content and reactivity of alkali silica on concrete bridge ... · content and reactivity of alkali...

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

Helsinki, 2013 8

«Content and reactivity of alkali silica on concrete

bridge structures»

SJSC «Latvian State Roads»

Riga Technical University

Aims:

– Analysis

– Collection

– Observations

– Recommendations

Helsinki, 2013 9

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

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Thank you!

Jūlija Ivanova

Julija.Ivanova@lvceli.lv