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26 volume. More detailed information on drying shrinkage Highly flowable SCC can develop at least 90% in-situ rela- can be found in Attachment D. tive compressive strength (core results) and modification Increase in S/A can lead to higher long-term drying factor of 1.4 for bond to horizontally embedded prestress- shrinkage. ing strands. More detailed information on bond to pre- The binder type does not have significant effect on drying stressing strands is presented in Attachment D. shrinkage but can significantly affect creep (e.g., SCC made Use of highly viscous SCC [plastic viscosity greater than with Type III cement and 20% fly ash exhibited higher creep 0.073 psis (500 Pas) or T-50 nearing 6 seconds (obtained than similar SCC proportioned with Type I/II cement from upright cone position)] should be avoided to ensure regardless of the binder content, w/cm, S/A, and use of thick- adequate self-consolidation. ening-type VMA). The w/cm does not have considerable effect on creep because 4.5 Structural Performance of the more predominant influence of other parameters such of AASHTO-Type II Girders as binder content, binder type, and S/A. SCC exhibits up to 20% higher creep after 300 days than The following conclusions and observations are based on the HPC made with similar w/cm but different paste vol- construction and testing of the full-scale precast, pretensioned ume. More detailed information on creep can be found girders: in Attachment D. With the casting from only a single location at midspan of 4.3 Code Provisions for the 31 ft (9.44 m) long girders, no visible segregation was Estimating Mechanical and observed and fewer "bug holes" were observed in the SCC Visco-Elastic Properties concrete than in the HPC. The transfer lengths were similar for the four concrete mix- Mechanical Properties tures and were considerably shorter than the values given Material coefficients of existing prediction models were in the 2007 AASHTO LRFD Specifications and the ACI modified to provide better prediction of mechanical proper- 318-05 code. ties of SCC for precast, prestressed concrete bridge elements. At time of prestress release at 18 hours, the coefficients on the The following codes are recommended: square root of the compressive strength used to determine the modulus of elasticity for the SCC mixtures were about ACI 209 and CEB-FIP codes with modified coefficients for 4% and 11% lower than those for the HPC mixtures. predicting compressive strength Due to the low elastic modulus and greater drying shrink- Current AASHTO 2007 model for predicting elastic age, greater elastic shortening losses and greater long-term modulus losses of prestress occurred, resulting in smaller cambers Current AASHTO 2007 model for estimating flexural for the SCC girders. strength The cracking moments for the SCC girders and the com- panion HPC girders were similar, and the uncracked and Visco-Elastic Properties cracked stiffnesses for all four girders were very similar. The cracking shears for all four girders were similar. Creep and shrinkage strains measured in experimental The four girders failed in shear after developing a significant factorial design were compared with values predicted by the number of wide shear cracks; shear crack widths just before AASHTO 2007, AASHTO 2004, ACI 209, CEB-FIP MC90, failure were greater than 0.24 in. (6 mm). The failure shears and GL 2000 (Gardner and Lockman, 2001) models. Coeffi- exceeded the nominal shear resistances predicted using the cients of the following models were modified to provide better approach given in 2007 AASHTO LRFD Specifications, prediction of visco-elastic properties for SCC: probably because of the strength and stiffness of the top and AASHTO 2004 model for estimating drying shrinkage bottom flanges of the girders. The flexural resistances of the HPC girders exceeded that AASHTO 2007 model for estimating creep predicted using the 2007 AASHTO LRFD Specifications. The flexural resistances of the SCC girders were within 1.5% 4.4 Homogeneity of In-Situ Strength and Bond to Reinforcement of the flexural resistance calculated using the approach pro- vided in the 2007 AASHTO LRFD Specifications. Highly flowable SCC should have adequate static stabil- The HPC girders exhibited higher ductilities than the cor- ity with maximum surface settlement, column segregation responding SCC girders. index, and percent static segregation of 0.5%, 5%, and 15%, The lower shear resistance and lower ductility experienced respectively, particularity for deep elements. by the SCC girders are probably due to the lower volume