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Annual Concrete Seminar 2015, 29 April 2015
Durability Design of Concrete Structures Enhanced by Protective Coating in Marine Environments
Jian-Guo DAI (Dr) Associate Professor Department of Civil and Environment Engineering The Hong Kong Polytechnic University
2
Outline of this presentation
1. Background 2. Importance of Protective Coating 3. Service Life Design of Marine Concrete
Structures with Protective Coating 3.1 Probabilistic theoretical model 3.2 Laboratory tests 3.3 Field tests
4. Conclusions
3 Deterioration of beams
Deterioration of slab Corrosion-induced crack
A durability failure is more often seen than a structural failure.
(Courtesy of Dr E. Kato)
Background: Steel corrosion in marine concrete structures
6
Background: Steel corrosion in marine concrete structures
Ironstone
steel cement
concrete
[high potential ]
[low potential]
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Anode Cathode Cathode Cathode Cathode
Moist concrete as an electrolyte
If anode and cathode are separated in an infinitesimal distance, then the cell is called micro-cell. If anode and cathode are separated distinctly from each other, then the cell is called macro-cell.
Background: Macro-cell and micro-cell corrosion
8
Background: volumetric expansion due to oxidation o
Fe
Fe 2 O 3
FeO Fe 3 O 4
Fe(OH) 2
Fe(OH) 3
Fe(OH) 3 .3H 2 O
Volume (cm Volume (cm 3 3 ) ) 1 0 2 3 4 5 6 7
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Propagation stage
Acceleration stage
Appe
aran
ce o
f det
erio
ratio
n
Service period
Stru
ctur
al p
erfo
rman
ce Corrosion initiation
Initiation of corrosion crack
Aesthetics problem; Interfering of the third part
Increasing loss of serviceability and safety
D C A B
C
Evolution of steel corrosion in marine concrete structures
Pay here? Pay here?
Deterioration stage
Initiation stage
Source: 港湾の施設の維
持管理技術マニュアル
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Importance of protective coating
青岛胶州湾大桥: 100 years http://news.163.com/11/0701/04/77RO0CH00001124J.html
杭州湾大桥: 100 years http://www.lyzn.com/Zhejiang/Class100/20143.html
港珠澳大桥:120 years http://finance.people.com.cn/n/2013/1202/c1004-23718232.html
Service life extension purpose
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Importance of protective coating
Initiation
Propagation
Acceleration
Deterioration
H2o
Preventive maintenance is very important!
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MLWL
MHWL
MLWL-1m
Marine atmosphere Splash zone
Tidal zone
Submerged zone
Below the sea bottom
Protective coating method
Cathodic protection
Importance of protective coating
Example: durability design concept in case of steel piles.
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Typical protective coating
1. Topical sealer
2. Penetrating sealer
1.1 Continuous film: e.g. epoxy
1.2 Thick coating: e.g. shotcrete
2.1 Pore-blocking treatment: e.g. sodium sil
2.2 Pore-lining treatment: e.g. silane
Bertolini et al. (2004)
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Durability design of surface protected concrete structures: Theoretical modeling
Code of Practice for Structural Use of Concrete 2013: Prescriptive design approach
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Durability design of surface protected concrete structures: Theoretical modeling ( ) ( )0,
21, 0 xC
tDxerfCtxC +
⋅
−=
( ) ( )[ ] ( )72 1015.3log47.814.05.4log ×+−+= CWCWD
( ) ( )[ ] ( )72 1015.3log74.58.135.19log ×+−−= CWCWD
where C(x, t) = chloride ion content at the depth of x (cm) and at time t (years) (kg/m3) C0 = chloride ion content on the concrete surface (kg/m3) D = apparent diffusion coefficient of chloride ions (cm2/year) erf = error function C(x,0) = content of initially included chloride ions (kg/m3)
2
2 ),(),(x
txCDt
txCap ∂∂
=∂
∂
Performance-based approach: e.g. JSCE2012
Splash zone Distance from the coast (km) Near the coastline 0.1 0.25 0.5 1.0
13.0 9.0 4.5 3.0 2.0 1.5
for ordinary Portland cement
for blast-furnace slag cement
C0
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Durability design of surface protected concrete structures: Theoretical modeling
Threshold concentration
Steel reinforcement
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Durability design of surface protected concrete structures: Theoretical modeling
表面处
理层
2
2
1 xCD
tC
∂∂
=∂∂
10 hx <<
2
2
2 xCD
tC
∂∂
=∂∂
21 hxh <<
∑∞
=
−+=1
20 )exp()(
nnnn txfACC λ
+<<−−
<<=
21122122
11
11
},/)(cos[)/cos()/sin(0 ),/sin(
)(hhxhDhhx
DhDh
hxDxxf
nn
n
n
n λλ
λλ
0 10 20 30 40 500
1
2
3
氯离子浓度
(混凝土质量百分比) %
氯离子扩散深度(m m )
有限元 式(
Chl
orid
e co
ncen
trat
ion
Depth (mm)
FEM Equation
20
( ) ( )Pr ,f tP t C x c t C= = ≥
Durability design of surface protected concrete structures: Theoretical modeling
Probabilistic approach
e.g., Duan et al. (2005) Duan, A., Dai, J.G. and Jin, W.L. (2015), Probabilistic Approach for Durability Design of Concrete Structures in Marine Environment, ASCE, Journal of Materials in Civil Engineering, 27, Special Issue on Sustainable Materials and Structures, A4014007.
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Durability design of surface protected concrete structures Theoretical model Variable Mean COV Distribution
D2 6×10-6
mm2/s 0.20 Log-normal
C0 2.0% 0.30 Log-normal h1 7.72mm 0.21 Log-normal h2 61.49mm 0.16 Normal n 0.25 0.20 Normal
Ct 0.5% —— Constant
0 20 40 60 80 1000
20
40
60
80
100
腐蚀概率(
%)
时间 (年)
Dc
Dc/2 Dc/5 Dc/10 Dc/15 Dc/20
腐蚀概率:90%
Time (year)
Pf=
Freq
uenc
y
Concrete cover thickness
Cor
rosi
on
prob
abili
ty(%
)
22
Durability design of surface protected concrete structures: Laboratory tests
Surface impregnation
Dai, J.G., Akira, Y., Wittmann, F. H. , Yokota, H. and Zhang, P. (2010), Water Repellent Surface Impregnation for Extending the Service Life of RC Structures in Marine Environment: the role of cracks, Cement and Concrete Composites, 32(2): 101-109.
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Durability design of surface protected concrete structure: Laboratory tests
ASTM C1585-04 Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic Cement Concretes
0 200 400 600 8000
3
6
9
12
15
18
21
毛细吸水量
(g)
时间 (s0.5)
65-8-0 65-8-1 65-8-2
Wat
er a
bsor
ptio
n (g
)
24
Durability design of surface protected concrete structure: Laboratory tests
Charge passed (c) >4000 2000~
4000 1000~2000 100~1000 <100
Chloride ion penetrability High Moderate Low Very low Negilible
0 60 120 180 240 300 360
4
5
6
7
电流
(mA)
时间 (分)
B7 B8 B19
ASTM C1202-12 Standard test method for electrical indication of concrete’s ability to resist chloride ion penetration
25
Durability design of surface protected concrete structure: Laboratory tests
Seawater Immersion Tests (e.g. NT BUILD 43: Accelerated Chloride Penetration)
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Durability design of surface protected concrete structure: Laboratory tests
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.0
0.3
0.6
0.9
1.2
1.5
氯离
子浓
度
(混凝
土质
量百
分比
)%
氯离子扩散深度(m m )
B26-2
0 5 10 150.0
0.1
0.2
0.3
0.4
氯离
子浓
度
(混
凝土
质量
百分
比) %
氯离子扩散深度 (m m )
试验值 回归值
45-1-2
Scanning electron microscope (SEM) analysis
Potentiometric titration method
27
Durability design of surface protected concrete structure: Laboratory tests
Sea water
Evaluation of surface protected cracked concrete
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Durability design of surface protected concrete structure: Laboratory tests
Non-treated concrete (with cracks) (by means of neutron
radiography)
Contact time with water: 0 min 1 min 30 min
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Durability design of surface protected concrete structure: Laboratory tests
Contact time with water: 0 h 2 h 48 h
Surface protected concrete (with cracks) (by means of neutron
radiography)
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Durability design of surface protected concrete structure: Laboratory tests
0.1mm
0.2mm
0.4mm
Non-treated concrete (with cracks)
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Durability design of surface protected concrete structure: Laboratory tests
0.1mm
0.2mm
0.4mm Surface protected concrete (with
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Durability design of surface protected concrete structure: Field tests Long-term
exposure Accelerated
test
Field exposure site in Port and Airport Research
Institute, Japan
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Durability design of surface protected concrete structure: Field tests
Shenzhen West Governmental Port (深圳西部政府码头)
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Durability of marine concrete structures is a very important issue. For a 120-year service life design, supplementary protective measures for concrete is deemed necessary based on a preventive maintenance strategy.
Conclusions
Probabilistic performance-based approach is needed for use to predict the service life of surface protected marine concrete structures.
Appropriate methods are needed for deployment to evaluate both laboratory and field performance of surface protected concrete to obtain reliable input parameters for durability design.
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Thank you for you attention.
Jian-Guo Dai at [email protected] Associate Professor Department of Civil and Environmental Engineering The Hong Kong Polytechnic University