碱环境下不同应力水平GFRP筋抗拉性能试验

基于ACI 440.3R-04规定的试验方法，对60 ℃碱环境下应力水平分别为0、25%和45%的玻璃纤维塑料（GFRP）筋的抗拉性能进行了试验研究。试件数量共90根，侵蚀时间分别为3.65、18、36.5、92、183天。采用SEM对腐蚀前后GFRP筋的微观形貌进行了观测，发现碱溶液造成了GFRP筋内部结构致密性的降低，且随着应力水平的增加，其降低愈发明显。在60 ℃碱溶液中侵蚀183天后，应力水平为0和25%的GFRP筋的抗拉强度分别下降了48.81%和55.56%，而弹性模量仅分别下降了5.47%和5.73%，应力水平为45%的GFRP筋则出现了断裂现象。GFRP筋的吸湿试验表明，OH^-离子在GFRP筋中的扩散过程符合Fick定律。在分析了应力水平、侵蚀时间等参数对GFRP筋抗拉性能影响的基础上，基于Fick定律提出了碱环境下带应力GFRP筋抗拉强度的退化模型。

Experimental study on tensile properties of GFRP rebars under different stress levels as exposed to alkaline solution

According to the ACI440.3R-04, the tests consisting of 90 glass fiber reinforced plastic (GFRP) rebars in 60 ℃ of the alkaline solution for 3.65, 18, 36.5, 92 and 183 d, were conducted to evaluate the tensile properties of GFRP rebars at different stress levels(0, 25%, 45%). The micro-formation of the GFRP rebars surface was surveyed by SEM. It indicates that the bonds between fibers and resin of GFRP rebars in the corrosion region becomes loose, and with the stress levels increase, the interfacial debonding between fiber and resin of GFRP rebars becomes more significant. After being exposed to alkaline solution for 183 d, tensile strength of GFRP rebars at stress level of 0 and 25% decreases by 48.81% and 55.56%, while tensile elastic modulus of GFRP rebars decreases by 5.47% and 5.73%, respectively, and GFRP rebars at 45% stress level have been already destroyed. The results of moisture absorption test show that the absorption kinetics is satisfactorily described by Fick's law. In addition, based on the Fick's law, the tensile strength prediction degradation model of GFRP rebars under alkaline solution was proposed.