How First-Immersion Age Affects Wet Expansion of Dam Concrete: An Experimental Study

Abstract

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.