Tension stiffening effect and bonding characteristics of chemically prestressed concrete under tension

The tension stiffening effect of chemically prestressed concrete (CPC) under uniaxial tension was experimentally investigated and compared with those of reinforced concrete (RC). A special specimen profile was designed to avoid the effect from end parts. The tension stiffening of both RC and CPC were compared with the current tension stiffening model. The crack pattern was observed after loading. The results show that the CPC has superior tension stiffening than RC and the conventional model for RC substantially underestimates the tension stiffening of CPC. In addition, the number of cracks in CPC is less than in RC at the same load. Further investigation on bonding characteristics of CPC under tension was subsequently conducted. Effects of cross section's size and amount of expansive additive were also investigated. The strain distribution of rebar was measured from strain gages attached with 20 mm interval. Local bond, slip and average bond stress were then calculated. The results show that bond of CPC near loading end is higher than that of RC, although the average bond is almost same. The results of this study can partly explain some of unique tensile properties of CPC which can be related to its cracking resistance.