The infrastructure sector is under tremendous pressure to find reliable and durable solutions to tackle maintenance and upgrade existing structures to meet our ever changing needs. Owners and designers need to select repairs and retrofits solutions that are proven and which will perform as intended for the remaining life of the structure. Ultra-High Performance Concrete (UHPC) sold under the brand name Ductal ® by Lafarge North America Inc. (a member of LafargeHolcim) has been used throughout North America for over 15 years. The design community is increasingly familiar with the UHPC closure pour solutions for precast deck panels. This is now leading consultants to push the envelope and explore avenues where the durability of UHPC can be applied to other types of bridge repairs. This paper will provide a brief overview of four North American pier repair/retrofit projects. The CN Rail, Montreal, QC jacketing project; the Mission Bridge, Abbotsford, BC seismic pier retrofit; the Hooper Rd., Town of Union, NY connection of a new precast pier cap to existing columns; and the Hagwilget Bridge, New Hazelton, BC steel bent legs encasements will be reviewed. These "new" projects are now becoming references to guide owners and designers facing similar challenges where viable, durable and maintenance free solutions are required.

Deterioration of existing bridge decks, which usually originates with the deck cracking on the top surface, is a common problem in North America. It causes frequent repair of the decks to limit further damage resulting from water/chloride ingress. Superior engineering and durability properties facilitate the use of ultra-high performance concrete (UHPC) as an attractive alternative for a deck overlay, minimizing both deck deterioration and maintenance costs. Recently developed UHPC thixotropic mix designs, which are different from commonly used self-leveling UHPC, enable UHPC overlay to be used on decks with slopes and meet specific crowning requirements. The use of a UHPC thixotropic mix design with 3.25% of steel fibers was successfully evaluated under laboratory conditions by applying it on sloping deck surfaces with appropriate roughness between the normal concrete (NC) and UHPC. The feasibility of applying this technology in the field was then investigated on a small bridge for the first time in North America in May 2016. This paper presents the details about the laboratory evaluation, field implementation of UHPC overlay, and lessons learned from this first UHPC overlay project in North America.

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