Post on 15-Jan-2016
1
Barbara Lubelli1, Rob P.J. van Hees1,2, Henk P. Huinink3
Hygric dilation behaviour of NaCl contaminated lime-cement mortar
1 Delft University of Technology, The Netherlands
2 TNO BenO, Delft, The Netherlands
3 Eindhoven University of Technology, The Netherlands
7th European Conference SAUVEUR
Prague 31st May -2nd June 2006
2
COMPASS Project
Compatibility of plasters and renders with salt loaded substrates in historic buildings (2002-2005)
Main partners:
TNO BenO – NL (coordinator)
LRMH – F
TUE – NL
TUD – NL
CSIC IET – ES
LNEC - P
Main aims:
Model of transport & degradation mechanism
Requirements for plasters and renders
Accelerated crystallisation test
Experts system
www.compass-salt.org
3
NaCl damage mechanism
Sodium chloride does not reach high super-saturation
• “However, as it is not possible to obtain higher supersaturation than m/m0=2.2 of NaCl in levitated droplets, the occurrence of even higher supersaturation in pore solution is unlikely” [Steiger M., J. Cryst. Growth, 282,(3-4) 2005]
• “During this experiments with NaCl no supersaturation is found…” [Pel L. et al., Applied Physics letters, 81 (15) 2002]
In spite of this…
The NaCl damage mechanism is not fully understood.
therefore it can hardly develop high crystallization pressures.
4
…damage occurs
Venice (I)
La Rochelle (F)
Brouwershaven (NL)
5
Damage due to NaCl
0
5
10
15
20
25
30
35
40
HM
C (
w%
)
0 5 10 15 20 25 30depth (m m )
dried at 60C 0% R H
bulged layer
powder
No crypto-florescences
10-0357 (N) - Sanidine, K-rich, diso
05-0628 (*) - Halite, syn - NaCl47-1743 (C) - Calcite - CaCO346-1045 (*) - Quartz, syn - SiO2
File: 4bulknosalt.RAWFile: sample3030422.RAWFile: 6bulksalt.RAW
File: 5powdersalt.RAWFile: sample2030422.RAWFile: sample1030422.RAW
Lin
(C
ps)
5000
0
2-Theta - Scale
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
1 surface salt
2 powder salt
5 powder salt
6 bulk salt
3 surface no salt
4 bulk no salt
No expansive reaction
6
Hypothesis: differential dilation
High salt conc.
Low salt conc.
shear stresses at the interface
7
Experimental set-up
salt contamination by capillary rise from the bottom surface
lateral sides sealed with epoxy resin
evaporation surface
support
LVDT
blank specim en
balanceLVDT
LVD T
climatic cabinet
NaCl specimen
T & RH sensors
8.88 g
8
Hygric dilation
Dilation occurs during crystallization
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19tim e (days)
-0.1
0.0
0.1
0.2
0.3
0.4l /
l (
10
)
0
20
40
60
80
100
RH
(%
)-3
mas
s ch
ange
(g)
NaC
l spe
cim
en
R H N aC lcryst
R H air
N aC l
b lank
w eight change NaC l
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19tim e (days)
-0.1
0.0
0.1
0.2
0.3
0.4l /
l (
10
)
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
(g)
NaC
l spe
cim
en
R H N aC lcryst
R H air
N aC l
blank
w eight change NaC l
9
Hygric dilation
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14tim e (days)
-0.06
-0.04
-0.02
0.00
0.02
l /l
( 1
0 )
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
(g)
NaC
l spe
cim
en
N aC l
b lank
R H a ir
If the RHequ is not crossed, no irreversible dilation occurs
10
2 4 6 8 10 12 14 16 18 20 22 24tim e (days)
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4l /
l (
10
)
0
20
40
60
80
100
RH
(%
)-3
R H air
b lank
Damage mechanism
2 4 6 8 10 12 14 16 18 20 22 24tim e (days)
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4l /
l (
10
)
0
20
40
60
80
100
RH
(%
)-3
0
10
20
30
mas
s ch
ange
(g)
NaC
l spe
cim
en
R H a ir
b lank
N aC l
The dilation is irreversible and leads to damage
11
NaNO3 and KCl
0 1 2 3 4 5 6 7 8 9 10 11 12tim e (days)
-0.2
0.0
0.2
0.4
0.6
0.8
l / l
( 1
0 )
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
(g)
NaN
O s
peci
men
R H a ir
N aN O
blank
R H N aN Ocryst 3
3
3
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14tim e (days)
-0 .5
0.0
0.5
1.0
1.5
l / l
( 1
0 )
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
(g)
KC
l spe
cim
en
R H a ir
b lank
KC l
R H KC lcryst
12
ESEM investigation - NaCl
Salt layer
Salt layerPores >0.5m empty
Pores >0.5m empty
NaCl:
salt layer
13
ESEM investigation – NaNO3 and KCl
14
ESEM investigation – NaCl + inh.
agglomeration of NaCl crystals
NaCl crystals not adhering to the
substrate
NaCl + inh.:
no salt layer
15
Hygric behaviour NaCl + inh.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14tim e (days)
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
l / l
( 1
0 )
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
NaC
l+ fe
rroc
yani
de
R H a irN aC l
N aC l + ferrocyanide
No dilation occurs in presence of the inhibitor
16
Hygric behaviour – NaCl + inh.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20tim e (days)
-0 .5
0.0
0.5
1.0
1.5
l / l
( 1
0 )
0
20
40
60
80
100
RH
(%
)-3
-10
0
10
20
30
mas
s ch
ange
(g)
N aC l
N aC l + ferrocyanide
R H air
N aC l
N aC l + ferrocyanide
No dilation and no damage occurs in presence of a crystallization inhibitor
17
Conclusions
NaCl modifies the hygric dilation behaviour of a material.
Damage may result from the differential dilation between zones having different salt loads
A damage mechanism based on the mechanical interaction between salt and pore wall is proposed.
NaCl crystallizing as a layer on the pore walls causes irreversible dilation and damage during crystallization.
No dilation and no damage is observed when the same salt crystallizes without adhering to the pore wall.
18
Thanks for your attention