Effects of concrete composition on transmission length of prestressing strands

The bond behavior of prestressing strands in precast pretensioned concrete members, and its transmission length, depends on several factors. However, no consensus exists on the main parameters to be considered in the expressions to predict the transmission length. Usually when the concrete properties are considered, only the concrete compressive strength is included. This study analyzes the influence of concrete composition made up of different cement contents and water/cement ratios on the bond behavior in transmission of seven-wire prestressing strands. The bond properties and the transmission lengths have been determined. The results show that the influence of the water/cement ratio is very small for concretes with lows cement contents, but the influence of the water/cement ratio on the transmission lengths is highly significant when cement content is high. The effect of cement content in the transmission lengths can reveal different tendencies based on the level of the water/cement ratio.

► Bond performance is analyzed by the measurement of the strand force supported.
► Concrete composition affects the transmission length of prestressing strands.
► The ACI 318-08 provisions for transmission length result conservative.
► A new expression for transmission bond stress including cement content is proposed.
► A good adjustment for similar test conditions from the literature has been found.