In concrete structure repair projects, patch repair is one of the most commonly used methods. However, the bonding interface is often the weakest part of the overall repaired structure, and its performance affects the safety of the entire structure. In this study, different groups of cement specimens with similar exposed surface were prepared by splitting the cement paste samples with water–cement ratio of 0.4 and 0.2 into two halves from the middle point. The exposed/split surfaces were then activated in an oven at 600 °C, 700 °C and 800 °C (heating time 30 min and holding time 5 min) respectively, and the new cement pastes were poured on the treated surface of the old cement paste samples after the treated samples were cooled down to room temperature. The interface bonding strengths of different groups of samples were tested through a three-point bending test, and the interface microstructure and composition were analyzed through micro indentation, scanning electron microscopy, and X-ray diffraction tests. Among them, the interface bonding effect was the best with treatment temperature of 800 °C with an increase of more than 80 %. With this activation method, the old base cement can undergo rehydration reaction with the water in newly covered cement paste, thereby improving the bonding performance of the interface. However, high temperature can also cause microcracks on the surface of the old cement block, and it is necessary to control the activation temperature to achieve the required performance improvement. Combining mechanical tests, interface microstructure tests, and mechanism analysis, this study proposed and verified a method to improve the bonding interface strength between new and old cement pastes by high-temperature treatment on the surface of the old cement paste. Engineering applications were also discussed and explored.

中文翻译：

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通过对旧水泥浆体表面进行高温处理，提高新旧水泥浆体的粘结性能


在混凝土结构修复工程中，补片修复是最常用的方法之一。然而，粘接界面往往是整体修复结构中最薄弱的部分，其性能影响着整个结构的安全性。本研究通过将水灰比为0.4和0.2的水泥浆体样品从中间点劈成两半来制备具有相似暴露表面的不同组水泥试件。然后将裸露/分裂表面分别在 600°C、700°C 和 800°C 的烘箱中活化（加热时间 30 分钟，保温时间 5 分钟），并将新水泥浆体倒在旧水泥浆体的处理表面上。将处理后的样品冷却至室温后的水泥浆样品。通过三点弯曲试验测试不同组样品的界面结合强度，并通过显微压痕、扫描电镜和X射线衍射测试分析界面微观结构和成分。其中，处理温度为800℃时界面结合效果最好，提高了80%以上。通过这种活化方法，旧的基础水泥可以与新覆盖的水泥浆中的水发生再水化反应，从而改善界面的粘结性能。但高温也会导致旧水泥块表面产生微裂纹，需要控制活化温度以达到所需的性能改善。 结合力学试验、界面微观结构试验和机理分析，提出并验证了一种通过对旧水泥浆体表面进行高温处理来提高新旧水泥浆体粘结界面强度的方法。还对工程应用进行了讨论和探索。