High alumina cement is also called calcium aluminate cement and differs substantially from ordinary Portland cement (OPC). It has unique properties like chemical attack resistance, high-temperature resistance, and rapid strength development. This makes it an important component in a large range of applications.
The details about uses, advantages, and applications of high alumina cement are given in this blog.
Composition and Properties of High Alumina Cement
Chemical Composition
The composition of high alumina cement is given as follows:
- Silica – 3% to 8%
- Alumina – 37% to 41%
- Lime – 36% to 40%
- Iron Oxide – 9 to 10%
- Titanium – 1.5 to 2%
- Magnesium – 1%
- Insoluble Resides – 1%
The high content of alumina provides unique properties that distinguish it from normal cement.
Mechanical and Physical Properties of High Alumina Cement
Compressive Strength
The compressive strength of high alumina cement is between 40MPa to 80MPa for high alumina cement. While the compressive strength of ordinary cement is between 20 MPa to 40 MPa.
Flexural Strength
Generally, flexural strength is between 5MPa to 10MPa for high alumina cement. While the flexural strength of normal cement is 3 MPa to 5 MPa. This helps to withstand higher stress and thermal shocks.
Rapid Strength Development
The setting and hardening are rapid in high alumina cement compared to OPC. The initial setting time for high alumina cement can be less than 3.5 hours but for normal cement, the initial setting time is around 2 to 4 hours.
High Early Strength
The initial compressive strength can rise to 40 MPa within 24 hours. This is normally higher than OPC, as the initial compressive strength of OPC can be around 20 MPa within 24 hours.
High Temperature Resistance
High alumina cement can remain unaffected up to 1000 degrees Celsius. This makes them suitable for refractory applications.
Chemical attack resistance
High alumina cement has high resistance to sulfate, weak acids, and seawater. This makes it suitable for environments that are exposed to aggressive chemicals.
Low Heat of Hydration
During hydration, high alumina cement shows an exothermic reaction. This decreases the risk of thermal cracking in large pours. Also, high alumina cement forms aluminate hydrates like CAH10, C2AH8, and C3AH6. These materials can produce a dense matrix and help in the gain of high early strength.
Durability
High alumina cement has shown increased durability in aggressive environments. The main working principle is that high alumina cement based concrete has lower permeability. This helps decrease the absorption of harmful chemicals and improve longevity.
Uses of High Alumina Cement
High alumina cement can be used in various applications, mostly construction related. Due to its high temperature resistance it is used in refractory linings. It is also used in marine structures, precast compounds and any special civil engineering projects that require fast development of strength and aggressive chemical resistance.
Refractory Applications
High alumina cement is used in refractory applications like furnaces, boilers, kilns, and chimneys as it has the capability to endure extreme temperatures of up to 1000 degrees Celsius, in which it does not have any loss of strength. This capacity makes them suitable for environments where there is intense heat. Some of the environments are kilns, reactors, and furnaces. Their property to quickly obtain strength further improves their application in high temperature applications.
Chemical Resistant Concrete
Environments like wastewater treatment plants, chemical plants, and marine structures are exposed to aggressive chemicals. So, high alumina cement is used for its high durability. High alumina cement also offers resistance to sulfate attack or acid corrosion, thus, helping to increase the lifespan of the structures.
Rapid Repair Works
Properties like rapid setting and high early strength make high alumina cement suitable for emergency repair works. Some of them are road repairs, airport runways, and structural repairs in critical infrastructures. The repair based on high alumina cement in concrete can help in the quick restoration of functionality and reduce downtime.
High Temperature Construction
High alumina cement can be used in construction facilities that need high resistance to temperature. Some of them are incinerators, in which the wastes are burned at high temperatures, chimneys that must hold the heat gases and corrosive gases from industries and other high temperature industrial facilities. This type of cement has the capacity to maintain structural integrity in extreme heat conditions.
Underwater Constructions
The chemical resistance and ability to set underwater have made high alumina cement suitable to be used in underwater constructions. These constructions include piers, marine piles, and harbor installations. The rapid setting properties help in reducing time for potential washout, which helps in ensuring robust structures.
Sewer Infrastructure
High alumina cement has biogenic sulfide corrosion resistant properties. This makes it suitable for the construction of sewage infrastructure by reducing the corrosive effect of hydrogen sulfide gas. Thus, it helps increase the lifespan of manholes and sewage pipes.
Flooring and Tiling
High alumina cement is used in flooring and tiling applications where rapid installation and high early strength are needed. The use of high alumina cement ensures that the tiles and floors are installed quickly.
Case Study: HAC in Wastewater Treatment Plant
A wastewater treatment plant in Europe has used high alumina cement-based concrete for its primary containment structures. It has been observed that for over 10 years, the structures have shown only minimum degradation, even though they have been in constant contact with aggressive chemicals and biogenic sulfide. Hence, using high alumina cement has resulted in reduced maintenance costs and a longer life.
Conclusion
High alumina cement is an indispensable material because of its exceptional properties. They gain rapid strength, resistance to high temperatures, chemical resistance, and durability, making it a preferred choice for various applications. Their applications differ from critical infrastructure repairs to extreme industrial settings. This cement provides reliability and efficient solutions for various applications.
FAQs
The heat of hydration of high alumina cement is lower compared to normal cement. This helps in reducing risks of thermal cracking.
The amount of alumina content used in high alumina cement is between 37% – 41%.
The chemical resistance and ability to set underwater allows it to be used in marine constructions.
The structural integrity is maintained by its high strength.
The fast setting and early strength are the advantages of high alumina cement.