Recent advances in research on cementitious materials have led to development of a new class of market-ready materials with many times the strength and durability of conventional concretes. This emerging technology, known as ultra-high performance concrete (UHPC), could have a significant effect on the U.S. highway system. This article discusses the challenges that are limiting widespread implementation of projects using UHPC as well as the steps the Federal Highway Administration (FHWA) is taking to overcome these issues. The article also highlights the first three deployments of UHPC in U.S. highway bridge projects. FHWA has identified five reasons for the slow pace of UHPC deployment thus far: (1) manufacturers are unlikely to invest in innovative technologies unless they see a clear financial benefit; (2) owners (in this case government agencies) traditionally are risk-averse and tend to take measured responses when presented with innovative solutions to existing problems; (3) a lack of design code provisions relevant to the advanced properties of UHPC; (4) the limited number of applications of UHPC to date means that limited experience is available with regard to inspection, maintenance, and repair of UHPC structures; and (5) the higher cost of the constituent materials in UHPC results in a higher per-unit volume cost than conventional concretes. Research related to the development, properties, and application of UHPC is progressing despite these hurdles. Four FHWA research studies on UHPC are underway: a project to develop a modular precast, prestressed concrete decked girder system applicable to typical highway bridges; a project focused on developing an alternative to replacing deteriorated bridge decks when their superstructures remain viable; a project focused on quantifying the advanced structural and durability properties of UHPC; and a project to address issues of immediate importance to the industry tasked with fabricating UHPC components.
Samenvatting