Evaluation of Fiberglass Wrapped Concrete Bridge Columns

1
Evaluation of Fiberglass Wrapped Concrete Bridge
Columns
WHRP Project 0092-07-07

• August 13, 2008

2
Problem Statement

• The service life of reinforced concrete elements
  is limited by corrosion deterioration.
• Deicing salts (used to reduce the freezing point
  of water) contributes to the corrosion process in
  the reinforced concrete elements.
• Fiberglass wrap can provide a barrier to moisture
  and deicing salts to reduce the corrosion rate of
  the steel reinforcement and thus extend the
  service life of concrete columns.

Introduction
Background
Testing Methods
Field Data
Conclusions
3
Objectives and Methodologies

• The main purpose of this study is to assess the
  effectiveness of the fiberglass wrapping in
  reducing the corrosion rate of reinforced
  concrete columns.
• To evaluate the integrity of fiberglass wrapped
  concrete element, field tests including wave
  propagation methods, half-cell potential
  measurements, and Cl- ion content were conducted
  on wrapped and bare columns.

Introduction
Background
Testing Methods
Field Data
Conclusions
4
Concrete Deterioration Process

• Cracking - Spalling - Delamination.

Cracking due to iron oxides being formed.
Spalling off
Separation due to delamination
(Neville 1996)
Introduction
Background
Testing Methods
Field Data
Conclusions
5
Concrete Deterioration Model

• Diffusion time for chloride ions to penetrate
  (Ficks 2nd law)
• Corrosion time from corrosion initiation to
  first cracking
• Deterioration time for rehabilitation to be
  required

Service life
Deterioration
Corrosion initiation
Initial cracking
Cracking
Diffusion
Deterioration
Corrosion
Time
(Cady and Webers 1983)
Introduction
Background
Testing Methods
Field Data
Conclusions
6
Corrosion Process

• The potential difference between anode and
  cathode is the driving electrical force for the
  corrosion process.

(Mehta 1996 Liu 1996)
Introduction
Background
Testing Methods
Field Data
Conclusions
7
Corrosion Process

• The corrosion process is expressed as

Volume of hydrated ferric oxide (Fe2O3H2O)
Volume of metal ion (Fe)
ferrous hydroxide
gtgt
Hydrated ferric oxide rust
large tensile stresses In the concrete mass
Delamination of interface between steel and
concrete
(Mehta 1996)
Introduction
Background
Testing Methods
Field Data
Conclusions
8
Corrosion Process (Carbonation Chloride
infiltration)

• Carbonation and Cl- penetration are two major
  causes of corrosion and delamination of reinforce
  concrete structures.

Passive layer breakdown
Carbonation
Lowers pH
Chloride infiltration
Increasing chloride concentration
Reproduced chloride
Introduction
Background
Testing Methods
Field Data
Conclusions
9
Repairing Method Fiber Glass Wrapping

• Fiber Reinforced Plastic (FRP) has been widely
  used in the reinforcement for seismic loads and
  in the structural maintenance.
• The external fiber glass wrapping aims at
  preventing further chloride ingress and reducing
  the corrosion rate inside the reinforced concrete
  structure.

Fiber glass wrapped column
Fiber glass fabric
Introduction
Background
Testing Methods
Field Data
Conclusions
10
Fiber Glass Information

• In Wisconsin, the applied wrap is Tyfo fiber
  wrap.
• Two layers were applied at each column.
• The different colors indicate different years of
  application of the wraps (gray or white).

Introduction
Background
Testing Methods
Field Data
Conclusions
11
Fiber Glass Wrapping Rehabilitation in Wisconsin
May 2007
September 2007
Introduction
Background
Testing Methods
Field Data
Conclusions
12
Non-Destructive Evaluation Methodologies

• Three types of field and laboratory testing
  methods were used for evaluating integrity of
  structure and corrosion rate
• Travel-time tomographic imaging
• - P-wave propagation
• - Electromagnetic wave propagation (GPR)
• The risk of corrosion
• - Half-cell potential measurements
• Chloride ion content
• - Cl- intrusion test

Introduction
Background
Testing Methods
Field Data
Conclusions
13
P-wave Measurements

• The estimation of the internal of deterioration
  is evaluated by measuring the P-wave velocity
• Reductions in the wave velocity are an indication
  of the internal deterioration of the concrete

(Ryall 2001)
Introduction
Background
Testing Methods
Field Data
Conclusions
14
Elastic Wave Propagation

• Source instrumented hammer
• Receivers piezoelectric accelerometers

Piezoelectric transducer
Oscilloscope
Signal conditioner
Laptop computer
Introduction
Background
Testing Methods
Field Data
Conclusions
15
Ground Penetrating Radar

• Ground penetrating radar (GPR) technique is based
  on the propagation of high-frequency
  electromagnetic waves.
• The propagation of electromagnetic waves depends
  on the electrical conductivity (function of Cl-
  content )and the dielectric constant (function of
  water content) in the medium.
• GPR systems are increasingly being used for
  identifying the degree and extent of
  deterioration in reinforced concrete elements.

Introduction
Background
Testing Methods
Field Data
Conclusions
16
Electromagnetic Wave Propagation

• Sensors Software Inc. pulseEKKO system
• 200MHz GPR Antenna

GPR control box
receiver
Laptop computer
transmitter
Introduction
Background
Testing Methods
Field Data
Conclusions
17
Travel-Time Tomographic Imaging

• Modeling equation

S3
S4
L1,1
L1,2
or
S1
R1
t1
t2
S2
R2
R4
R3
where, the value of Li,k is the distance traveled
by ray I in pixel k
(Santamarina and Fratta 2005)
Introduction
Background
Testing Methods
Field Data
Conclusions
18
Half-Cell Potential

• The half-cell potential measurement is a method
  based on the evaluating the driving
  electrochemical potential of the corrosion
  process.

(http//www.ndtjames.com)
Half-cell potential circuitry (ASTM C876-91)
Introduction
Background
Testing Methods
Field Data
Conclusions
19
Half-cell Potential Measurements

• Half-cell potential measurements can detect
  highly corrosive area in column (90 risk of
  corrosion).

Introduction
Background
Testing Methods
Field Data
Conclusions
20
Location of Bridges

• 50 fiber wrapped columns in 13 Dane County
  bridges were visually inspected

Introduction
Background
Testing Methods
Field Data
Conclusions
21
Damaged Columns
Introduction
Background
Testing Methods
Field Data
Conclusions
22
Bridge B-28-45 on Interstate 94 Highway
Col. B
Col. C
Introduction
Background
Testing Methods
Field Data
Conclusions
23
Bridge B-28-45 on Interstate 94 Highway

• P-waves, GPR tests and half-cell potential
  measurements were conducted for constructing
  tomographic images

Introduction
Background
Testing Methods
Field Data
Conclusions
24
P-wave Velocity Profiles
Measurements parallel to traffic direction
Introduction
Background
Testing Methods
Field Data
Conclusions
25
Tomographic Imaging Configurations

• Vertical 14x14 196 rays

• Horizontal 7x16 112 rays

Introduction
Background
Testing Methods
Field Data
Conclusions
26
Column B Tomographic images
Section A (parallel to traffic)
Section B (perpend. to traffic)
Section A (parallel to traffic)
Section B (perpend. to traffic)
Introduction
Background
Testing Methods
Field Data
Conclusions
27
Column B Tomographic images
Sonic measurements
GPR measurements
Section A (parallel to traffic)
Section A (parallel to traffic)
Section B (perpend. to traffic)
Introduction
Background
Testing Methods
Field Data
Conclusions
28
Tomographic images for column B
GL. 0.8 m
GL. 0.4 m
Introduction
Background
Testing Methods
Field Data
Conclusions
29
Tomographic images for column C
Section A
Section B
Section A
Sonic measurements
GPR measurements
Introduction
Background
Testing Methods
Field Data
Conclusions
30
Half Cell Potential Measurements
Fall 2007
Introduction
Background
Testing Methods
Field Data
Conclusions
31
Half Cell Potential Measurements
Summer 2008
Introduction
Background
Testing Methods
Field Data
Conclusions
32
Half Cell Potential Measurements
Column C
Introduction
Background
Testing Methods
Field Data
Conclusions
33
Chlorine Ion Concentration Measurements
Bridge 28-45
Introduction
Background
Testing Methods
Field Data
Conclusions
34
Chlorine Ion Concentration Measurements
Bridge 53-71
Bridge 13-144
Introduction
Background
Testing Methods
Field Data
Conclusions
35
Summary and Conclusions

• Most cracks are initiated at the bottom of
  columns.
• Degraded concrete areas appear as low P-wave
  velocities zones with velocity ranging between
  2,0003,000 m/s.
• Degraded concrete areas appear as low EM wave
  velocities zones with ranging between 0.100.13
  m/ns.
• The use of both vertical and horizontal
  tomographic image permits constraining the
  location of degraded areas.

Introduction
Background
Testing Methods
Field Data
Conclusions
36
Summary and Conclusions

• Half-cell potential measurements show that
  corrosion activity continues after the
  application of the fiberglass wrapping as
  indicated by half-cell potential readings both
  above and below the wrapping.
• The effectiveness of fiberglass wrapping was
  evaluated by measuring Cl- contents. The results
  show that in heavily damaged columns, the
  maintenance operations does not seem to have
  reduced, the Cl- concentration.
• These observations indicate the possibility of
  continuing corrosion and the need to further
  maintenance of even fiberglass wrapping columns.

Introduction
Background
Testing Methods
Field Data
Conclusions
37
Acknowledgments

• Kyu-Sun Kim
• Alex Summit
• Prof. Jose Pincheira
• Andrew Hanz (WHRP)
• UW-Madison Civil and Env. Engineering
• Wisconsin Department of Transportation