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.

To achieve adequate flow and stability characteristics, self-consolidating concrete (SCC) typically has higher paste and lower coarse aggregate volumes than conventional concrete (CC). Because the coarse aggregate content directly affects aggregate interlock, SCC may not provide the same shear capacity as CC. This research investigated the influence of SCC aggregate and paste volumes on shear capacity and compared these results with those obtained from similar CC samples. Twelve SCC mixture proportions were evaluated with three main variables: two 16-hour release strengths (5 and 7 ksi), two aggregate types (river gravel and limestone), and three different volumes of coarse aggregate. Four CC mixture proportions were used as control mixtures and consisted of two release strengths (5 and 7 ksi) and two coarse aggregate types (river gravel and limestone). A total of 48 push-off samples (36 SCC and 12 CC samples) were fabricated and assessed for shear characteristics. The crack slip, crack width, normal stress, and shear stress were measured to evaluate the aggregate interlock of the SCC and CC. The relationships between these parameters are presented to illustrate the aggregate interlock behavior for samples containing SCC and CC. Energy absorption methods were used to quantitatively assess the aggregate interlock. These results indicate that the SCC samples tested in this research program exhibit less aggregate interlock than the CC samples.

The mix design deviations required to achieve self-consolidating concrete (SCC) have raised concerns on the effect that this may have on the bond performance of reinforcement. The paper summarizes an investigation on the effect of SCC mix proportioning on the bond behavior and bond-related parameters of transfer and development length of 13mm (0.5 in.) diameter prestressing strands. Three SCC mix designs that bound the common approaches to achieve SCC and a reference normally consolidated concrete (NCC) mix were used. Direct bond strength was assessed by simple strand pull-out tests. Using laboratory-scale T-beams, transfer length was evaluated by concrete surface strains and draw-in measurements, while development lengths were estimated through flexural tests. Results indicated the bond performance of strand in SCC to be lower than for NCC. Transfer and development lengths for SCC were longer than for NCC; yet, on average, these lengths still met the ACI code recommendations. Bond performance for the different SCC mixes was distinct, consistent and bounded by the extreme cases considered. Given the variability and uncertainties in the experimental methods and code equations, results from this study indicate that bond performance on SCC, as it pertains to anchorage lengths, is adequate.

Self Consolidating Concrete (SCC) is a recent advancement in the concrete industry. SCC is a type of concrete that can be placed without consolidation and has become widely accepted in the precast industry in the United States. The interest of SCC in bridge girders is also growing. This research program compares the prestress losses of SCC beams to those of conventional concrete with similar compressive strengths. The research program also compares the predicted losses to measured losses. A total of 20 prestressed beams were cast, and of those 20 beams, prestress losses were measured on 10 beams. Each beam was 6.5 inches (165 mm.) wide and contained two 0.60 inch (15.2 mm.) diameter prestressing strands. The beams measured 18 feet (5.5 m.) in length with a height of 12 inches (254 mm.). Two SCC mixtures were used to cast 7 beams and a conventional concrete mixture was used in the remaining 3 beams. The SCC and conventional beams had concrete compressive strengths that ranged from approximately 7 to 10 ksi (48 to 69 MPa) at release and 10 to 13 ksi (69 to 90 MPa) at 28 days. Prestress losses were measured through the use of vibrating wire strain gages. Early test results indicate that at similar compressive strengths, there was little difference between the losses of the SCC beams versus those of the conventional concrete beams. For all beams, the measured losses (excluding relaxation) ranged from 19.2 ksi to 25.6 ksi (132 to 177 MPa) at an average age of 124 days.

While the characteristics of self-consolidating concrete (SCC) do not affect the bending capacity, there is an influence on the bond strength and shear capacity. The effect on the bond behavior of strands in SCC is a subject of some controversy in current literature. Therefore, pull-out tests and full-scale tests on the transfer length have been performed to describe the bond capacity of SCC with gradual release of prestress. It is shown that the bond behavior depends on the concrete mixture. The bond capacity of SCC containing limestone powder is comparable to conventional vibrated concrete while the bond capacity of SCC with fly ash is reduced by approximately 20%. The shear capacity of prestressed beams has been determined by tests with different shear reinforcement ratios. The tests revealed that SCC does not significantly influence the shear capacity although the smaller aggregates and the higher content of cement paste reduce the crack-friction capacity.