Effect of coating on bond between reinforcing steel bars and concrete

Corrosion of reinforcement in concrete is considered the most im-portant cause of deterioration of structural concrete and hence it has seri-ous effects on the national income. Reinforcement corrosion can beminimized by using epoxy coated reinforcement in new construction,barrier coatings for non-contaminated structures, and cathodic protec-tion for existing salt-cantaminated structures. Practical application ofsuch methods should not impair the bond between steel bars and concrete.The goal of the present investigation is to investigate the resistance ofR.e. pull-out specimens to corrosion when these specimens are exposedto aggressive solutions and the resulting deterioration of bond betweenthe embedded steel bars and surrounding concrete. Two groups of pull-out pecimens with coated steel bars embedded in coated and uncoaredconcrete cylinders are used. Another two groups with uncoated steel barsembeded in coated and uncoated cylinders are also tested. Specimensform each group are submerged for a peroid of six months in aggressivesolutions with chloride ion [Cl”} concentrations of 0.05, 0.5, 5.0, and10.0 % and sulphate ion [S04 ] concentrations of 0.05,0.5,5.0 and 7.5%and mixed solution with 3.% [Cl] + 3.% [S04]’ It was found that epoxycoat on steel bars has good effect on long-term protection against bonddeterioration, especially, in case of chloride ion attack. Barrier coat onconcrete has also a positive effect on long-term protection of concreteagainst bond deterioration, especially, in case of sulphate attack.