This article presents an investigation into the effects of natural seawater and sea sand on the behaviour of unconfined and fibre-reinforced polymer-confined concrete. The experimental programme covered compression tests of a large number of standard concrete cylinders, which were prepared from the following four series of concrete: (1) the reference normal concrete, (2) sea-sand concrete, (3) seawater concrete (SwC), and (4) seawater sea-sand concrete. The concrete cylinders were either unconfined or confined with externally wrapped carbon fibre-reinforced polymer jackets to be tested at various ages from the early to the long term. This article presents the results of the first-phase tests, which covered a total of 48 specimens from the four series of concrete, with a half of them tested in the unconfined condition at the ages of 7 and 28 days, and another half tested with either one-ply or two-ply carbon fibre-reinforced polymer jackets at 28 days. The results show that at the ages of 7 and 28 days, the unconfined concrete specimens prepared with seawater and/or sea sand developed a slightly higher compressive strength, as compared to those prepared from normal concrete. When confined with carbon fibre-reinforced polymer jackets, the compressive stress–strain responses of concrete with or without seawater and/or sea sand were very similar. The use of seawater and sea sand did not seem to have significant effects on the compressive strength, ultimate axial strain and stress–strain responses of confined concrete, and the ultimate strain capacity of carbon fibre-reinforced polymer jackets neither. The test results were also compared with the predictions of an existing analysis-oriented stress–strain model for fibre-reinforced polymer-confined concrete. It is shown that the compressive strength, ultimate axial strain, stress–strain responses and dilation behaviour of the carbon fibre-reinforced polymer-confined concrete with or without seawater/sea sand can be reasonably well predicted.

中文翻译：

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天然海水和海砂对无侧限和碳纤维增强聚合物有侧限混凝土抗压性能的影响

本文研究了天然海水和海砂对无侧限和纤维增强聚合物有约束混凝土的性能的影响。实验程序涵盖了大量标准混凝土圆柱体的压缩试验，这些圆柱体由以下四个系列的混凝土制成：(1) 参考普通混凝土，(2) 海砂混凝土，(3) 海水混凝土 (SwC) , (4) 海水海砂混凝土。混凝土圆柱体要么是不受约束的，要么是用外部包裹的碳纤维增强聚合物护套来约束的，以便在从早期到长期的不同年龄进行测试。本文介绍了第一阶段试验的结果，其中涵盖了来自四个系列混凝土的 48 个试样，其中一半在 7 天和 28 天的无侧限条件下进行了测试，另一半在 28 天时使用单层或两层碳纤维增强聚合物夹克进行测试。结果表明，在 7 天和 28 天时，与用普通混凝土制备的无侧限混凝土试件相比，用海水和/或海砂制备的无侧限混凝土试件的抗压强度略高。当使用碳纤维增强聚合物护套进行限制时，无论是否含有海水和/或海砂，混凝土的压缩应力-应变响应都非常相似。海水和海砂的使用似乎对约束混凝土的抗压强度、极限轴向应变和应力应变响应以及碳纤维增强聚合物护套的极限应变能力没有显着影响。测试结果还与现有的纤维增强聚合物约束混凝土应力应变模型的预测进行了比较。结果表明，无论是否含有海水/海砂，碳纤维增强聚合物约束混凝土的抗压强度、极限轴向应变、应力应变响应和膨胀行为都可以很好地预测。