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High Alumina Aggregate: Introduction

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Ishika cmi
High Alumina Aggregate: Introduction

High alumina aggregate is a type of ceramic aggregate material that has superior physical and chemical properties compared to conventional aggregates like gravel or sand. It is widely used in specialized construction applications where high strength, corrosion and heat resistance are required.


What is High Alumina Aggregate?

High alumina aggregate, as the name suggests, refers to an aggregate material that is primarily composed of alumina (aluminum oxide). It typically contains more than 70% alumina by weight. The alumina is formed into aggregate particles through sintering at very high temperatures ranging from 1700°C to 2000°C. This intense sintering process binds the alumina particles strongly and creates an extremely durable ceramic structure.

Apart from alumina, High Alumina Aggregate may also contain minor amounts of other oxides like silica, iron oxide, titanium oxide etc. depending on the raw material composition. The high alumina content and sintering process endows the aggregate with unique physical properties such as high strength, hardness, thermal shock resistance, corrosion resistance and chemical inertness.

Properties of High Alumina Aggregate

Physical Properties

- Compressive strength: High alumina aggregate has excellent compressive strength, typically over 300 MPa which is much higher than ordinary concrete aggregates. This allows it to withstand heavy loads.

- Hardness: On the Mohs hardness scale, high alumina aggregates range from 9 to 9.5. This makes it very resistant to abrasion and damage.

- Low water absorption: Due to its impermeable ceramic structure, high alumina aggregates absorb less than 1% water, much lower than normal aggregates.

Chemical Properties

- Acid and alkali resistance: It is highly resistant to attack by acids, alkalis and solvents commonly used in chemical plants and laboratories.

- Corrosion resistance: High alumina aggregates do not corrode or degrade when exposed to corrosive environments. This makes it suitable for applications involving corrosion.

- Inertness: The material is chemically inert and does not react with or leach harmful substances into surrounding materials like concrete.

Thermal Properties

- High temperature resistance: With a heat deflection point over 1500°C, it can withstand continuous operating temperatures up to 1000°C without deterioration.

- Thermal shock resistance: Rapid heating and cooling causes no damage due to its low coefficient of expansion, allowing use in applications involving thermal cycling and shocks.

Applications of High Alumina Aggregate

Due to the unique physical and chemical make-up, high alumina aggregate finds extensive usage in the following specialized fields:

Industrial Floors

- Chemical plants: Used in flooring, channels and trenches subjected to corrosive chemicals.

- Pharmaceutical facilities: Suitable for use in areas dealing with strong acids and solvents.

- Semiconductor industry: Used in cleanrooms for its non-contaminating properties.

Refractories

- Furnace linings: High temperature resistant aggregate for lining furnaces, kilns and incinerators.

- Crucible inserts: Used to line industrial crucibles for melting metals.

Waste Treatment

- Sewage treatment plants: Finds application in channels and drainage systems.

- Incinerator floors: Utilized in floors of industrial and medical waste incinerators.

Other Structures

- Airport runways: Used as an aggregate in runways and taxiways for aircraft.

- Marine structures: Suitable for use in piers and jetties requiring acid and corrosion resistance.

Advantages of Using High Alumina Aggregate

Some key advantages of using high alumina aggregate compared to ordinary aggregates include:

- Higher strength - Allows thinner sections and lighter structures to be built.

- Corrosion resistance - Eliminates need for protective coatings, saving maintenance costs.

- Heat resistance - Enables applications in high temperature processes up to 1000°C.

- Chemical inertness - Does not react with or contaminate surrounding materials.

- Lower permeability - Prevents infiltration of water and chemicals into structures.

- Long service life - Durable ceramic material retains properties with minimal deterioration.

- Thermal shock resistance - Withstands rapid heating/cooling cycles without damage.

- Non-contaminating - Hygienic for use in pharmaceutical and food processing plants.

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