content and reactivity of alkali silica on concrete bridge ... · content and reactivity of alkali...
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Helsinki, 2013
1
Content and reactivity of alkali silica
on concrete bridge structures
Julija Ivanova
SJSC «Latvian State Roads»
Helsinki, 2013 2
General overview of bridges in Latvia
Total amount: 943 bridges
Distribution of building material: Distribution of static system:
0
10
20
30
40
50
60
70
80
Simplysupported
Continuous Frame Cantilever Arch
73
11 10 3 3
100 %
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3
Distribution by building years
0
50
100
150
200
250
300
350
3 1 4 3 14 34 26
108
308
181
114
48
97
2
Examples of bridges in Latvia
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Reinforced concrete bridges in Latvia
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104-year-old bridge over the Gauja river
105-year-old bridge over the Salaca river
Examples of the effects of alkali-silica
on Latvian brigdes
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Helsinki, 2013 7
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«Content and reactivity of alkali silica on concrete
bridge structures»
SJSC «Latvian State Roads»
Riga Technical University
Aims:
– Analysis
– Collection
– Observations
– Recommendations
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SiO2 + 2NaOH + H2O = Na2SiO3∙2 H2O
Silica Alkali Water Alkali-silica gel
Conditions for ASR:
1. Alcali content in cement
2. Reactivity of aggregates
3. Humidity
Alkali-silica reaction
Influence of humidity on alkali-silica reaction
Time, (month)
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Exp
ansi
on, (
%)
Relative air humidity in Latvia:
65 ÷ 96 %
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Alkali content in concrete structures S
ourc
e
Alkali from cement
Alkali from aggregate
Alkali from admixture
Alkali from external source (de-icing salt)
‼
‼
0,8
m3/k
m N
aC
l
Expansion if
Eqv. Na2O > 3 kg/m3
Requirements for concrete composition
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1. National annex of Latvian standard to European standard EN 206-1-1
9. Table:
Criteria of low alkali content cement
Widely-used cement in LV:
• CEM I 42,5 (N,R)
Alkali content of cement in Latvia
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Na2Oekv. = 0,9 %
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Reactivity of aggregates
Aggregate expansion capacity influenced by alkali content
Non-active aggregates ‼
Reaction
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Riga Technical University's laboratory
RILEM AAR-2 test
2 concrete mixtures (3 patterns each)
Cement + Granite
Cement 1000 g
Aggregate 2250 g
Water 500 g
Cement + Sand
Cement 1000 g
Aggregate 2250 g
Water 487 g
Expansion test
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Measurement results:
Mixture: Cement + Granite
Design.: V I-Gr Time,
days 1. pat. , mm 2. pat. , mm 3. pat. , mm Av., mm Av., %
0 0 0 0 0,000 0,000 2,5 0,000 0,000 0,000 0,000 0,000
4 0,000 0,000 -0,002 -0,001 0,000 5 0,004 0,001 -0,001 0,001 0,001 7 0,008 0,001 0,000 0,003 0,002
10 0,006 0,002 0,000 0,003 0,002 12 0,010 0,009 0,000 0,006 0,004 14 0,013 0,012 0,010 0,012 0,007
Mixture: Cement + Sand Design.: V I-Sm
Time, days 1. pat. , mm 2. pat. , mm 3. pat. , mm Av., mm Av., %
0 0 0 0 0,000 0,000 2,5 0,000 -0,002 -0,004 -0,002 -0,001
4 0,000 -0,002 -0,004 -0,002 -0,001 5 0,010 0,010 0,011 0,010 0,006 7 0,023 0,010 0,021 0,018 0,011
10 0,020 0,013 0,021 0,018 0,011 12 0,015 0,022 0,025 0,021 0,013 14 0,021 0,022 0,024 0,022 0,014
Expansion deformation
Expansion deformation
0,014 < 0,10
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«Bridge Specifications 2005»
Feature Aggregate type Precised
requirement
Reactivity of alkali, max. expansion
in 52 weeks (%)
Coarse
aggregates 0,04
Reactivity of alkali, max.
expansion in 14 days (%)
Coarse
aggregates0,1
Max. water absorption % from
aggregate volume
Coarse
aggregates 1,00
Max. expansion in 20 weeks % Fine aggregates 0,10
Max. content of particles which size
< 0,063 mm, from fine aggregate, % Fine aggregates 3,00
P M A E
Max. water-cement ratio - 0,55 0,45 0,4
Min. class of concrete strength C12/15 C25/30 C35/45 C40/50
Min. class of cement strength 32,5 42,5 42,5 42,5
Min. cement content in concrete, kg/m3
260 300 320 340
Max. ash and cement ratio - 0,33 0,33 0,33
Max. micro-silicon and cement ratio - 0,11 0,11 0,11
Equivalent alkali Na2Oeq content in
cement, (%)- ≤ 0,60 ≤ 0,60 ≤ 0,60
Max. equivalent alkali Na2Oeq
content in concrete, kg/m3- ≤ 3,0 ≤ 3,0 ≤ 3,0
Chloride content class
Cl 0,40
Cl 0,20 Cl 0,20 Cl 0,20
Cl 0,20
Cl 0,10
Min. air content in fresh concrete (%)
from total volume 4,5 4,5 4,5 4,5
Min. air content in hardened concrete
(%) 4,0 4,0 4,0 4,0
Frost resistance test - good good good
Environmental impact classesAttribute
Requirements for aggregates
Criteria for concrete
‼
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EU requirements for concrete in aggressive environments
Equivalent alkali Na2Oeq content in cement, [ % ]
Equivalent alkali Na2Oeq content in concrete, [ kg/m3 ]
Poland
Denmark
France
Holland
Norway
Belgium
Portugal
United Kingdom
Germany
≤ 3.0
≤ 2,5 - 5
Expansion test
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Conclusions
ASR
Alkali Reactivity Humidity
Durability
