本技术说明简要介绍了混凝土结构中冷关节的无损评价。我们将审查结构工程师和质量控制实验室如何利用NDT方法来评估冷关节或周围混凝土的质量和完整性。
What is Cold Joint in Concrete?
Cold joints in concrete primarily happen when there is a significant delay between different concrete pours. For examples, if there is an interruption or delay in the concrete delivery or in concreting operations, the first batch may start to set. This increases the chance that these two batches do not intermix properly.
混凝土中冷关节的无损评价
In General, cold joints in concrete do not create an integrity issue; this is specially true if the structural member is under compression. However, there is a chance that a poor bond between two batches of concrete create a weak zone, with potential voids. Non-Destructive Evaluation of Cold Joints in Concrete can help identify the extent of these potential defects.
1. Ultrasonic Pulse Velocity (UPV)
Ultrasonic Pulse Velocity (UPV)是一种有效的非破坏性测试（NDT）方法，用于混凝土材料的质量控制，并在冷关节或周围评估混凝土完整性。Ultrasonic testing of concreteis an effective way for quality assessment and uniformity, and crack depth estimation. The test procedure has been standardized as “Standard Test Method for Pulse Velocity through Concrete” (ASTM C 597, 2016).
#UPV can help engineers evaluate the quality and uniformity of concrete close to the joint area. When there is a significant change in the pulse velocity, it can be related to the quality of concrete.
2.Impact-Echo
Impact-Echois a nondestructive test method for evaluating concrete and masonry structures. Generally, a pulse is generated by an impact at one single point. The resulting stress wave propagates in all directions. In this regard, the generated wave lacks the directionality of a pulse that is generated by a large transducer (as in the case ofULTRASONIC PULSE VELOCITY)
3. Rebound Hammer
Rebound Hammeris non-destructive test method for evaluating the homogeneity of concrete and evaluating surface hardness. The test can be used for comparative study of surface hardness of concrete over a large area. The rebound hammer test can be performed in different angles, and the measurements should be corrected for the direction of the test.
在大面积中，该测试可用作快速且经济高效的筛选工具，以识别差的位置，或者更容易受到内部空隙或异常的区域。
Other Solutions
Taking concrete cores have long been used to assess quality and strength of concrete. Concrete cores can help identify potential week points, and help engineers with physical condition of concrete. The downside of this method is the damage to the concrete integrity, and potential damage to the steel reinforcement.