ncrd2011 presentation kolio

8/4/2019 NCRD2011 Presentation Kolio

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Nordic Concrete Research Symposium 2011Hmeenlinna, Finland 30.5. - 1.6.2011

Arto KliTampere University of Technology, Department of Structural Engineering

Jukka LahdensivuTampere University of Technology, Department of Structural Engineering

The Calculated Need for Repair of ConcreteFacades in Finland


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Department of Structural Engineering, Arto Kli2

AGENDA

- Finnish building stock

- Focus and motivation

- Degradation model

- Calculation results

- Conclusions

The Calculated Need for Repair of ConcreteFacades in Finland


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FINNISH BUILDING STOCK

In all 2,7 million apartments of which 1,2 million in apartmenthouses.

That is 56 000 buildings = about 44 million m2 of concrete facade

975 000 balconies

Approximately 8 m2 of concrete facade per inhabitant

About 3 families out of 4 have their own balcony (given that a familyconsists of 2+2 persons)


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Why the Repair Need Calculations are needed

Over 70 % of the national wealth is invested in built

environment and 49 % in buildings.

Two main concerns are the facades and the plumbing

of buildings.State of the Built Environment

-report , RIL, 2011

Relatively young buildings from 1960s and 1970s

have required extensive repairs.

The calculation provides help in planning facade

repairs by quantifying the need.


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Focus of the calculation

The calculation includes prefabricated concrete facades and balconies in

Finland from 1965 to 1995.

Degradation induced repair need, the effect of annual repairs is not included

Time period of 2010 2050 in 5 year intervals.

Repair costs (/m2 or /balcony) are estimates from 2009

0

2000

4000

6000

8000

10000

12000

14000

-1920

1921 -1939

1940 -1959

1960 -1969

1970 -1979

1980 -1989

1990 -1999

2000 -2009

buildings

Finnish apartment houses

Source: Statistics Finland, 2009

Facades in the finnish building stock

Other

Metal

Wood

Tile

Concrete

Prefabricated

concrete

Rendering

Source: VTT, 2005


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Degradation model for prefabricated facades

For assessing the repair needs of a group ofbuildings

Based on condition assessments conducted onconcrete facades

Distribution of key properties that correlate closely

with the major degradation mechanisms

Adjusting the results

-extent of repair need

-cost of the repairs

Group of

buildings

- Input data

- type house

Analysis

(based on the input data)

The condition of

facades of the right

surface type


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Degradation model for prefabricated facades

Frost weathering of concrete

Freezing of concrete pore water creates hydraulicpressure in capillary voids

Commonly protected with air entraining

Corrosion of facade reinforcement

Corrosion protection of reinforcement is destroyeddue to ingress of CO2 or chlorides

Capillary void

Protective

pore

Water

CO2

Carbonationfront

Corrosion

speed

A/cm2]

Criticalhumidity

RH [%]


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FIELDINVESTIGATIONS

LABORATORYTESTS

EXAMINATION OF

DESIGN DOCUMENTS

DEGRADATION:

- Existence

- Extent

- Degree

- Reasons

- Impact

- Rate of Progressin the Future

CONCLUSIONS:functioning and condition

remaining service life

safety

repair needs

VISUAL

INSPECTION


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Some basic data from the database

A condition investigation report includes information on:

- cover depths of steel bars, carbonation depth of concrete, porosityof concrete, thickness of insulation layer etc. in numerical form.

- Information is also in verbal form, like thin-section analyses,

situation and amount of visual damage, condition of coatings etc.

Condition assessment reports from 947 buildings


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Frost weathering

of concrete

No visible

Local

Extensive

Protectivecoating

Patchrepair

Cladding repair

No needfor repairs

Visiblefrost

damage

Protectivepore coefficient

0,20

Protectivepore coefficient

0 0,19

28%

( 0,72 * 0,57 = 0,41)

72% 57%

3%

40%

( 0,72 * 0,40 = 0,29)

2%

29%

41%

( 0,72 * 0,03 = 0,02)

1

2

3

4

5

0 10 20 30 40 50 60 70 80

extentofdamage

time [years]

1 NO VISIBLE DAMAGE

2 LOCAL DAMAGE

3 EXTENSIVE DAMAGE

inland

pr < 0,10

inland

pr 0,10 -0,15

inlandpr 0,15 - 0,19

coastal area

pr < 0,10

coastal area

pr 0,10 -0,15

coastal area

pr 0,15 -0,19

Degradation model: Frost Weathering

The situation in 1970s

facades


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Distributionof

carbonation depths

Distribution of

cover depthsCorroding

reinforcement

Corrosion of

reinforcement

Reinforcement in corrosive state. (estimating a reasonable

depth to which repairs are extended)

Cover depth exceeds

the carbonation

depth

No need for repairs

Carbonation has

reached the cover

depth

85%

Situation in 2011:

15%

Situation in 2026:

Distributions of carbonation depths and cover depths in

brushed painted facades from 1970 - 1974

76%

24%

Degradation model: Corrosion of the Reinforcement

Cover depths of steelbars, Balcony frame

Single measurements 32 676 piece from 653

buildings

0

5

10

15

20

25

0-4

5-9

10-1

4

15-19

20-2

4

25-29

30-3

4

35-39

40-4

4

45-49

>50

Cover depth [mm]

Share[%]


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Calculation results.


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A sample was gathered randomly from 5 localities tocharacterize the facades in Finnish apartment houses.

The sample group consists of 418 buildings from 1965 1995.

Initial properties

0 %10 %20 %30 %40 %50 %60 %70 %80 %90 %

100 %

Surfaces of Concrete Facades in the sampleexposed aggregate

brushed, painted

tile surfaced

form surfaced, painted

clinker surfaced

brushed, unpainted

form surfaced,

unpaintedfloated, painted

white concrete

0

20

40

60

80

100

120

140

160

180

Building age distribution in the sample

Facades

Balconies


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The repair cost of cladding repair is 1,9 times the cost ofpatch repair and 4,9 times the cost of protective coating.

The price level is set constant over Finland.

Initial properties

Facades [/m2] Balconies [/balcony]

Protective coating 40 Protective coating 2000

Patch repair 100 Patch repair 5000

Cladding repair 195 Renewal 9000


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Calculation results, current state

0 %

20 %

40 %

60 %

80 %

100 %

Repair Needs of Prefabricated Concrete

Facades 2010

cladding repair

Patch repair

protective coating

protective coating not possible

no repair need

The share of claddingrepair is 5 10 %.

Patch repair is

currently the biggest. There is a remarkable share ofrough surfaces where protectivecoating is not applicable.

Approximately of these facades require repair or maintenanceof some extent.

Protective coating


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0 %

20 %

40 %

60 %

80 %

100 %

Repair Needs of Prefabricated Concrete

Balconies 2010

renewal

patch repair

protective coating

no repair need

Calculation results, current state

The need for renewalis 12 19 %.

Patch repair

Approximately half of the balconiescan be protected with coating.

Only 13 21 % of balconies do not require repair or maintenance.


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Calculation results, propagation

0

500 000

1 000 000

1 500 000

2 000 000

volumeofrepairs[m2]

The repair need of facades in Helsinki

Cladding repair

Patch repair

Protective coating

The repair need of facades in Helsinki.

The worst case scenario. (situation where facades degrade freely)


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Calculation results, propagation

The repair need increases 1.8 % annually.

The effect of the more expensive cladding repair to the totalcosts accumulated is major.

The model is ideal in a sense that only the damaged areas arerepaired.

0

100 000 000

200 000 000

300 000 000

400 000 000

500 000 000

value[]

Value of the Repair Need 2010

peittv korjaus

paikkaus ja pinnoitus

suojaava pinnoitus

0

100 000 000

200 000 000

300 000 000

400 000 000

500 000 000

Value of the Repair Need 2050

peittv korjaus

paikkaus ja pinnoitus

suojaava pinnoitus


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The value of the repair needs of prefabricated concrete facades and balconiesis

At the moment 3.5 billion (43 % facades, 57 % balconies)

The average increase is 1.8 % annually for the time period 2010 2050

The 1.8 % means annually 63 million repair costs for these facades andbalconies alone to maintain their present health.

The possibility to use protective coatings is utilized

Calculation results, expenses


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The model is based on data from existing structures and

represents the actual state that the structures are in.

This is a statistical examination reliable only in larger groups of

buildings with a useful range of the model limited to 1965 1995due to the limitations of the database. It is also limited to buildingsconsisting of prefabricated units. (Currently the main interest in Finland)

Compared to the estimations of annual facade renovation volume theannual repair need is lower. The model is ideal.

Conclusions


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There is still time for the use of lighter protective repair measures.

Anticipating repairs and the use of protective measures can help

lower the annual repair costs.

Developing protective coating for exposed aggregate facadescould enhance the possibilities to preserve the 1970s and 1980s buildingstock.

Conclusions


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Thank you for your [email protected]

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