1、Standard Method of Test for Nonlinear Impact Resonance Acoustic Spectroscopy (NIRAS) for Concrete Specimens with Damage from the AlkaliSilica Reaction (ASR) AASHTO Designation: T 379-181Technical Section: 3c, Hardened Concrete Release: Group 1 (April) American Association of State Highway and Transp
2、ortation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T 379-1 AASHTO Standard Method of Test for Nonlinear Impact Resonance Acoustic Spectroscopy (NIRAS) for Concrete Specimens with Damage from the AlkaliSilica Reaction (ASR) AASHTO Designation: T 379-181Technical
3、Section: 3c, Hardened Concrete Release: Group 1 (April) 1. SCOPE 1.1. This test method covers determination of material nonlinearity in concrete laboratory specimens prepared in a manner and subjected to conditions of accelerated alkali-reactivity of aggregate. It is assumed that the nonlinearity du
4、e to elastic hysteresis is a dominant mechanism for the material nonlinearity in concrete specimens with alkalisilica reaction (ASR) damage and that this nonlinearity is directly proportional to the ASR damage occurring in the specimens. This method may not be necessarily applicable to other forms o
5、f damage. 1.2. The values stated in SI units are to be regarded separately as standard. The values in inch-pound units are shown in parentheses and are for informational purposes only. 1.3. This standard does not purport to address all of the safety problems associated with its use. It is the respon
6、sibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. ASTM Standard: C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Sili
7、ca Reaction 3. SUMMARY OF TEST METHOD 3.1. A prismatic concrete sample, prepared according to specifications for mix composition and geometry in ASTM C1293, is excited in the fundamental transverse mode of vibration by a low-amplitude impact at the center of the specimen. The vibration at one end of
8、 the sample is measured using an accelerometer and recorded using an oscilloscope. A series of at least 10 impacts of varying force are made to the specimen and the responses, the time-domain signals, are recorded. Signal processing is performed to measure the frequency and amplitude of the fundamen
9、tal resonance peaks from the frequency spectra of the recorded time-domain signals. The normalized frequency shift is plotted against the signal amplitude where the slope of this plot is the nonlinearity parameter, , that is used to classify material nonlinearity. 2018 by the American Association of
10、 State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-3c T 379-2 AASHTO 3.2. An initial test is performed just after demolding at 23.5 0.5 h and prior to exposure in the test environment specified in ASTM C1293, with subsequent tests made a
11、fter periods of exposure to the acceleratory test environment. Note 1The frequency of subsequent testing will depend upon the anticipated relative reactivity of the aggregate. That is, concrete containing less reactive aggregate or concrete containing supplementary cementitious materials at dosage r
12、ates expected to suppress ASR may be tested at less frequent intervals, such as every 2 to 3 months. For aggregates of unknown reactivity, tests should be initially performed every 2 weeks, and the interval can be increased after 2 months. Note 2After demolding, the measured nonlinearity parameter m
13、ay be higher than will be typical for a sample; often, within 4 weeks (28 days), the measured nonlinearity will decrease to a more stable value. 4. SIGNIFICANCE AND USE 4.1. This test method is applicable to concrete prisms where damage by ASR due to reactive aggregate and aggregate/binder combinati
14、ons is a concern. 4.2. This test method is intended to provide the user with a procedure to assess the potential for a fine or coarse aggregate used in concrete to experience ASR damage, under exposure conditions outlined in ASTM C1293. 5. APPARATUS 5.1. The apparatus for inducing alkalisilica react
15、ion shall conform to ASTM C1293. 5.2. AccelerometerAn accelerometer capable of measuring frequencies up to 10 kHz with less than 5 percent error, weighing less than 3 g (0.11 oz). 5.3. OscilloscopeAn oscilloscope capable of a sampling rate of 250 kHz or higher with a record length of 0.4 s. 5.4. Imp
16、act HammerA lightweight hammer with a maximum mass (weight) of 142 g (5 oz) is recommended. 5.5. Instant AdhesiveA surface-insensitive instant adhesive is recommended for attachment of the accelerometer. A fast curing gel-type adhesive (e.g., cyanoacrylate) can be applied more consistently than adhe
17、sives with higher viscosity. 5.6. Support MatSpecimens shall be placed on a thick and compliant, commercially available vibration damping/isolation support mat for testing. 6. SIGNAL ACQUISITION 6.1. The sampling rate for the oscilloscope shall be set to 500 kHz. 6.2. The signal acquisition window (
18、signal record length) shall be set to 0.4 s. 6.3. Signal acquisition shall be triggered by an electrical signal from the accelerometer. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-3c T 379-3 AASH
19、TO 7. PROCEDURE 7.1. For each aggregate type, three or more specimens shall be tested and the nonlinearity parameter is averaged over the specimens. 7.2. Before testing, allow specimens to cool to room temperature in a moist environment for 16 4 h, as detailed in ASTM C1293. 7.3. Place specimen on a
20、 support mat as shown in the schematic in Figure 1. Expansion measurements for the specimen, as described in ASTM C1293, can also be done before this test for comparison with nonlinearity measurements. Figure 1 Schematic of Test Setup 7.4. Generously apply adhesive to the accelerometer mount and att
21、ach the accelerometer to the end of the specimen along the centerline, as shown in Figure 2. If the attachment surface is severely deteriorated, it is recommended to polish the surface with sandpaper as needed to achieve a level surface for the accelerometer. OscilloscopeSupport MatPowerSupplyAccele
22、rometerImpact ForceConcrete Specimen 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-3c T 379-4 AASHTO Figure 2Example of Proper Accelerometer Placement on Sample with Adequate Surface Quality 7.5. S
23、et the oscilloscope to wait for the trigger by an acceleration signal to start data acquisition. 7.6. Lightly strike the specimen at its center with the impact hammer. 7.7. Save the recorded data. 7.8. Reset the oscilloscope to wait for the trigger to start the next data acquisition. 7.9. Repeat the
24、 procedures in Sections 7.6 through 7.8 at least ten times, each time with a higher strength impact (Notes 3 and 4), while monitoring the acceleration signal displayed on the oscilloscope screen (Note 5). Note 3The objective is to obtain measurements with at least ten different impact strengths; the
25、refore, while it may be convenient to increase the impact strength with each subsequent strike, it is not necessary, as long as the strikes are made at different strengths. Note 4If the impact strength is too high, the relation between frequency change and amplitude will not be linear. It is recomme
26、nded to keep the impact excitation as low as possible. Note 5The amplitude of the acceleration signal is linearly proportional to the impact strength. 7.10. Transform data to the frequency domain using a fast Fourier transform (FFT) algorithm and record frequency and amplitude of the fundamental res
27、onance peak for each impact. 7.11. Assuming the frequency at the lowest strength impact is the linear resonance frequency (Note 6), f0, take the difference between the resonance frequency of higher-strength impacts and the linear resonance frequency, f0 f, and normalize by the linear resonance frequ
28、ency. A typical set of resonance curves is shown in Figure 3. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-3c T 379-5 AASHTO Figure 3Example of Typical Resonance Curves Illustrating Amplitude Depe
29、ndent Resonance Frequency Shift Note 6To ensure that f0is the linear resonance frequency, resonance frequencies measured at a few very light impacts are compared to see if they are within a 1 to 2 percent range. 7.12. Plot the normalized frequency change, (f0 f)/f0, against the resonance peak amplit
30、ude as shown in Figure 4. 7.13. Perform a linear fit to the plotted data and take the slope as the nonlinearity parameter as shown in Figure 4. Figure 4Illustration of Resonance Frequency Shift as a Function of Amplitude 7.14. The recorded nonlinearity can be used as a parameter related to the level
31、 of ASR damage in the specimen at the test date. 7.15. Repeat the procedures in Sections 7.3 through 7.14 for all specimens. Frequency (kHz)Amplitude(V)9876543210 103f0 ff02.2 2.3 2.4 2.5 2.6 2.7 2.81Amplitude (V)(f0f) /f00.030.0250.020.0150.010.00500.0050 0.002 0.004 0.006 0.008 0.01Linear Fit = 3.
32、783 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-3c T 379-6 AASHTO 7.16. Return specimens to the storage environment, inverting the upper end as compared with the previous storage period, as descr
33、ibed in ASTM C1293. 8. INTERPRETATION OF RESULTS 8.1. After the initial 28 days of aging (see Note 2), preliminary results (Note 7) suggest that the aggregate under assessment may be considered alkali-reactive if the nonlinearity parameter of its concrete prism specimen measures 0.2 or more during t
34、he 12-month test period (Note 8). Nonlinearity parameters between 0.05 and 0.2 may suggest some potential for ASR and the aggregate should be further evaluated (Note 7). (Note that additional testing is needed to (1) validate this limit for a broad range of aggregate mineralogy and reactivity and (2
35、) establish limit and test duration for concretes containing supplementary cementitious materials and/or lithium-containing admixtures.) Note 7These values are based on the observations made during testing performed at Georgia Tech and are subject to change. Note 8For some concretes, the nonlinearit
36、y parameter may reach a peak and then subsequently decrease. This is believed to be due to crack widening and crack filling with gel, which affects the nonlinearity of the specimen. This decrease should not be taken as an indication of decreasing reactivity. 9. REPORT 9.1. Record the nonlinearity pa
37、rameter for each specimen. 9.2. Record the average nonlinearity of three replicate specimens. 9.3. Record all data as required by ASTM C1293. 10. PRECISION AND BIAS 10.1. The precision of this test method has not yet been established. 10.2. BiasSince there is no accepted reference material for deter
38、mining the bias of this test method, no statement is being made. 11. KEYWORDS 11.1. Concrete; ASR; alkalisilica reaction; NIRAS; nonlinear acoustics. 1Formerly AASHTO Provisional Standard TP 109. First published as a full standard in 2018. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
