Bond Characteristics of Coated Reinforcing Steel Bars with Reference to Deformation of Concrete Beams

A major cause of reinforced concrete deterioration especially in coastal and moist prone areas is corrosion. It has become a threat to reinforced concrete structural integrity throughout the service life of the structural member, and it calls for endless remedial activities with its accompanying economic and safety implications. Expensive remedial measures- galvanization, epoxy coating and fiber-reinforce polymers - are used to prevent corrosion as approved by previous studies. The present study explored the use of cost effective oil paint brands (mat, red-oxide and gloss Leyland paints in Ghana) to variably coat reinforcing steel bars to ascertain their bond strength in concrete while preventing corrosion. There were zero, one, two and three coats averaging 72 µm, 129 µm and 220 µm film thickness of 1-coat, 2-coat and 3-coat respectively for exploration. Double pull-out test was conducted on 120 concrete prisms (size 150 x 150 x 200 mm), centrally reinforced with coated rebars. Loading rate of 0.5kN/s was adopted and data was processed and analyzed by one-way ANOVA. The results indicated that no significant difference exist between paint coated and uncoated reinforcing steel bars on local bond and slip quality for all the selected paint brands used in this study. Though facially, one-coat of paint showed better bonding (18%) quality over zero-coat, two-coat and three-coat were at par with zero-coat, indicating decreasing bond with increasing coat. But reinforcing bar type and size were not affected by the coating. The implication is that the selected oil paint brands would not adversely affect local bond strength, and hence cracking and deflections in concrete when they are used to coat reinforcing bar to prevent corrosion, and therefore recommended for application to reduce maintenance cost.