ABSTRACT Concrete is the most widely used construction material in contemporary construction technology. In particular, it holds an important place in the building industry in the world. Since concrete is a nonhomogeneous material, determining the strength of concrete accurately is quite difficult. In this respect, to check the mechanical properties of concrete in-situ, nondestructive test (NDT) methods can be used. They are useful as they do not damage concrete; however, these test results are sometimes deceptive. To reduce these deceptive results, destructive test methods were proposed to increase the accuracy of nondestructive methods. The objective of this study is to determine the strength of concrete with different characteristic strengths using destructive and NDT methods, and to establish new relationships between the compressive strength of concrete and Schmidt rebound values, and ultrasonic wave velocities. For this purpose, 101 concrete cube samples were prepared. After 7 and 28 days of curing, Schmidt rebound and ultrasonic wave velocity tests were applied as NDT methods. New formulations and graphs were established by carrying out a multiple regression analysis between the ultrasonic wave velocities, Schmidt rebound values, and compressive strengths. Thus, a new combined NDT method was developed with a nomogram. Furthermore, the applicability and accuracy of the formula and graph obtained were investigated by comparing the results of core samples from existing structures. The most important findings obtained from the study are summarized below. The concrete strength can be determined with nondestructive formulas obtained with an accuracy of 85%. High strength concrete cube samples are obtained in-house with 1.6% deviation, and core samples in-situ can be obtained with 7.3% deviation with the newly developed NDT nomogram. These test results show that the newly developed NDT formulas in this study are a very good alternative for determining concrete strength in-situ.

中文翻译：

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通过组合无损检测方法确定混凝土抗压强度的新列线图建议

摘要 混凝土是当代建筑技术中使用最广泛的建筑材料。特别是，它在世界建筑业中占有重要地位。由于混凝土是一种非均质材料，因此准确确定混凝土的强度非常困难。在这方面，为了现场检查混凝土的力学性能，可以使用无损检测 (NDT) 方法。它们非常有用，因为它们不会损坏混凝土；然而，这些测试结果有时具有欺骗性。为了减少这些欺骗性的结果，提出了破坏性测试方法来提高非破坏性方法的准确性。本研究的目的是使用破坏性和无损检测方法确定具有不同特征强度的混凝土的强度，并在混凝土的抗压强度和施密特回弹值以及超声波速度之间建立新的关系。为此，准备了 101 个混凝土立方体样品。固化 7 天和 28 天后，施密特回弹和超声波速度测试作为无损检测方法应用。通过在超声波速度、施密特回弹值和抗压强度之间进行多元回归分析，建立了新的公式和图表。因此，开发了一种具有列线图的新组合 NDT 方法。此外，通过比较现有结构岩心样品的结果，研究了所得公式和图表的适用性和准确性。从研究中获得的最重要的发现总结如下。混凝土强度可以用非破坏性公式确定，准确度为 85%。高强度混凝土立方体样品是在内部获得的，偏差为 1.6%，使用新开发的 NDT 列线图可以在现场获得核心样品，偏差为 7.3%。这些测试结果表明，本研究中新开发的无损检测公式是原位确定混凝土强度的非常好的替代方案。