The document summarizes research measuring the mass loss and shear strength of different preservative-treated pine lumber specimens after a six-month humidity exposure. The research team measured the copper content, moisture content, specific gravity, mass loss of driven and undriven fasteners, and single shear strength of specimens treated with ACQ, CA, CCA, ESP, MCA, and untreated pine. The results showed ACQ had a significant decrease in mass of fastener coating and reductions in stiffness and load capacity after exposure. While mass loss occurred for some treatments, most did not show significant changes in strength, though longer exposures may reveal more differences. The study demonstrates mass loss of fasteners is possible in above-ground, wet

1. Mass Loss and Shear Strength
Changes of PPT Lumber for a
Six Month Humidity Exposure
Daniel Hindman, Associate Professor, Wood Science and Forest Products
C. Ryan Bamberg, Structural Engineer, Naval Facilities Command
Paul D. Timko, Structural Engineer Intern, Cromwell Architects
John C. Bouldin, Graduate Assistant, Wood Science and Forest Products
Lance D. Shields, Graduate Assistant, Civil Engineering
Ralph Rupert, Director, Center for Unit Load and Design
Jose Maria Villasenor, Graduate Assistant, Wood Science and Forest
Products
Lori Koch, Graduate Assistant, Wood Science and Forest Products
Chayanika Mitra, Graduate Assistant, Building Construction
Gi Young Jeong, Instructor, Chonnam University

2. Schedule
 Introduction
 Current Literature
 Objective
 Methods
 Results
 Conclusions

3. The History of Treated Wood
 January 1, 2004
 Voluntary removal of CCA from
residential use
 Why?
◦ Concerns over leaching of chromium and
arsenic
 Subsequent EPA rulings do not ascribe a
danger to CCA treated material

4. Current PPT Lumber Used
 Copper Based Materials
◦ Copper Azole (CA or CA-B)
◦ Alkaline Copper Quat (ACQ)
 Borate Based Treatments
◦ Usually limited use
◦ Envirosafe Plus – Borate and Polymer, Rated
for Above Ground Use
 Others?

5. Lack of Research
 General lack of research on alternative
PPT
 Kear et al. (2005) states ACQ corrosion
rate may be 5X CCA using AWPA E-12
 What is the effect of exposure on
strength of PPT lumber?
◦ Loss of strength of wood due to moisture
◦ ‘Corrosion’ of fastener (sacrificial layer)
◦ Migration of corrosion products in
surrounding wood

6. The Word ‘Corrosion’
 Corrosion is a multifaceted issue
Change in Fastener Diameter
Electrochemical Behavior  What Is the Effect Upon


Amount of Moisture  Connection Strength?
Loss of Strength of Wood 
 ASTM A 90 Procedure for Mass Loss of
Coating

7. OBJECTIVE: MEASURE THE SHEAR
STRENGTH AND MASS LOSS OF
DIFFERENT PPT LUMBER
•Compare mass loss for driven and undriven fasteners
•Compare the mass loss and shear strength of PPT
specimens at two different environmental conditions

8. Materials – Table of Materials
Name Treatment Species Grade # Specimens # Specimens
Group Initial Exposure
ACQ Alkaline Copper SP No. 2 10 20
Quaternary
CA Copper Azole Mixed SP No. 2 10 20
CCA Chromated Copper SP No. 1 10 20
Arsenate
ESP Envirosafe Plus Mixed SP No. 2 10 20
MCA Micronized Copper Azole SP No. 2 10 20
SP None (Control) SP No. 2 10 20
Initial Conditions : 16% EMC, Conditioned within laboratory,
considered at equilibrium
Exposure Conditions: 19% EMC for 6 months

9. Test Specimen
 Allows measurement of BOTH:
◦ ASTM D 5764 single shear connection
strength
◦ ASTM A 90 mass loss of coating
 10d common galvanized nails

10. Single Shear Testing

11. All material conditioned to 16% EMC
for several months
Initial Condition Testing 6 Months
•10 specimens per treatment 90 degrees F
ASTM A 90 (driven) 90% RH
•10 nails ASTM A 90
(undriven)
•10 specimens per treatment Exposure Condition Testing
for ASTM D 5764 20 specimens per treatment
ASTM D 5764
ASTM A 90
MC / SG Determination

12. Results – Copper Content, MC, SG
Wood Cu or CuO, MC SG Initial SG
Treatment % wt. Exposure Exposure
ACQ 0.531% 23.1% 0.47 0.48
CA 0.249% 23.6% 0.47 0.48
CCA 0.159% 23.6% 0.53 0.54
ESP N/A 25.9% 0.5 0.5
MCA 0.264% 22.7% 0.49 0.46
SP 0.000% 23.6% 0.46 0.47
 Highest copper content for ACQ, lowest for CCA
(ESP not tested)
 MC values were higher than expected, but
consistent
 SG values were similar between exposures

13. Mass Loss of Initial Driven and
Undriven Fasteners
Type of Nail Wood Mass of Coating, p-value of Undriven
Treatment g/m2 (COV) Comparison (α=0.05)
Undriven N/A 556.9 (17.3%) --
Driven ACQ 641.4 (21.0%) 0.100
CA 564.5 (13.2%) 0.819
CCA 548.7 (16.0%) 0.240
ESP 519.7 (15.1%) 0.268
MCA 583.8 (10.4%) 0.361
SP 527.4 (16.4%) 0.329
 No significant differences in mass loss for the act
of driving the nails
 Variability may be due to wood particles on nails

15. Mass loss of Initial Driven and
Exposure Fasteners
Type of Wood Mass of Average Mass p-value of Exposure
Nail Treatment Coating, g/m2 loss, g/m2 Comparison (α=0.05)
(COV)
Undriven N/A 556.9 (17.3%) -- --
Driven ACQ 468.1 (18.3%) 89.1 0.004
CA 534.0 (18.1%) 23.2 0.454
CCA 603.9 (16.3%) -46.7 0.136
ESP 508.1 (14.5%) 49.1 0.180
MCA 519.7 (14.0%) 37.5 0.177
SP 579.8 (18.1%) -22.6 0.479
 ACQ had significantly different mass loss from
undriven values
 CCA and SP had mass gains, showing variability of
measurements

16. Comparison of Single Shear Testing
Wood Stiffness 5% Offset Load Ultimate Load
Treatment % Diff p-value % Diff p-value % Diff p-value
ACQ 66.2% 0.039 -27.3% 0.026 0.3% 0.982
CA 58.4% 0.022 33.1% 0.097 4.9% 0.553
CCA 14.3% 0.477 -11.2% 0.298 -7.3% 0.335
ESP -10.3% 0.520 1.8% 0.865 -10.7% 0.074
MCA 11.3% 0.443 -11.6% 0.244 0.3% 0.964
SP 12.8% 0.532 -13.3% 0.219 -9.9% 0.290
 α = 0.05
 % Difference = (Exposure-Initial)/Initial * 100%

17. Discussion of Results
 For ACQ material, significant differences
were found for:
◦ Mass loss after exposure
◦ Stiffness and 5% offset load after exposure
 CA has significant difference for stiffness
but not mass loss
 No significant differences for ultimate
load
 Longer exposure times would increase
differences

18. Practical Situations
 90 degrees F and 90% RH = 19% EMC,
with actual measurements of 23-24 % MC
 These conditions are NOT extreme
 Possible in humid crawlspaces, typical of
Southern United States
 In above ground situations, measureable
mass loss of galvanized fasteners can
occur in PPT lumber!

19. Conclusions
 Act of driving fastener did not create
significantly different mass of coating
values
 ACQ showed significantly different mass
of coating, stiffness and 5% offset load for
initial and exposure samples
 Mass loss (corrosion?) can occur in
relatively benign (but wet) conditions

20. Acknowledgements
The group would like to acknowledge Amelia Lumber
for supplying materials

21. Thanks!