ASTM D4688-99(2013)
(Test Method)Standard Test Method for Evaluating Structural Adhesives for Finger Jointing Lumber
Standard Test Method for Evaluating Structural Adhesives for Finger Jointing Lumber
SIGNIFICANCE AND USE
4.1 This test method is specifically designed to measure the performance of adhesives in finger joints manufactured under production line conditions.
4.2 The results of the test method may be used to certify an adhesive as suitable for finger jointing lumber under production-line conditions where the intended end use of the finger jointed lumber will be in a structural glued laminated timber. When the test results are to be used for certification of an adhesive for this purpose, use a standard wood species and a standard finger profile. Standard species may be found in Table 1 of Specification D2559. Two standard finger profiles commonly used in the manufacture of structural glued laminated timber industry are shown in Fig. 1.3
4.3 This test method is not intended for quality control as the test assemblies are selected for their absence of defects usually found in run-of-the-mill lumber and finger joints.
SCOPE
1.1 This test method is designed to evaluate adhesives for finger jointing lumber used in the manufacture of structural glued laminated timber. It tests the tensile strength of joints under the following treatments; dry with no treatment, wet after one vacuum-pressure soak treatment, and wet after cyclic boil-dry treatment.
1.2 The values stated in SI units are to be regarded as the standard. The values given 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D4688 −99(Reapproved 2013)
Standard Test Method for
Evaluating Structural Adhesives for Finger Jointing Lumber
This standard is issued under the fixed designation D4688; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.3 sample, n—agroupoffingerjointassembliesobtained
from a finger joint production line for statistical purposes.
1.1 This test method is designed to evaluate adhesives for
3.2.3.1 Discussion—In the laminating industry the term
finger jointing lumber used in the manufacture of structural
sample is used for an individual finger joint assembly.
glued laminated timber. It tests the tensile strength of joints
1 3
3.2.4 specimen, n—an individual strip, ⁄4 by 1 ⁄8 (approxi-
under the following treatments; dry with no treatment, wet
mately)by12in.(6.4by35by305mm),cutfromafingerjoint
after one vacuum-pressure soak treatment, and wet after cyclic
assembly for the tension test described in this test method.
boil-dry treatment.
1.2 The values stated in SI units are to be regarded as the
4. Significance and Use
standard. The values given in parentheses are for information
4.1 This test method is specifically designed to measure the
only.
performance of adhesives in finger joints manufactured under
1.3 This standard does not purport to address all of the
production line conditions.
safety concerns, if any, associated with its use. It is the
4.2 The results of the test method may be used to certify an
responsibility of the user of this standard to establish appro-
adhesive as suitable for finger jointing lumber under
priate safety and health practices and determine the applica-
production-line conditions where the intended end use of the
bility of regulatory limitations prior to use.
finger jointed lumber will be in a structural glued laminated
2. Referenced Documents timber. When the test results are to be used for certification of
an adhesive for this purpose, use a standard wood species and
2.1 ASTM Standards:
a standard finger profile. Standard species may be found in
D907Terminology of Adhesives
Table1 of Specification D2559. Two standard finger profiles
D2559Specification for Adhesives for Bonded Structural
commonly used in the manufacture of structural glued lami-
Wood Products for Use Under Exterior Exposure Condi-
nated timber industry are shown in Fig. 1.
tions
4.3 This test method is not intended for quality control as
3. Terminology
the test assemblies are selected for their absence of defects
usually found in run-of-the-mill lumber and finger joints.
3.1 Definitions—Many terms in this test method are defined
in Terminology D907.
5. Apparatus
3.2 Definitions of Terms Specific to This Standard:
5.1 Test Machine, capable of applying a calibrated tensile
3.2.1 billet, n—a piece cut from a vertical finger joint
force up to 23 kN (5000 lbf), equipped with Templin (wedge-
assembly as an intermediate step in making specimens.
action) grips with grip area of 38 by 75 mm (1 ⁄2 by 3 in.).
3.2.2 finger joint assembly, n—ashortportionoftwoboards
5.2 Vacuum Pressure Vessel, capable of drawing and hold-
joinedattheirendsbyafingerjointobtainedfromafingerjoint
ingavacuumofatleast635mm(25in.)ofmercury(sealevel)
production line for testing, frequently referred to as an assem-
for 30 min, holding a pressure of 620 6 35 kPa (75 6 2 psi)
bly.
for 30 min, and capacity to ensure that all of the specimens are
at least 51 mm (2 in.) below the water level during the
This test method is under the jurisdiction of ASTM Committee D14 on
complete vacuum-pressure cycle.
Adhesives and is the direct responsibility of Subcommittee D14.30 on Wood
Adhesives.
5.3 Tank for Boiling, capacity such that all specimens are at
Current edition approved Oct. 1, 2013. Published October 2013. Originally
least51mm(2in.)belowthewaterlevelforthedurationofthe
approved in 1987. Last previous edition approved in 2005 as D4688–99 (2005).
boil cycles.
DOI: 10.1520/D4688-99R13.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on AmericanInstituteofTimberConstruction,7012S.RevereParkway,Suite140,
the ASTM website. Englewood, CO 80112.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4688−99 (2013)
FIG. 2 Finger Joint Assembly and Specimen Descriptions
6.2.3 Plane the second face of the assembly until the finger
on the surface is feathered maintaining 35-mm (1 ⁄8-in.)
assembly thickness or nearly so.
NOTE 1—It is more important to feather the finger than to maintain the
35-mm (1 ⁄8-in.) thickness.
6.2.4 Cuttheassemblytoa305-mm(12-in.)lengthwiththe
finger jointed area at the center.
6.2.5 Rip individual specimens 6.4-mm ( ⁄4-in.) thick (Fig.
1) from the assembly starting with the jointed edge of the
assembly (see 6.2.2) against the saw guide. A thin hollow-
ground rip saw blade is preferred but the important criteria is
the straightness of the cut. Check cut specimens for uniform
thickness throughout. Thickness shall not vary by more than
NOTE 1—Recommended by American Institute of Timber Construc-
3 0.5 mm (0.02 in.). Number the specimens in order from one
tion.
side of the assembly to the other.
FIG. 1Standard Joint Profiles for Certification Tests
6.3 Vertical Joint (Fig. 2(b)):
6.3.1 Joint one edge of the finger joint assembly.
6.3.2 Joint one face of the finger joint assembly.
5.4 Oven, capable of operating continuously for 20 h at 63 6.3.3 Withthejointededgeagainstthesawguide,ripbillets
6 2°C (145 6 5°F) with sufficient air circulation to lower the 40 mm (1 ⁄16 in.) wide from the assembly.
moisturecontentofthegroupofspecimensto8%within20h.
NOTE 2—The 40-mm (1 ⁄16-in.) dimension is not critical but this
5.4.1 Timer, to shut the oven off automatically is desirable.
dimension must be enough to allow feathering the fingers in following
steps.
6. Specimen Preparation
6.3.4 Joint and plane the sides of each billet so the exposed
6.1 Obtain a sample consisting of either 20 horizontal or sides of the fingers are feathered as described in 6.2.1 and
vertical finger joint assemblies from a finger joint production 6.2.3.
line.Theboardsmustbenominal2by4-in.or2by6-in.Reject 6.3.5 Rip four individual specimens of 6.4-mm ( ⁄4-in.)
any assembly with obvious defects in the lumber or joint. thickness from each billet of the assembly as in 6.2.5. Number
the specimens in order from one side of the assembly to the
6.2 Horizontal Joint (Fig. 2(a)):
other. Use the same order for each assembly.
6.2.1 Joint one face of each assembly until the finger on the
surface is feathered as shown in Fig. 2(c). 6.4 Inspect specimens for defects. Assemblies yielding
6.2.2 Joint one edge of the assembly for end cutting and specimens that have obvious strength-reducing characteristics
ripping at a later stage. such as: low visual density, knots, steep slope of grain,
D4688−99 (2013)
compression wood, compression failures, decay, pitch pockets, (0.20 in./min). Maintain a space of 210 66mm(6 6 0.25 in.)
or stress risers due to errors in specimen preparation, may be between the ends of the jaws of the grips. Record the load at
rejected. If specimens with questionable strength characteris-
failure.
tics are tested they shall be identified by appropriate notes on
NOTE 3—Be very careful to align the specimen with the principal axis
the report form prior to exposure and testing.
ofthetestgrip.Failuretodothiswillincreasethevariabilityoftheresults.
6.5 Conditionallspecimenstoequilibriummoisturecontent Markings or spacers on the grips, or some other device is recommended
to ensure proper front-to-rear alignment, and a plumb bob or other device
(EMC) at 23 6 2°C (73 6 4°F) and 50 to 65 6 5% relative
is recommended to ensure the vertical alignment.
humidity. Monitor the weight periodically to determine when
equilibrium is reached.
7.1.2 Determine the failure mode using the criteria given in
Annex A1 independent of any knowledge of the strength test
6.6 Weighallspecimenstothenearest0.01gandrecordthe
result.
weight. Measure the width and thickness of the specimens to
the nearest 0.25 mm (0.010 in.) and record the measurements.
7.2 Cold Water Vacuum-Pressure Soak Test:
6.7 Randomly assign two specimens from each of the 20
7.2.1 As described in 6.7, assign 40 specimens to this test.
finger joint assemblies in the sample to each test (that is, dry,
Place all 40 specimens in a vacuum-pressure vessel with
soak, and boil). (Note this requires only six specimens from
spacers between them so that water has free access to all
eachassembly,theotherspecimensareextra.)Fig.3showsthe
surfaces. Fill the vessel with tap water at 18.5 to 27.5°C (65 to
source and distribution of the specimens.
80°F)sothatallspecimensareatleast51mm(2in.)belowthe
surface of the water. After filling, seal the vessel and draw a
7. Procedure
vacuum of at least 635 mm (25 in.) of mercury (sea level).
7.1 Dry Test (No Treatment): Hold the vacuum for 30 min, then release the vacuum and
7.1.1 As described in 6.7, assign 40 specimens to this test. apply pressure of 620 6 35 kPa (75 6 2 psi). Hold this
Test each specimen to failure by loading at a rate of 5 mm/min pressure for 2 h, then release. Remove the specimens from the
NOTE 1—Thus: 20 assemblies×2 specimens/assembly=40 specimens/test.
FIG. 3Flowchart of the Source and Allocation of Individual Test Specimens
D4688−99 (2013)
pressure vessel and place them submerged in water at room outliers (test values outside the range expressed by the upper
temperature until tested. and lower adjacent values).
7.2.2 Wipe the surface of each specimen with a dry cotton
25th percentile = Q1 = the value below which 25 % of the observations
fall.
cloth or paper towel and test wet as described in 7.1.1. Record
50th percentile = Q2 = the value below which 50 % of the observations
the load at failure.
fall.
7.2.3 After the specimens have dried, determine the failure
75th percentile = Q3 = the value below which 75 % of the observations
fall.
mode as described in 7.1.2. Record the failure mode.
Upper adjacent value = the largest observation equal to or less than
7.3 Cyclic Boil Test:
the quantity Q3+1.5(Q3− Q1).
7.3.1 As described in 6.7, assign 40 specimens to this test.
Lower adjacent value = the smallest observation greater than or equal
to the quantity Q1−1.5(Q3− Q1).
Place all 40 specimens in the boil tank with spacers so that
Outliers = observations greater than the upper adjacent
water has free access to all surfaces. Fill with water such that
value or less than the lower adjacent value.
the specimens are at least 51 mm (2 in.) below the water level.
8.4 Calculate the mean and standard deviation. Specimens
Boil specimens for 4 h, then dry them in an oven at 63 6 2°C
exhibiting failure mode 6 may be excluded from the calcula-
(145 65°F)withsufficientaircirculationtolowerthemoisture
tion. Include specimens with failure modes 1, 2, 3, 4, and 5 in
content to 8% (ovendry basis) in no more than 20 h.
the calculation unless the strength value is an outlier or the
NOTE 4—The rate of air circulation, the size of the load of specimens
wood is of poor quality (such as compression wood, etc.).
in the oven, and the spacing of the specimens greatly affect drying time
and the steepness of the moisture gradient in the specimen. Variation of
9. Report
these factors strongly affects the repeatability of the test method. If
repeatability (within-laboratory variability) or reproducibility (between
9.1 Include the following general information in the report:
laboratories) is important, the drying variables must be maintained as
9.1.1 Complete identification of the adhesive tested includ-
constant as possible from one series of tests to the next. If this is not
ing type, source, manufacturers’ code numbers, form, and any
possible, the drying should be conducted so that the specimens reach 8%
other pertinent information,
moisture content within the same drying period in every test. One way to
9.1.2 Adhesive application and bonding conditions used to
dothisistomonitortheweightofthespecimensandadjusttheovenvents
so the specimens reach the target 8% moisture in 15 to 20 h.As an aid in
prepare the finger jointed boards,
following moisture content, the weight of specimens at 8% moisture
9.1.3 Conditioning procedure used before testing,
contentisabout96%oftheirweightat12%moisturecontent.Thedrying
9.1.4 Temperature and relative humidity of the test room,
time required can be established with some of the extra specimens cut
9.1.5 Number of finger joint assemblies represented in the
from the 20 assemblies.
test, and
7.3.2 Repeat the boil-dry cycle five more times; except
9.1.6 Number of specimens per assembly tested in each test
during the final cycle do not dry the specimens. Cool the
(dry, soaked, and boiled),
specimens to room temperature submerged in water and keep
9.2 Include the following statistical information in the
them there until they are tested.
report:
7.3.3 Test wet in tension as described in 7.2.2. Record the
9.2.1 The range of test values,
load at failure.
9.2.2 The 25th, 50th, and 75th percentile values,
7.3.4 After the specimens have dried, determine the failure
9.2.3 The upper and lower adjacent values,
mode as described in 7.1.2. Record the failure mode.
9.2.4 Outliers identified by finger joint assembly and speci-
NOTE 5—Nonmandatory guidelines for joint performance follow:
men number,
Mode 1 — An unacceptable failure.
9.2.5 Failure mode 6 specimens identified by finger joint
Modes 2 and 3 — Unconditionally acceptable failure.
assembly and specimen number,
Modes 4, 5, and 6 — Conditionally acceptable failure if strength is
acceptable.
9.2.6 Specimenswithdefectsofmaterialorbondingdiscov-
ered after testing identified by finger joint assembly and
8. Calculation of Results
specimen number,
8.1 Calculate the tensile stress at failure in megapascals
9.2.7 The mean and standard deviation, and
(pounds-forcepersquareinch)astheloadatfailureinnewtons
9.2.8 The statistical mode (most frequent value) of the
(pounds-force) divided by the cross-sectional area of the
observed failure modes.
2 2
specimen expressed to the nearest mm (0.01 in. ).
8.2 Estimate the 25th, 50th, and 75th percentiles for the 10. Precision and Bias
group of specimens in the following manner:
10.1 Ameasureoftheprecisionofthistestmethodcovering
8.2.1
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