, some other liquid), is usually prepared at the work site. Some special mortars, including refractory cements, are delivered in the form of prepared solutions.