I first started working with Ultra High Performance Concrete in 2015 after being approached by some guys from a French Cement Company at the World of Concrete. They were looking for a portable Mixer that could easily be transported to and from bridge sights. With these mixers they wanted to make a new and unique type of concrete, exceptionally strong, for bonding joints and resurfacing the road. This material was UHPC or Ultra High Performance Concrete.
I had heard about UHPC a few times earlier in my career, and I had once, in Quebec been shown a test piece that was being considered for a culvert repair. The piece its self was small 30cm x 30cm and only 1cm thick, but so strong it could be dropped on a concrete shop floor without taking damage. It was impressive, but I didn't hear much about it for several years
We did a lot of testing at Mixer Systems to determine the correct type of mixer for the job and how it should be configured for safe and easy use and transport. Since those days we've done a lot of variations on those early portable mixers and plants.
I also have a very good friend, Craig Heaney of Envel Facade, whose company builds wall claddings with UHPC and they are truly works of art. Envel is currently finishing up a special cladding project in Chicago, creating giant concrete excerpts from the speeches of former U.S. President Barack Obama for the exterior of the new Obama Presidential Library.
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| A recent image posted by Envel |
Below is a quick article I created for The Illinois Precast Association Newsletter: Written for you by ChatGPT answering: Tell me about Ultra High Performance Concrete
UHPC
By: ChatGPT
Ultra High Performance Concrete (UHPC) is a class of advanced concrete that is distinguished by its exceptional strength, durability, and durability compared to conventional concrete. It is often used in applications where superior performance is required, such as in the construction of bridges, high-rise buildings, and other infrastructure projects.
Here are some key characteristics and benefits of UHPC:
1. Composition:
UHPC is made from a mixture of:
· Cement: Often uses a special type of cement such as Portland cement or blends with pozzolanic materials.
· Silica fume: Used as a supplementary cementitious material to improve strength and durability.
· Fine aggregates: Such as silica sand or other fine-grained materials.
· Superplasticizers: These help achieve a highly workable mix without increasing the water content.
· Steel or synthetic fibers: These are commonly incorporated to enhance the mechanical properties of the concrete, improve crack resistance, and reduce brittleness.
2. Strength:
UHPC can achieve compressive strengths in the range of 150 MPa (megapascals) to over 200 MPa, significantly higher than conventional concrete, which typically has strengths around 25-40 MPa. This makes UHPC suitable for structural applications where high load-bearing capacity is needed.
3. Durability:
UHPC exhibits excellent resistance to environmental factors such as freeze-thaw cycles, chemical attacks (from chlorides or sulfates), abrasion, and corrosion. This is particularly beneficial in harsh environments like coastal areas or regions exposed to deicing salts.
4. Workability:
Despite its high strength, UHPC has excellent workability due to the use of superplasticizers, which enable the concrete to flow and be molded into complex shapes without sacrificing its integrity.
5. Longevity:
Due to its superior resistance to cracks and environmental deterioration, UHPC can extend the lifespan of infrastructure significantly. It is often used in applications where long-term durability is essential, such as bridges and offshore structures.
6. Applications:
· Bridges: UHPC is ideal for bridge decks, bridge components, and other structural parts due to its high strength and durability.
· Architectural Features: Its ability to be molded into thin, complex shapes makes it popular in architectural designs.
· High-rise Buildings: UHPC is used in the construction of high-rise buildings, where the high compressive strength is advantageous.
· Infrastructure: It’s used in infrastructure projects like tunnels, pavements, and barriers, particularly where enhanced durability is needed.
7. Cost:
While UHPC is more expensive than regular concrete due to the special materials and processes involved, its long-term durability and lower maintenance costs can make it more cost-effective in the long run for certain high-performance applications.
8. Sustainability:
UHPC can contribute to sustainability goals due to its longevity and resistance to degradation, which can reduce the need for repairs and replacements. Additionally, some mixes of UHPC incorporate recycled materials or industrial byproducts, enhancing its environmental credentials.
9. Challenges:
· Mixing and Handling: The process for mixing UHPC is more demanding than for regular concrete, requiring precision in terms of ingredients and mixing procedures.
· Curing: Proper curing is essential to achieve its full strength, often requiring heat treatment or extended curing times.
· Specialized Equipment: Construction using UHPC might require specialized molds, mixing equipment, and placement techniques, which can make it less accessible for small-scale or less-experienced contractors.
In conclusion, Ultra High Performance Concrete represents a significant advancement in concrete technology, offering unmatched strength, durability, and versatility, especially in challenging environments. However, the complexity and cost of producing and working with UHPC should be carefully considered when planning its use.