Korjauskonseptien kestävyyden

näkökohtia ja suositukset

rakennusteollisuudelle

Tomi Toratti

VTT Technical Research Centre of Finland

2 02/05/2012

Reference publications

D2.2 Guidelines for the use of building physical modelling

methods and tools in the development of sustainable refurbishment

technologies for external walls.

D4.2 General renovation concepts – Durability

D7.2 Guidelines for building industry

3 02/05/2012

D2.2 Guidelines for the use of building physical modelling

methods and tools in the development of sustainable

refurbishment technologies for external walls.

Methods to calculate building physical performance of walls

- Thermal performance

- Moisture control

- Durability (mould)

- Indoor air

Use of WuFi program

Practical guideline on how to carry out the calculations

- Inputs

- Analysis of output

- State of art in mould models

4 02/05/2012

D4.2 General renovation concepts – Durability

5 02/05/2012

Service load

Dead loadClimatic stresses

Biological factors

Stresses of

building envelopes

29.9.2011 - v12

Wind

Bending

Cracks

Falling down

Snow

Bending

Cracks

Falling down

Thermal

expansion

Bending

Cracks

Falling down

Own weightBending

Supported

structuresBending

Cracks

Creep Bending

Cracks

ShrinkageBending

Cracks

UV-radiation

Fading

Degradation

Ageing

Wind

Bending

Cracks

Falling down

Rain

Mois ture accumulation

Mould

Rotting

Salt migration

Fros t damages

Corrosion

Snow

Bending

Cracks

Falling down

Indoor air moistureMois ture accumulation

Mould

Temperature changesBending

Cracks

Freeze - thaw

Disintegration

Loss of strength

Peeling off

Fros tCracks

Breakage

Carbon dioxideCarbonation

Air pollutantsCorrosion

MouldHealth risks

Aesthetic aspects

RottingLoss of strength

InsectsAesthetic aspects

Loss of strength

PestsAir leakages

Health risks

6 02/05/2012

Frost damage

Corrosion

Degradation

Carbonation

Overload

Wetting - drying

Freeze - thaw

Moisture

Temperature changes

Salt migration

Solar radiation

Fire

Deterioration

mechamisms

2.10.2011 - v33

Peeling offPainting

Rendering

Cracking

Concrete

Masonry

Fragile porous materials

Rus tingSteel

CorrosionMetals

Glass

CrackingPlas tics

BreakagePlas tics

Becoming fragilePolymers

Plas tics

Loss of strengthPolymers

Plas tics

CrackingPolymers

Plas tics

CorrosionSteel bars

CrackingConcrete

BendingCladding materials

Supporting s tructures

BreakageCladding materials

Supporting s tructures

CrashCladding materials

CrackingTimber

ShrinkageTimber

Coating damagesPainting

CrackingConcrete

Rendering

Peeling offPainting

Rendering

Loss of strengthConcrete

Masonry

DisintegrationConcrete

Masonry

RottingOrganic materials

EnlargeningOrganic materials

Loss of

therm al insulationInsulation materials

Loss of strength

Timber

GypsumBoards

Filler

MouldingOrganic materials

Surfaces

Mois ture accumulationPorous materials

BendingSupporting s tructures

AgeingPolymers

Painting

Loss of strengthPlas tics

Polymers

Becoming fragilePolymers

Plas tics

Fretting

Bricks

Mortar

Concrete

Peeling offPainting

Rendering

Fading

Coatings

Organic materials

Colour pigments

AgeingPolymers

Painting

DegradiationPlas tics

Polymers

BurningOrganic materials

Loss of strengthMetals

CrackingConcrete

7 02/05/2012

Tools available for durability assessment

Moisture and heat transfer

Moisture sources: Interior: diffusion, air leakages

Exterior: Driving rain

Built-in: construction moisture

Mould growth analysis (all materials)

Frost attack, carbonation and reinforcement corrosion (Concrete)

8 02/05/2012

Calculation

WUFI Pro 4.2

9 02/05/2012

Calculation, 1% rain penetration

WUFI Pro 4.2

Rendering on insulation + 0,2% rain leakage

10 02/05/2012

11 02/05/2012

30 90 8010020

Min villa PUR

Viistosade vuoto 1% Ei sadevuotoja

12 02/05/2012

30 90 801003020

Viistosade vuoto 1% Ei sadevuotoja

13 02/05/2012

Degredation models 1

Internal Frost Attack

Internal Frost attack was evaluated based on the theory of Göran Fagerlund (theory of Critical Degree of Saturation). The progress of frost attack depends on the factor KN (depending on the number of freeze-thaw cycles) and the excess of critical degree of saturation at each freeze-thaw cycle

RDM is degree of damage or relative dynamic modulus (0 <

RDM < 1)

N number of critical freezing events,

S active degree of saturation at the moment of freezing,

Scr critical degree of saturation,

KN coefficient of degradation.

A, B and C are constants

Vcap is volume of all capillary pores (and other water filled

pores smaller than capillary pores),

Vair;tot total volume of air pores,

Vair;cr critical volume of (water filled) air pores

)(10

crN

N SSKE

ERDM

NB

NAK

C

N

totaircap

craircap

crVV

VVS

;

;

14 02/05/2012

Degredation models 2

Carbonation

Carbonation was evaluated using a modified carbonation coefficient. It depends on the relative humidity, temperature and possible internal cracking (RDM). The limit state of carbonation was the thickness of concrete cover.

xca is depth of carbonation, mm

xca increase of carbonation depth, mm,

kca carbonation coefficient, mm/a0.5

t increment of time, a

RDM degree of damage or relative dynamic modulus (0 <

RDM < 1).

relative humidity, %

T temperature, oK,

caca xx

tx

RDMkx

ca

ca

232.1)1(64.01(

875,05,0

0, )293/()172,3221.3( Tkk caca

15 02/05/2012

Degredation models 3

Corrosion of reinforcement

Corrosion of reinforcement starts when carbonation reaches the depth f reinforcement. Corrosion rate depends on relative humidity and temperature. The limit state of corrosion is cracking of concrete cover (serviceability limit state) or critical depth of corrosion (ultimate limit state).

s is depth of corrosion, m

s increase of corrosion depth, m,

cT temperature corrector factor,

t increment of time, a

relative humidity, %

T temperature, oC,

pbs is portion of blastfurnice slag from the total amount of

binder, %,

c concrete cover, mm

d diameter of reinffocment, mm

ss

00.195.015

95.02

29.0141 67.1

100

whentcs

and

whents

p

cs

T

bs

T

47 )30(106.1 TcT

)1(100; RDMd

cms sls

5;

ds uls

16 02/05/2012

Degradation models 4

Mould growth

Mould growth index M can be determined by using the temperature and relative humidity histories of the subjected material surfaces.

M is mould growth index

s increase of corrosion depth, m,

relative humidity, %

T temperature, oC, pbs is portion of blastfurnice slag from the total

amount of binder, %,

c concrete cover, mm

d diameter of reinffocment, mm

2

max100100 crit

crit

crit

crit

RH

RHRHC

RH

RHRHBAM

tkkt

M

MM

m

21

1

hoursRHTtm )02.66ln9.13ln68.0exp(247

0,)(3.2exp1max max2 MMk

Sensitivity class k1 k2

(Mmax)

RHmi

n

M<1 M>1 A B C %

Very sensititive (vs)

Sensitive (s)

Medium resistant (mr)

Resistant (r)

1

0.578

0.072

0.033

2

0.386

0.097

0.014

1

0.3

0

0

7

6

5

3

2

1

1.5

1

80

80

85

85

17 02/05/2012

Jyväskylä, Original structure, MW

Jyväskylä , MW

-40

-30

-20

-10

0

10

20

30

40

50

60

0 50 100 150 200 250 300 350

Time (days)

Te

mp

era

ture

(oC

)

Orig Front

Orig Back

Jyväskylä , MW

80

90

100

110

120

130

140

150

160

170

180

0 50 100 150 200 250 300 350

Time (days)

Wa

ter

co

nte

nt

(kg

/m3)

Orig Front

Orig Back

Wcritical

30 90 80

Jyväskylä , MW

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140

Time (years)

Co

rro

sio

n (

rela

tive

to

lim

it s

tate

)

Orig Front

Orig Back

MW

Time of repair = 65 years

18 02/05/2012

30 90 8010020

Jyväskylä, Concept E1, MW

Jyväskylä , MW

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140

Time (years)

Corr

osio

n (

rela

tive to li

mit

sta

te)

Orig Front

Orig Back

Before repair:

relative to serviceability

limit state

After repair:

Relative to ultimate limit state

Jyväskylä , MW

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140

Time (years)

Mo

uld

Gro

wth

In

de

x

Orig Front

Orig Back

MW MW

Repair

Repair

19 02/05/2012

30 90 8010020

Jyväskylä, Concept E1, PUR

Jyväskylä , PUR

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100 120 140

Time (years)

Corr

osio

n (

rela

tive to li

mit

sta

te)

Orig Front

Orig Back

Before repair:

relative to serviceability

limit state

After repair:

Relative to ultimate limit state

MW PUR

Jyväskylä , PUR

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140

Time (years)

Mo

uld

Gro

wth

In

de

xOrig Front

Orig Back

Repair

Repair Temporary mould problem

20 02/05/2012

30 90 80 50

ESP

MW

or

PUR

Interior refurbishment, I

21 02/05/2012

Important considerations

Air tightness

Water vapour permeability decreases towards the outside surface

Driving rain leakages are harmful

Ventilated facade improves the drying potential of the wall

22 02/05/2012

Refurbishment Concept E1, E2 – additional insulation laid on the original

outer core of the sandwich and covered by a layer of rendering.

- External added insulation - existing wall becomes warmer and drier

- Avoid structural layers between 2 vapour tight insulations (PUR, EPS)

- Frost attack

23 02/05/2012

Refurbishment Concept I – additional insulation laid on the interior side

- Condensation risk if vapour tight layers are in the existing wall,

- Thermal bridges are created between floor and wall junctions

24 02/05/2012

External insulation (E) - New outer service with retrofit insulation – effect on Fire Safety

A = Small houses

B = Terraced houses

C = Multi storey

External structures/layers:

Thin non-combustible =

Metal, rendering, etc.

Combustible = Wood, PVC,

etc.

Non-combustible

insulation = Mineral

wool

Combustible

insulation = EPS/XPS,

PUR/PIR, cellulose

based, etc.

E1 = Insulation fixed

without air gap

E2 = Insulation fixed

with air gap and

wind protection

WALL TYPE

BUILD

ING

TYPE

Type of external

structure/layer Type of insulation

Score

E1 E2

W2_Sandwich

element; concrete

panel + concrete

panel

C Concrete or similar Non-combustible 0 0

Combustible 0 -1

Thin non-

combustible

Non-combustible 0 0

Combustible -1 -2

Combustible Non-combustible -1 -2

Combustible -2 -2

Assessments of the refurbishment External insulation’s effect on the fire safety of the external wall and facade

25 02/05/2012

Recommendations

Considering durability aspects of the wall, excessive moisture is harmful.

Excessive moisture levels may cause mould to develop in the wall. This

may be a risk considering also the indoor air quality.

Considering fire safety, to reach the intended fire safety level for multi-

storey buildings, it is recommended to use non-combustible (=A1 or A2-s1,

d0 reaction to fire class) or at least B-s1, d0 class external boards/layers.

Considering structural stability the assessment of the load bearing capacity

of the existing walls must include a verification to ensure that it can

withstand the mounting of fastening points.

Considering buildability, the aspects which need to be checked are the

needs of space, availability of materials, work force, quality of

workmanship. These will depend on the project at hand and on the local

conditions.