Durability of CFRP-confined seawater sea-sand concrete (SSC) columns under wet-dry cycles in seawater environment

Fiber-reinforced polymer (FRP) composites have become increasingly popular as an external confining device for seawater sea-sand concrete (SSC) due to their excellent durability and material properties. Many studies have been carried out on the short-term behavior of FRP confined SSC under compression. However, relatively limited work is available on its durability, and most of the existing tests were conducted using the accelerated test approach in the laboratory rather than on-site field exposure. Against this background, the long-term behavior of carbon FRP-confined SSC columns with different wrapping schemes under wet-dry cycles in seawater environ-ments was experimentally explored in this paper. Seventy-six specimens were tested to investigate the effects of the wrapping schemes, the clear spacing ratios of FRP and the exposure time. Test results reveal that long-term exposure has little influence on the failure modes of wrapped specimens and different trends are observed for compressive strength retentions and strength enhancement ratio retentions because of the influence of uncon-fined compressive strength. The correlation analysis is also conducted to examine the relationships among several discussed parameters and a new strength model is derived by introducing the proposed strength degradation coefficients into existing formulas. Compared with experimental observations, the new model can provide satisfactory strength predictions for the exposed FRP-confined concrete under natural marine environments.

Automated summary

This paper experimentally explores the long-term behavior of carbon FRP-confined SSC columns with different wrapping schemes under wet-dry cycles in seawater environments. The results show that long-term exposure has little influence on the failure modes of wrapped specimens, and different trends are observed for compressive strength retentions and strength enhancement ratio retentions due to the influence of unconfined compressive strength. Furthermore, a new strength model is derived by introducing the proposed strength degradation coefficients, which can provide satisfactory strength predictions for the exposed FRP-confined concrete under natural marine environments.