An experimental program was developed to investigate the time-dependent behavior of prestressed concrete beams constructed with high-strength self-consolidating concrete (SCC). The study involved eight concrete T-beams, each prestressed with a single deformed wire. Four of the beams were cast with high-strength self-consolidating concrete, while the other four were cast with conventional high-strength concrete. Half of the beams were loaded with a sustained load 29 days after release while the other half of the beams were kept unloaded. Testing consisted of monitoring concrete and reinforcement strains, prestress losses, and beam camber for a period of 300 days after release. Elastic modulus, creep, and shrinkage tests were simultaneously conducted on companion cylinder specimens to better define the material properties of the two mixes used in the study. Results showed that the time-dependent behavior of the high-strength SCC beams was inherently similar to that of the conventional high-strength concrete beams. However, the measured time-dependent prestress losses and camber were significantly greater for the self-consolidating high-strength concrete. Complex prediction methods that are flexible enough to consider the actual material properties of the SCC or HSC were found to do the best job of predicting results.

The precast industry has always been looking for ways to improve production. Be that ease of casting or finishing, faster turnaround or better economics due to less damage or reduced concrete costs. The advent of self consolidating concrete (SCC) has enabled some of these aspects to be realised. The development of SCC and new mixture design procedures has improved certain facets of the precast industry. However, the excessive use of fillers or very high cement contents has had equal drawbacks for the use of SCC in this environment. With the advances in software allowing very precise particle packing analyses to be made of the materials, new mix designs with lower total binder contents - and little or no fillers - are possible. Designs with supplementary cementitious materials (SCMs), including silica fume, can be very effective for SCC, not only giving excellent flow and non-segregation, but also enhancing the finished quality of the concrete. This paper reviews the use of silica fume in SCC, information from the Technically Optimised Piling Concrete (TOPIC) research in the UK, and gives examples of the use in some precast operations in Sweden.

SP-247CD This CD-ROM is a collection of papers prepared for a session held at the ACI 2007 Fall convention in Puerto Rico on the hardened properties and performance of SCC developed for use in precast prestressed applications. The papers relate to SCC in prestressed applications and are organized as follows: 1) mixture proportioning; 2) mechanical properties; 3) time-dependent deformations; 4) flexural and shear behavior; 5) bond behavior; 6) prestress losses; and 7) the structural behavior of full-scale precast prestressed elements made with SCC.

As a part of an ongoing study at the University of Minnesota, self-consolidating concrete (SCC) has been developed successfully with locally available materials from two precast concrete plants for use in precast prestressed bridge girders in the State of Minnesota. Four SCC mixes (i.e., two mixes per plant) were designed, evaluated, and used to cast four SCC precast prestressed bridge girders. Variations in the SCC mixes included cementitious materials (ASTM Type I and Type III cement, and Class C fly ash), natural gravel and crushed stone as coarse aggregate, and several admixtures. In addition to SCC girders, a conventional concrete girder was cast simultaneously on the same precasting bed for each plant. The girders were instrumented to monitor both short-term and long-term performance, which included transfer length, camber, and prestress losses. In addition, companion cylinders were cast to monitor compressive strength and modulus of elasticity over time. The test results indicate that the overall performance of the SCC girders was comparable to that of conventional concrete girders and could be predicted using existing design equations.

The use of Self-Consolidating Concrete (SCC) is becoming more prevalent in both building and bridge applications. Newcrete Products in Roaring Spring, Pennsylvania has experience with use of an SCC mix in parking structure members such as double-tee sections. While SCC is not yet widely used in bridge members in Pennsylvania, this application is also of interest. Newcrete in cooperation with Penn State University developed a program for bond evaluation of the Newcrete SCC mix. The objectives of the program are as follows: 1) to compare the Newcrete SCC mix with the current design code requirement for transfer length, 2) to determine the pull-out capacity of the strand in the SCC mix with the Moustafa test, 3) evaluate the failure mode at ultimate, and 4) compare the results of the SCC mix with a standard (non-SCC) Newcrete mix.