Prestress losses of double-tee girders cast with lightweight self-consolidating concrete

• Prestress losses were measured for two, full size double-tee beams.
• The beams were cast with lightweight self-consolidating concrete.
• Prestress losses were measured continuously from detensioning until 26 days after casting.
• The AASHTO-LRFD Approximate Method provided the most accurate estimation of prestress losses.

Prestress loss estimation is a necessary and important procedure in design of pretensioned concrete girders. The current specifications were developed from the experimental results of normal-weight concrete that are possibly inaccurate in estimating prestress losses for members cast with lightweight self-consolidating concrete (SCC). This study measures prestress losses for two full-scale double-tee girders cast with sand-lightweight SCC. Expanded clay, which had a specific gravity of 1.25 and an absorption capacity of 15%, was used as the lightweight coarse aggregate for the designed concrete mixture. The prestress losses were measured for 26 days and at 83 days using vibrating wire strain gauges attached to prestressing strands, after which the tested girders were then used in the construction of a parking garage. The experimental results indicated that the modulus of elasticity of lightweight SCC can be predicted using a correction factor of 0.99. The measured elastic-shortening loss was slightly lower than the predicted values. The predicted time-dependent losses, however, significantly over-estimated the measured results, which yielded the over-estimation of total prestress losses that varied from 86% to 153%.