Technologies & innovation

About Aluminates

CALCIUM ALUMINATES HYDRAULIC CEMENTS WITH MULTIPLE PROPERTIES

Calcium aluminates or hydraulic cements
"Calcium aluminates, "alumina cements" or "high alumina cements" are obtained by the reaction at high temperature of lime (from limestone) and alumina (contained in natural minerals like bauxite). The product obtained after cooling is a hard mineral: calcium aluminate clinker.

• Crushed or screened, it is used as an aggregate. The composition and colour - ranging from the purest white to jet black - depends on the proportion of each raw material.
• Ground into a fine powder, the clinker becomes calcium aluminate cement (CAC) which forms a paste when mixed with water. This has the ability to harden very quickly: it forms a rigid solid within 24 hours.

Diversity of calcium aluminate applications
There are two distinct ways to use calcium aluminates: as high-performance binders and as mineral reagents in a variety of industries.

• As binders, calcium aluminates are used in concretes and mortars for specialised applications for their properties of resistance to corrosion, abrasion and heat combined with rapid hardening and the ease of controlling grading variations.
  Calcium aluminate cements are also used in combination with other fine components. Hydraulic binders with new properties are then obtained. In this way, aluminates act as both a complex hydraulic binder and a mineral reagent interacting with the other components in the mix.
• As reagents, calcium aluminates are found in non-hydraulic systems. This is the case in metallurgical treatments (iron and steel industry, foundry) where specific grades of calcium aluminate are used for their low-temperature melting properties and for trapping molten metal impurities.