Development of a dual-layer silica fume-epoxy resin composite coating to enhance durability and interfacial bond for FRP bars in alkaline concrete environments

Le résumé fourni par la source

The susceptibility of fiber reinforced polymer (FRP) bars to alkaline degradation in concrete environments remains a critical durability challenge. This study develops an innovative dual-layer silica fume-epoxy resin composite coating (SF-ERC), comprising an inner epoxy/silica fume hybrid layer (SF+ER) and outer layer of silica fume (SFC). The influence of the inner SF+ER layer on the durability of FRP bars was investigated, and the optimal mix proportion of this layer was determined. Subsequently, the effect of the complete SF-ERC on the bond strength at the FRP bar-concrete interface was investigated. The results indicate that the silica fume dispersed in the inner layer can consume alkaline substances through the pozzolanic reaction. This provides a spatial corrosion-inhibition effect, thereby effectively enhancing the durability of FRP bars. After 180 days of immersion corrosion, the water absorption, dissolved resin, and mechanical property loss rate of the optimal inner SF+ER layer coated specimens were only 16.59 %, 15.96 %, and 31.51 % of those of the uncoated specimens, respectively. The outer SFC layer not only serves as an additional corrosion-inhibition barrier, but also promotes the formation of a new C-S-H gel protective layer through the pozzolanic reaction. Moreover, the SF-ERC alleviates the problem of bond weakening typically linked to conventional single epoxy coatings and further enhances the bond strength. After 90 days of immersion in seawater, the interfacial bond strength of FRP bars coated with SF-ERC increased by 18.32 % compared to those coated solely with epoxy resin.

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