Assessment of concrete columns repaired with fiber reinforced mortar through damage indexes and numerical model

Following previous research, the current paper describes the results of an experimental program concerning the repair of reinforced concrete columns by fiber reinforced thixotropic mortar, preformed to analyze and quantify the influence of casting deficiencies on the behavior of the repaired structural element. Ten columns (section scale 1:2) were designed according to the requirements of ductility orientated codes' design with variables the percentages of initial construction damages and the confinement ratio (0.075:0.15). All were tested in axial compression with repeated cycles up to failure. For comparison reasons, one column of each confinement category, yet healthy, was constructed and tested as reference specimen. A numerical study was conducted for further investigation of the behavior of the thixotropic mortar as repair material and a new empirical model is propose to predict the behavior of the repaired element. The results indicate that: (a) surpassing a damage limit, buckling of steel occurs but is not included in the model so the post-peak behavior of suitably repaired elements is lower than predicted, (b) confinement ratio is primer mechanism that acts favorably on the elements' capacity, (c) the proposed model comes in remarkable agreement with the experimental results, making it a safe assessment method with the use of damage indexes proposed without expertise non-destructive methods.