Influence of anti-corrosive coatings on the bond of steel rebars to repair mortars

Patch repairs are common in the rehabilitation of reinforced concrete structures, mainly bridges but also buildings, exposed to carbonation and chloride ingress. This technique includes the following steps: (i) removal of damaged concrete; (ii) cleansing of corroded steel rebars; (iii) application of anti-corrosive coating; and (iv) application of a repair mortar.Although the application of an anti-corrosive coating is common practice, part of most manufacturers’ guidelines and, moreover, a mandatory step in some countries standards, it is important to assess if it decreases the bond of steel rebars to the repair mortar, in which case the anti-corrosive protection of the rebars should be assured in an alternative way.The experimental study herein described includes 72 pull-out tests and it was conducted aiming to characterise the bond strength of the rebar-to-mortar interface and, subsequently, to define the most adequate procedure concerning the anti-corrosive protection of the rebars.In summary, it can be stated that it is advisable to always apply cementitious coatings to plain rebars whereas it should be avoided for ribbed rebars since, in this case, the loss of average bond strength due to coatings can reach 40%.

► Bond strength of rebar-to-mortar interfaces with anti-corrosive coating is studied.
► Seventy-two pull-out specimens have been produced with three commercial solutions.
► Plain and ribbed rebars, corroded/non-corroded, with/without coating are compared.
► In terms of bond strength cementitious coatings should be applied to plain rebars.
► Whereas for ribbed rebars the loss of strength due to coatings can reach 40%.