ASTM C215-19

Standard Test Method for Fundamental Transverse, Longitudinal, and<brk/> Torsional Resonant Frequencies of Concrete Specimens

SIGNIFICANCE AND USE
5.1 This test method is intended primarily for detecting changes in the dynamic modulus of elasticity of laboratory or field test specimens that are undergoing exposure to weathering or other types of potentially deteriorating influences. The test method may also be used to monitor the development of dynamic elastic modulus with increasing maturity of test specimens.  
5.2 The value of the dynamic modulus of elasticity obtained by this test method will, in general, be greater than the static modulus of elasticity obtained by using Test Method C469/C469M. The difference depends, in part, on the strength level of the concrete.  
5.3 The conditions of manufacture, the moisture content, and other characteristics of the test specimens (see section on Test Specimens) influence the results obtained.  
5.4 Different computed values for the dynamic modulus of elasticity may result from different modes of vibration and from specimens of different sizes and shapes of the same concrete. Therefore, it is not advisable to compare results from different modes of vibration or from specimens of different sizes or shapes.
SCOPE
1.1 This test method covers measurement of the fundamental transverse, longitudinal, and torsional resonant frequencies of concrete prisms and cylinders for the purpose of calculating dynamic Young's modulus of elasticity, the dynamic modulus of rigidity (sometimes designated as “the modulus of elasticity in shear”), and dynamic Poisson's ratio.  
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.

General Information

• Status: Published
• Publication Date: 30-Nov-2019
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.64 - Nondestructive and In-Place Testing

Relations

• Refers: ASTM C31/C31M-24a - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Apr-2024
• Refers: ASTM C670-24a - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Feb-2024
• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM C670-24 - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C31/C31M-24 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jan-2024
• Refers: ASTM C125-19a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 15-Dec-2019
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM C125-19 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2019
• Refers: ASTM C125-18b - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Oct-2018
• Refers: ASTM C125-18a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jul-2018
• Refers: ASTM C42/C42M-18 - Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
• Effective Date: 15-Mar-2018
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM C31/C31M-18 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jan-2018
• Refers: ASTM C125-18 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2018

Overview

ASTM C215-19 is the established standard test method for determining the fundamental transverse, longitudinal, and torsional resonant frequencies of concrete specimens, including prisms and cylinders. This method allows for calculation of the dynamic Young’s modulus of elasticity, the dynamic modulus of rigidity (also known as the modulus of elasticity in shear), and the dynamic Poisson’s ratio. The test is non-destructive, preserving the integrity of specimens for ongoing evaluation.

This standard is primarily employed to monitor changes in the dynamic elastic properties of concrete due to weathering, maturity, or potential degradation. By precisely measuring resonant frequencies, ASTM C215-19 supports the quality assessment and structural evaluation of concrete materials in both laboratory and field environments.

Key Topics

• Scope of Application: Addresses measurement techniques for fundamental resonant frequencies to compute key dynamic moduli and Poisson’s ratio in concrete specimens.
• Test Methodology:
  • Forced Resonance Method: Employs an electro-mechanical device to induce and monitor vibrations, identifying resonant frequencies via a pickup unit and display.
  • Impact Resonance Method: Utilizes an impactor and accelerometer to excite and capture vibrational responses, with frequency analysis conducted by digital tools.
• Specimen Considerations:
  • Shape and size of the specimens affect results; only cylindrical and rectangular prismatic specimens are suitable.
  • Environmental conditions and specimen properties, such as manufacturing process and moisture content, can influence dynamic modulus outcomes.
• Precision and Reliability: Provides guidance on precision for single-operator and multilaboratory measurements, with recognized best practices and guidance for reliable data collection.

Applications

ASTM C215-19 is integral to several aspects of concrete quality control and structural assessment:

• Durability Monitoring: Detects changes in dynamic modulus to assess deterioration from cyclic freeze-thaw, chemical attack, or aging.
• Maturity Evaluation: Tracks elastic property development in curing or maturing concrete to predict in-service behavior.
• Research and Development: Used in materials laboratories to characterize the dynamic elastic properties of new or modified concrete mixes.
• Compliance and Acceptance: Supports validation of material properties for regulatory or project specifications in infrastructure, bridges, and buildings.
• Nondestructive Testing: Enables repeated evaluation of specimens without causing damage, essential for longitudinal studies or quality assurance programs.

Related Standards

ASTM C215-19 is used in conjunction with several other ASTM standards emphasizing concrete specimen preparation, testing, and terminology:

• ASTM C31/C31M – Practice for Making and Curing Concrete Test Specimens in the Field
• ASTM C42/C42M – Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
• ASTM C125 – Terminology Relating to Concrete and Concrete Aggregates
• ASTM C192/C192M – Practice for Making and Curing Concrete Test Specimens in the Laboratory
• ASTM C469/C469M – Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression
• ASTM C670 – Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• ASTM E1316 – Terminology for Nondestructive Examinations

ASTM C215-19 facilitates consistent, accurate measurement of key concrete properties, providing vital information for durability analysis, structural integrity assessment, and ongoing quality assurance in the concrete industry. By adhering to this standard, professionals can ensure reliable monitoring and enhanced longevity of concrete structures.

Standards Content (Sample)

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.
Designation: C215 − 19
Standard Test Method for
Fundamental Transverse, Longitudinal, and
Torsional Resonant Frequencies of Concrete Specimens
This standard is issued under the fixed designation C215; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* C192/C192M Practice for Making and Curing Concrete Test
Specimens in the Laboratory
1.1 This test method covers measurement of the fundamen-
C469/C469M Test Method for Static Modulus of Elasticity
tal transverse, longitudinal, and torsional resonant frequencies
and Poisson’s Ratio of Concrete in Compression
of concrete prisms and cylinders for the purpose of calculating
C670 Practice for Preparing Precision and Bias Statements
dynamic Young’s modulus of elasticity, the dynamic modulus
for Test Methods for Construction Materials
of rigidity (sometimes designated as “the modulus of elasticity
E1316 Terminology for Nondestructive Examinations
in shear”), and dynamic Poisson’s ratio.
1.2 The values stated in SI units are to be regarded as 3. Terminology
standard. No other units of measurement are included in this
3.1 Definitions—Refer toTerminology C125 and the section
standard.
related to ultrasonic examination in Terminology E1316 for
1.3 This standard does not purport to address all of the definitions of terms used in this test method.
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- 4.1 The fundamental resonant frequencies are determined
mine the applicability of regulatory limitations prior to use. using one of two alternative procedures: (1) the forced reso-
1.4 This international standard was developed in accor- nance method or (2) the impact resonance method. Regardless
dance with internationally recognized principles on standard- of which testing procedure is selected, the same procedure is to
ization established in the Decision on Principles for the be used for all specimens of an associated series.
Development of International Standards, Guides and Recom-
4.2 Intheforcedresonancemethod,asupportedspecimenis
mendations issued by the World Trade Organization Technical
forced to vibrate by an electro-mechanical driving unit. The
Barriers to Trade (TBT) Committee.
specimen response is monitored by a lightweight pickup unit
on the specimen. The driving frequency is varied until the
2. Referenced Documents
measured specimen response reaches maximum amplitude.
2.1 ASTM Standards: The value of the frequency causing maximum response is a
C31/C31M Practice for Making and Curing Concrete Test resonant frequency of the specimen. The fundamental frequen-
Specimens in the Field cies for the three different modes of vibration are obtained by
C42/C42M Test Method for Obtaining and Testing Drilled proper location of the driver and the pickup unit.
Cores and Sawed Beams of Concrete
4.3 In the impact resonance method, a supported specimen
C125 Terminology Relating to Concrete and Concrete Ag-
is struck with a small impactor and the specimen response is
gregates
measured by a lightweight accelerometer on the specimen.The
output of the accelerometer is recorded. The fundamental
frequency of vibration is determined by computing the ampli-
This test method is under the jurisdiction of ASTM Committee C09 on
tude spectrum of the recorded waveform or counting zero
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
crossings in the recorded waveform.The fundamental frequen-
C09.64 on Nondestructive and In-Place Testing.
cies for the three different modes of vibration are obtained by
Current edition approved Dec. 1, 2019. Published January 2020. Originally
approved in 1947. Last previous edition approved in 2014 as C215 – 14. DOI: proper location of the impact point and the accelerometer.
10.1520/C0215-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Significance and Use
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.1 This test method is intended primarily for detecting
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. changes in the dynamic modulus of elasticity of laboratory or
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C215 − 19
NOTE 1—The typical frequency range for this test method is 100 to
fieldtestspecimensthatareundergoingexposuretoweathering
12 000 Hz. It is recommended that the calibration of the variable
or other types of potentially deteriorating influences. The test
frequency audio oscillator be checked at least annually against suitably
method may also be used to monitor the development of
calibrated electronic equipment.
dynamic elastic modulus with increasing maturity of test
6.1.2 Pickup Circuit—The pickup circuit shall consist of a
specimens.
pickup unit, an amplifier, and an indicator. The pickup unit
5.2 The value of the dynamic modulus of elasticity obtained
shall generate a voltage proportional to the displacement,
by this test method will, in general, be greater than the static
velocity,oraccelerationofthetestspecimen,andshallbesmall
modulus of elasticity obtained by using Test Method C469/
in mass so as to not affect the vibrational frequency of the test
C469M. The difference depends, in part, on the strength level
specimen by more than 1 %.The pickup unit shall be free from
of the concrete.
spurious resonances in the normal operating range (see Note
5.3 The conditions of manufacture, the moisture content, 1). The pickup circuitry shall have a controllable output of
sufficientmagnitudetoactuatetheindicator.Theindicatorshall
and other characteristics of the test specimens (see section on
Test Specimens) influence the results obtained. consist of a voltmeter or a milliammeter that shows the relative
amplitude of the signal from the pickup unit.
5.4 Different computed values for the dynamic modulus of
6.1.3 Connection to Display—The driver signal and the
elasticity may result from different modes of vibration and
pickup signal shall be connected to the horizontal and vertical
from specimens of different sizes and shapes of the same
sweeps, respectively, of a real-time graphic display such as an
concrete. Therefore, it is not advisable to compare results from
oscilloscope or a data acquisition system with monitor. The
different modes of vibration or from specimens of different
displayed pattern is used to confirm that the driver frequency at
sizes or shapes.
maximum signal amplitude is the resonant frequency of the
specimen.
6. Apparatus
NOTE 2—For routine testing of specimens whose fundamental fre-
6.1 Forced Resonance Apparatus (Fig. 1):
quency may be anticipated to be within known limits, a meter-type
6.1.1 Driving Circuit—The driving circuit shall consist of a
indicator may be sufficient for determining the fundamental resonant
variable frequency audio oscillator, an amplifier, and a driving
frequency. It is, however, strongly recommended that the graphic display
unit. The oscillator shall be calibrated to read within 62%of
be used. The graphic display will confirm that the driver frequency at
maximum amplitude of pickup response corresponds to the specimen’s
the true frequency over the range of use (see Note 1), and the
fundamental resonant frequency, and is necessary when testing specimens
manufacturer shall provide instructions for periodic verifica-
for which the fundamental frequency range is not known beforehand. See
tion of the calibration. The combined oscillator and amplifier
Note 6 for additional guidance on using the graphic display.
shall be capable of delivering sufficient power output to induce
6.1.4 Specimen Support—The support shall permit the
vibrations in the test specimen at frequencies other than the
specimen to vibrate freely (Note 3). The locations of the nodal
fundamentalandshallbeprovidedwithameansforcontrolling
points for the different modes of vibration are described in
the output. The driving unit for creating the vibration in the
Notes 6-8. The support system shall be dimensioned so that its
specimen shall be capable of handling the full power output of
resonant frequency falls outside the range of use (from 100 to
the oscillator and amplifier. The driving unit is used in contact
12 000 Hz).
withthetestspecimenorseparatedfromthespecimenbyanair
gap. The oscillator and amplifier shall be capable of producing
NOTE 3—This may be accomplished by placing the specimen on soft
rubber supports located near the nodal points or on a sponge rubber pad.
power that does not vary more than 620 % over the frequency
range and, in combination with the driving unit, shall be free
6.2 Impact Resonance Apparatus (Fig. 2):
from spurious resonances that will be indicated in the output.
6.2.1 Impactor—The impactor shall be made of metal or
rigid plastic and shall produce an impact duration that is
sufficiently short to excite the highest resonant frequency to be
measured. The manufacturer shall indicate the maximum
resonant frequency that can be excited when the impactor
strikes a concrete specimen with surfaces formed by a metal or
plastic mold.
NOTE 4—A 19-mm diameter solid steel ball mounted on a thin rod to
FIG. 1 Schematic of Apparatus for Forced Resonance Test FIG. 2 Schematic of Apparatus for Impact Resonance Test
C215 − 19
produce a hammer is capable of exciting resonant frequencies up to about
8.2 Transverse Frequency:
10 kHz when impacting a smooth concrete surface.A110 g steel ball peen
8.2.1 Support the specimen so that it is able to vibrate freely
hammer may act similarly. Larger steel balls will reduce the maximum
in the transverse mode (Note 6). Position the specimen and
resonant frequencies that can be excited. As an approximate guide, the
driver so that the driving force is perpendicular to the surface
maximum frequency that can be excited by the impact is the inverse of the
ofthespecimen.Locatethedriverattheapproximatemiddleof
impact duration.
the specimen as shown in Fig. 3a. Place the pickup unit on the
6.2.2 Sensor—The sensor shall be a piezoelectric acceler-
specimen so that the direction of pickup sensitivity coincides
ometer with a mass less than 30 g and having an operating
with the vibration direction. Position the pickup near one end
frequency range from 100 to 15 000 Hz. The resonant fre-
of the specimen.
quency of the accelerometer shall be at least two times the
8.2.2 Force the test specimen to vibrate at varying frequen-
maximum operating frequency.
cies. At the same time, observe the indication of the amplified
6.2.3 Frequency Analyzer—Determine the frequency of the
outputofthepickup.Ifanoscilloscopeorothergraphicdisplay
specimen vibration by using either a digital waveform analyzer
is used, connect the driver signal to the horizontal sweep of the
or a frequency counter to analyze the signal measured by the
display and connect the pickup signal to the vertical sweep.
sensor. The waveform analyzer shall have a sampling rate of at
Record the fundamental transverse frequency of the specimen,
least 2.5 times the maximum expected frequency to be mea-
which is the frequency at which the indicator shows the
sured and shall record at least 2048 points of the waveform.
maximumreadingandobservationofthegraphicdisplayorthe
The frequency counter shall have an accuracy of 61 % over
nodal points indicates fundamental transverse vibration (Note
the range of use.
6). Adjust the amplifiers in the driving and pickup circuits to
NOTE 5—The maximum frequency that can be measured using a digital
provide a satisfactory indication. To avoid distortion, maintain
waveform analyzer and the fast Fourier transform method is one-half the
the driving force as low as is feasible for good response at
sampling frequency; for example, a sampling frequency of 30 kHz will
resonance.
allowmeasuringresonantfrequenciesupto15kHz.Asamplingfrequency
of 2.5 times the expected frequency is called for in case the actual
NOTE 6—For fundamental transverse vibration, the nodal points are
frequency exceeds the expected maximum frequency to be measured. The
located 0.224 of the length of the specimen from each end (approximately
frequency resolution in the amplitude spectrum is the sampling frequency
the quarter points). Vibrations are a maximum at the ends, approximately
divided by the number of points in the waveform.
three fifths of the maximum at the center, and zero at the nodal points;
6.2.4 Specimen Support—Support shall be provided as
therefore, movement of the pickup along the length of the specimen will
inform the operator whether the specimen is vibrating in its fundamental
specified in 6.1.4 for the forced resonance method.
transverse mode. An oscilloscope or other graphic display may also be
7. Test Specimens used to determine whether the specimen is vibrating in its fundamental
transversemode.Ifthepickupislocatedattheendofthespecimen,which
7.1 Preparation—Make the cylindrical or rectangular pris-
is vibrating in its fundamental transverse mode, the display will show an
matic test specimens in accordance with Practice C192/
inclined elliptical pattern. If the pickup is placed at a node, the display
C192M,PracticeC31/C31M,TestMethodC42/C42M,orother shows a horizontal line. If the pickup is placed at the center of the
specimen, the display will be an elliptical pattern but inclined in the
specified procedures. Specimen shapes other than cylinders
opposite direction to when the pickup was placed at the end of the
and rectangular prisms cannot be used to determine dynamic
specimen.Thedisplaycanalsobeusedtoverifythatthedrivingfrequency
elastic properties in accordance with this test method.
is the fundamental resonant frequency. Resonance can occur if the driving
frequency is a fraction of the fundamental frequency. In this case,
7.2 Measurement of Mass and Dimensions—Determine the
however, the displayed pattern will not be an ellipse.
mass and average length of the specimens within 60.5 %.
8.3 Longitudinal Frequency:
Determine the average cross-sectional dimensions within
8.3.1 Support the specimen so that it is able to vibrate freely
61%.
in the longitudinal mode (Note 7). Position the specimen and
7.3 Limitations on Dimensional Ratio—Specimens having
driver so that the driving force is perpendicular to and
either small or large ratios of length to maximum transverse
approximately at the center of one end surface of the specimen.
direction are frequently difficult to excite in the fundamental
Place the pickup unit on the specimen so that the direction of
transverse mode of vibration. Best results are obtained when
pickupsensitivitycoincideswiththevibrationdirection,thatis,
this ratio is between 3 and 5. For application of the formulas in
the longitudinal axis of the specimen (see Fig. 3b).
this test method, the ratio must be at least 2. For measurement
8.3.2 Force the test specimen to vibrate at varying frequen-
of longitudinal resonant frequency, the specimen shall have a
cies. At the same time, observe the indication of the amplified
circular or square cross-section and the length shall be at least
output of the pickup. Record the fundamental longitudinal
two times the diameter for a cylinder or at least two times the
frequency of the specimen, which is the frequency at which the
side dimension for a prism.
indicator shows the maximum reading and observation of the
8. Determination of Resonant Frequencies—Forced graphic display or the nodal point indicates fundamental
Resonance Method
longitudinal vibration.
8.1 Different modes of vibration and the corresponding
NOTE 7—For the fundamental longitudinal mode, there is one node and
resonant frequencies are obtained by proper locations of the itislocatedatthecenterofthespecimen.Vibrationsareamaximumatthe
ends.
driver and the pickup units (see Note 6, Note 7, and Note 8).
The mode of vibration to be used depends on the requirements 8.4 Torsional Frequency:
of the specifier of the test or of other standards that refer to this 8.4.1 Support the specimen so that it is able to vibrate freely
test method. in the torsional mode (Note 8). Position the specimen and
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C215 − 14 C215 − 19
Standard Test Method for
Fundamental Transverse, Longitudinal, and
Torsional Resonant Frequencies of Concrete Specimens
This standard is issued under the fixed designation C215; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers measurement of the fundamental transverse, longitudinal, and torsional resonant frequencies of
concrete prisms and cylinders for the purpose of calculating dynamic Young’s modulus of elasticity, the dynamic modulus of
rigidity (sometimes designated as “the modulus of elasticity in shear”), and dynamic Poisson’s ratio.
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 safety, health, and healthenvironmental 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.
2. Referenced Documents
2.1 ASTM Standards:
C31/C31M Practice for Making and Curing Concrete Test Specimens in the Field
C42/C42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
C125 Terminology Relating to Concrete and Concrete Aggregates
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C469/C469M Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
E1316 Terminology for Nondestructive Examinations
3. Terminology
3.1 Definitions—Refer to Terminology C125 and the section related to ultrasonic examination in Terminology E1316 for
definitions of terms used in this test method.
4. Summary of Test Method
4.1 The fundamental resonant frequencies are determined using one of two alternative procedures: (1) the forced resonance
method or (2) the impact resonance method. Regardless of which testing procedure is selected, the same procedure is to be used
for all specimens of an associated series.
4.2 In the forced resonance method, a supported specimen is forced to vibrate by an electro-mechanical driving unit. The
specimen response is monitored by a lightweight pickup unit on the specimen. The driving frequency is varied until the measured
specimen response reaches a maximum amplitude. The value of the frequency causing maximum response is thea resonant
frequency of the specimen. The fundamental frequencies for the three different modes of vibration are obtained by proper location
of the driver and the pickup unit.
This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.64 on
Nondestructive and In-Place Testing.
Current edition approved Dec. 15, 2014Dec. 1, 2019. Published January 2015January 2020. Originally approved in 1947. Last previous edition approved in 20082014 as
C215 – 08.C215 – 14. DOI: 10.1520/C0215-14.10.1520/C0215-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C215 − 19
4.3 In the impact resonance method, a supported specimen is struck with a small impactor and the specimen response is
measured by a lightweight accelerometer on the specimen. The output of the accelerometer is recorded. The fundamental frequency
of vibration is determined by using digital signal processing methods computing the amplitude spectrum of the recorded waveform
or counting zero crossings in the recorded waveform. The fundamental frequencies for the three different modes of vibration are
obtained by proper location of the impact point and the accelerometer.
5. Significance and Use
5.1 This test method is intended primarily for detecting changes in the dynamic modulus of elasticity of laboratory or field test
specimens that are undergoing exposure to weathering or other types of potentially deteriorating influences. The test method may
also be used to monitor the development of dynamic elastic modulus with increasing maturity of test specimens.
5.2 The value of the dynamic modulus of elasticity obtained by this test method will, in general, be greater than the static
modulus of elasticity obtained by using Test Method C469/C469M. The difference depends, in part, on the strength level of the
concrete.
5.3 The conditions of manufacture, the moisture content, and other characteristics of the test specimens (see section on Test
Specimens) influence the results obtained.
5.4 Different computed values for the dynamic modulus of elasticity may result from different modes of vibration and from
specimens of different sizes and shapes of the same concrete. Therefore, it is not advisable to compare results from different modes
of vibration or from specimens of different sizes or shapes.
6. Apparatus
6.1 Forced Resonance Apparatus (Fig. 1):
6.1.1 Driving Circuit—The driving circuit shall consist of a variable frequency audio oscillator, an amplifier, and a driving unit.
The oscillator shall be calibrated to read within 62 % of the true frequency over the range of use (about(see Note 1100 to 12 000
Hz). ), and the manufacturer shall provide instructions for periodic verification of the calibration. The combined oscillator and
amplifier shall be capable of delivering sufficient power output to induce vibrations in the test specimen at frequencies other than
the fundamental and shall be provided with a means for controlling the output. The driving unit for creating the vibration in the
specimen shall be capable of handling the full power output of the oscillator and amplifier. The driving unit is used in contact with
the test specimen or separated from the specimen by an air gap. The oscillator and amplifier shall be capable of producing a voltage
power that does not vary more than 620 % over the frequency range and, in combination with the driving unit, shall be free from
spurious resonances that will be indicated in the output.
NOTE 1—The typical frequency range for this test method is 100 to 12 000 Hz. It is recommended that the calibration of the variable frequency audio
oscillator be checked periodically against signals transmitted by the National Institute of Standards and Technology radio station WWV, or against suitable
electronic equipment such as a frequency counter, the calibration of which has been checked previously and found to be adequate.at least annually against
suitably calibrated electronic equipment.
6.1.2 Pickup Circuit—The pickup circuit shall consist of a pickup unit, an amplifier, and an indicator. The pickup unit shall
generate a voltage proportional to the displacement, velocity, or acceleration of the test specimen, and shall be small in mass so
as to not affect the vibrational frequency of the test specimen by more than 1 %. The pickup unit shall be free from spurious
resonances in the normal operating range (see Note 1). The pickup circuitry shall have a controllable output of sufficient magnitude
to actuate the indicator. The indicator shall consist of a voltmeter or a milliammeter that shows the relative amplitude of the signal
from the pickup unit.
FIG. 1 Schematic of Apparatus for Forced Resonance Test
C215 − 19
6.1.3 Pickup Circuit—Connection to Display—The pickup circuit shall consist of a pickup unit, an amplifier, and an indicator.
The pickup unit shall generate a voltage proportional to the displacement, velocity, or acceleration of the test specimen, and the
vibrating parts shall be small in mass so as to not affect the vibrational frequency of the test specimen by more than 1%. The pickup
unit shall be free from spurious resonances in the normal operating range of 100 to 12 000 Hz. Either a piezoelectric or magnetic
pickup unit meeting these requirements is acceptable. The amplifier shall have a controllable output of sufficient magnitude to
actuate the indicator. The indicator shall consist of a voltmeter or a milliammeter that shows the relative amplitude of the signal
from the pickup unit. The driver signal and the pickup signal shall be connected to the horizontal and vertical sweeps, respectively,
of a real-time graphic display such as an oscilloscope or a data acquisition system with monitor. The displayed pattern is used to
confirm that the driver frequency at maximum signal amplitude is the resonant frequency of the specimen.
NOTE 2—For routine testing of specimens whose fundamental frequency may be anticipated to be within known limits, a meter-type indicator is
satisfactory may be sufficient for determining the fundamental resonant frequency. It is, however, strongly recommended that the graphic display be used.
The graphic display will confirm that the specimen is vibrating at its driver frequency at maximum amplitude of pickup response corresponds to the
specimen’s fundamental resonant frequency, and is necessary when testing specimens for which the fundamental frequency range is not known
beforehand. See Note 6 for additional guidance on using the graphic display.
6.1.4 Specimen Support—The support shall permit the specimen to vibrate freely (Note 3). The locations of the nodal points for
the different modes of vibration are described in Notes 6-8. The support system shall be dimensioned so that its resonant frequency
falls outside the range of use (from 100 to 12 000 Hz).
NOTE 3—This may be accomplished by placing the specimen on soft rubber supports located near the nodal points or on a sponge rubber pad.
6.2 Impact Resonance Apparatus (Fig. 2):
6.2.1 Impactor—The impactor shall be made of metal or rigid plastic and shall produce an impact duration that is sufficiently
short to excite the highest resonant frequency to be measured. The manufacturer shall indicate the maximum resonant frequency
that can be excited when the impactor strikes a concrete specimen with surfaces formed by a metal or plastic mold.
NOTE 4—A 19-mm diameter solid steel ball mounted on a thin rod to produce a hammer is capable of exciting resonant frequencies up to about 10
kHz when impacting a smooth concrete surface. A 110 g steel ball peen hammer may act similarly. Larger steel balls will reduce the maximum resonant
frequencies that can be excited. As an approximate guide, the maximum frequency that can be excited by the impact is the inverse of the impact duration.
6.2.2 Sensor—The sensor shall be a piezoelectric accelerometer with a mass less than 30 g and having an operating frequency
range from 100 to 15 000 Hz. The resonant frequency of the accelerometer shall be at least two times the maximum operating
frequency.
6.2.3 Frequency Analyzer—Determine the frequency of the specimen vibration by using either a digital waveform analyzer or
a frequency counter to analyze the signal measured by the sensor. The waveform analyzer shall have a sampling rate of at least
2.5 times the maximum expected frequency to be measured and shall record at least 2048 points of the waveform. The frequency
counter shall have an accuracy of 61 % over the range of use.
NOTE 5—The maximum frequency that can be measured using a digital waveform analyzer and the fast Fourier transform method is one-half the
sampling frequency; for example, a sampling frequency of 30 kHz will allow measuring resonant frequencies up to 15 kHz. A sampling frequency of
2.5 times the expected frequency is called for in case the actual frequency exceeds the expected maximum frequency to be measured. The frequency
resolution in the amplitude spectrum is the sampling frequency divided by the number of points in the waveform.
6.2.4 Specimen Support—Support shall be provided as specified in 6.1.36.1.4 for the forced resonance method.
7. Test Specimens
7.1 Preparation—Make the cylindrical or rectangular prismatic test specimens in accordance with Practice C192/C192M,
Practice C31/C31M, Test Method C42/C42M, or other specified procedures. Specimen shapes other than cylinders and rectangular
prisms cannot be used to determine dynamic elastic properties in accordance with this test method.
7.2 Measurement of Mass and Dimensions—Determine the mass and average length of the specimens within 60.5 %.
Determine the average cross-sectional dimensions within 61 %.
7.3 Limitations on Dimensional Ratio—Specimens having either small or large ratios of length to maximum transverse direction
are frequently difficult to excite in the fundamental transverse mode of vibration. Best results are obtained when this ratio is
FIG. 2 Schematic of Apparatus for Impact Resonance Test
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between 3 and 5. For application of the formulas in this test method, the ratio must be at least 2. For measurement of longitudinal
resonant frequency, the specimen shall have a circular or square cross-section and the length shall be at least two times the diameter
for a cylinder or at least two times the side dimension for a prism.
8. Determination of Resonant Frequencies—Forced Resonance Method
8.1 Different modes of vibration and the corresponding resonant frequencies are obtained by proper locations of the driver and
the pickup units (see Note 6, Note 7, and Note 8). The mode of vibration to be used depends on the requirements of the specifier
of the test or of other standards that refer to this test method.
8.2 Transverse Frequency:
8.2.1 Support the specimen so that it is able to vibrate freely in the transverse mode (Note 6). Position the specimen and driver
so that the driving force is perpendicular to the surface of the specimen. Locate the driver at the approximate middle of the
specimen as shown in Fig. 3a. Place the pickup unit on the specimen so that the direction of pickup sensitivity coincides with the
vibration direction. Position the pickup near one end of the specimen.
8.2.2 Force the test specimen to vibrate at varying frequencies. At the same time, observe the indication of the amplified output
of the pickup. If an oscilloscope or other graphic display is used, connect the driver signal to the horizontal sweep of the display
and connect the pickup signal to the vertical sweep. Record the fundamental transverse frequency of the specimen, which is the
frequency at which the indicator shows the maximum reading and observation of the graphic display or the nodal points indicates
fundamental transverse vibration (Note 6). Adjust the amplifiers in the driving and pickup circuits to provide a satisfactory
indication. To avoid distortion, maintain the driving force as low as is feasible for good response at resonance.
NOTE 6—For fundamental transverse vibration, the nodal points are located 0.224 of the length of the specimen from each end (approximately the
quarter points). Vibrations are a maximum at the ends, approximately three fifths of the maximum at the center, and zero at the nodal points; therefore,
movement of the pickup along the length of the specimen will inform the operator whether the specimen is vibrating in its fundamental transverse mode.
An oscilloscope or other graphic display may also be used to determine whether the specimen is vibrating in its fundamental transverse mode. If the
pickup is located at the end of the specimen, which is vibrating in its fundamental transverse mode, the display will show an inclined elliptical pattern.
If the pickup is placed at a node, the display shows a horizontal line. If the pickup is placed at the center of the specimen, the display will be an elliptical
pattern but inclined in the opposite direction to when the pickup was placed at the end of the specimen. The display can also be used to verify that the
driving frequency is the fundamental resonant frequency. Resonance can occur if the driving frequency is a fraction of the fundamental frequency. In this
case, however, the displayed pattern will not be an ellipse.
FIG. 3 Locations of Driver (or Impact) and Needle Pickup (or Accelerometer)
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8.3 Longitudinal Frequency:
8.3.1 Support the specimen so that it is able to vibrate freely in the longitudinal mode (Note 7). Position the specimen and driver
so that the driving force is perpendicular to and approximately at the center of one end surface of the specimen. Place the pickup
unit on the specimen so that the direction of pickup sensitivity coincides with the vibration direction, that is, the longitudinal axis
of the specimen (see Fig. 3b).
8.3.2 Force the test specimen to vibrate at varying frequencies. At
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