Development Length of 0.6 in. Prestressing Strands in Precast, Prestressed Calcium Sulfoaluminate Cement Concrete
Abstract
Calcium sulfoaluminate cement is a very rapid setting, hydraulic cement that releases
approximately half as much carbon dioxide during production as conventional portland
cement. Calcium sulfoaluminate cement produces concrete with high early strength,
excellent durability, and limited shrinkage. These properties have the potential to
substantially improve the speed of production and performance of precast products.
The compressive strength typically required for prestress release at an age of 18-24
hours can be reached in just a few hours, without the need for heat curing. Three series
of 6.5 in. by 12 in. by 18 ft long rectangular beams prestressed with 0.6 in. prestressing
strands were cast to evaluate the effect of calcium sulfoaluminate cement concrete age
at the time of prestress release on bond behavior and prestress losses. One series of
calcium sulfoaluminate beams was cast with prestress release targeted for a
compressive strength of 3500 psi at approximately 2 hours of age and a second set with
prestress release at 24 hours of age, at which time the compressive strength was
significantly higher. A series of conventional concrete beams with a similar
compressive strength at release was also cast for comparison. Surface strain and strand
end slip were measured to evaluate transfer length and vibrating wire strain gages were
embedded to evaluate prestress losses. The CSA specimens with vibrating wire strain
gages yielded reduced prestress losses compared to conventional concrete. The
specimens also showed no significant detrimental effects of early age prestress transfer
and similar transfer lengths for rapid setting and conventional concrete. Code predicted
transfer and development lengths proved reasonable for the CSA specimens.
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- OU - Theses [2188]