Effect of scc mixture proportioning on transfer and development length of prestressing strand

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.