蒸养混凝土中GFRP筋微观结构与抗拉性能分析

Microstructure and tensile properties of GFRP bars embedded in steam-curing concrete

为了研究服役前蒸养养护过程对混凝土中玻璃纤维材料(glassfiber reinforced plastic,GFRP)筋抗拉强度的劣化程度,减小不同养护制度下混凝土中GFRP筋抗拉性能设计的误差,本文从微观与宏观角度分析标准养护制度(20℃)、蒸养养护制度(40℃、60℃、80℃)对混凝土中GFRP筋微观结构及抗拉性能的影响。并为减小混凝土中GFRP筋抗拉性能测试的难度及对GFRP筋裸筋耐久性研究成果的拓展,同时针对裸筋与混凝土包裹两种试验方法中的GFRP筋微观及抗拉性能进行研究。研究结果表明:不同养护制度对混凝土中GFRP筋的微观结构与抗拉强度的劣化程度随养护温度的提高而不断增大;不同养护制度对混凝土中GFRP筋抗拉强度的劣化影响与裸筋有所不同;并且不论是养护制度的影响还是试验方法的影响,都随直径的增大而有所降低。基于GFRP筋抗拉试验数据建立了与养护温度、直径同时相关的不同试验方法差异性方程,实现通过裸筋养护试验预测不同养护制度下混凝土中GFRP筋抗拉强度的衰减率。

To fully consider the deterioration degree of the tensile strength of a GFRP bar embedded in concrete during the process of steam-curing and before service,and to reduce the error of the tensile property design of the GFRP bar under different curing systems,influences of the standard-curing system(20℃)and steam-curing system(40℃,60℃,80℃)on the microstructure and tensile properties of the GFRP bars in concrete are analyzed using both micro and macro perspectives.To reduce the difficulty involved in testing the tensile strength of the GFRP bar in concrete,and to further contribute to the wealth of literature written on the durability of the bare GFRP,the microstructure and tensile properties of a GFRP bar are analyzed using two different test methods and with both bare bar and concrete coverage.Results show that the deterioration degree of the microstructure and the tensile strength of the GFRP bar in concrete with different curing systems increase with an increase in the curing temperature.In addition,results show that the influence of different curing systems on the tensile strength of the GFRP bar in concrete is different from that with the bare bar.Furthermore,no matter the effect of the curing system or the effect of the test method decreases with the increase of the diameter.Finally,based on tensile test data of the GFRP bar,difference coefficient equations are established for different test methods in relation to the curing temperature and diameter;these equations can be used to predict the attenuation of tensile strength of the GFRP bar in concrete under different curing systems when using the bare bars test.