2012-256 - Originals 6 - Burrard Bridge Evaluation Report - Levelton

8/10/2019 2012-256 - Originals 6 - Burrard Bridge Evaluation Report - Levelton

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Bridge Evaluation ReportBurrard Street Bridge

Prepared for:

Associated Engineering (BC) Ltd.300-4940 Canada WayBurnaby, BC V5G 4M5

Attention: Mr. Shane Cook, P.Eng.


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Bridge Evaluation Report

Burrard Street Bridge


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TABLE OF CONTENTS

1 INTRODUCTION ....................................................................................................................... 1

2 DECK SOFFIT AND SUBSTRUCTURE ................................................................................... 1

2.1

VISUAL REVIEW............................................................................................................... 1

2.2 LABORATORY TESTING.................................................................................................... 22.2.1 Water-Soluble Chloride Ion Content ......................................................................... 2

2.2.2

Extracted Cores ......................................................................................................... 2

3 DECK SURFACE ...................................................................................................................... 2

3.1 VISUAL REVIEW............................................................................................................... 33.2

CORROSION POTENTIAL MEASURMENTS.......................................................................... 4

3.3 LABORATORY TESTING.................................................................................................... 53.3.1 Water-Soluble Chloride Ion Content ......................................................................... 5

4 CONCRETE PARAPETS .......................................................................................................... 5

4.1

VISUAL REVIEW............................................................................................................... 5

4.2

LABORATORY TESTING.................................................................................................... 5

4.2.1 Extracted Cores ......................................................................................................... 54.2.2 Water-Soluble Chloride Ion Content ......................................................................... 6

5 INTERPRETATION OF FINDINGS ........................................................................................... 6

5 1 D C SO S S C 6


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1 INTRODUCTION

As part of their contract with the City of Vancouver for the condition assessment anddevelopment of rehabilitation strategies for the Burrard Street Bridge, Associated EngineeringLtd. has engaged Levelton Consultants Ltd. to conduct the following:

A brief visual review of the visible concrete portions of the substructure and samplingfrom select areas of the substructure to assess water-soluble chloride ion content, pH,and the presence of alkali-silica reactivity (ASR). It is understand that Associated hasconducted a visual detailed survey of the structure, complete with recording size andlocation of observed deterioration.

Visual review of the concrete parapet along the west side of the bridge and sampling atselect locations to determine water-soluble chloride ion content, pH, and the presence ofalkali-silica reactivity (ASR).

Sampling from the top side of the concrete deck in the north and southbound curb lanes,and the southbound bike lane to assess the condition of the deck and to determine thewater-soluble chloride ion profile. The original scope of this sampling was to removethree 2 m x 10 m strips of asphalt and conduct sampling, and delamination and half-cellsurveys on the exposed concrete deck. However, due to the prohibitive cost of removal

and disposal of the asbestos-impregnated asphalt the City requested that the survey beconducted by extraction of a number of cores.

The following presents the findings of the investigation and recommendations for repairs andrehabilitation with respect to the concrete portions of the structure.


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There is evidence that many of the expansion joints are leaking, which has resulted in corrosion-related deterioration on several of the concrete members adjacent to the joints and on the piersbelow the joints. The extent of the deterioration indicates that there has been active corrosionwithin the structure for several years.

Most of the onshore piers are in good condition with minor corrosion-related deterioration orminor cracking which is most likely a result of expansion due to ASR.

2.2 LABORATORY TESTING

2.2.1 Water-Soluble Chloride Ion Content

Concrete powder samples were collected from various locations throughout the deck soffit andsubstructure. Samples were collected by drilling into the concrete with a 25 mm diameter drill bit.

At all locations, except Location 1, the water-soluble chloride ion content is below the corrosioninitiation threshold of 0.030.05% by mass of concrete.

New concrete generally has a pH greater than 12.0. When steel is in a highly alkalineenvironment (pH >10.0) a passive layer forms on the steel surface which protects the steel fromaggressive corrosion (in the absence of chlorides). When atmospheric carbon dioxide diffusesinto the concrete a chemical reaction occurs which lowers the pH; when the pH drops below

about 10 the passive layer is no longer stable and the steel is no longer protected fromcorrosion. The pH of the concrete powder samples at several of the locations is slightly lowerthan that typically observed in new concrete, however, at all locations the pH is above thegenerally accepted threshold for carbonation-induced corrosion. These results indicate that thedepth of carbonation is minimal.

Table C1 in Appendix C presents the sample locations and test results; Photos 7 through 15 also


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3.1 VISUAL REVIEW

The concrete deck is reinforced with undeformed round bars varying from 10 to 15 mm indiameter, and square bars that are approximately 10 mm in section. Due to the layer of asphalton top of the concrete deck it was not always possible locate reinforcing steel and collect asample by coring.

Table 1 presents a summary of the condition of the extracted cores; the category Brokenapplies to cores that Levelton had to break into several pieces to extract; these cores generallycorrespond to the location where the half-cell equipment was grounded, so no reading could betaken at this location.Table 2 presents a summary of the condition of the rebar sampled from thedeck.

As can be seen from Tables 1 and 2 the majority of the deterioration observed is in the two

under-deck truss spans and the north approach. It should be noted that the review of the deckcarried out under this program is quite limited given the size of the structure, however, it doesindicate that there has been some corrosion-related deterioration within the concrete deck and isuseful in targeting future surveys and repairs.

Table 1: Summary of Core Condition

Number of Cores

Span Lane Good

Vertical

Crack Broken Delamination

South ApproachNorthbound 8 2 1 0

Southbound 8 0 1 1

South UnderdeckTruss Span

Northbound 2 0 1 0

Southbound 1 0 1 3


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Table 2: Summary of Rebar Condition

Number of Cores

Span Lane Good Fair PoorNone

Visible

South ApproachNorthbound 4 2 1 4

Southbound 2 4 0 4

South UnderdeckTruss Span

Northbound 0 1 1 1

Southbound 2 1 2 0

Main SpanNorthbound 0 1 0 5

Southbound 1 1 0 3

North UnderdeckTruss

Northbound 0 2 2 2

Southbound 1 2 1 1

North ApproachNorthbound 1 3 0 1

Southbound 1 2 1 0

Total 12 19 8 21

3.2 CORROSION POTENTIAL MEASURMENTS

Corrosion potential values provide information about the probability of active corrosion of therebar embedded in concrete. Based on Leveltons experience, active corrosion of steel in bridgedecks is often observed when potential values are more negative than about -200 mVCSEand thechloride levels at the rebar are elevated.

At most core locations corrosion potential measurements were taken on the exposed concrete


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Table 4: Summary of Corrosion Potential Measurements

Number of Readings

Corrosion Potential

(ASTM C876)

South

Approach

South

Under-deckTruss

Main

Span

North

Under-deck

North

Approach

>10%(>-200 mVCSE)

6 0 4 2 3

Uncertain(-200 to -350 mVCSE)

10 3 1 6 6


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4.2.2 Water-Soluble Chloride Ion Content

Levelton extracted concrete powder samples from five locations in the west parapet and testedthe samples for water-soluble chloride ion content and pH. At all locations the water-solublechloride ion content is below the generally accepted corrosion initiation threshold limit of 0.03-0.05% by mass of concrete and the pH of at all sample locations is greater than 10.0. Completetest results are presented in Table C3 in Appendix C.

5 INTERPRETATION OF FINDINGS

In general, the concrete elements of the Burrard Bridge are in relatively good condition for their

age. The notable exception is the parapets, which are showing advanced deterioration in theform of spalling. It is noted that the bridge was constructed prior to the use of air entrainment forfreeze-thaw protection, using what is likely to be relatively high-permeability concrete. Hence, theobserved deterioration is likely the result of freeze-thaw attack, ASR, and rebar corrosion actingtogether.

Elsewhere, localized spalling and deterioration is observed, but generally the concrete is soundand in good condition.

Some evidence of early-stage ASR is present. More extensive laboratory analysis, together within-situ monitoring is required to assess the future progression of this form of deterioration.

5.1 DECK SOFFIT AND SUBSTRUCTURE

Throughout the deck soffit there are numerous spalled areas which have exposed the reinforcing


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The corrosion potential measurements at many of the sample sites indicate an uncertainprobability of corrosion, and review of the condition of rebar exposed during sampling indicatesthat the steel is generally in good condition at most locations. Chloride ion concentrations atmost locations are quite low, which indicates that the waterproofing membrane and theasbestos-modified asphalt have done a reasonably good job of protecting the concrete deck.

The samples were taken from the northbound curb lane, and the current southbound curb andbike lanes; until recently the current southbound bike lane was the curb lane for vehicular traffic.These lanes were chosen as they are where the most advanced deterioration would be expectedto occur. However, it should be noted that this is a very small sample size, particularly given thesize of the structure and it is difficult develop a complete assessment of the condition of thedeck.

In general, the deck was found to be in sound condition with localized deterioration. If left in its

current state, the corrosion-related deterioration will continue to accumulate, eventuallynecessitating extensive repairs.

5.3 PARAPETS

The parapets are generally in poor condition with extensive spalling throughout, which hasexposed the reinforcing steel extensively. At several locations these spalls have been coatedwith paint, however, as with the deck soffit, this method provides only minimal protection to steel,

and it is likely that the spalls will continue to expand.

Laboratory testing indicated that the chloride concentrations and pH levels have not reached thegenerally accepted corrosion initiation thresholds; however, it is obvious that there are activedeterioration mechanisms within the parapets. The deterioration is likely the result ofsimultaneous freeze-thaw attack, ASR, and corrosion.

Th t f l t d d i i ifi t d it i t t d th t d bl i


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Prepare the substrate surface and rebar by sandblasting or hydromilling to removedbruised concrete and corrosion product.

Reinstate the concrete using class C-1 concrete as specified in CSA-A23.1-09, or usinga suitable proprietary repair product. Alternatively, concrete can be reinstated using an

appropriate wet-mix shotcrete.

The cracks noted in the sidewalk soffits are likely due to shrinkage of the concrete shortly afterconstruction. It appears that there is some leakage through these cracks, however, there isminimal corrosion-related deterioration associated with the cracks.

To repair the cracks it would be possible to inject them with epoxy resin, however, it may bemore advantageous to apply a waterproofing membrane on the top surface of the sidewalks toprevent moisture migration. If this approach is taken, existing spalls and delaminations would

need to be repaired as described above, however, there would be no need to inject the cracks.The choice of repair technique will depend on the Citys plans for the sidewalk in the future.

Other than protecting the structure from exposure to moisture, little can be done to mitigate theprogression of the ASR noted in the structure. However, lab testing indicates that the reaction isnot advanced and, given the age of the structure it is likely that the rate of the reaction is quiteslow. Further analysis and monitoring over several years is required in order to determine aprognosis for the ASR.

6.2 DECK SURFACE

While the extent of the deck survey is not sufficient to estimate the quantity of deteriorationthroughout the deck surface, it does indicate that in some locations there has been a failure ofthe waterproofing membrane which has allowed chlorides to build up to, and exceed, thecorrosion initiation threshold. Levelton recommends that a more extensive survey of the deck,


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APPENDIX A

PHOTOGRAPHS


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Photo 1: South Approach, East Elevation


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Photo 6: Corrosion-Related Deterioration in Deck Soffit


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Photo 8: Sample Locations in Span 31


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Photo 10: Sample Locations on Pier 6


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Photo 12: Sample Locations on Span 14


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Photo 14: Sample Locations Near Bent 13


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Photo 16: West Parapet Looking South


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Photo 18: Deterioration in West Parapet


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APPENDIX BCORE LOG


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Core 1

Length = 76 mmDiameter = 100 mm

MSA. = 30 mm

Condition of Core = Minorcorrosion staining

Size of Rebar = 15Mundeformed bar

Direction of Rebar = L

Condition of Rebar = Good


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Core 2

Length = 75 to 90 mm

Diameter = 100 mm

MSA. = 30 mm

Condition of Core = Good

Size of Rebar = 10MUndeformed bar

Direction of Rebar = T

Condition of Rebar = Fair, somesurface corrosion


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Core 4


Diameter = 100 mm

MSA. = 30 mm



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Core 5


Diameter = 100 mm

MSA. = 30 mm

Condition of Core = Corebroken into pieces


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Core 6


Diameter = 100 mm

MSA. = 45 mm

Condition of Core = 0.5 mmwide vertical crack.

Size of Rebar = 15M




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Core 7

Length = 80 mm

Diameter = 100 mm

MSA. = 25 mm


Size of Rebar = NV

Direction of Rebar = NV

Condition of Rebar = NV

Core 8

Length = 107 mm

Diameter = 100 mm

MSA. = 25 mm


Size of Rebar = NV



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Core 9


Diameter = 100 mm

MSA. = 25 mm


Size of Rebar = 10MUndeformed bar /15M

Direction of Rebar = T/L

Condition of Rebar = Both barsare in poor condition withsignificant surface corrosion


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Core 11

Length = 50 mm

Diameter = 100 mm

MSA. = 45 mmCondition of Core = Good

Size of Rebar = 10M bar withsquare cross section

Di ti f R b T


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Core 13


Diameter = 100 mm

MSA. = 25 mm


Size of Rebar = 10M square/10M undeformed


Condition of Rebar = Poor,significant corrosion spots onboth bars


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Core 14

Length = 30 mm

Diameter = 100 mm

MSA. = 25 mm

Condition of Core = Core brokein pieces

Size of Rebar = 10Msquare/10M undeformed


Condition of Rebar = Both barsare in fair condition with somesurface corrosion

Core 15


Diameter = 100 mm

MSA. = 20 mm


Size of Rebar = NV



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Core 17

Length = 73 mm

Diameter = 100 mm

MSA. = 40 mm


Size of Rebar = NV



Core 18

Length = 45 mm

Diameter = 100 mm

MSA. = 25 mmCondition of Core = Good

Size of Rebar = 10Msquare/10M underformed

Di ti f R b T/L


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Core 19

Length = 60 mm

Diameter = 100 mm

MSA. = 25 mm


Size of Rebar = NV



Core 20

Length = 80 mm

Diameter = 100 mm

MSA. = 45 mmCondition of Core = Core brokein two pieces

Size of Rebar = NV

Di ti f R b NV


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Core 21


Diameter = 100 mm

MSA. = 25 mm

Condition of Core = Good,minor honeycombing

Size of Rebar = NV




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Core 23

Length = 115 mm

Diameter = 75 mm

MSA. = 25 mm



Direction of Rebar = L:



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Core 25

Length = 90 mm

Diameter = 75 mm

MSA. = 30 mm

Condition of Core = Corelocated over a vertical crack inasphalt. Two vertical cracksextend to depth of rebar anddelamination at the level of


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Core 26

Length = 78 mm

Diameter = 75 mm

MSA. = 25 mm

Condition of Core = Core brokein three pieces





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Core 27

Length = 98 mm

Diameter = 75 mm

MSA. = 30 mm






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Core 29

Length = 65 mm

Diameter = 75 mm

MSA. = 20 mm

Condition of Core = Core inpieces and delamination at thelevel of rebar



Condition of Rebar = Fair, somecorrosion


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Core 31


Diameter = 75 mm

MSA. = 30 mm

Condition of Core = Core inpieces and delamination at thelevel of rebar

Size of Rebar = 10M


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Core 33

Length = 30 mm

Diameter = 75 mm

MSA. = 30 mm

Condition of Core = Core inpieces and delamination at thelevel of rebar.


Direction of Rebar = LCondition of Rebar = Poor, lotsof surface corrosion

Core 34


Diameter = 75 mm

MSA. = 30 mm

Condition of Core = Core brokeat level of rebar

Size of Rebar = 15Md f d b


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Core 35

Length = 55 mm

Diameter = 75 mm

MSA. = 25 mm





Core 36


Diameter = 75 mm

MSA. = 20 mm

Condition of Core = Core brokeat level of rebar

Size of Rebar = 10Msquare/10M undeformed bar


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Core 38

Length = 60 mm

Diameter = 100 mm

MSA. = 20 mm


Size of Rebar = NV



Core 39

Length = 30 mm

Diameter = 100 mm

MSA. = mm

Condition of Core = Core brokeinto multiple pieces

Size of Rebar = 15Msquare/15M


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Core 40

Length = 20? mm

Diameter = 100 mm

MSA. = mm

Condition of Core = Core brokeinto multiple pieces

Size of Rebar = 15M




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Core 42

Length = 55 mm

Diameter = 100 mm

MSA. = 40 mm


Size of Rebar = NV



Core 43

Length = 45 mm

Diameter = 100 mm

MSA. = 20 mm

Condition of Core = Core brokeinto two pieces



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Core 44


Diameter = 100 mm

MSA. = 25 mm




Condition of Rebar = ???

Core 45

Length = 85 mm

Diameter = 100 mm

MSA. = 15 mm


Size of Rebar = NV



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Core 47

Length = 65 mm

Diameter = 75 mm

MSA. = 25 mm

Condition of Core =Delamination at the level ofrebar and significant corrosionstaining



Condition of Rebar = Poor, lotsof corrosion visible


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Core 48

Length = 25 mm

Diameter = 100 mm

MSA. = 20 mm

Condition of Core =Delamination at level of rebarand corrosion staining


Direction of Rebar = TCondition of Rebar = Poor,significant corrosion visible


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Core 49

Length = 70 mm

Diameter = 75 mm

MSA. = 15 mm

Condition of Core =Delamination at the level ofrebar

Size of Rebar = 10Msquare/10M square

Direction of Rebar = T/TCondition of Rebar = Good/Fair,few corrosion spots


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Core 51

Length = 60 mm

Diameter = 75 mm

MSA. = 25 mm

Condition of Core = Good.

Size of Rebar = 15Mundeformed/15M undeformed

Direction of Rebar = L/L

Condition of Rebar =

Good/Good


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Core 53


Diameter = 75 mm

MSA. = 30 mm



Di ti f R b T


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Core 54


Diameter = 75 mm

MSA. = 25 mm



Direction of Rebar = L/L

Condition of Rebar = Good/Fair,

many corrosion spots


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ore 56

Length = 70 mm

Diameter = 100 mm

MSA. = 30 mm

Condition of Core = Core brokeinto pieces

Size of Rebar = NV



Core 57


Diameter = 100 mm

MSA. = 25 mm

Condition of Core = Core brokeinto multiple pieces.Delamination at a depth of 23mm. There appears to be anoverlay


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Core 58

Length = 60 mm

Diameter = 100 mm

MSA. = 25 mm

Condition of Core =

Size of Rebar = NV



Core 59

Length = 115 mm

Diameter = 100 mm

MSA. = 20 mm


Size of Rebar = 15M



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Core 60


Diameter = 100 mm

MSA. = 40 mm




Condition of Rebar =

Transverse bar is in faircondition with some surfacecorrosion. Longitudinal bar isgenerally in good condition withminor surface corrosion


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APPENDIX CWATER-SOLUBLE CHLORIDE ION CONTENT TEST RESULTS

T bl C1 W t S l bl Chl id I C t t


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Table C1: Water-Soluble Chloride Ion ContentDeck Soffit and Substructure

Sample Sample LocationTest

Increment(mm)

Water-SolubleChloride IonContent (%

mass ofConcrete)

pH

1 North Abutment

0-20 0.202 11.7

40-60 0.232 11.9

60-80 0.159 11.8

2East side of East Girder in

Span 31

0-20 0.053 10.7

20-40 0.011 11.9

40-60


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TABLE C2:Water-Soluble Chloride Ion ContentDeck Surface

Span Core

Chainagefrom SouthAbutment

(m)

RebarDepth (mm)

Half-CellPotential(mVCSE)

TestIncrement

(mm)

Water-SolubleChloride Ion

Content (% mass of

Concrete)

achSpan

1 28.2 72 Ground

0-20


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TABLE C2:Water-Soluble Chloride Ion ContentDeck Surface (continued)

Span Core


(m)

Rebar Depth(mm)


TestIncrement

(mm)

Water-SolubleChloride Ion Content

(% mass of

Concrete)

51 384.6 51 -1860-20


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TABLE C2:Water-Soluble Chloride Ion ContentDeck Surface (continued)

Span Core


(m)

Rebar Depth(mm)

Half-Cell

Potential(mVCSE)

Test

Increment(mm)

Water-SolubleChloride Ion Content

(% mass ofConcrete)

South

Approach

Span

60 20. 72 -345

0-20 0.014

20-40 0.020

40-60 0.012

60-80 0.077

80-110


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TABLE C2:Water Soluble Chloride Ion Content Deck Surface (continued)

Span Core


(m)

Rebar Depth(mm)


TestIncrement

(mm)

Water-SolubleChloride Ion Content(% mass of Concrete)

MainSpan

19 580.0 82 -192

0-20 0.006

20-40 0.005

40-60


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TABLE C2:Water Soluble Chloride Ion Content Deck Surface (continued)

Span Core


(m)

Rebar Depth(mm)


TestIncrement

(mm)


NorthUnder-deckTrussSpan

26 741.6 30 -1320-20 0.012

20-40 0.017

36 732.3 20 Ground

0-20 0.032

20-40 0.030

40-59 0.026

37 720.5 30 -145

0-20


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C ate So ub e C o de o Co te t ec Su ace (co t ued)

Span Core


(m)

Rebar Depth(mm)


TestIncrement

(mm)


34 769.3 86 -217

0-20


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TABLE C3:Water-Soluble Chloride Ion ContentParapets

SampleTest

Increment(mm)

Water-SolubleChloride Ion

Content (% massof Concrete)

pH

1

0-20 0.025 11.9

20-40 0.020 12.3

40-60 0.016 12.4

60-80 0.013 12.4

80-100 0.007 12.4

100-120 0.006 12.4120-140


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APPENDIX DGENERAL ARRANGEMENT

SOUTH ABUTMENT


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L0 L1 L2 L3 L4 L5 L6 L7 L8 L 9 L1 0

L0 L2 L4 L6

L8 L0 L2 L4 L6

L8 L10

U0 U2 U4 U6

U8 U0 U2 U4 U6

U8 U10

L0

U0

L2

U2

L4

U4

U1

U2

U3 U4 U5 U6 U7

U8

U9

NORTH ABUTMENT

L6

U6

L8

U8

L10

U10 U2 U4

L6

U6

L8

U8

L2 L4

U0

L0


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EASTWEST

WESTNO-POST

BARRIERBRIDGEDECK

STRINGERS, TYP.FLOORBEAM

EAST NO-POST

BARRIER

WEST EXTERIOR

PARAPET

EAST EXTERIOR

PARAPET

EASTBIKELANEWEST SIDEWALK WEST BIKE LANE

CONTINUOUS EDGE

FASCIABEAM

CONTINUOUS EDGE

FASCIABEAM

B C D E F G H I J KA

EASTTOPCHORD

EASTTRUSS

VERTICALS, TYP.

EASTBOTTOM

CHORD

DIAGONAL

BRACINGS,TYP.

WESTTRUSS

VERTICALS, TYP.

WEST BOTTOM

CHORD BOTTOM BRACINGS,

TYP.

WESTNO-POST

BARRIERBRIDGEDECK

EASTWEST

EASTOUTRIGGE

EASTGIRDER

EAST

DIAPHRAGM

EAST COLUMNMIDDLE COLUMNWESTCOLUMN

WESTOUTRIGGER

WESTGIRDER

WEST

DIAPHRAGM

EAST NO-POST

BARRIER

WEST EXTERIOR

PARAPET

EAST EXTERIOR

PARAPET

EASTBIKELANEWESTSIDEWALK WESTBIKELANE

CONTINUOUS EDGE

FASCIABEAM

CONTINUOUS ED

FASCIABEAM

Documents

2012-256 - Originals 6 - Burrard Bridge Evaluation Report - Levelton