模拟混凝土环境下GFRP筋抗压性能加速老化试验研究

参照ACI 440.3R-04提供的试验方法，将90根玻璃纤维增强塑料（GFRP）筋分别放入40℃、60℃和80℃的模拟混凝土溶液中进行加速老化试验，侵蚀时间分别为3.65 d、18.0 d、36.5 d、92.0 d和183.0 d，分析了温度、侵蚀时间、SiO2含量等参数对GFRP筋受压力学性能的影响。研究表明：侵蚀183.0 d后，40℃、60℃、80℃模拟混凝土环境下的GFRP筋抗压强度较侵蚀前分别下降了29.59%、39.12%和47.62%，其抗压弹性模量分别下降了10.12%、12.47%和19.06%。采用扫描电子显微镜（SEM）对侵蚀前后GFRP筋的微观形貌进行了观测，发现侵蚀后GFRP筋的劣化区域内纤维与周围树脂之间出现了明显的脱粘现象，而且随着温度的提高这种脱黏现象更加明显。采用X射线荧光光谱分析仪（XRF）分析了侵蚀前后GFRP筋的SiO2含量变化，结果表明随着侵蚀时间的增加，模拟混凝土环境下GFRP筋中SiO2含量呈递减趋势；侵蚀前GFRP筋中SiO2含量为62.11%，在40℃、60℃和80℃模拟混凝土环境下侵蚀183.0 d后，GFRP筋中SiO2含量较侵蚀前分别下降到52.05%、50.66%和47.65%。基于XRF分析提出了模拟混凝土环境下GFRP筋抗压强度的预测模型。

Accelerated aging test for evaluation of compressive properties of GFRP rebars under simulated concrete environment

According to the ACI 440.3R-04, the tests consisting of 90 glass fiber reinforced plastic (GFRP) rebars in 40℃, 60℃ and 80℃ of the simulated concrete environment for 3.65 d, 18.0 d, 36.5 d, 92.0 d and 183.0 d, were conducted to evaluate the compressive properties of GFRP rebars in terms of temperature, corrosion time and SiO2 content of the GFRP rebars. The results reveal that after being exposed to simulated concrete environment for 183.0 d at 40℃、60℃ and 80℃, the compressive strength of GFRP rebars decreases by 29.59%, 39.12% and 47.62%, and the compressive elastic modulus of GFRP rebars decreases by 10.12%, 12.47% and 19.06%, respectively. The micro-formation of the GFRP rebar surface was surveyed by scanning electron microscopy (SEM), indicating that the bonds between fibers and resin of GFRP rebars in the corrosion region become loose, and with the temperature increased, the interfacial debonding between fiber and resin of GFRP rebars become more significant. The change in SiO2 content of the GFRP rebars was studied by X-ray fluorescence spectrometer (XRF). The results show that with the corrosion time increased, the SiO2 content of GFRP rebars under simulated concrete environment shows a decreasing trend. The SiO2 content in GFRP rebars which is 62.11% before corrosion decreases to 52.05%, 50.66% and 47.65% after being exposed to 40℃, 60℃ and 80℃ of simulated concrete environment for 183.0 d, respectively. In addition, based on the analysis of XRF, compressive strength prediction model of GFRP rebars under simulated concrete environment was proposed.