DataPDF Available

Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks - Powerpoint presentation

Authors:

Figures

No caption available
… 
No caption available
… 
No caption available
… 
No caption available
… 
No caption available
… 
Content may be subject to copyright.
Assessment, Upgrading and Refurbishment of Infrastructures
IABSE Conference, Rotterdam, May 6 - 8, 2013
MONITORING OF REINFORCEMENT
CORROSION IN FIELD EXPOSED
CONCRETE BLOCKS
Henrik Erndahl Sørensen¹, Dorthe Mathiesen¹
Ulf Jönsson², Christian Munch-Petersen³
¹Danish Technological Institute
²Femern A/S, ³Emcon A/S
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
2
INTRODUCTION
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Chloride induced reinforcement corrosion is typically the main
concern for durability of marine structures
Service life modeling of marine structures are based on
estimates of the chloride penetration and the chloride
threshold concentration (CTC) for corrosion initiation
A standard test method for determination of CTC-values are
not established
(RILEM TC 235-CTC are currently working on it)
Anode ladders for corrosion monitoring have been installed in
many structures, but in many cases the evaluation of data
from HCP-values have been difficult
3
FIELD EXPOSURE SITE
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
New immersed tunnel
(Femern A/S)
Field exposure site
4
FIELD EXPOSURE SITE
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
5
ANODE LADDERS
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
6
CONCRETE BLOCKS
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
7
CONCRETE MIX DESIGNS
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Three instrumented concrete blocks
No. 1: Mix A
Low-alkali SR Portland cement
CEM I 42,5 N (HS/EA/≤ 2)
No. 2: Mix F
84% low-alkali SR Portland cement
12% fly ash
4% silica fume
No. 3: Mix K
Slag cement
CEM III/B 42,5 N
w/b ratio
0.40
Anode cover
depth Approx. 10, 20, 30 and 40 mm
Details regarding cement composition and concrete mix designs are
presented in the full paper on the CD-rom
8
FIELD EXPOSURE
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
9
SELECTED DATA FROM MIX A
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Marine exposure
Monitoring
system
installed
10
SELECTED DATA FROM MIX A
11
SELECTED DATA FROM MIX A
12
SELECTED DATA FROM MIX A
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Marine exposure
Monitoring system installed
13
SELECTED DATA FROM MIX A
14
CORROSION INITIATION
Mix/Ladder No.
Date/exposure time
mV drop
Remarks
Mix A/No
. 1
05
-10-2011/342 days
387 mV
Repassivation
Mix A/No
. 2
05
-10-2011/342 days
447 mV
Corrosion continues
Mix A/No
. 4
05
-10-2011/342 days
295 mV
Repassivation
Mix F/No
. 2
13
-12-2010/46 days
286 mV
Corrosion continues
Mix F/No
. 4
25
-03-2011/148 days
263 mV
Corrosion continues
Observations of anodes with of possible corrosion initiation:
So far, corrosion initiation has not been observed on anodes in Mix K
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
15
CORROSION INITIATION
Typical values for half-cell potential and linear polarisation resistance on
passive anodes:
Observations on corroding anodes show that the half-cell potential (HCP)
with time drops to values below -800 mV vs. ERE20 and the linear
polarisation resistance (LPR) drops to values in the range 100-400 Ohm.
Exposure conditions Immersed zone Splash zone
Concrete composition Mix A Mix F Mix K Mix A Mix F Mix K
HCP (mV vs. ERE20) -300 -400 -600 -200 -300 -300
LPR (kOhm) 1-3 1-5 1-5 1-3 1-3 1-5
HCP-values are measured against the ERE20 reference electrode
(Mn/MnO2). Correction to CSE reference electrode (Cu/CuSO4) is done by
adding 100 mV.
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
16
CORE DRILLING
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
17
POSITION OF CORES
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Two cores were
drilled from similar
positions in all three
blocks
Top cores were
placed between the
two corrosion
ladders
Bottom cores were
placed directly over
the outmost
horisontal anode After repair
After core drilling
18
INSPECTION OF ANODES
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Mix K: Only initial rust is seen on the
electrode
(No indication of corrosion initiation from
the monitoring data)
Mix F: Three rusting spots is seen on the
electrode and also in the concrete
(Clear indication of corrosion initiation
from the monitoring data)
Mix A: Only initial rust is seen on the
electrode
(Clear indication of corrosion initiation
from the monitoring data)
19
INSPECTION OF ANODES
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Mix F: Three rusting spots
is seen on the electrode
and also in the concrete
interface (arrows).
These three spots were
dark just after breaking
the sample, but became
brown before the photo
was taken.
20
CHLORIDE PROFILES
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
21
CHLORIDE THRESHOLD VALUES
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
Mix no./exposure zone
Corrosion activity
Chloride threshold value
[%
Cl by mass of concr.]
Mix A / Splash zone
No
corrosion
>0,08
Mix A / Immersed zone
Corrosion on 1
st anode
>0,22 and <0,34
Mix F / Splash zone
No
corrosion
>0,09
Mix F / Immersed zone
Corrosion on 1
st anode
>0,10 and <0,36
Mix K / Splash zone
No
corrosion
>0,10
Mix K / Immersed zone
No
corrosion
>0,07
The chloride content at the depth of the anodes has been calculated from the
curve fitted parameters at 532 days of marine exposure
22
CONCLUSIONS
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
The combined use of HCP and LPR measurements might be
applicable to give a more safe detection of corrosion initiation
in concrete structures. However the number of observations
are still too limited to make a final conclusion.
The ongoing experiment is expected to show, how this setup
can be used to determine in-situ chloride threshold values and
thereby producing valuable input to service life modeling of
chloride exposed structures.
23
ACKNOWLEDGEMENT
Monitoring of Reinforcement Corrosion in Field Exposed Concrete Blocks
Presented by: Henrik E. Sørensen, Danish Technological Institute
The present work has been performed in a cooperation
between Femern A/S and the Concrete Expert Centre
The Concrete Expert Centre is a cooperation between the
Danish Technological Institute and the Danish Technological University
ResearchGate has not been able to resolve any citations for this publication.
ResearchGate has not been able to resolve any references for this publication.