1.1 本试验方法包括测定纵向超声波应力波脉冲在混凝土中的传播速度。该试验方法不适用于其他类型的应力波通过混凝土的传播。 1.2 以国际单位制表示的值应视为标准值。本标准不包括其他测量单位。 1.3 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 超声脉冲速度， 五、 混凝土中的纵向超声波应力波与其弹性财产和密度有关，关系如下: 哪里: E = 动态弹性模量， μ = 动态泊松比，以及 ρ = 密集 5.2 该试验方法适用于评估混凝土的均匀性和相对质量，指示是否存在空隙和裂缝，以及评估裂缝修复的有效性。它也适用于指示混凝土财产的变化，以及在结构调查中，以估计劣化或开裂的严重程度。如果用于监测随时间变化的条件，应在结构上标记测试位置，以确保在相同位置重复测试。 5.3 混凝土的饱和度影响超声波脉冲速度，在评估测试结果时必须考虑该因素( 注1 ). 此外，饱和混凝土中的超声脉冲速度对其相对质量的变化不太敏感。 注1: 饱和混凝土中的超声波脉冲速度可能高达5 % 高于干混凝土。 3. 5.4 超声波脉冲速度与测试对象的尺寸无关，前提是来自边界的反射波不会使直接发射脉冲的到达时间的确定变得复杂。测试对象的最小尺寸必须超过超声波振动的波长( 注2 ). 注2: 振动的波长等于超声波脉冲速度除以振动频率。 例如，频率为54 kHz，脉冲速度为3500m/s，波长为3500/54000=0.065m。 5.5 测量的准确性取决于操作员精确确定换能器之间距离的能力以及精确测量超声波脉冲传输时间的设备的能力。接收的信号强度和测量的传输时间受到传感器与混凝土表面耦合的影响。必须向传感器施加足够的偶联剂和压力，以确保稳定的传输时间。接收信号的强度还受行进路径长度以及受试混凝土中裂缝或劣化的存在和程度的影响。 注3: 可以通过查看接收波形的形状和幅度来验证正确的耦合。 波形应具有衰减的正弦形状。该形状可以通过示波器或设备固有的数字化显示器的输出来查看。 5.6 该测试方法中的测量量是渡越时间，根据该渡越时间可根据换能器之间的距离计算“表观”超声脉冲速度。并非所有形式的劣化或损坏都会改变材料的超声波脉冲速度，但它们会影响超声波脉冲从发射器传播到接收器的实际路径。例如，载荷引起的裂纹将增加超声脉冲的真实路径长度，从而增加测量的超声脉冲传输时间。无法测量真实路径长度。由于计算中使用了从发射到接收换能器的距离，即使材料的实际超声脉冲速度没有改变，裂纹的存在也会导致“表观”脉冲速度的降低。 许多形式的开裂和劣化本质上是定向的。它们对渡越时间测量的影响将受到它们相对于脉冲行进路径的方向的影响。 5.7 使用该试验方法获得的结果不应被视为测量强度的手段，也不应被认为是确定现场混凝土弹性模量是否符合设计假设的充分试验。试验方法中的纵向共振法 第215页 建议用于确定现场混凝土试样的动态弹性模量，因为不必知道泊松比。 注4: 如果情况允许，可通过测定多个混凝土试样的超声脉冲速度和抗压强度（或弹性模量）来建立速度强度（或速度模量）关系。 该关系可作为通过对混凝土进行进一步脉冲速度试验来估计强度（或弹性模量）的基础。参考ACI 228.1R 4. 为发展和使用这种关系的程序提供指导。 5.8 该程序适用于现场和实验室测试，无论样本的大小或形状在可用脉冲产生源的限制范围内。 注5: 目前可用的测试设备将路径长度限制为最小约50mm，最大约15m，这部分取决于生成信号的频率和强度。路径长度的上限部分取决于表面条件，部分取决于正在调查的内部混凝土的特性。接收传感器处的前置放大器可用于增加可测试的最大路径长度。 最大路径长度通过使用相对较低共振频率（20至30 kHz）的换能器来获得，以最小化混凝土中信号的衰减。（换能器组件的共振频率决定混凝土中的振动频率。）对于信号损耗不是主要因素的较短路径长度，最好使用50kHz或更高的共振频率，以实现更准确的传输时间测量，从而提高灵敏度。 5.9 由于钢中的超声波脉冲速度是混凝土中的两倍，因此在钢筋附近测得的超声波脉冲速率将高于相同成分的素混凝土。如果可能，避免在平行于脉冲传播方向的钢附近进行测量。

1.1 This test method covers the determination of the propagation velocity of longitudinal ultrasonic stress wave pulses through concrete. This test method does not apply to the propagation of other types of stress waves through concrete. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 The ultrasonic pulse velocity, V , of longitudinal ultrasonic stress waves in a concrete mass is related to its elastic properties and density according to the following relationship: where: E = dynamic modulus of elasticity, μ = dynamic Poisson's ratio, and ρ = density. 5.2 This test method is applicable to assess the uniformity and relative quality of concrete, to indicate the presence of voids and cracks, and to evaluate the effectiveness of crack repairs. It is also applicable to indicate changes in the properties of concrete, and in the survey of structures, to estimate the severity of deterioration or cracking. If used to monitor changes in condition over time, test locations are to be marked on the structure to ensure that tests are repeated at the same positions. 5.3 The degree of saturation of the concrete affects the ultrasonic pulse velocity, and this factor must be considered when evaluating test results ( Note 1 ). In addition, the ultrasonic pulse velocity in saturated concrete is less sensitive to changes in its relative quality. Note 1: The ultrasonic pulse velocity in saturated concrete may be up to 5 % higher than in dry concrete. 3 5.4 The ultrasonic pulse velocity is independent of the dimensions of the test object provided reflected waves from boundaries do not complicate the determination of the arrival time of the directly transmitted pulse. The least dimension of the test object must exceed the wavelength of the ultrasonic vibrations ( Note 2 ). Note 2: The wavelength of the vibrations equals the ultrasonic pulse velocity divided by the frequency of vibrations. For example, for a frequency of 54 kHz and a pulse velocity of 3500 m/s, the wavelength is 3500/54000 = 0.065 m. 5.5 The accuracy of the measurement depends upon the ability of the operator to determine precisely the distance between the transducers and of the equipment to measure precisely the ultrasonic pulse transit time. The received signal strength and measured transit time are affected by the coupling of the transducers to the concrete surfaces. Sufficient coupling agent and pressure must be applied to the transducers to ensure stable transit times. The strength of the received signal is also affected by the travel path length and by the presence and degree of cracking or deterioration in the concrete tested. Note 3: Proper coupling can be verified by viewing the shape and magnitude of the received waveform. The waveform should have a decaying sinusoidal shape. The shape can be viewed by means of outputs to an oscilloscope or digitized display inherent in the device. 5.6 The measured quantity in this test method is transit time, from which an “apparent” ultrasonic pulse velocity is calculated based on the distance between the transducers. Not all forms of deterioration or damage actually change the ultrasonic pulse velocity of the material, but they affect the actual path for the ultrasonic pulse to travel from transmitter to receiver. For example, load-induced cracking will increase the true path length of the ultrasonic pulse and thus increase the measured ultrasonic pulse transit time. The true path length cannot be measured. Because the distance from transmitting to receiving transducer is used in the calculation, the presence of the cracking results in a decrease in the “apparent” pulse velocity even though the actual ultrasonic pulse velocity of the material has not changed. Many forms of cracking and deterioration are directional in nature. Their influence on transit time measurements will be affected by their orientation relative to the pulse travel path. 5.7 The results obtained by the use of this test method are not to be considered as a means of measuring strength nor as an adequate test for establishing compliance of the modulus of elasticity of field concrete with that assumed in the design. The longitudinal resonance method in Test Method C215 is recommended for determining the dynamic modulus of elasticity of test specimens obtained from field concrete because Poisson's ratio does not have to be known. Note 4: If circumstances warrant, a velocity-strength (or velocity-modulus) relationship may be established by the determination of ultrasonic pulse velocity and compressive strength (or modulus of elasticity) on a number of specimens of a concrete. This relationship may serve as a basis for the estimation of strength (or modulus of elasticity) by further pulse-velocity tests on that concrete. Refer to ACI 228.1R 4 for guidance on the procedures for developing and using such a relationship. 5.8 The procedure is applicable in both field and laboratory testing regardless of size or shape of the specimen within the limitations of available pulse-generating sources. Note 5: Presently available test equipment limits path lengths to approximately 50-mm minimum and 15-m maximum, depending, in part, upon the frequency and intensity of the generated signal. The upper limit of the path length depends partly on surface conditions and partly on the characteristics of the interior concrete under investigation. A preamplifier at the receiving transducer may be used to increase the maximum path length that can be tested. The maximum path length is obtained by using transducers of relatively low resonant frequencies (20 to 30 kHz) to minimize the attenuation of the signal in the concrete. (The resonant frequency of the transducer assembly determines the frequency of vibration in the concrete.) For the shorter path lengths where loss of signal is not the governing factor, it is preferable to use resonant frequencies of 50 kHz or higher to achieve more accurate transit-time measurements and hence greater sensitivity. 5.9 Because the ultrasonic pulse velocity in steel is up to double that in concrete, the ultrasonic pulse velocity measured in the vicinity of the reinforcing steel will be higher than in plain concrete of the same composition. If possible, avoid measurements close to steel parallel to the direction of pulse propagation.