Self consolidating concrete for precast prestressed concrete bridge elements
With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for CC and SCC girders with a compressive strength greater than 10 ksi (70 MPa).The author found that girder-deck systems with Type A SCC girders exhibit similar flexural performance as deck-systems with CC girders.The AASHTO LRFD (2006) equations for computing the cracking moment, nominal moment, transfer length, development length, and prestress losses may be used for SCC girder-deck systems similar to those tested in this study.For environments exhibiting freeze-thaw cycles, a minimum 16-hour release strength of 7 ksi (48 MPa) is recommended for SCC mixtures.
To correlate these results with full-scale samples and investigate structural behavior related to strand bond properties, four girder-deck systems, 40 ft (12 m) long, with CC and SCC pretensioned girders were fabricated and tested.Thereby minimized also are noise levels in concrete plants and at construction sites, plus aggregate segregation, honeycombing, and voids in the mix.Overall concrete quality is improved with the eradication of such vibration-related problems as under vibration, over vibration, and damage to the air void structure.18-12) is underway to develop SCC mixes, structural design parameters, and construction specifications for precast/prestressed concrete elements.
Whatever conventional concrete can do, SCC can do better, faster, and cheaper, especially for concrete elements with special textures, complex shapes, and congested reinforcements, contends Myint Lwin, Director of the Federal Highway Administration's (FHWA) Office of Bridge Technology.
We are using it now on all products on every project for Nebraska, says Concrete Industries' Mark Lafferty.