SS9901-CS060123TCB AECOM
Turner Collie & Braden
January 23, 2006
Mr. Kenneth M. Griffin, P.E.
Director of Engineering & Public Works
City of Coppell
PO Box 9478
Coppell, TX 75019
Subject: DeForest Lift Station Coating Pull-off Testing
Dear Mr. Griffin:
TCB has reviewed the results from the bond strength testing performed by Steel Inspectors of Texas,
Inc. on the wet well coating applied at the DeForest Lift Station. According to the inspection report
prepared by Steel Inspectors, bond strength testing was performed in accordance with ASTM D4541
(Standard Test Method for Puli-Off Strength of Coatings Using Portable Adhesion Testers) as required
in Specification Section 09902. The following is a summary of the test procedure performed by the
Steel Inspectors technician:
· Adhesion test dollies were glued in place using Loctite glue.
· After allowing the adhesive to cure (_+1 day), the technician scribed around the dollies down to
the concrete to ensure only the coating directly beneath the test dolly was tested. This is
standard procedure for thick film coatings.
· An Elcometer 0-1,000 psi adhesion tester was attached to the dolly and a force was applied to
the dolly normal to the test surface. The fome was gradually increased and monitored until a
plug of material was detached.
· The technician recorded the pull-off strength and the nature of the failure. The nature of the
failure was reported as the percent coating cohesion failure (coating removed with dolly),
percent concrete cohesion failure (concrete removed with dolly) and percent glue failure (no
coating or concrete removed with dolly) based on observations of the dolly following testing.
Coating application at the DeForest Lift Station occurred on December 16 and 17, 2005. XXXX
applied the Raven 405 coating system. Steel Inspectors glued dollies in place on December 22 and
performed pull-off tests on December 23, 2005. Table 1 summarizes the testing results as provided
by Steel Inspectors. A copy of the inspection report is attached.
Table 1. Summary of DeForest Lift Station Wet Well Coating Puli-Off Strength Testing
'Date Pull-off
Coating Strength
Location Applied (psi) Failure Mode
Ceiling 12-16-05 425 80% coating cohesion / 20% concrete cohesion
North wall 12-16-05 325 100% coating cohesion
South wall 12-17-05 400 50% coating cohesion / 50% concrete cohesion
East wall 12-17-05 325 70% coating cohesion / 30% glue failure
West wall 12-17-05 600 80% coating cohesion / 20% glue failure
Both the pull-off strength and the failure mode were considered in evaluating the test results. Pull-off
strength is generally expected to approach the tensile strength of the substrate, which in this case are
the concrete surfaces of the wet well. The tensile strength of concrete is typically approximately 10
Mr. Kenneth M. Griffin, P.E.
Januaw 23,2006
Page 2
percent of the compressive strength. For the DeForest Lift Station, 4,000 psi concrete (28-day
strength) was used, meaning pull-off strengths of approximately 400 psi were anticipated.
Although the pull-off strength is more critical in assessing the quality of surface preparation and
coating application to predict performance of the coating system, failure mode should also be
considered. Ideally, the failure mode should be primarily concrete cohesion. Coating cohesion failure,
indicated by a rough, gritty failure surface, can also be an acceptable failure mode, depending on the
pull-off strength. Adhesive failure of the coating to the concrete or adhesive failure within the coating
raise concerns about future performance of the coating system. Disbonding of the coating from the
concrete can indicate poor surface preparation or failure to follow the manufacturer's requirements for
coating application. When the coating delaminates, it typically indicates a re-coat window was missed
during application. The coating failure surface is smooth if adhesive failure has occurred.
Coatings on the ceiling, south wall and west wall exhibited acceptable pull-off strength. However, the
pull-off strengths reported for the north and east walls were on the Iow end of the anticipated range. In
addition, the failure mode for both was primarily coating cohesion. TCB recommended that additional
pull-off strength tests be performed on the north and east walls to further evaluate the coating system.
Steel Inspectors conducted the re-testing on January 17 (glued dollies in place) and January 18
(performed pull-off strength tests). The results of the testing are summarized in Table 2. A copy of the
inspection report is attached.
Table 2. Summary of DeForest Lift Station Wet Well Coating Puli-Off Strength Re-Testing
'Date Pull-off
Coating Strength
Location Applied (psi) Failure Mode
North wall 12-16-05 300 60% coating cohesion /40% concrete cohesion
East wall 12-17-05 275 2% coating cohesion / 98% concrete cohesion
TCB obtained the dollies from all tests from the City to examine the failure surfaces. All coating
failures were cohesive in nature, which indicates proper coating application. In no case did the
coating disbond from the concrete or from itself. While the pull-off strengths for the north wall and east
wall were at the Iow end of the anticipated range, the re-testing showed concrete cohesion failure.
The results show acceptable adhesion of the coating to the concrete substrate has been achieved.
TCB reviewed the results of the testing with engineers at Raven Lining Systems, the coating
manufacturer. Raven indicated that they are comfortable accepting the results. A copy of the email
correspondence with Raven is attached. Therefore, TCB recommends acceptance of the results of
the pull-off testing for the coating system at the DeForest Lift Station.
Please feel free to contact me at 972-735-30§6 if you have any questions.
Sincerely,
Erika K. Cooper, P.E.
Project Manager
Attachments:
Pull-off testing results for DeForest Lift Station Wet Well (12-22-05 & 12-23-05)
Pull-off re-testing results for DeForest Lift Station Wet Well (1-17-06 & 1-18-06)
Email correspondence with Raven Lining Systems, Inc.
c: File
TCB AECOM
Blank Page 1 of 5
Cooper, Erika
From: Wierzchowski, Steve [swierzchowski@ravenlining,com]
Sent: Monday, January 23, 2006 9:04 AM
To: Cooper, Erika
Subject: RE: Adhesion Testing
Erika,
After reviewing the test data and the pictures of the test dollies I would conclude that acceptable results have been obtained.
The photos indicate that the failures in the plane of the coating were cohesive and not adhesive which would indicate intercoat
delamination. The retests indicated acceptable values and failure mode with the concrete substrate. All results show that
acceptable adhesion of the coating to the substrate has been achieved. If adhesion to the substrate was questionable the
results would have been Iow psi readings with the failure point at the intersection of the coating and the substrate with no
substrate pulled with the dolly. Some of the test results did indicate Iow psi readings for cohesive failure within the coating
but this could be due to scoring of the dolly which can induce fractures in the coating especially in colder temperatures. For
example, the test on the the west wall with 600 psi and 80% cohesive failure would be typical of a cohesive failure of this
product, while failures at 300 pi would be considered Iow. I would suspect that if tests were performed at the same locations
when the substrate temperature was over 70F there would be higher results. Overall, I would feel comfortable accepting
these results.
Steve Wierzchowski
sw~e[~ravenlining corn
1024 North Lansing -Tulsa, OK 74106
(918) 584-2810 ~ (918) 582-4311 Fax
(918) 527-9856 Cell
From: Cooper, Erika [mailto:erika.cooper@tcb.aecom.com]
Sent: Monday, Januaw 23, 2006 6:43 AM
To: Wierzchowski, Steve
Subject: RE: Adhesion Testing
Steve,
Attached are photos of the dollies. The photos are named to correspond to the results provided in my previous email
(Test 1 indicates initial testing, re-test indicates 2® test on nodh and east walls). Those are the complete results. 5 tests
were done on December 23, and the re-tests were done on January 18. One mistake in my previous email - dollies were
glued on December 22 and pulled on December 23 for the first test (not on December 23 and December 27 as stated
below).
Also, the west wall was tested on December 23 with the following results (fax copy of the results cut this line off):
Test 1 West wall 600 psi
80% coating cohesion failure / 20% glue failure
The surfaces of the coatings on the dollies are gritty, which would seem to indicate coating cohesion failure (as opposed
to adhesion).
Any input you have would be greatly appreciated. The City has requested a recommendation from us on the coatings
asap, as they are trying to wrap up the construction on the lift station. However, I want to make sure we are comfortable
with the coating application.
Thanks once again for all the help.
Erika
Erika Cooper, P.E.
Project Manager
972.735.3056
1/23/2006
Blank Page 2 of 5
TCB
17300 Dallas Parkway, Suite 1010
Dallas, Texas 75248
T 972.735.3000 F 972.735.3001
E erika~cooper@tcb aecom,com
The information contained in this transmission is a confidential communication intended for the use of the individual or entily name0 above. If the reader of this
message is not the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited.
..... Original Message .....
From: Wierzchowski, Steve [mailt:o:swierzchowski@ravenlining.com]
Sent-' Friday, January 20, 2006 2:17 PM
To; Cooper, Erika
C¢: Hughes, .loanne; Love, Wayne
Subject-' RE: Adhesion Testing
Erika,
I believe you are on the right track. The retest does indicate more acceptable results. I would like to see the test
results for all the dollies just to look at trends if you have them. Having all that data to look at might give an indication
as to what the average results are and the necessity to look further at a particular area. Just looking at the numbers
for the North and East walls I would comment that while the adhesion value is a little Iow the fact that failure did occur
into the substrate indicates that there is an acceptable level of adhesion. By looking at the actual dollies you can infer
further details based upon the amount of substrate that was retained on the dolly and what the substrate composition
was at the failure point. These are some of the things to evaluate when looking at marginal results.
If possible email me some close up pics of the actual dollies.
Thanks,
Steve Wierzchowski
sw!er@raven!ining corn
1024 North Lansing - Tulsa, OK 74106
(918) 584-2810 - (918} 5824311 Fax
{918) 527-9856 Cell
From.' Cooper, Erika [mailto:erika.cooper@tcb.aecom.com]
Sent: Friday, January 20, 2006 9:29 AM
To: Wierzchowski, Steve
Subject: RE: Adhesion Testing
Steve,
Below are the results from the adhesion testing for the project I discussed with you (Raven 405 applied to new
concrete in a lift station, applied December 16 and 17, 2005)):
Initial testing: December 23 (dollies glued), December 27 (pulled dollies)
Ceiling 425 psi
North wall 325 psi
South wall 400 psi
East wall 325 psi
80% coating cohesion / 20% concrete cohesion
100% coating cohesion
50% coating cohesion / 50% concrete cohesion
70% coating cohesion / 30% glue failure
Re-testing of the north and east walls: January 17 (dollies glued), January 18 (pulled dollies):
North wall 300 psi
East wall 275 psi
60% coating cohesion / 40% concrete cohesion
98% concrete cohesion / 2 % coating cohesion
The testing laboratory did verify that they scribed around the dollies down to concrete prior to pulling. According to
1/23/2006
Blank Page 3 of 5
the City inspector, the coating failures felt grainy. I'm going to stop by the site and pick up the dollies in the next day
or two so I can take a look at them.
What is your take on the results? Based on our conversation, it seems that these are reasonable results. The psi at
failure is a little Iow on the north and east walls, but the fact that there was a higher percentage of concrete cohesion
failure during the re-test seems to be a positive sign.
really appreciate your help on this!
Thanks,
Erika
Erika Cooper, P.E.
Project Manager
972.735.3056
TCB
17300 Dallas Parkway, Suite 1010
Dallas, Texas 75248
..... Original Message .....
1/23/2006
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