alumina cement[ə′lüm·ə·nə si′ment]
a rapid-hardening hydraulic binding material; a product of the fine grinding of clinker produced by roasting (prior to smelting or calcining) of the raw mix, which consists of bauxites and limestone material. The raw mix is roasted and smelted in blast furnaces, electric furnaces, rotary kilns, or cupola furnaces. According to the content of A1203 in the finished product, a distinction is made between ordinary alumina cement (up to 55 percent) and high-alumina cement (up to 70 percent). The smelting temperature of a raw furnace charge of ordinary alumina cement is 1450°-1480° C, whereas for high-alumina cement it is 1700°-1750° C.
Alumina cement is characterized by a rapid increase in strength, a high degree of exothermy during hardening, increased resistance to corrosion in sulfate environments, and high fire resistance. In comparison with portland cement, alumina cement makes possible the production of concretes and mortars with higher density and water resistance.
I. V. KRAVCHENKO