The Effect of Addition Potassium Permanganate on Bond Strength of Hot-Dip Galvanized Plain Bars with Cement Paste.

In this paper, the effect of gradually increasing amounts of KMnO 4 (10 -4 , 10 -3 , 10 -2 mol·L -1 ) in cement paste on the bond strength of a plain hot-dip galvanized steel bar was evaluated. The open-circuit potential of HDG samples in cement paste with various additions of MnO 4 - was monitored in order to follow a transfer of zinc from activity to passivity. Furthermore, the influence of the addition of these anions on the physicochemical properties of normal-strength concrete or cement paste was evaluated by means of hydration heat measurements, X-ray diffraction analysis, and compressive strength. The effective concentration of MnO 4 - anions prevents the corrosion of the coating with hydrogen evolution and ensures that the bond strength is not reduced by their action, which was determined to be 10 -3 mol·L -1 . Lower additions of MnO 4 - anions (10 -4 mol·L -1 ) are ineffective in this respect. On the other hand, higher additions of MnO 4 - anions (10 -2 mol·L -1 ), although they ensure the corrosion of the coating in fresh concrete without hydrogen evolution, but affect the hydration process of the cement paste that was demonstrated by slight water separation.