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1. Understanding calcium aluminate cement

Calcium aluminate cement is a super refractory material. It is made by melting or sintering alumina and calcium oxide contributing minerals to produce monocalcium aluminate clinker, which is subsequently pulverized. The setting properties of calcium aluminate cement and its ability to withstand high temperature and chemical attack are far superior to those of Portland cement. The temperatures that calcium aluminate cement materials can withstand is staggering for those who would normally consider traditional refractory natural materials such as refractory clay.

The purest theoretical calcium aluminate would have a ratio (molar weight) CaO:Al2O3 of 35:65. The best real world materials contain about 30% CaO and 70% Al2O3 with very low impurities (eg iron, silica, sodium). These products have the best rheological properties. Higher percentages of alumina can increase service temperatures (up to a whopping 1900 degrees Celsius!) at the expense of strength and workability. A company produces products with an aluminium cement content of 40 to 80%. Advances in particle size distribution and installation technology have made it possible to exceed the capabilities of traditional refractory brick installation. The percentage of calcium aluminate cement in the mortar mix can also be reduced while improving the mechanical properties and increasing the service temperature.

2. Application of calcium aluminate cement

Due to its relatively high cost, calcium aluminate cement is used in many restricted applications where the properties achieved justify the cost: in architectural concrete where rapid strength development is required, even at low temperatures. As a protective liner against microbial corrosion, for example in sewer infrastructure. In refractory concrete, strength is required at high temperatures. As an ingredient in hybrid cement formulations, properties such as ultra-rapid strength development and controlled expansion are required. In sewer networks because of their high resistance to bio-sulfide corrosion.

Today, the biological corrosion resistance properties of calcium aluminate cement are mainly used in three application areas: ductile iron pipes for wastewater have an inner lining made of calcium aluminate cement mortar, and concrete pipes for sewers can be used in full mass made of calcium aluminate cement concrete or calcium aluminate cement mortar lining, repairing human-accessible sewer infrastructure with 100% calcium aluminate mortar using one of the following installation methods: low pressure wet blasting, rotating head wet blasting, or high pressure dry blasting (spray gun).

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