Ultra-High Performance Concrete
Ultra-High Performance Concrete or UHPC is a type of concrete that has steadily grown in popularity due to its increased durability and strength over traditional concrete. The US Army Corps of Engineers first used UHPC in the 1980’s, but it wasn’t until 2000 that it became commercially available in the US. Since then, more professionals, including PCI precast producers, have been using UHPC in projects ranging from bridges to buildings.
What is UHPC?
UHPC is characterized by several things including ultra-high compressive strength, high pre-cracking, and post-cracking tensile strength, and enhanced durability due to high density and discontinuous port structure. While there are numerous advantages that UHPC brings to projects that will be covered later in this article, the overall benefit of UHPC is the elimination of reinforcing steel and the material’s ability to self-compact.
UHPC is made by combining portland cement, supplementary cementitious materials, reactive powers, limestone/quartz, fine sand, water reducers, and water. Fibers are included in the mix to help provide the strength and durability that UHPC is known for. Fibers can range from brass-coated thin wire to glass fibers mainly used for architectural applications.
UHPC can come in a prepackaged mixture or as local material-based mixtures. Prepackaged UHPC mixtures have several benefits including more selective raw materials, assured batching consistency, and reduced batching times. UHPC made from local materials has slightly different benefits such as lower cost and the ability to be tailored to project needs, but it requires local expertise and verification testing.
PCI has a pre-recorded UHPC webinar free to view which gives a more in-depth description of UHPC at the link below.
What are the benefits?
UHPC’s durability has been extensively tested and it has been found to respond exceedingly well to extreme conditions that standard concrete struggles with. UHPC’s testing has been completed in three main areas and includes:
Freeze/thaw resistance: Testing has shown UHPC retained 100% of its material properties after 600 thaw/freeze cycles.
Chloride permeability: Testing has shown UHPC has extremely low chloride migration, less than 10% of normal concrete.
Abrasion resistance: Testing has shown UHPC has 2x the abrasion resistance of normal concrete.
Aside from its durability benefits, UHPC brings a host of other advantages to projects. UHPC can be produced using local materials which reduce its cost. Overall, UHPC is also a lighter material per foot which results in less expensive shipping and spans can be designed for longer lengths. UHPC isn’t restricted to structural precast components; it can be designed for architectural cladding as well. Best of all, because of UHPC’s durability, it has about double the lifespan of standard concrete which makes it a better choice for the environment in the long run.
Cor-Tuf, a PCI Associate member of FPCA, has created and tested their own UHPC mixture and provides precast components to the Florida region. Below is a video they created that shows multiple tests of their UHPC piling and demonstrates just how durable and strong UHPC components can be.