UHPC HT and Refractory - The difference

UHPC HT Products

UHPC, Ultra High Performance Concrete, is a combination of a cement, micro particles and wear resistant (very hard) particles. Due to the 

micro particles it is possible to create a perfect physical packing ensuring improved chemical reactions. These chemical reactions secures the formation of minerals with superior properties at room temperature. Hence around 60% of the full strength will be obtained after 48 hours. Final strength of a UHPC is 100-250 MPa / 14500-36250 psi.

Water added to UHPC to secure a proper 

rheology is limited, and shortly after setting there will be no more free water in the system, as all water will be bond in the structure of the chemical reactions.

When heating UHPC HT the risk of cracking due to evaporation of water is limited. However too fast heating of a virgin installation could lead to this. Hence it is recommended to firstly heat up the installation at a rate of 50°C/hr. The heating does not contribute to the strength of the system however it will increase the rate of strength building.

Refractories

Unshaped refractories typically contains an alumina cement as the bonding material and other metallic minerals depending on the 

temperature and environment it is installed. Water is mixed in to create the right rheology for installation. As such this product at ambient 

temperature can be viewed as an ordinary mortar. As such the product is relative porous and strength at ambient temperature is not likely 

to exceed 45 MPa. This system will also reach around 60% of final strength after 48 hours of hydration.

This system will contain free water after installation, hence there is a risk of cracking when heated. Hence it is necessary to heat it at specific heating rate in order to avoid such cracks. In order for refractories to work they need to be heated so that the metallic minerals is calcinated 

and sintered into the wanted minerals with the needed properties.

Comparison

The strength and density of UHPC HT is a lot higher than that of refractories. Hence these products will be better at withstanding inner pressure from internal water evaporation, reducing the risk of cracks and ultimate process destruction of the product.

UHPC HT does not need heat to form the minerals needed in the mix in order to obtain the properties. 

Heat will however increase the rate of property formation.