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.
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info@hhbc-consulting.de
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