ASTM C1851-18(2023)
(Practice)Standard Practice for Determining the Extent of Cracking in a Sealant using the Difference between the Compressive and Tensile Modulus
Standard Practice for Determining the Extent of Cracking in a Sealant using the Difference between the Compressive and Tensile Modulus
SIGNIFICANCE AND USE
5.1 The intent of this practice is to quantitatively determine the amount of cracking of a sealant relative to an unexposed or uncracked sample. Some samples of sealant have been observed to exhibit some degree of cracking some period after installation. The degree of cracking is assessed visually in a qualitative manner that takes into account the area of the cracks at the exposed surface of the sealant, but does not take into account the depth or profile of the cracks. The degree of cracking in the sealant has been used as an indication of performance change.
SCOPE
1.1 This practice covers a procedure for quantitatively determining the extent of cracking in a sealant sample by evaluating the difference between the measured compressive and tensile modulus of a sealant relative to an unexposed or uncracked version of the same sealant. The cracks will reduce the area of the sealant in the tensile modulus, but in the compressive modulus measurement they will not change the area over which the modulus is determined.
1.2 The values in SI units are to be regarded as standard. The values in parentheses are for information only.
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
Relations
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: C1851 − 18 (Reapproved 2023)
Standard Practice for
Determining the Extent of Cracking in a Sealant using the
Difference between the Compressive and Tensile Modulus
This standard is issued under the fixed designation C1851; 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.
1. Scope 3. Terminology
1.1 This practice covers a procedure for quantitatively 3.1 Definitions:
determining the extent of cracking in a sealant sample by 3.1.1 For definitions of terms used in this practice, refer to
evaluating the difference between the measured compressive Terminologies E631 and C717.
and tensile modulus of a sealant relative to an unexposed or
4. Summary of Practice
uncracked version of the same sealant. The cracks will reduce
4.1 This practice consists of measuring the modulus of the
the area of the sealant in the tensile modulus, but in the
sealant usingTest Method C1735 in both tension and compres-
compressive modulus measurement they will not change the
sion. Once these values have been determined the formula
area over which the modulus is determined.
presented in this practice will be used to determine the degree
1.2 The values in SI units are to be regarded as standard.
ofcrackinginthesealantrelativetoanunexposedoruncracked
The values in parentheses are for information only.
sample of the same sealant.
1.3 This standard does not purport to address all of the
4.2 The motivation for this practice is to quantitatively
safety concerns, if any, associated with its use. It is the
determine the extent of cracking in the sealant. This measure-
responsibility of the user of this standard to establish appro-
ment is currently determined with a qualitative measure of
priate safety, health, and environmental practices and deter-
cracking determined by visual inspection. The degree of
mine the applicability of regulatory limitations prior to use.
cracking has been used as a measure of performance for
1.4 This international standard was developed in accor-
sealant.
dance with internationally recognized principles on standard-
4.3 This practice will enable determination of the percent of
ization established in the Decision on Principles for the
cracking of a sealant relative to an unexpected or uncracked
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical vesion of the same sealant.
Barriers to Trade (TBT) Committee.
5. Significance and Use
5.1 The intent of this practice is to quantitatively determine
2. Referenced Documents
2 the amount of cracking of a sealant relative to an unexposed or
2.1 ASTM Standards:
uncracked sample. Some samples of sealant have been ob-
C717 Terminology of Building Seals and Sealants
served to exhibit some degree of cracking some period after
C719 Test Method for Adhesion and Cohesion of Elasto-
installation. The degree of cracking is assessed visually in a
meric Joint Sealants Under Cyclic Movement (Hockman
qualitativemannerthattakesintoaccounttheareaofthecracks
Cycle)
at the exposed surface of the sealant, but does not take into
C1735 Test Method for Measuring the Time Dependent
account the depth or profile of the cracks. The degree of
Modulus of Sealants Using Stress Relaxation
cracking in the sealant has been used as an indication of
E631 Terminology of Building Constructions
performance change.
6. Procedure
This practice is under the jurisdiction of ASTM Committee C24 on Building
Seals and Sealants and is the direct responsibility of Subcommittee C24.20 on 6.1 The modulus of the sealant is determined in compres-
General Test Methods.
sion and separately in tension usingTest Method C1735.These
Current edition approved Jan. 1, 2023. Published January 2023. Originally
values are determined from a new sample (the unexposed
approved in 2018. Last previous edition approved in 2018 as C1851 – 18. DOI:
reference without any cracking), and the sample of interest.
10.1520/C1851-18R23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.2 From the four modulus measurements obtained from
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Test Method C1735, determine the value of the modulus at
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 100 s for each of these four conditions:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1851 − 18 (2023)
6.2.1 New Sample (the unexposed reference without any eter measures the change in modulus that is not due to crack
cracking), compression (E ), formation. The details of the derivation of these two expres-
100,bo,C
6.2.2 New Sample (the unexposed reference without any sions (Eq 1 and Eq 2) are detailed in Appendix X1.
cracking), Tension (E ), Additionally, a worked example is presented in Appendix X2.
100,bo,T
6.2.3 Test Sample, Compression, (E ),
100,C
6.2.4 Test sample, Tension (E ). 7. Report
100,T
6.3 Insert the four values determined in 6.2 into the follow- 7.1 Report the following information:
ing two empirically derived relationships: 7.1.1 Identification of the sealant measured, including type,
source, manufacturer code number, curing conditions
E 5 d·E $1 2 a f 2 ~1 2 a !f % (1)
100,T 100,bo,T 2 2
employed,
E 5 d·E ~1 2 a f! (2)
100,C 100,bo,C 1
7.1.2 Identification of the substrates,
6.4 In these expressions, the experimentally determined
7.1.3 Name and description of primers that were used, if
values should be used, a = 0.118 and a = 0.562. With these
any,
1 2
expressions and the values determined in 6.3, there are two
7.1.4 Number of specimens tested,
equations and two unknowns.
7.1.5 Description of the sealant appearance.
7.1.6 The value calculated for f. This can be reported as the
6.5 Solve for the two remaining undermined values f and d.
calculated 0-1 value or if multiplied by 100 as % cracked.
Theunknown frepresentsthefractionofcracksandhasavalue
7.1.7 The value calculated for modulus change not attrib-
between 0 and 1. Since Eq 1 is quadratic, f will have two
uted to cracking, d.
values. Only the positive value should be used. The d param-
8. Keywords
The derivation of these relationships are shown in Appendix X1 and Appendix
X2 of this practice. 8.1 compression; cracks; modulus; sealant; tension
APPENDIXES
X1. ANALYSIS OF A CRACKED SEALANT
X1.1 A Test Method C719 sealant sample is characterized X1.2 The black circles in this plot are the pre-exposure
using Test Method C1735. This standard yields a modulus results from the Test Method C1735 tensions tests. The
versus time curve for the sealant. This performed in both compression baseline results would look very similar.
tension and compression. See Fig. X1.1.
X1.3 The sample experiences some type of exposure. The
sample is removed from the exposure and once again Test
MethodC1735isperformedintwotests,compressionmodulus
and tensile modulus. In Fig. X1.1, a series of Test Method
C1735 tensile modulus results after different exposures are
plotted.At this point it is important to note that the curve shape
is the same but the exposure has caused the modulus to be
lower.
X1.4 Instead of keeping the entire time dependence, the
changes to the entire curve can be represented by a single time
point. An arbitrary choice of 100 s after the stress relaxation
component of the Test Method C1735 test is chosen to be far
enough away from the complications associated with imposed
strain and not too long to start to see extensive relaxation of the
sealant affecting the sealant. The modulus value recorded at
100 s is represented by: E . So now we have four values for
the 100 s modulus determined by the four Test Method C1735
tests:
X1.4.1 Theinitial(baselinemodulus)intension: E , T, bo.
X1.4.2 The value in tension after some exposure b: E , T.
X1.4.3 The initial (baseline modulus) in compression: E ,
C, bo.
X1.4.4 The value in compression after some exposure b:
FIG. X1.1 Modulus versus Time Curve E , C.
C1851 − 18 (2023)
X1.5 Now we can use the following expressions: in the center of the sealant or near the interface with the
substrate.The side refers to the location of the crack relative to
E 5 d·E $1 2 a f 2 ~1 2 a !f % (X1.1)
100,T 100,bo,T 2 2
the front or back of the sealant or from the side.The symmetric
E 5 d·E 1 2 a f (X1.2)
~ !
100,C
...
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