Design of filling self-stressing concrete to use in strengthening of columns by prefabricated jacketing

Abstract

This study proposes the design and characterization of an expansive self-compacting concrete (SCC) with self-stressing properties for its use as a filling in reinforcement systems by external prefabricated jacketing. The self-compacting characteristic ensures the correct filling of the inner space and the characteristic of expansiveness (self-stressing) guarantees a correct transmission of tensions from the column to the prefabricated reinforcement jacket. In the design, a K-type expansive agent based on calcium sulfoaluminate is used in the doses of 10% and 15% and the influence of its addition on the fresh properties and the compressive strength on the reference mix of SCC is analysed. The restrained expansion is evaluated in prisms by the standard method ASTM C878 and by means of an alternative method based on a double ring device that simulates the configuration of reinforcement systems using carbon fiber reinforced polymers (CFRP) or steel external jacketing. Finally, the efficiency of the proposed strengthening system is compared to that usually used for CFRP jacketing directly glued on the element like concrete specimens and reinforced concrete columns. The results show that the double-ring based test device presents a high degree of correlation with the prism-based standard method and that the proposed strengthening based on filling self-stressing SCC and external prefabricated jacketings is an efficient solution that allows to move from a passive reinforcement system (CFRP jacketing glued directly to the column) to an active one that allows the reinforcement to contribute from the initial moments of the cast-in-place of the self-stressing SCC.