Ultra-High Performance Concrete (UHPC) is a new class of concrete that is exceptionally strong and durable. It is not only ideal for traditional applications of regular concrete, but it also allows for new applications of concrete in areas such as contemporary design that involve thinner components or complex shapes.
The Ultra-High Performance Concrete market size is expected to grow at a compound annual growth rate (CAGR) of 7% between 2017 and 2023, according to a report published by Market Research Future. This is not surprising given the many uses and benefits of UHPC and the encouragement of its use by the Federal and state governments for many infrastructure projects.
We take a closer look at UHPC, including how it is made, its benefits, how it is being used, and the support it is receiving from the U.S. government as an innovative building material.
What makes Ultra-High Performance Concrete different?
According to the Federal Highway Administration (FHWA), UHPC is defined as a cementitious composite material of an optimized gradation of granular constituents, a water-to-cementitious materials ratio less than 0.25, and a high percentage of discontinuous internal fiber reinforcement.
Roughly 75-80% of the ingredients of UHPC are the same as compared to regular concrete – cement, gravel, sand, and water. It is the remaining 20-25% of ingredients that make UHPC unique.
In UHPC, integrated fibers are added to the concrete mix. The fibers vary from polyester to fiberglass bars, basalt, steel, and stainless steel. Each of these integrated fibers create a progressively stronger end product, with steel and stainless steel delivering the greatest gains in strength.
UHPC became commercially available in the United States in 2000. It has already been used in many state infrastructure projects, and it is being considered for use in many future projects given its longevity and lower lifecycle cost. For a full list of UHPC bridges in the United States, consult this resource from FHWA.
The benefits of UHPC
- Longer useful life – UHPC has an estimated longevity of more than 75 years. Regular concrete typically lasts only 15-25 years before needing to be replaced.
- Lighter weight – Concrete wall panels designed with UHPC are 25-33% thinner. This means less material is required to build the panels, and footing requirements to support structures are reduced.
- Strength – Regular concrete has a compressive strength of 4,000 pounds per square inch (psi). UHPC has a compressive strength of 30,000 psi once fully cured. Some mix techniques can even achieve 50,000 psi. It also has a tensile strength of 1,700 psi.
- Extremely resistant to environmental degradation – Traditional concrete starts to deteriorate in as little as 28 freeze/thaw cycles. A study of untreated UHPC was conducted by the University of New Brunswick, Canada. The samples were placed at the mid-tide level of a marine exposure site in 1995. The results showed the samples were impervious to water, had negligible surface damage, and had resisted 12 (now more than 20) years of more than 1,000 freeze/thaw cycles and storms.
- Lower carbon footprint – Structures built with UHPC require less material given its lighter weight and reduced foot requirements. Projects using UHPC are often more environmentally friendly, reducing traffic congestion and on-site construction time as in the case of Accelerated Bridge Construction (ABC). Additional information on this method and other UHPC applications is provided further down in this post.
- Flexibility – UHPC is more flexible than regular concrete. This makes it ideal for making structures that involve more complex, architectural design, while still delivering on strength and durability.
- Ductility – UHPC can be stretched out into thinner sections under tensile stress, unlike regular concrete.
- Moisture resistant – UHPC has a higher density than regular concrete. This makes it virtually impossible for ordinary water to penetrate the surface of UHPC.
- Fireproof – Some mixtures of UHPC have been shown to be fire resistant. The mixtures demonstrating this property had slightly more than 3% steel fibers and 0.60% polypropylene by volume.
- Impact resistance – UHPC can absorb three times greater energy than regular concrete. Under impact loading, UHPC was twice as strong as regular concrete and dispersed up to four times as much energy.
- Chemical resistance – UHPC does not deteriorate when exposed to such chemicals as de-icing solutions and sulfates.
- Adhesiveness – UHPC – unlike regular concrete – is ideal for the application of adhesive bonding. It can be used for adhesive connections with other materials, such as rigid board insulation, siding, cured ordinary concrete, and many other building materials.
- Reduced maintenance – The many benefits of UHPC directly translate to less maintenance requirements. Structures last longer and require less upkeep.
- Cost savings – While UHPC may require a larger upfront cost when compared to traditional concrete, this new concrete technology delivers a much lower lifecycle cost. Less material is required for construction projects, and footing and support requirements are reduced. Construction can be completed more quickly with prefabricated UHPC elements, delivering cost savings in several areas of construction. The extended longevity of UHPC virtually eliminates maintenance costs and drastically extends the life of the product. When the cost of UHPC is spread out across the life of the product, it has extensive cost benefits over standard concrete.
- Accelerated Bridge Construction (ABC) – Accelerated Bridge Construction uses prefabricated bridge components to replace and repair existing bridges in a more cost-effective and safer manner. UHPC is ideal for the field-cast connections used in the ABC method. For a deeper dive on ABC bridge construction, check out our recent blog. (Link to CT010618 when ready)
- Bridge girders – Bridge girders are a main structural component used to support bridge decks and traffic loads for short and medium-span bridges. UHPC is ideal here given its strength and durability.
- Bridge decks – The use of precast bridge decks made from UHPC allow for critical bridge components to be replaced quickly. This reduces the disruption to traffic and keeps on-site construction to a minimum.
- Seismic columns – The strength and durability of UHPC make it ideal for use in seismic columns for bridges. This is an innovative way to design earthquake-resistant bridge columns.
- Tunnels – UHPC has been recommended for use in tunnels due to its fire resistance and strength, qualities that are extremely important for this type of structure.
- Wind turbine towers – Wind power is a growing energy source. UHPC components allow for the creation of taller wind turbine towers. This increases the output of towers, generating more renewable energy.
- Highway infrastructure – UHPC is the answer to concerns about highway infrastructure deterioration, repair, and replacement. It’s longer life and lower lifetime cost makes it the ideal way to repair and replace existing roads and bridges so they will last longer.
- Security and blast mitigation – The compressive strength and tensile resistance of UHPC have led to its use for security and blast mitigation for critical infrastructure. Studies have shown that UHPC concrete slabs demonstrate improved damage tolerance.
Every Day Counts
The U.S. Federal and many state governments are strongly recommending that UHPC be used in all future bridge construction projects, including the repair of existing bridges.
The FHWA also advocates the use of UHPC through its Every Day Counts (EDC) program. EDC identifies and utilizes innovative technologies to reduce project timelines, increase safety, reduce traffic delays, and lessen the environmental impact of construction at the state and local levels.
Every two years, the FHWA works with state and local transportation departments, governments, and other vested parties to identify the latest innovations to support. The EDC-3 Innovations for 2015-2016 and the EDC-4 Innovations for 2017-2018 include the use of UHPC connections for prefabricated bridge elements and systems (PBES), making it a favored concrete technology for these applications.
Contractors and builders who want to increase their chances of winning bids on future infrastructure projects should consider the government’s preference for this new concrete technology.
Ultra-High Performance Concrete vastly widens the possibilities for applications of concrete. The combination of its strength, durability, flexibility, and resistance to damage from the elements makes UHPC clearly favorable to regular concrete. Projects last longer and require less upkeep and maintenance. Projects can also be completed faster with less interruption to local traffic patterns and environmental damage. The U.S. government clearly values UHPC and the many benefits it brings to infrastructure projects, making it an important concrete technology for builders and contractors to learn about and use.
Photo Source: Peter Buitelaar Consultancy and design by FDN in Eindhoven the Netherlands