This study aims to assess the degradation of below-grade concrete of nuclear power plants (NPP) in Japan, considering possible acid and sulfate attacks. A survey on the underground environments of several NPPs and residential buildings across the country was conducted, and their associated concrete performance was evaluated where concrete samples from core drillings were available. Moreover, acid and sulfate exposure tests on mortar specimens lasting for up to four years were carried out in the laboratory to simulate actual field situations. The effects of exposure conditions, such as solution concentrations, temperature, and immersion conditions, were examined. The surveyed environments were classified into non-aggressive or slightly aggressive environments. The concrete core samples investigated showed insignificant degradation and satisfactory strength after 40 years of exposure. The laboratory test results showed that the accelerated tests using highly concentrated solutions could exacerbate the extent of decalcification and even alter the degradation mechanism for magnesium sulfates. Therefore, a close-to-reality concentration is preferred for reproducing field situations. The carbonation/neutralization depth was used as an indicator to estimate the degradation extent. The measured values in the laboratory using low-concentration solutions correlated well with the field results, suggesting that the below-grade concrete’s degradation in the NPPs investigated may be less than 10 mm after 60 years of exposure.

本研究旨在评估日本核电站 (NPP) 下等级混凝土的降解情况，同时考虑可能的酸和硫酸盐侵蚀。对全国多座核电厂和住宅建筑的地下环境进行了调查，并在可获得岩心钻孔混凝土样品的情况下评估了它们的相关混凝土性能。此外，在实验室中对砂浆试样进行了长达四年的酸和硫酸盐暴露试验，以模拟实际现场情况。检查了暴露条件的影响，例如溶液浓度、温度和浸泡条件。被调查的环境分为非攻击性或轻微攻击性环境。所研究的混凝土核心样品在暴露 40 年后显示出轻微的退化和令人满意的强度。实验室测试结果表明，使用高浓度溶液进行加速测试会加剧脱钙程度，甚至改变硫酸镁的降解机制。因此，接近现实的浓度是再现现场情况的首选。碳化/中和深度用作估计降解程度的指标。实验室中使用低浓度溶液的测量值与现场结果具有很好的相关性，这表明所研究的核电厂中的劣质混凝土在暴露 60 年后可能小于 10 毫米。实验室测试结果表明，使用高浓度溶液进行加速测试会加剧脱钙程度，甚至改变硫酸镁的降解机制。因此，接近现实的浓度是再现现场情况的首选。碳化/中和深度用作估计降解程度的指标。实验室中使用低浓度溶液的测量值与现场结果具有很好的相关性，这表明所研究的核电厂中的劣质混凝土在暴露 60 年后可能小于 10 毫米。实验室测试结果表明，使用高浓度溶液进行加速测试会加剧脱钙程度，甚至改变硫酸镁的降解机制。因此，接近现实的浓度是再现现场情况的首选。碳化/中和深度用作估计降解程度的指标。实验室使用低浓度溶液的测量值与现场结果有很好的相关性，这表明所研究的核电厂中低于等级的混凝土在暴露 60 年后可能小于 10 毫米。接近现实的浓度是再现现场情况的首选。碳化/中和深度用作估计降解程度的指标。实验室中使用低浓度溶液的测量值与现场结果具有很好的相关性，这表明所研究的核电厂中的劣质混凝土在暴露 60 年后可能小于 10 毫米。接近现实的浓度是再现现场情况的首选。碳化/中和深度用作估计降解程度的指标。实验室中使用低浓度溶液的测量值与现场结果具有很好的相关性，这表明所研究的核电厂中的劣质混凝土在暴露 60 年后可能小于 10 毫米。