The durability of seawater sea-sand concrete (SSC) and/or sea-sand concrete (SC) structures exposed to harsh marine environments is crucial to their service life. In this study, we investigated the capillary water absorption of SSC, SC, and ordinary concrete (OC) with different water–binder ratios (i.e., 0.38 and 0.28) in deionized water and composite saline solutions. The results showed that the cumulative water absorption of OC, SC, and SSC in the composite saline solution were lower than that in deionized water. In deionized water, the cumulative water absorption of OC is the largest, followed by those of SC and SSC. However, in composite saline solution, the cumulative water absorption of the three types of concrete with a low water–binder ratio at less than 6 h was similar; after that, SSC exhibited the highest absorption, followed by SC and OC. Moreover, the initial water absorption rate in deionized water was approximately four times higher than that in the composite saline solution. In contrast, for concrete with a low water–binder ratio, the secondary water absorption rate (after 6 h) was approximately two times lower in deionized water than in the composite saline solution. The free shrinkage of the three concrete types have been measured up to the age of 210 d. The results showed that under the same curing age, the shrinkage strain of OC was the largest, followed by those of SC and SSC. Based on the GL2000 model, a new prediction model for the shrinkage of SSC and/or SC was established by introducing an expansion effect coefficient. The proposed model could accurately predict the development of the shrinkage strain in OC, SC and SSC.

中文翻译：

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海水海砂混凝土毛细管吸水率和自由收缩表征

暴露在恶劣海洋环境中的海水海砂混凝土（SSC）和/或海砂混凝土（SC）结构的耐久性对其使用寿命至关重要。在这项研究中，我们研究了不同水胶比（即0.38和0.28）的SSC、SC和普通混凝土（OC）在去离子水和复合盐水溶液中的毛细管吸水率。结果表明，复合盐水溶液中OC、SC、SSC的累积吸水率均低于去离子水中。去离子水中，OC的累积吸水率最大，其次是SC和SSC。但在复合盐溶液中，三种低水胶比混凝土在6 h以内的累积吸水率相似；之后，SSC 的吸收率最高，其次是 SC 和 OC。此外，去离子水中的初始吸水率大约是复合盐水溶液中的四倍。相反，对于低水胶比的混凝土，去离子水中的二次吸水率（6小时后）大约比复合盐水溶液低两倍。测量了三种混凝土类型的自由收缩直至 210 d 的龄期。结果表明，相同养护龄期下，OC的收缩应变最大，其次是SC和SSC。在GL2000模型的基础上，引入膨胀效应系数，建立了SSC和/或SC收缩的新预测模型。所提出的模型可以准确预测 OC、SC 和 SSC 中收缩应变的发展。