不同侵蚀环境下GFRP筋抗拉性能退化试验

Experiment on tensile properties of GFRP bars exposed to different aggressive environments

为研究GFRP(glass fiber reinforced polymer)筋在不同侵蚀环境下的抗拉性能,对侵蚀前后GFRP筋进行了拉伸试验,重点分析了侵蚀环境类别和暴露时间对GFRP筋抗拉性能的影响.采用了两种侵蚀方式:一是直接将GFRP筋浸泡在碱、盐和清水溶液中,浸泡周期为180 d;二是将GFRP筋埋置于混凝土梁内,加载后将梁置于大气和氯盐干湿环境中,周期为366 d.借助扫描电子显微镜SEM(scanning electron microscopy)对埋置于混凝土梁内GFRP筋的微观结构变化及其损伤机制进行了分析.试验及分析结果表明:GFRP筋的抗拉性能随溶液直接浸泡时间的增加出现不同程度的降低,浸泡180 d后,GFRP筋的抗拉强度在碱、盐和清水溶液中分别退化30.0%、21.3%和11.3%;对于混凝土梁内GFRP筋,366 d后其抗拉强度下降约为10%;结合试验结果和SEM微观结构分析,可认为导致GFRP筋抗拉性能退化的主要原因是纤维与树脂基体黏结性能降低.最后,基于Arrhenius模型对GFRP筋在两种侵蚀方式下的抗拉性能退化进行了拟合分析,并对其在碱、盐直接浸泡和混凝土梁内环境下的长期性能进行了预测.

To explore the tensile properties of glass fiber reinforced polymer(GFRP)bars exposed to different aggressive environments,the tensile properties of GFRP bars before and after conditioned were tested.Effects of environmental categories and exposure periods on the tensile properties of GFRP bars were analyzed.The GFRP bars were conditioned in two different ways:the first part of GFRP bars were directly immersed in different solutions(alkaline solution,salt solution,and tap water)with the immersion period of 180 days;and the second part of GFRP bars were embedded in sustained-loaded concrete beams exposed to outdoor air and NaCl solution in drying-wetting cycles with the total period of 366 days.Scanning electron microscopy(SEM)was used to analyze the microstructure changes of the GFRP bars placed in concrete beams.Test and analytical results show that the tensile properties of the GFRP bars immersed in aggressive solutions had different degrees of degradation with increasing exposure period.After 180 days of exposure to solutions,the tensile strength decreased by 30.0%,21.3%,and 11.3%in alkaline solution,salt solution,and tap water,respectively.For the GFRP bars embedded in concrete,the average loss of the tensile strength of the bars was about 10%after 366 days.Based on the test results and SEM microstructure analysis,it can be deduced that the main reason of the degradation of conditioned GFRP bars is the debonding between the fibers and the resin matrix.Finally,the tensile strength degradation of GFRP bars under two conditions were fitted based on Arrhenius model.In addition,the long-term performance predictions of GFRP bars exposed to alkaline solution and salt solution and embedded in concrete beams were proposed,respectively.