2. Description of bridge
• Location of the bridge:
Chemin Côte-des-Neiges(North)/Chemin Remembrance(West)
3. Description of bridge
• Ownership of infrastructure:
It is under municipal ownership and jurisdiction of the City of
Montreal.
• Function:
It is used as a link between the downtown area and residential
areas such as Cote des Neiges and Mont-Royal while also
providing access for a return road under the bridge.
4. Description of bridge
• Bridge composed of:
oMajor Structural Components:
Concrete: Beams, columns, foundations, bridge deck
Steel: Reinforcing bars, stirrups, ties
oMinor Structural Components:
Steel railings, concrete barriers, asphalt on the bridge
deck
5. DESCRIPTION OF PERFORMANCE
AND LOADING CRITERIA
• Usage of the
Structure:
oThe bridge contains 3
lanes of one-way traffic
with no apparent
congestion.
oOverloaded trucks are
prohibited.
oNo sidewalk for
pedestrians.
6. DESCRIPTION OF PERFORMANCE
AND LOADING CRITERIA
• The structure is exposed to the following
conditions:
o De-icing salts
o Car exhaust, although it might not be severe, as there were
no apparent traffic congestion on or below the bridge.
o Retaining walls, column bases and supports all are in contact
with soil & groundwater. No obvious drainage system is
present.
7. DISCUSSION OF PRELIMINARY
FINDINGS
• The main cause of deterioration in the bridge appears to be
corrosion. It is evident all along the bridge deck and most of
the columns due to spalling of the concrete cover and rust
staining.
9. DISCUSSION OF PRELIMINARY
FINDINGS
• Rust and efflorescence of salt are apparent on the side and
under the bridge deck as reddish/orange and white stains
respectively.
11. RECOMMENDATIONS CONCERNING
FUTURE ACTIONS
• According to the records of la Ville de
Montreal, the deterioration rating is 68, hence
it is in a “Deficient” state.
• A plan to eliminate the overpass is in place.
However, if this does not happen before 2015,
repairs will be done to the overpass.
12. RECOMMENDATIONS CONCERNING
FUTURE ACTIONS
• Since the bridge is in deficient state and not a
critical one, no immediate action is required
even though the overpass is severely
damaged.
• If however repairs are done today, they would
cost less than as planned in 2015 since
deterioration due to corrosion and sulfate
attacks would increase exponentially with
time.
20. Structural/loading factors which may
increase/diminish the risk
• Dynamic loading
• Fatigue loads
• High permanent snow load
• Heavy dynamic natural loads
21. Testing for Corrosion
Short-Pulse Radar:
Will be used to detect the reinforcing steel locations
Will also detect delamination in the bridge deck.
One of the only available methods that works through asphalt overlays.
Rolling Pachometer:
Will be used to find the location of the reinforcing steel and compared
with the results of the short-pulse radar to achieve higher accuracy.
The rate of deterioration of the bars can be found in terms of a reduction
of its relative size.
A damage map can then be created and analyzed.
22. Testing for Efflorescence & ASR
Lab Test of Effloresced Solid:
A sample of the effloresced solid will be tested in the lab to
determine its composition.
UV Fluorescence technique for ASR:
This is a destructive test.
A solution of uranyl acetate solution is sprayed
on a fresh fracture surface.
A viewing box that emits UV light is used to
detect the affected regions.
This technique is fast, easy and accurate.
Will be used on bridge deck and rail end.
23. Testing for Carbonation
Phenolphthalein Test:
Will be used to determine the rate of
Carbonation.
A fractured surface will be sprayed with
phenolphthalein turning the concrete
pink, and carbonated areas will remain
unchanged.
If carbonation is found to be extensive, a core can be taken
along with chemical profiling to find the “depth of
carbonation”.
It is fast, cheap and reliable.
Will be tested mainly on the columns
24. Test for Transport Properties
The ISAT will be used to analyze transport properties as
it is not affected by carbonation and chloride content.
Initial Surface Absorbtion Test (ISAT):
It’s a semi-destructive technique
Field concrete must have been exposed to at least 48
hours of ambient temperature and humidity.
The rate of water absorbed into an unsaturated
concrete surface is measured.
Results will be used to determine the concrete’s
surface transport properties.
It will be applied on the bridge deck.
25. Test for Compressive Strength
Use core data if available
Pullout test:
Will be used to estimate the compressive strength of concrete in-situ.
Shear strength can be also be found as the test measures a combination of tensile and shear
strength.
Should be performed on a few different locations along the beam and columns to achieve a more
global estimation of compressive strength.
26. Testing for Sulphate Attack
Schmidt Rebound Hammer:
Hammer should be regularly calibrated.
Will be used predominantly along column length at regular intervals to
determine whether there is a relative loss in compressive strength at the
column base that can be possibly attributed to sulphate attack, calling for
more in-depth investigations.
27. Corrosion Repair
Members to be repaired: bridge deck and the columns
Chloride Removal:
• Electrochemical Chloride Extraction (ECE) – ONLY if justified
by chloride concentrations as it will disrupt traffic and cause
additional costs to this already expensive method.
Concrete Removal (used for concrete above the bridge deck):
• By impacting – using a pneumatic chipping hammer.
• By hydro removal – whenever the use of the pneumatic
hammer is not applicable.
Undercutting and Exposing Rebar:
• Should be done around and under all corroded rebar, so
that the rebar’s full circumference could be cleaned.
• Replace steel if 25% of cross-sectional area is lost (or 20% if
the 2 bars are in close proximity).
*NOTE: Structural review required before removal of significant
amounts of concrete to determine if support (e.g. shoring) is
required*
28. Corrosion Repair
Preventative Measure (before placing new concrete):
• Installing a discrete sacrificial anode – Zinc “puck”.
• Should be connected at joints of rebars for maximum efficiency.
• Care should be taken in placing the “pucks” to ensure that all the
steel rebar is protected.
Concrete Placement (used for concrete below the bridge deck):
• The surface should be cleaned from bond inhibiting materials by
hydroblasting.
• Form and pump placement will be implemented as it is works well
for overhead and vertical applications where congested
reinforcement is present (columns, beams, deck, and rail ends).
Consolidation and bonding is provided by the formwork pressure.
Preventative Measure (after placing new concrete):
• Applying a thin epoxy or mortar overlay all over surface to prevent
further ingress of chlorides and moisture. The epoxy would be
placed on the structural members
*NOTE: The membrane should suffice after applying ECE, but the zinc
pucks will be added for additional protection*
29. ASR Repair
Members to be repaired: bridge deck
Chemical injection with lithium salts and CO2:
• Should be done in conjunction with the
electrochemical chloride removal where the
lithium ions will replace the chlorides in the
concrete.
• Its use along with ECE may justify both their
costs
Preventative measure:
• Applying a thick overlay of ASR resistant
concrete to encapsulate the affected region and
prevent ingress of moisture.
• ASR ceases at RH < 85%
30. Crack Repair
When extensive cracking is present, it could lead
to deleterious effects and durability issues, thus
an action should be taken.
For passive cracks:
• The overlay provided for corrosion and ASR
repairs should be sufficient to provide a
moisture barrier
For active cracks:
• There were big cracks at the bottom and at the
side of the bridge deck which made us suspect
that these cracks would be active.
• Stitching of the cracks to provide a tensile force
to prevent further propagation and also acts to
close them.
• Done in conjunction with the overlays provided
before as it does not seal moisture on its own.
31. Crack Repair
The repair technique also depends on the
type of member and the location of the
crack.
For non-structural members (rail ends):
• Rout and Seal technique will be used to fill
significant cracks with flexible sealant to
minimize chemical and physical ingress.
• This method is used for its simplicity.
• It requires minimum 6mm opened space
to take sealant. In some cases, flexible
sealants and specialized coatings are used
for flexurally active cracks.
32. Crack Repair
For structural members (columns, beams and deck):
• Drilling and Plugging technique is used to core
deep and straight cracks. Then a rigid
impermeable plug of bitumen or mortar material
is inserted to replace the crack and the
deteriorated concrete around it.
• Good for walls or beams with deep vertical cracks
Preventative Measure:
• During the repairs of active cracks, NDT monitoring
such as Acoustic emission, crack width
measurement, crack inventory should be
implemented for preventative maintenance to
detect any potential crack formation. The acoustic
emission will be placed to monitor the active
cracks in the structural members, and the return
period for the crack width measurement and the
inventory will be 5 years as the bridge is in critical
condition.
33. Preventative Measures
Discrete sacrificial anode – Zinc “puck”
• Placed strategically on rebar exposed
during undercutting
• To prevent incipient anode forming
adjacent to new patch
Thin bonded overlay
• Epoxy/Mortar
• Compatibility
• Applied to columns, deck, beams and
rail ends
• Prevent further ingress of moisture and
deleterious agents
34. Preventative Measures
Thick unbonded overlay
• Concrete with its own reinforcement
• Bridge resurfacing (deck only)
• Limit permeability of underlying
concrete
• Compatibility not an issue
35. Long-term Maintenance & Monitoring
Acoustic Emission
• Set-up along deck, columns and the ends of the beams.
• Set a threshold value
• Record counts above threshold value
• Determine crack location
• Evaluate whether new crack or old one propagating
36. Long-term Maintenance & Monitoring
ILRIS-3D – Intelligent Laser Ranging and
Imaging System
o Condition status model
• Reverse engineering and load
modeling of structure
• Data is complete
• No traffic interruption
• Can be combined with monitoring
under a load test
o Micro-damage analysis
• High density scans to reveal
hairline cracks
• Apparent in both bare and coated
surfaces
37. Long-term Maintenance & Monitoring
Routine Inspection
• Should be scheduled every 2 years at the least.
• Mostly visual to determine any deterioration that is initiating
• Evaluate effectiveness of repairs done
• Crack width measurement
• Crack inventory
