Abstract
Hydropower dams are subjected to soft water penetration during their service lives. Concrete deterioration due to calcium leaching will decrease the durability of concrete and affect dam safety. The long-term performance of concrete dams due to calcium leaching should be evaluated and predicted accurately to complete reinforcement work in a timely manner. In this paper, a methodology that combined microscopic tests and numerical analysis to evaluate the long-term performance of dam concrete due to calcium leaching is proposed. The current state of concrete is evaluated by analyzing the components of sediments and seepage water through microscopic and spectroscopic tests, such as X-ray photoelectron spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry. The long-term degradation of concrete was predicted by utilizing a multi-scale model of calcium leaching, which considered the micro-pore structure of cement hydrates flux with time. The simulated results using this calcium leaching model showed a good agreement with other experiments. Finally, a real case study including field inspection was performed and the long-term durability of dam concrete was predicted through microscopic tests and finite element analysis method. It implies that the proposed method could provide calculation and theoretical basis for the durability analysis of concrete dams due to calcium leaching.
Highlights
Concrete dams are designed to store water, mostly soft water, throughout their lifetime
X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and multi-scale models of calcium leaching were used to evaluate the degree of damage to dam concrete due to calcium leaching
The following conclusions can be drawn from the present study: (1) According to the water seepage and solid sediments in the corridor of a concrete dam, it is proved that there is a certain degree of calcium leaching in concrete dams according to a combination of various detection methods
Summary
Concrete dams are designed to store water, mostly soft water, throughout their lifetime. Calcium leaching of dam concrete is common in China because reservoir water is usually soft and has medium soluble corrosivity [1]. At the macro-level, these concrete structures are prone to problems, such as loss of strength, performance degradation, and shortened service life under long-term soft water penetration [2,3]. At the micro-level, this phenomenon is due to calcium ions in the concrete pore solution diffusing into the soft water under the concentration gradient, causing a soluble phase of cement hydration products, such as calcium hydroxide (Ca(OH)2 ), calcium-silicate-hydrate gel (C-S-H gel) and other solid calcium, to dissolve and be lost [4,5]. When decreasing pH [7], increasing in transport properties [8], increasing in porosity [9,10], and other properties changing [6] in concrete due to mechanical or other effects, such as undesigned cracks, calcium leaching rate might be significantly altered
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