ACI PRC-239.1 : 2024

Description: Ultra-high-performance concrete (UHPC) has emerged as a basis for compelling applications in the infrastructure, architecture, security, and even the consumer goods markets. UHPC enables the design, fabrication, construction, and delivery of structural and architectural elements that are distinct from those made of conventional concrete and steel in terms of their structural form, resilience, constructability, and aesthetics. These qualities have led to an increase of its use around the world. There have been major advancements since the American Concrete Institute formed a technical committee focused on UHPC in 2011, leading to the publication of an Emerging Technology Report (ACI PRC-239). However, as interest and demand continue to increase, a fundamental question has arisen: What is UHPC?

In a broad sense, UHPC is a material with mechanical and durability properties that exceed those attainable with conventional or high-performance concretes, including low permeability, high compressive strength, and sustained post-cracking tensile resistance. UHPC’s durability properties are largely attributable to a dense cementitious matrix that has a discontinuous pore structure that inhibits the ingress of deleterious substances, such as chlorides. UHPC typically exhibits tensile ductility and toughness, attributable to the inclusion of an ample volume of fiber reinforcement. Refer to Fig. 1 for a pretensioned beam undergoing flexural testing.

This class of concrete may be referred to by various names in different parts of the world. Ultra-high-performance fiber-reinforced concrete (UHPFRC) and ultra-high-performance fiber-reinforced cementitious composite (UHPFRCC) may each be encountered. In North America, the “fiber-reinforced” and “cementitious composite” portions of those alternate names have generally been dropped in favor the more succinct term, UHPC.