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UPDATE REPORT 20
MONTHS AFTER TERMARUST OVERCOATING High Pressure (5,000 psi) And Overcoating of a historic (1915) truss bridge on Route 778 over the Middle River - in With the Termarust High Ratio Co-Polymerized Calcium Sulfonate coating system
For the Staunton District Cleaning & Coating by Structural Coatings, Inc. Coating Materials from Termarust Technologies, Project Painting Date: August,
2005 UPDATE REPORT 20 MONTHS AFTER TERMARUST
OVERCOATING
By: Craig A. Ballinger, P.E. Termarust Technologies Phone: 888-279-5497 [press
4 to transfer call] Email: cballinger@termarust.com OVERVIEW This report provides some
background information and pictures on the cleaning and painting portion of
work that was done on this bridge, in the summer of 2005, for the Virginia DOT
and updated after a site visit on April 20, 2007 20 months after the
pressure wash cleaning (with Chlor*Rid) and overcoat painting with the
Termarust high ratio co-polymerized calcium sulfonate coating system. The bridge is an old (1915)
truss bridge, that is located in a rural area of the Staunton District of the
Commonwealth (State) of The project involved doing
some structural repairs to the bridge and then painting the
superstructure. Because of this the
contract would go to a General Contractor and not to a painting contractor, who
would usually prefer to use sandblasting and apply a traditional three-coat
zinc-based coating system. However, it
was recognized that the latter method would not stop further development of
active crevice corrosion and pack rust that was reducing the structural
integrity and load capacity of connections in the 90-year old steel truss. It is important to note that
after the bridge was pressure washed it was found that at least 85% of the
steel surfaces had between 2.0 and 25 mils of tightly adhered (LEAD-BASED) paint that the State did
not have to pay for disposal of. Also
note as seen in the pictures the containment tarps were allowed to be
removed after the pressure washing was completed. Shown below are references,
contract and bid cost information, procedures for cleaning and painting, and
pictures of the bridge and the cleaning and painting operations. UPDATE OBSERVATIONS OF THE APRIL 20, 2007
SITE VISIT
On this date, 20 months
after the bridge was pressure wash cleaned and painted, the bridge was
visited to look at the condition of the Termarust coating and whether there
were any problems with the coating
and/or any continued corrosion. Photos No. 19 through 26
provide an overview of what was observed, which is summarized below: 1. The Termarust coating appears to be in
excellent condition. 2. It may be seen that the color of the
Termarust coating has not faded in color. 3. It was observed that there are a few
small areas of dark colored stains on small portions of a few connection, for
example see Photo 24. These areas are
believed to be where the water (from pressure washing) was not completely
removed during the air pressure blow-down of the connections with the
result that the Termarust TR2200 Penetrant and the TR2100 Topcoats (which have
a polar attraction to steel) have pushed the rusty water out of the
connections and onto the surface of the connection and then they wetted the
steel and chemically stopped further corrosion. The
fact that these areas have a dark color (rather than bright red) indicates
that the active corrosion in the connections has been stopped. Also, it has been found on other projects
that this dark stain is just on the surface of the adjacent areas and it can
usually be wiped off. It
should be recognized that stopping corrosion on internal portions of such
connections usually cannot be done.
Thus, this is an important attribute of the Termarust TR2200 Penetrant;
which can penetrate into such spaces and chemically stop corrosion. 4. It was also seen that there are a very
few areas (not shown) where the Termarust coating has been scraped off of the
steel but there has been no undercutting and delamination of the Termarust coating
and no further damage to the integrity of the coating is expected. It is believed that
these small areas of damaged coating were caused by a Contractor when work on
the timber deck was being completed and when the guard rails were being installed. REFERENCES Park Thompson Bridge
Engineer Phone: 540-332-9104 Painting Contractor Structural Coatings, Inc., Contact Person: Grady White Cost
Information It is important to note that this was a bridge
rehabilitation project that was finished by painting the truss. The project involved: (1) removal of the
existing timber deck and replacing the longitudinal beams under the deck, (2)
installing a new timber deck, and then (3) painting the truss, including the
longitudinal eye-bars at the deck level. Factors that were of major concern to the VDOT
District Bridge Engineer: 1) Stopping further development of crevice
corrosion and pack rust (in the connections of the truss) that were reducing
the load capacity of the truss, 2) Minimizing the cost for the entire
project, and 3) Minimizing the time that the bridge
would be closed to local traffic and keeping it open during the school
year. It was recognized that: ·
The
Termarust coating system will chemically stop corrosion; including
crevice corrosion and pack rust,
in addition to being an excellent barrier coating system. It is common in ·
It
is not
unusual to save more than 50% of total Project Cost for painting
projects where the cleaning was with 5,000 psi pressure washing and application
of the Termarust one-coat system vs. sandblasting and application of a
traditional 3-coat zinc based system (that will not stop crevice corrosion and
pack rust). Since this project involved
structural rehabilitation work, and not just painting, the contract had to go
to a General Contractor, not a painting contractor that would usually prefer to
use sand blasting and application of a traditional three-coat zinc-based
coating. In order to gather
comparative cost information for using pressure washing and overcoat the
remaining existing (tightly adhered) paint with the Termarust system vs.
sandblasting and a traditional coating system the bid documents had the
following requirements: 1.
Only two acceptable paint systems: Alternate
A a zinc-rich single component
moisture cure polyurethane primer, micaceous iron oxide filled single component
moisture cure polyurethane intermediate coat, and a micaceous iron oxide filled
single component moisture cure polyurethane or aliphatic polyurethane topcoat
with expected preparation by sandblasting. Alternate
B The proprietary paint
system
manufactured by Termarust
Technologies; which recommends preparation with a 5,000 psi pressure
washing with Chlor*Rid in the final wash water (to remove soluble salts; e.g.
chlorides, nitrates and sulfates which respectively create hydrochloric acid,
nitric acid, and sulfuric acid) [see www.chlor-rid.com
for technical information on this topic]. 2.
The (General) Contractor had to submit
two bid prices: 1) The cost of repair work + use of the
Alternate A paint system, and 2) The cost of repair work + use of the
Alternate B paint system (the Termarust coating system, with preparation with
pressure washing) Obviously the General Contractor(s)
wanted to submit the lowest prices possible in order to be selected for the
contract award. The following table shows
bid information that was published on the VDOT website. It may be seen that the bids
from both contractors showed a cost savings by using pressure washing and the
Termarust system. It may also be seen
that by awarding the contract to Contractor No. 1 the State saved $63,860 by using pressure washing and the
overcoating with the one-coat Termarust coating system; which will stop
crevice corrosion and pack rust in the connections of the truss bridge. Here it is also important to
note that after the bridge was pressure washed it was found that at least 85%
of the steel surfaces had between 2.0 and 25 mils of tightly adhered (LEAD-BASED) paint that the State did
not have to pay for disposal of. This
also permitted a reduction in the amount of paint needed for the project; i.e.
10 mils dry film thickness (DFT) over bare steel and tight rust and only 5 mils
DFT over tight paint. The cost savings by using Termarust
CLEANING AND APPLICATION PROCEDURES The following Termarust
standard procedures were followed: 1. Pressure wash clean the bridge with a
5,000 psi pressure washer (at a 6 standoff distance) with clean water with an
additive of Chlor*Rid to remove non-visible salts; e.g. chlorides. (For
more information on Chlor*Rid see www.chlor-rid.com) 2. With dry compressed air blow dry all
connections (and cross-over points on built-up lattice members. (almost all superstructure
members) 3. Apply Termarust TR2200 Penetrant into
all open connections 4. Apply a caulk (or stripe) coat of
Termarust TR2100 into/onto edges of connections 5. Spot prime areas of bare steel and tightly
adhered rust with 5 mils DFT of Termarust TR2100 6. Overcoat the entire area with another 5
mils DFT of TR2100. It is important to note
that steps 3 through 6 are done immediately after each other; i.e. wet-on-wet;
which is why the Termarust system is considered to be a One Coat system. The final result was: ·
5
mils DFT on tight paint, ·
10
mils DFT on bare steel and tight rust, and ·
20
mils DFT over connections. PICTORIAL OVERVIEW The following pictures provide a pictorial overview
of the project.
Photo 1 Bridge in 2004, before painting.
Photo 2 Bridge in 2004. (see
Photo 26)
Photo 3 Bridge in 2004. (see Photo 20)
Photo 4 Bridge in 2004.
Photo 5 Tarps for containment for pressure washing Note the tarps extend 18 above top of bridge but
top is open.
Photo 6 Flow-through tarp and filter fence contain
paint chips.
Photo 7 Underside of containment.
Photo 8 5,000 psi pressure washing, standoff
distance less than 6.
Photo 9 Truss member cleaned by pressure washing,
ready for painting. (see Photos 18 and 21)
Photo 10 Bottom of tie rod assembly cleaned and
ready for painting. (see Photo 25)
Photo 11 Pin/truss assembly cleaned and ready for
painting.
Photo 12 Top of portal truss cleaned and ready for
painting.
Photo 13 Top of portal frame cleaned and ready for
painting Note: most of pack rust under longitudinal member has
been removed by pressure washing.
Photo 14 Film thickness gage shows 4.5 mils of
existing tightly adhered lead-based paint. (At least 85% of the bridge had 2.0 to 25 mils of
tightly adhered paint, after pressure washing)
Photo 15 Applying TR2200 Penetrant to connections. [Note the
containment tarps were removed after pressure washing]
Photo 16 Applying TR2100 Topcoat, for caulk/stripe
coat and spot priming over bare steel and tight rust.
Photo 17 Painting the bridge from two scissor
lifts.
Photo 18 Painting completed. (see Photo 21)
Photo 19 20 Months after painting. (see Photo 16)
Photo 20 20 Months after painting. (see Photo 3)
Photo 21 20 Months after painting. (see Photos 9
and 18).
Photo 22 20 Months after painting. (see Photos 3
and 20)
Photo 23 20 months after painting. (see Photos 3
and 20)
Photo 24 20 Months after painting corrosion in
connection has been stopped. (see Note 3 on Page 3)
Photo 25 20 Months after painting. (See Photos 4 and
10)
Photo 26 20 Months after painting. (see Photo 2) |
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