On the effect of time-dependent deformations on the behaviour of patch-repaired reinforced concrete short columns

This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members.