Seismic Retrofit of RC Short Columns with Textile-Reinforced Alkali-Activated or Cement-Based Mortars

The effectiveness of textile-reinforced mortars (TRM) utilized as jacketing overlays that are applied to short, shear-critical reinforced concrete (RC) columns was investigated experimentally and verified analytically in this study. Moreover, the possibility of replacing the standard ordinary portland cement (OPC) matrix with an alternative alkali-activated material (AAM) in the TRM retrofitting technique was explored. Seven rectangular-shaped RC columns were constructed with a shear span-to-height ratio of 1.5. Four of the seven specimens were constructed to be more ductile with closely spaced shear reinforcement, and the rest had their stirrups positioned at larger spacings. Both series of columns were retrofitted with two and four layers of TRM jacket overlays, which were made from uncoated carbon textiles and AAM or OPC-based mortar. They were subjected to cyclic loading combined with a constant vertical load. The control (unretrofitted) specimens exhibited brittle failure, and the retrofitted specimens performed significantly better for deformation capacity, with a clear shift in the failure mode toward shear-flexure. The load capacity of the jacketed columns was governed by yielding in the longitudinal reinforcement. An important result is that AAM-based TRM jacketing is not inferior to its OPC-based counterpart.