refractory cements

タイトルまたは説明

High Alumina Cement Description High alumina cement is a rapid-hardening cement made by fusing at 1, **0° to 1, **0° C (2, **0° to 2, **0° F) a mixture of bauxite and limestone in a reverberatory or electric furnace or in a rotary kiln. It also can be made by sintering at about 1, **0° C (2, **0° F). Suitable bauxites contain *0 to *0 percent alumina, up to *5 percent iron oxide, not more than 5 percent silica, and *0 to *0 percent water of hydration. High alumina cement is produced by preparing raw material consisting of applicable bauxite and limestone, burning the raw material and grinding into cement The high alumina cement can resist a high temperature at which a relative high temperature at which a relative high strength still remains. Its refractoriness increases with the content of CA2. Therefore it is suitable to make refractory concrete as a binder. Depending on the refractory aggregate (fireclay, high aluminum)used, the refractory concrete made of the cement can be used below ***0°C. Although the early strength of high alumina cement develops rapidly, its later strength decreases. The rates of castable conversion and strength reduction relates to atmospheric temperature and humidity. In the saturated steam at *5°C, the conversion is complete in *8d and the strength decreases to the minimum, in the dry air below *0°C, the conversion is very slow. So the HAC is not suited to use in building engineerings. If it is used in construction, matters needing attention given in the appendix GB**1 must be followed . In order make use of strong points of HAC and overcome its weak point, cement scientists in the world have developed various modified HAC and overcome its weak point, cement scientists in the world have developed various modified HAC series: self-stressing cement, expansive cement, impermeable non-shrinkage cement, rapid hardening high strength aluminates cement. Special rapid hardening setting-controlled aluminates cement and so on. These alumina cement