INTERNATIONAL SEMINAR: The Thaumasite Form of Sulfate Attack of Concrete
THAUMASITE FORMATION IN LIMESTONE FILLER CEMENT
MORTAR UNDER SULFATE AND CHLORIDE EXPOSURE
S M Torres 1,2 , C J Lynsdale1, R N Swamy 2 , J H Sharp 3
Ordinary Portland cement BS ENV 197-1 CEM I (0 and 5% CaCO3), Portland-limestone
cement CEM II/A-L (15% CaCO3) and Portland-composite cement mortar CEM II/B-M
(8.5% Metakaolinite and 15% CaCO3) have been tested in sulfate solution alone (0.60% SO4
as MgSO4.7H20), sulfate combined with chloride (0.5, 1.0 and 2.0% Cl as NaCl) and
synthetic sea water at 5 and 20oC for 44 weeks. The mortar prisms - mix proportion 1:2.5:0.5
(binder:sand:water/binder)- were cured in water for seven days and 21 days in air at room
temperature. Prior to immersion in each specific solution, the prisms were cut in to
2x2x2cm3 cubes. The conditions of the samples were assessed by means of visual inspection,
X-ray diffraction (XRD) and Infrared spectroscopy (IRS).
Under the exposure conditions studied in this work, preliminary results suggest that the
deterioration in samples exposed to combined sulfate/chloride solutions seems to depend on
temperature, chloride concentration, carbonate content and cement type. At 20oC, chloride
seems to mitigate the sulfate attack in all mixes in all concentration levels. Nevertheless,
samples immersed in combined chloride/sulfate solution at 5oC presented much higher degree
of deterioration, which increased as CaCO3 increased. All samples containing limestone
presented higher levels of damage as the chloride/sulfate increased, but this trend does not
seem to be linear. The most intense attack was found in samples with 15% CaCO3 that were
immersed in 1.0%Cl, in which higher content of octahedron Si was found. The presence of
Thaumasite/Ettringite type of phases indicates that a thaumasite type of sulfate attack caused
the damage. The exact mechanism is still under investigation. OPC CEM I with 5% limestone
filler was more damaged than OPC without any replacement. Mortars containing CEM II/BM with Metakaolinite did not present any sings of deterioration throughout the period of this
investigation in both sulfate alone or combined chloride and sulfate solutions, at both
temperatures.
___________________________________________________________________________
Centre for Cement and Concrete
1 Department of Civil and Structural Engineering
2 Department of Mechanical Engineering
3 Department of Engineering Materials
University of Sheffield, Mappin Street,
Sheffield, S1 3JD.
C
M A
Thaumasite formation in Limestone Filler
Cement Mortar Under Sulfate and
Chloride Exposure
Sandro Marden Torres
Dr Cyril Lynsdale
Prof RN Swamy2
Prof JH Sharp3
1,2
1
The University of Sheffield
Centre for Cement and Croncrete
1 Department of Civil and Structural Engineering
2 Department of Mechanical Engineering
3 Department of Engineering Materials
Scholarship sponsored by CAPES/Brazil
Background
ƒ
ƒ
ƒ
ƒ
ƒ
As far as combined chloride and sulfate is
concerned, it is well documented that chloride
usually mitigates sullfate attack
The general view is that chloride only affect
reinforced concrete due to corrosion
Unreinforced concrete is only affected by Cl at
extremely high concentration
TEG-2000/2002 report identified the need for
further investigation on the effect of TSA on the
chloride bind capacity of cements.
No research has yet been published so far.
Background
Regourd et al 1978,
Walkley et al 1983
Slater et al 2002
Hobbs et al 2000
Sibbick et al 2002
Brown et al 2000
Diamond 2002
Thamasite formation in a sea defence
(dike wall) after 40 years
Woodfordite in some dolomite, unhydrite and
mudstone grouts immersed in 30% Cl brine after 56
days
thaumasite has probably not have any chloride
binding capacity, since higher concentration of
chlorides have been found at deeper sites across
affected concrete sections
•Extensive damage of a pier few years
after construction
It formed at temperatures higher than
usually expected: In California state
USA, where substantial amount of
chloride was found among sulfates and
carbonates
OBJECTIVES
ƒAssess the role of chlorides on the formation of
thaumasite in limestone filler cement mortar
ƒEvaluate the performance of cement-based systems
incorporating metakaolinite with respect to
susceptibility to thaumasite formation
ƒEvaluate changes in the engineering properties and
microstructure of Portland cement mortar due to
exposure to chloride and/or sulfate ingress and
thaumasite formation
ƒExplore the usefulness of non-destructive tests in
predicting the onset of thaumasite formation.
ƒInvestigate the effect of carbonation on susceptibility
of long-term mortar prisms to TSA in solutions
containing chloride and/or sulfate ions.
Materials
Table 1: materials selected
Component
Material
Fine
aggregate
German Normensand
(a European Standard quartzite sand)
Cement
BS ENV 197-1 CEM I (0 and 5% CaCO3)
BS ENV 197-1 CEM II/A-L (15% CaCO3)
BS ENV 197-1 CEM II/B-M (8.5%MK+15% CaCO3)
MetaStar 501:Metakolinite (>95%)
Carboniferous limestone (>98%CaCO3)
Pozzolan
Filler
Chemical composition
OXIDES
LIMESTONE
(%)
OPC
(%)
Metakaolinite
(%)
SiO2
0.86
20.82
55.4
Al2O3
0.08
5.30
40.5
Fe2O3
0.34
2.08
0.65
CaO
56.25
64.78
0.01
MgO
0.58
0.98
0.12
SO3
0.22
3.28
-
K2O
0.05
0.57
2.17
Na2O
0.08
0.20
0.13
42.01
1.36
1.0
Loss on
ignition
CLINKER
CONTENT
(%)
C3S
49.41
C2S
22.42
C3A
10.53
C4AF
6.33
Solution composition
g/l
sulfate in all solutions
chloride M5
chloride M10
chloride M20
chloride in sea
sulfate in sea water
6.00
5.00
10.00
20.00
21.14
2.79
% in
sulfate
solution
BRE
by mass
0.60
0.50
1.00
2.00
2.11
0.28
mol/l
0.06
0.14
0.28
0.56
0.60
0.03
class
IV
IV
IV
IV
III
III
MIXES
CEMENT LIMESTONE METAKAOLIN/ SAND/
water/
BIND (cement) BINDER binder
Water
/cement
1
0
0
2.5
0.5
0.5
0.95
0.05
0
2.5
0.5
0.53
0.85
0.15
0
2.5
0.5
0.588
0.765
0.15
0.085
2.5
0.45
0.588
Experimental Programme
Parameters
CaCO3 concentration
Temperature
Microstructure
Ionic concentration
Water
0.60%SO4
0% 5% 15%
Metakaolin+
Limestone filler
5oC
20oC
0.60%SO4 + 0.5%Cl
0.60%SO4 + 1.0%Cl
0.60%SO4 + 2.0%Cl
5 years 15% in air
Seawater
•XRD
•IRS
•Visual inspection
•SEM/BEI/EDS
•pH
Eng. Properties
•Visual inspection
•Change in mass
•Change in length
•Dynamic modulus
of elasticity
•Ultrasonic Pulse
Velocity
Samples after 12 weeks at 5oC
W
OPC
5%LF
15%LF
15LF+8.5MK
M
M5
M10
M20
SEA
Samples after 24 weeks at 5oC
W
0PC
5%LF
15%LF
15LF+8.5MK
M
M5
M10
M20
SEA
Samples after 32 weeks at 5oC
W
0PC
5%LF
15%LF
15LF+8.5MK
M
M5
M10
M20
SEA
Samples after 44weeks at 5oC
W
0PC
5%LF
15%LF
15LF+8.5MK
M
M5
M10
M20
SEA
Samples after 44 weeks at 20oC
W
0PC
5%LF
15%LF
15LF+8.5MK
M
M5
M10
M20
SEA
15%LF AT 5oC 24 weeks
0.60%SO4 + 2.0%Cl
0.60%SO4 + 1.0%Cl
0.60%SO4 + 0.5%Cl
0.60%SO4
15% LF after 40 weeks
<q
q
q
c
a
20oC
0.60%SO4 + 2.0%Cl
e
e
b
e e
g
e
0.60%SO4
5oC
et
0.60%SO4 + 2.0%Cl
0.60%SO4
et
0.0
10.0
e
a
e
e
c
e
cg
e g
et
e
ct
et
t t
20.0
a
a
a
ba
c
q
e
q
a
q
c
c
q
c
q a
b a
c
et
et
q
c
q
t
t
t
g
g
c
et
30.0
40.0
50.0
2Theta
OPC after 40 weeks
<q c
<q
20oC
e
e
0.60%SO4 + 2.0%Cl
e
0.60%SO4
5oC
<g
e
et
0.60%SO4 + 2.0%Cl
et
0.60%SO4
0.0
10.0
b
e
et
e
e <q g
e
e
e
q
b
e
g
e
g
e
et
e et
t
t
et et
e
t
20.0
et
30.0
Cc
40.0
50.0
2Theta
Reaction product within corroded
material
0.60%SO4
phase
0%
12.39
gggg
eee
10.15
ee
bb
11.98
et et et
12.10
gg
eee
10.17
20oC
20oC
pH
et et
et et et
15%
phase
pH
12.41
5oC
5oC
0.60%SO4 + 2.0%Cl
et et et
e
b
aaa
11.71
11.81
CONCLUSIONS
ƒ
ƒ
After 44 weeks, chloride seems to mitigate the sufate
attack in all mixes exposed at 20oC, where ettringite
precipitated within the corroded material.
Combined action of chloride and sulfate seems to be
more deleterious than sulfate alone at 5oC, when
thaumasite primary risk factors are present:
ƒ Increases as calcium carbonate content increases
ƒ Seems to be non-linear since 1.0%Cl caused more damage than
2.0%Cl and also varied with CaCO3 content (15%>5%>0%)
ƒ Ettringite/Thaumasite type phases were responsible for the
attack
ƒ
Mixes containing limestone filler and metakaolinite did
not develop any sign of damage in any solution at both
5oC and 20oC after 12 months of exposure