Effect of sulfate attack on the stress–strain relationship of FRP-confined concrete
Effect of sulfate attack on the stress–strain relationship of FRP-confined concrete
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DOI：
10.1016/j.conbuildmat.2015.12.038
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发表时间：
2016-05
影响因子：
7.4
通讯作者：
Yingwu Zhou;Mali Li;L. Sui;F. Xing
中科院分区：
文献类型：
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作者：
Yingwu Zhou;Mali Li;L. Sui;F. Xing
海洋地区的混凝土结构经常遭受硫酸盐侵蚀，导致结构性能恶化。纤维增强复合材料(FRP)的外粘结是改善这些混凝土结构力学性能的有效方法。因此，本文对FRP约束硫酸盐侵蚀混凝土柱的力学性能进行了研究。采用硫酸盐溶液高温干湿循环加速腐蚀试验，模拟外部硫酸盐腐蚀环境。对直径150 mm、高度300 mm的30根圆柱体进行一段时间的硫酸盐暴露，然后用玻璃钢夹套进行约束。所有的柱子都是轴心受压到破坏。记录了硫酸盐侵蚀后无约束混凝土的强度劣化和FRP约束硫酸盐侵蚀混凝土的应力应变关系。为了定量表征硫酸盐侵蚀对混凝土的力学损伤，定义了混凝土强度劣化率和混凝土超声波速变化率两个损伤指标。对这两个损伤指标之间的高度相关性进行了检测和建模。根据上述两个损伤指标，量化了硫酸盐诱导损伤对FRP约束混凝土柱的极限强度、应变能力、初始弹性模量和应变硬化模量的影响。在此基础上，建立了应力应变关系模型。对测试结果的对比分析表明，该模型可以提供相当准确的预测。由于利用超声波无损检测方法可以方便地测量硫酸盐侵蚀混凝土的超声速变化率，所提出的应力应变关系模型对FRP加固硫酸盐侵蚀混凝土柱的设计和全寿命周期评估具有重要意义。
Concrete structures in marine areas frequently suffer from sulfate attack, which causes structural performance deterioration. External bonding of fiber reinforced polymer (FRP) is an effective method to improve the mechanical performance of these concrete structures. Thus, this paper presents a study of mechanical performance of FRP-confined sulfate-attacked concrete columns. An accelerated corrosion test by sulfate solution in a high-temperature dry–wet cycle was introduced to simulate the external sulfate corrosion environment. Thirty circular columns with a diameter of 150 mm and a height of 300 mm were subjected to sulfate exposure for a range of time periods and then confined with FRP jackets. All the columns were axially loaded to failure. Both the strength deterioration of the unconfined concrete after sulfate corrosion and the stress–strain relationship of the FRP-confined sulfate corroded concrete were recorded. Two damage indexes, i.e., the concrete strength deterioration rate and the rate of change in ultrasonic velocity of concrete, were carefully defined to quantitatively characterize the mechanical damage to the concrete due to sulfate attack. High correlation between these two damage indexes is detected and modeled. The effect of sulfate-induced damage on the ultimate strength, strain capacity, initial elastic modulus, and strain-hardening modulus of FRP confined concrete columns is quantified in terms of the two above damage indexes. On this base, a stress–strain relationship model is finally developed. A comparative analysis of the test results indicates that the model can provide reasonably accurate predictions. As the rate of change in ultrasonic velocity of concrete by sulfate attack can be measured easily using an ultrasonic non-destructive testing method, the proposed stress–strain relation model is of great significance to the design and life-cycle assessment of FRP strengthened sulfate-corroded concrete columns.