Date of this Version
Report SPR-P1(08)P310 Final Report 26-1120-0037-001
Ultra-High Performance Concrete (UHPC) is a new class of concrete that has superior performance characteristics compared to conventional concrete. The enhanced strength and durability properties of UHPC are mainly due to optimized particle gradation that produces a very tightly packed mix, extremely low water to powder ratio, and use of steel fibers. The unique strength and durability properties of UHPC make it an attractive material for precast prestressed bridge girder construction. However, commercial UHPC mixes currently available in the US market cost about 10 times the cost of conventional concrete mixes, in addition to the need for special mixing and curing procedures that are not convenient to most precasters. The general objective of this project was to promote the use of UHPC in bridge construction. The specific objectives included: 1) a review of the various UHPC mixes developed in North America, Europe, and Japan and a comparison of them in terms of economics and performance characteristics; 2) development of non-proprietary UHPC mix that was optimized in terms of the total cost of production while providing a final compressive strength of at least 18 ksi; 3) evaluation the mechanical properties of the developed mixes; and 4) investigate the application of the developed mixes to standard precast prestressed concrete bridge I-girders. The developed mixes consist of type III cement, fine sand, class C fly ash, silica fume, high range water reducer, and water. Steel fibers are eliminated due to their high cost and Grade 80 ksi welded wire reinforcement (WWR) was used instead to substitute for the loss in the tensile/shear capacity. The results of the laboratory tests and the full-scale girder tests indicated that the developed mixes are attainable using practical and affordable mixing and curing procedures and their mechanical properties are superior to those of the mixes currently used in Nebraska.