Bond performance of a hybrid coating zinc-rich epoxy incorporating nano-ferrite for steel rebars subjected to high temperatures in concrete

Abstract

The main issues in common steel rebar coatings are the reduction in bond strength and inconvenience to high temperatures. Inspired by these facts, a hybrid coating zinc-rich epoxy (ZRE) incorporating nano-ferrite (NF) (NF-ZRE) was prepared with different percentages. The performance of bond strength was studied at different temperatures up to 600 °C in the presence of ZRE coating. In addition, the results of the uncoated specimens and other categories with an additional layer of Sikadur-31 (SDE) epoxy bonding coating over ZRE coating (SDE-ZRE) were compared. This experiment was performed for two different mixes, namely, normal (MN) and silica fume mixes (MSF). The effect of adding NF with different percentages of ZRE on bond strength in the MSF mix was investigated, and all results at distinct temperatures were compared. The compressive strength test and scanning electron microscopy (SEM) were conducted to explain the obtained results of bond strength. Results showed that the residual bond strength of uncoated and ZRE-coated specimens in the MSF mix was better than that of MN at temperatures up to 400 °C. The specimens with SDE-ZRE were deboned at temperatures over 300 °C. Furthermore, the residual bond strengths of specimens incorporating NF-ZRE, specifically in 2% NF, recorded the greatest values at high temperatures up to 500 °C. All the attained results were verified and emphasized through the compressive strength test and SEM.