Mechanical Properties and Corrosion Mechanism of GFRP Rebar in Alkaline Solution

Abstract:

Steel corrosion is one of the main problems of concrete structure durability. Compared with the steel, GFRP rebar has the advantages of high strength, low density and good corrosion resistance. Therefore, GFRP becomes a good choice to replace steel bar in concrete structure. Since GFRP material is susceptible to the alkaline conditions, it is necessary to clarify the mechanical properties and corrosion mechanism of GFRP rebar in such an alkaline environment of interior concrete. In this study, the artificial accelerated corrosion tests of two kinds of GFRP rebar (epoxy and unsaturated polyester resin matrix) were conducted at 60 °C in alkaline solution up to 90 days. Then the tensile strength tests of GFRP rebar were carried out. The solution PH values, the tensile strength and mass loss of GFRP rebar were measured. The testing results show that the mass of GFRP rebar had rarely changed, but the tensile strength reduced about 30% after 90-day immersion test in alkaline solution. During the test, the PH value of the alkaline solution decreased from 13.62 to around 12.85, which indicated that the hydroxyl ions of the alkaline solution had been consumed. The ester bonds in resin matrix may hydrolyze in alkaline solution and the bonding interface between fiber and resin can be damaged progressively. It can cause the performance degradation of GFRP rebar. In addition, the relationship between the loss of tensile strength and the reduction of PH can be determined. That means the durability of GFRP rebar in concrete can be enhanced by controlling or limiting the alkalinity when producing concrete. Finally, the GFRP rebar of epoxy resin matrix shows higher retention values of tensile strength and better alkali resistance than those of UPR matrix rebar after 90d immersion in the alkaline solution. The obtained results in this paper can provide application reference of GFRP materials in civil engineering.

• Periodical: Key Engineering Materials (Volume 665)
• Pages: 217-220
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.665.217
• Online since: September 2015
• Authors: Ji Ze Mao, Hong Wei Zhang, Jian Fu Lv, Dao Guang Jia, Shi Kai Ao
• Keywords: Alkaline Solution, Corrosion, GFRP Rebar, Tensile Strength

References

[1] Wang Wei, Xue Weichen: Accelerated aging tests for evaluations of tensile properties of GFRP rebars exposed to alkaline solution. J. Build. Mater. Vol. 15 (2012), pp.760-766.

[2] H.S. OH, D.Y. MOON, and S.D. KIM: An investigation on durability of mixture of alkali-resistant glass and epoxy for civil engineering application. Procedia Eng. Vol. 14 (2011), pp.2223-2229.

DOI: 10.1016/j.proeng.2011.07.280

[3] J.P. Won, S.J. Lee, Y.J. Kim: The effect of exposure to alkaline solution and water on the strength-porosity relationship of GFRP rebar. Compos. Part B-Eng. Vol. 39 (2008), pp.764-772.

DOI: 10.1016/j.compositesb.2007.11.002

[4] Zhang Xinyue, Ou Jinping: Durability experimental research on resistance of acidic, alkali, salt solution and freeze-thaw properties of FRP bar. J. of Wuhan UNIV. of Technology-Mater. Sci. Ed. Vol. 29 (2007), pp.33-46.

[5] Wang Wei, Meng Yanling, Qian Wenjun: Durability of FRP bars exposed to alkaline corrosion environment. CN. Synthetic Resin and Plastics Vol. 26 (2009). pp.27-30.

[6] Li Chenchen, Yu Aimin, and Wang Yinglai: Durability of FRP Rebars in Alkaline Environment of Concrete. Build. Sci. Vol. 29 (2013), pp.47-51.