Both lightweight concrete and SCC have the potential for increased transfer length. Lightweight concrete has a lower elastic modulus and greater shrinkage than normalweigh concrete. SCC also has the potential for greater shrinkage and a higher paste content than other concrete, and the chemical admixtures used for SCC may also affect transfer length. An increase in fluidity for a given watercement ratio w/c has been shown to result in reduced bond
capacity.13 Typical SCC mixtures are proportioned with either a high content of fine material, and as a result paste, or a viscosity-modifying admixture. Pullout testing by
Burgueño and Haq4 on 0.5 in. (13 mm) prestressing strand indicated a lower bond strength for SCC mixtures than for conventionally consolidated mixtures and that the mixtures
with higher fine-material contents had greater differences. The type of fine material in an SCC mixture was shown to have a marked effect on bonding capability by Hegger et
al.,6 with better bond measured when angular powder particles (which also produced a stronger matrix) were used. Longer transfer lengths or poorer bond strength have been measured for SCC mixtures containing fly ash than for conventional concrete with only portland cement,5,14 while SCC mixtures containing only portland cement15-17 or slag cement18 exhibited similar behavior to conventional concrete. However, in some cases similar performance was observed for SCC mixtures containing fly ash and conventional concrete.13,16 The use of viscosity-modifying admixtures
has in some cases been shown to lead to reduced early-age compressive strength and bond strength for SCC.5