Influence of a biopolymer admixture on corrosion behaviour of steel rebars in concrete

Among the multitude of concrete structure pathologies, corrosion of rebars is one of the most important problems of concrete durability. In the context of sustainable development, it appears of primary importance to develop new means to protect the rebars against corrosion. This study aims to develop a new eco‐friendly and corrosion‐inhibiting admixture based on EPS 180 exopolysaccharides, biopolymers used in coatings already studied for the corrosion inhibition on steel in seawater. C15 rebars embedded in CEMI and CEMV cement paste containing EPS 180 were immersed in natural seawater and their electrochemical behaviour was studied using open circuit potential measurements and electrochemical impedance spectroscopy. These tests highlight the decrease of the cathodic reaction kinetics due to the EPS 180 action at the rebars surface, and the absence of effect on the passive layer. Capillary imbibition tests carried out on cement paste and mortars showed that although limiting the imbibition kinetics for cement pastes, the EPS 180 did not influence the water imbibition of mortars. Tests comparing capillary imbibition of soaked cement pastes and mortars with EPS 180 solution and the same samples containing the EPS 180 admixture highlight that the corrosion inhibition induced by EPS 180 admixture is more due to the modification of the cement – rebars interface than to the clogging of the cement porous network.