How long can fiber reinforced polymer sustain concrete structures? Scientists answer

In modern society, we find that the majority of our infrastructure (buildings, bridges, tunnels, etc.) is made of ageing concrete. A recently developed cost-effective method of sustaining this infrastructure is external coating with fiber reinforced polymer (FRP) composites. But is this a temporary patch or a durable solution? Not much research has looked into this question. Now, a 13-year-long study published in Composites Part B finally finds out, taking us one step closer to the wide-spread utilization of this solution.

In the FRP-strengthening of concrete, glass or carbon fiber reinforced polymer (GFRP or CFRP) composites are bonded onto concrete using an epoxy adhesive. These sheets provide additional support and strengthen the concrete structures by protecting them from harsh environmental conditions, such as high moisture levels and temperatures. But the problem is, these same environmental conditions can potentially degrade the concrete-FRP bond as well, causing the FRP protection system to fail prematurely.

Prof. Jaeha Lee from Korea Maritime and Ocean University, a lead researcher in the 13-year study, says, “The information available on FRP-concrete bond behavior following sustained loads in different environments is very limited, particularly for periods beyond two years.”

The researchers tested both CFRP and GFRP systems under various indoor and outdoor environmental conditions for change in a parameter called the debond onset strain. This is a measure of the deformation that occurs before failure; larger strains are usually preferred to forewarn failure.

The researchers found that environmental conditions had a significant impact on bond behavior. At the end of 13 years, larger reductions in debond strains were observed in outdoor beams than indoor beams. Further, the bond behavior varied between materials: changes in debond strain were negligible in indoor CFRP beams, while in indoor GFRP beams, there was a notable decrease.

Prof. Lee stresses the importance of such tests for future use stating: “If the long-term durability of concrete-FRP interfaces is evaluated, the use of this strengthening system is expected to increase with minimum investment. This will be great for affordably maintaining a safer city by minimizing the risk of collapse or damage of existing structures.”

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Reference

DOI: https://doi.org/10.1016/j.compositesb.2021.109180

Authors: Jaeha Lee¹, Jinhoo Kim², Charles E. Bakis² and Thomas E. Boothby²

Affiliations:     

1. Korea Maritime & Ocean University, Korea
2. Pennsylvania State University, USA

About National Korea Maritime & Ocean University 

South Korea’s most prestigious university for maritime studies, transportation science and engineering, the National Korea Maritime & Ocean University is located on an island in Busan. The university was established in 1945 and since then has merged with other universities to currently being the only post-secondary institution that specializes in maritime sciences and engineering. It has four colleges that offer both undergraduate and graduate courses.  

Website: http://www.kmou.ac.kr/english/main.do

About the author

Jaeha Lee is a professor of civil engineering at Korea Maritime and Ocean University (KMOU). His group is recently developing fiber reinforced cement composite and FRP strengthened structures for concrete facilities and structures against impact loadings. Before coming to KMOU, he was a senior researcher at Korea Institute of Nuclear Safety (KINS). In 2010, He received a Ph.D. in civil engineering from the Pennsylvania State University.