Thermal Prestress Losses in Normal- and High-Early-Strength Concrete
Songhee Lee, Sangmin Shin, and Chadon Lee
Appears on pages(s):
analysis; high-early-strength concrete (HESC); pretensioning; retensioning test; steam curing; test; thermal prestress loss
In this study, 14 retensioning test results from specimens made of normal concrete (NC) and high-early-strength concrete (HESC) were analyzed to estimate thermal prestress loss (ΔfT). All the specimens were pretensioned with a monostrand of 12.7 mm (0.5 in.) in diameter but were subjected to different steam-curing regimes. Analytical expressions were presented for stress changes in the strand during the curing process and subsequent retensioning tests as well as for the temperature at bonding between the strand and surrounding concrete. The results showed that the amount of ΔfT increased in proportion to the temperature increase at bonding regardless of the type of concrete. The application of steam-curing regimes adapted to HESC for design compressive strengths of 30 and 50 MPa (4.4 and 7.3 ksi) contributed to a reduction in ΔfT by 67% and 42% on average, respectively, compared with those for NC subjected to typical curing conditions.