As its name denotes, heat-resistant concrete is the concrete which can resist high temperatures. The main ingredient used for making refractory concrete is high alumina cement or calcium aluminate cement.
When high alumina cement undergoes high temperature, they will experience a little amount of expansion but it would have the considerable strength to take the usual load.
The most used aggregate for heat-resistant concrete is crushed aggregate with alumina cement. Sometimes these aggregates can be called as a refractory aggregate. This concrete has the capability to resist temperature up to 1400 degree Celcius.
What are the types of refractory concrete?
There are two types of refractory concrete, the first one is high-grade heat-resistant concrete and the second one is low-grade heat-resistant concrete.
The first high-grade refractory concrete can resist high temperature or it can resist high heat against the hot faces.This type of refractory concrete can be used for hot faces instrucments. Hot face instruments are any material which is under the direct attack of heat orgin.
Examples of hot face instruments are gas burner, wood fire etc…
The second type of heat resisting concrete is low grade heat resistant concrete.It can be used for the attack against low heat conditions.
What are the advantages of heat resistant or refractory concrete?
The advantages of refractory concrete are
- They have high resistance towards thermal expansion and shrinkage
- No strength loss after firing.
What are ingredients used for making of refractory cement?
- Refractory aggregate (Crush sand from the river)
- Refractory cement ( Calcium aluminate cement)
- Lime (CaO)
In the below section I am going to answer some of your questions regarding this temperature resist concrete?
What about the strength of heat-resistant concrete after the fire?
When concrete is fired almost 600-degree Celcius, the hydraulic bond begins to decrease. This makes a reduction in concrete compressivev strength.
When heats exceeds 600 drgree celcius, the ceramic bond starts to form.The formation of ceramic bond happends between the cemenet and aggregate.At this stage, concrete shows higher strength but after cooling its strength starts to decreasing.
Shrinkage and Thermal expansion
You know that at higher temeprature any material starts to expand, similar phenomenon begins here also. While heating, the water molecules from the pores will escape. This leads to shrinkage of concrete.
During this shrinkage, crakcs starts to forming. If the crakcks are very high, the exterior waster materials starts to entering inside the concrete, this creates more problem.
Reinforcement of steel
The high heat directly causes a decrease in steel-concrete bond and likely melting at critical heat, but it can also create concrete spalling and changing steel properties.
The bond between concrete and steel drop at 300 degree Celcius and if it is raised, the concrete begins to spall and produce a crack. At greater heat, steel reinforcement can fail its purpose and the behavior of steel in concrete will no longer be useful.
What are the applications of refractory concrete?
Used for chmneys
They can be used for making station for the launching of rockets.