Upon immersion in water, dam concrete undergoes wet-expansion deformation due to infiltration of moisture. To investigate how first-immersion age affects the wet expansion of dam concrete, wet-expansion tests with five different first-immersion ages (7, 14, 28, 60, and 90 days) are conducted under unified test conditions. Firstly, the statistical model of measured strain of concrete specimen before immersion in water is established, following which the thermal expansion coefficient and autogenous volume strain of the concrete are obtained. Next, based on the measured strain after immersion in water, we separate the wet-expansion strain of concrete specimens with five different first-immersion ages and then calculate the wet-expansion coefficient of each specimen. Finally, the equivalent age theory is introduced to establish an eight-parameter wet-expansion strain model based on equivalent first-immersion age and equivalent immersion time, and an optimization algorithm is used to identify the parameters of the models. The test results show that as the immersion time increases, the wet-expansion strain gradually increases until it becomes stable. The smaller first-immersion age will result in a larger stable wet-expansion strain, but when the first-immersion age is over 28 days, the stable wet-expansion strain becomes independent of the first-immersion age and tends to a similar value at approximately 20 με. The evolution of wet-expansion coefficient is similar to that of wet-expansion strain, and it tends to 3.6 × 10 −3 when the first-immersion age is over 28 days. Additionally, the calculated wet-expansion strain based on the eight-parameter model is in good agreement with the measured value, which indicates the feasibility of this model.

中文翻译：

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初浸龄期如何影响大坝混凝土的湿膨胀：一项试验研究

大坝混凝土浸入水中后，由于水分的渗入而发生湿胀变形。为了研究初浸龄期如何影响大坝混凝土的湿胀，在统一的试验条件下进行了五种不同初浸龄期（7、14、28、60 和 90 天）的湿胀试验。首先建立了混凝土试件浸水前实测应变的统计模型，得到了混凝土的热膨胀系数和自体体积应变。接下来，根据浸水后测得的应变，我们将具有五个不同初浸龄期的混凝土试件的湿膨胀应变分开，然后计算每个试件的湿膨胀系数。最后，引入等效龄期理论，建立了基于等效初浸龄期和等效浸泡时间的八参数湿胀应变模型，并采用优化算法对模型参数进行辨识。试验结果表明，随着浸泡时间的增加，湿胀应变逐渐增加，直至趋于稳定。较小的初浸龄期将导致较大的稳定湿胀应变，但当初浸龄期超过 28 天时，稳定湿胀应变与初浸龄期无关，并趋向于相似的值约 20 με。湿胀系数的演化与湿胀应变相似，首次浸渍龄期超过28天时趋于3.6×10 -3 。此外，