Corrosion Resistance and Bond Strength of Steel Bars Coated with Calcium Silicate Modified Enamel

摘要

This study investigates the corrosion resistance and bond strength of mortar cylinders reinforced with uncoated steel bars (UN) and steel bars coated with two types of enamel: pure enamel (PE) and calcium silicate modified enamel (ME). The addition of calcium silicate is aimed to increase the bond strength of enamel coating with surrounding concrete by chemical reaction. Two groups of 18 pullout specimens were prepared, each with one steel bar placed along the centerline of a mortar cylinder. Steel bar was pulled out of the mortar cylinder to characterize the bond strength at the steel/mortar interface. The effects of mortar curing time (28 days and 60 days) were investigated. For corrosion performance, another group of 9 mortar cylinders reinforced with UN, PE and ME coated steel bars were immersed in 3.5 wt.% NaCl solution for 6 months. The corrosion evolution was monitored monthly using electrochemical impedance spectroscopy (EIS). The experiments indicated that the bond strength could be increased by three times and seven times when a steel bar was coated with PE and ME, respectively. The significant steel-concrete bond increase with ME resulted from the increased surface roughness and the chemical bonding of embedded calcium silicate particles in surrounding mortar. EIS results showed that both PE and ME could increase the corrosion resistance of steel bars in mortar cylinder. The increase in corrosion resistance was as high as 50 times and 3 times when the steel bar was coated with PE and ME.