Bond Behavior of 0.6 in. (15.2 mm) Prestressing Strand in Belitic Calcium Sulfoaluminate (BCSA) Cement Concrete

An investigation into the bonding capabilities of 0.6 in. (15.2 mm) prestressing strands cast in belitic calcium sulfoaluminate (BCSA) cement concrete beams was performed to determine if the current ACI development length requirements for prestressing strands are applicable to BCSA cement. Portland cement and BCSA cement concrete beam specimens of one mixture design were cast, with varying concrete ages at prestress release. Transfer lengths were determined for 28 days after casting using surface strain measurements and strand end slip. Prestress losses were measured using vibrating wire strain gauges and were compared to the AASHTO and PCI/Zia et al. methods. Flexural tests were performed to determine if adequate flexural bond performance was achieved with the specified development length. The BCSA prestressed concrete beams performed at least as well as the portland cement control specimens with regards to transfer length, development length, and flexural performance even when prestress release was performed at 2 hours after casting. Measured prestress losses for BCSA cement concrete beams were significantly less than predicted using the currently available methods. More work is needed to extend these findings to other mixture designs and water-cement ratios (w/c).