SULFURIC ACID RESISTANCE OF AUTOCLAVED CEMENTITIOUS
MATERIALS CONTAINING y-2CaO･SiO2 AND QUARTZ
Yuriko Tsuburaya*, Tokyo Institute of Technology, Japan
Nobuaki Otsuki, Tokyo Institute of Technology, Japan
Tsuyoshi Saito, Tokyo Institute of Technology, Japan
Saphouvong Khamhou, Tokyo Institute of Technology, Japan
36th Conference on OUR WORLD IN CONCRETE & STRUCTURES: 14 - 16 August 2011,
Singapore
Article Online Id: 100036055
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36 Conference on Our World in Concrete & Structures
Singapore, August 14-16, 2011
SULFURIC ACID RESISTANCE OF AUTOCLAVED CEMENTITIOUS
MATERIALS CONTAINING
γ-2CaO･
･SiO2 AND QUARTZ
Yuriko Tsuburaya*, Nobuaki Otsuki1, Tsuyoshi Saito1 and Saphouvong Khamhou1
Tokyo Institute of Technology, Japan
2-12-1, S6-11, Ookayama, Meguro-ku, Tokyo, Japan
e-mail: <[email protected]>
Keywords: Sulfuric acid, γ-2CaO･SiO2, quartz, Autoclave curing
Abstract. Nowadays, high durability as high performance of concrete is increasing in
demand for the construction industry. Meantime, the research on the high durability
cementitous material using γ-2CaO ･ SiO2 (hereafter”γ-C2S”) has received much
attention due to its high durable properties. γ-C2S does not react with water under
normal curing condition but it well reacts in high temperature and high pressure
circumstances. The high durability cement-based material mixed with γ-C2S for the
long term purpose has been reported in recent years.
However, the experiment on the durability performance especially in the sulfuric
acid which is the severe environment, such as sewerage, for concrete and mortar has
not been investigated yet. Therefore, this study aims to evaluate an effect of the
γ-C2S and quartz substitution ratio on the sulfuric acid resistance in autoclaved
cementitious material.
In order to find out the optimum mix proportion, various mix proportions of mortar
and concrete mixed with γ-C2S and quartz were prepared. Specimens were
conducted pre-curing at 65℃ and 100%RH for 4 hours. The de-molding specimens
were autoclaved at 180 ℃ and 1MPa for 8 hours. Then, the specimens were
immersed in the pH1 H2SO4 solution at 20ºC for 20 weeks. During the immersion,
weight change and visual observation were carried out.
The results show that the highest sulfuric acid resistance was obtained with
autoclave curing a 30% or higher of γ-C2S replacement ratio and 50% quartz
replacement for total binders. These results suggest that, using γ-C2S and quartz with
autoclave curing is able to give the excellent sulfuric acid resistance in concrete.
1.
INTRODUCTION
Nowadays, the use of concrete in engineered barriers is being considered in the construction of
radioactive waste disposal facilities. The concrete needs to obtain the durability which is dimensional
stability and chemical stability. Furthermore, in the Middle East region, wherein sulfate soil is
[1]
abundantly found, and in the hot spring or sewerage pipe, wherein sulfuric acid attack is found .
_________________________
1
Tokyo Institute of Technology, Japan
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
The sulfate attack and sulfuric acid attack on the concrete structure is serious problem. The concrete
needs to obtain the durability which is high resistance against external ions. For these purposes, it is
obvious, that high durability concrete is in demand.
On the other hand, the research on the high durability of the cement-based
based material using
γ-2CaO·SiO2 (hereafter”g-C2S”) is focused. γ-C2S does not react with water under normal curing but it
reacts well with CO2 gas. The cement-based
cement
material, mixed with γ-C2S and resulted densified surface
[2]
through carbonation curing, has high durability for the long term purpose was reported . Furthermore,
the amount of 1.1nm tobermorite (5CaO·6SiO2·5H2O, hereafter ”tobermorite”) which has high
[3]
shrinkage resistance is increased by mixing γ-C2S and conducting the autoclave curing. Saito al at
have proposed the concept of material design for high durability cement-based
based material in high
shrinkage resistance. Ass shown in Fig.1,
Fig.1 using autoclave curing tobermorite is generated in the
hardened body and using carbonation curing permeability resistance to external aggressive ions such
as chloride ion becomes higher by densifying the surface on the hardened body.
However, the experiment on the durability performance especially in the sulfuric acid which is the
severe environment, for concrete and mortar has not been investigated yet. Therefore, this study aims
to evaluate an effect of the γ-C
C2S and quartz substitution ratio on the sulfuric acid resistance in
autoclaved cementitious material.
Figure. 1 Concept of material deign for high durability cement-based
cement based material
2. EXPERIMENTAL DETAILS
2.1. Materials use
Table 1 shows the chemical composition of OPC, γ-C2S, and Quartz. Blaine
ine specific surface
2 -1
2 -1
2 -1
areas of OPC,γ-C2S,Quartz are 3310cm
3310
·g , 3060cm ·g and 3870cm ·g respectively.
respectively
Table Chemical composition (mass%)
Table.1
OPC
γ-C2S
Quartz
SiO2
Al2O3
Fe2O3
CaO
SO3
f.CaO
Density
3
(g/cm )
Blane*
2
(cm /g)
21.6
35.0
93.3
5.08
1.7
1.6
2.93
0.10
1.4
64.5
61.9
-
1.95
-
0.4
-
3.16
3.01
2.66
3310
3060
3870
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
2.2. Mix proportions, Method of manufacturing and curing
Table.2 shows the mix proportions of mortal specimens and the names. And Table.3 shows the
mix proportions of concrete specimen and the named. The mixed mortar and concrete were casted in
a mold that volume are 4cm×4cm ×16cm and φ20cm×30cm and 4cm thick.
After molding, initial curing with 100% RH at 65℃ is done for 4 hours. Then the molds are
removed from the specimened and autoclaved for 8 hours under 1MPa at 180℃.
Table. 2 Mix proportions and the symbol of cement mortal specimens
Name
Q:γ-C2S:OPC
Series
Quratz50
Series
Quratz40
Series
Quratz30
0-0-100(Ref)
0-0-100(Ref+AC)
50-0-50
50-20-30
50-30-20
50-40-10
40-0-60
40-36-24
30-0-70
30-42-28
B/W
(%)
32.9
3
Quantities
W
148
148
148
148
148
148
148
148
148
148
OP
C
450
450
225
135
90
45
270
108
315
126
(kg/m )
γ-C2S
S
Quarz
MT150
0
0
0
90
135
180
0
162
0
189
1831
1831
1795
1791
1783
1788
1803
1802
1809
1801
0
0
225
225
225
225
180
180
135
135
0.00
0.00
3.37
2.88
2.68
2.56
3.37
2.59
4.27
3.00
Autoclave
Curing
×
○
○
○
○
○
○
○
○
○
Table. 3 Mix proportions and symbol of Concrete specimens
Name
Q:γ-C2S:OPC
B/W
(%)
0-0-100(Ref)
0-0-100(Ref+AC)
Series
Quratz50
Series
Quratz40
Series
Quratz30
50-0-50
50-20-30
50-30-20
50-40-10
40-0-60
40-36-24
30-0-70
30-42-28
32.9
Quantities
3
(kg/m )
W
OPC
γ-C2S
S
G
Quarz
MT150
148
148
148
148
148
148
148
148
148
148
450
450
225
135
90
45
270
108
315
126
0
0
0
90
135
180
0
162
0
189
924
924
906
904
903
902
910
906
913
909
907
907
889
887
881
886
893
889
896
892
0
0
225
225
225
225
180
180
135
135
0.00
0.00
3.37
2.88
2.68
2.56
3.37
2.59
4.27
3.00
Autoclave
Curing
×
○
○
○
○
○
○
○
○
○
2.3 Sulfuric acid Exposure Test
After autoclaved curing, the designed mortar specimens were exposed to the solution of H2SO4
with pH1 at 20℃ for 20 weeks. In order to maintain pH value, the solution was exchanged every
1week.
2.4 Evaluation on Performance
2.4.1 Compressive Strength before exposure of Concrete
The test specimen was concrete pile with dimension of φ20cm×30cm and 4cm thick were
prepared to measure compressive strength. The test was carried out according to JIS A1136 “Method
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
of test for compressive strength of pile concrete”. Three specimens of each mix proportion were
prepared and the result of measurement is the mean values of 3 specimens.
2.4.2 Weight change of mortar during exposure and Photograph
The mortar specimen with dimension of 4cm×4cm ×16cm were prepared for this test. Three
mortar samples of the same mixing were prepared. Before exposure, these specimens were weighted.
During submerging test, specimens were measured to weight on the 1, 2, 3, 5days, 1, 2, 3, 5, 7, 10, 13,
and 20 weeks.
And after exposure test, mortar specimens were taken pictures to observe these surfaces.
3. RESULTS AND DISCUSSION
3.1 Compressive Strength before exposure
Figure.2 shows compressive Strength of concrete pile before exposure test. As you can see,
amount of Quartz, it means compare the Series Quratz50, Series Quratz40 with Series Quratz30, it
is found that, the less amount of Quartz, the more the compressive strength. This result is in
[4]
accordance with the study of George W. WASHA with report that, the mix proportion of 30% silica,
70% cement is maximum compressive strength. Up to the composition (30% silica, 70% cement), the
compressive strength decreased uniformly with increasing silica additions.
(MPa)
120.0
Series Quartz30
Series Quartz40
100.0
Series Quartz50
80.0
60.0
40.0
20.0
0.0
Figure. 2
Compressive Strength before exposure in concrete pile
It should be noted that in case of Quartz50, with the low amount of cement were added, but the
compressive strength shows only 0.9percent decrease, because γ-C2S reacted well in autoclaved
curing, and tobermorite which contribute compressive strength had been generated. Therefore, the
specimen, which include 50precent quartz and more than 30% γ-C2S, compressive strength
maintained at 70MPa.
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
3.2 Weight change during exposure
Figure.3 and figure.4 show weight change during 20 weeks exposure. In figure.3, Quartz
percentage is changed from 30% to 50%. Weight is more decreased, when percentage of Quartz the
more decrease. Furthermore, in case of Series Quartz50, it could be confirmed that the sulfuric acid
resistance improved in addition by increasing the ratio of γ-C2S. It is contemplated that hydration
products which are tobermorite and other products are changed due to replacement ratio of γ-C2S or
Quartz.
20
15
50-30-20
Weight change(%)
10
5
50-0-50
40-36-24
0
40-0-60
-5
0-0-100(Ref+AC)
0-0-100(Ref)
30-42-28
-10
-15
30-0-70
-20
0
20
40
60
80
100
(days)
140
120
Figure. 3 Effect of quartz weight change during 20 weeks exposure in mortar
20
(%)
15
50-40-10
50-30-20
Weight change(%)
10
5
50-0-50
0
50-20-30
-5
0-0-100(Ref+AC)
-10
0-0-100(Ref)
-15
-20
0
20
40
60
80
100
120
(days)
140
Figure. 4 Effect of γ-C2S in weight change during 20 weeks exposure in mortar
In figure.4, Quartz percentage is 50%. From figure.4, 0-0-100(Ref) and 0-0-100(Ref+AC)
specimens which do not include γ-C2S or Quartz are very deteriorated, and it could be confirmed that
weight loss accelerates rapidly from almost 21 days. Furthermore, in case of 50-0-50 and 50-20-30
specimens, it could be confirmed that weight loss start from 35 days, on the other hand, in case of
50-30-20 and 50-40-10 specimens, up to 140 days weight loss do not start. It means 50-30-20 and
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
50-40-10 specimens have high resistance against sulfuric acid. It could be concluded that the amount
of tobermorite or residual γ-C2S after autoclaved curing contributed to the resistance of this mix
proportions.
The visual observation of mortar specimens was carried out after exposure test for 20 weeks.
Figure.5 shows the photos of external appearance of mortar after 20 weeks immersion. The surfaces
of 50-30-20 and 50-40-10 are remained the sign of the marker. However in the other specimens, there
are nothing the sign. Furthermore, 0-0-100(Ref) and 0-0-100(Ref+AC) specimen begins to melt from
the surface, and the volume decreases by about 3mm of the surface.
0-0-100（Ref）
0-0-100（Ref+AC）
40-0-60
50-0-50
40-36-24
50-20-30
30-0-70
50-30-20
30-42-28
50-40-10
Figure. 5 The photos of mortar specimens
In the specimens which include Quartz, the volume decrease on
the surface becomes a layer, peels off, and falls. As shown in figure.6,
which show the surface layer.
Figure.6 The surface layer
From weight change and visual observation it could be confirm that, the highest sulfuric acid
resistance was obtained with autoclave curing in higher than 30% γ-C2S replacement and 50% quartz
replacement for total binder. These results suggested that, using γ-C2S and quartz with autoclave
curing was able to give the excellent sulfuric acid resistance in concrete.
T. Tsuburaya, N. Otsuki, T. Saito and S. Khamhou
4. CONCLUSIONS
The conclusions of this study are as follows:
1) With autoclave curing and using γ-C2S, the specimen, which include 50% quartz and more than
30% γ-C2S, compressive strength maintains at 70MPa. Furthermore, it could be confirmed that the
maximum compressive strength was obtained at 30% of quartz replacement ratio, though the
amount of quartz increased (40% or 50 % of quartz) the compressive strength decreased.
2) The highest sulfuric acid resistance was obtained with autoclave curing in case of over 30% γ-C2S
replacement and 50% quartz replacement for total binder. These results suggested that, using
γ-C2S and quartz with autoclave curing was able to give the excellent sulfuric acid resistance in
concrete.
REFERENCE
[1]H. Matsusita, Y. Sagawa, T. Sato : Classification of Probability of Deterioration of Concrete by
Sulfate Attack Based on Investigation Results of Sulfate Content of Ground, Doboku Gakkai
Ronbunshuu E,Vol.66, No.4, pp.507-519, 2010.12
[2]K. Watanabe, K. Yokozeki, R. Ashizawa, N. Sakata, M. Morioka: High durability cementations
material with mineral admixtures and carbonation curing, Waste Management, No.26,
pp.752-757(2006)
[3]T. Saito, E. Sakai, M. Morioka, M. Daimon: Carbonation Reaction of Calcium Silicate Hydrates by
Hydrothermal Synthesis at 150℃ in OPC- γ-Ca2・SiO4- α‐quartz System, Journal of Advanced
Concrete Technology, Vol.5, No.3, pp.333-341(2007)
[4] GEOREGE W. WASHA and ACI committee 516: High pressure Steam Curing Modern Practice, and
Properties of Autoclaved Products, Journal of the American Concrete Institute, No.62-53,
pp.869-908(August 1965)
[5] Jan Skalny, Jacques Marchad, and Ivan Odler: Sulfate Attack on Concrete, First published 2002 by
Spon Press, 11 New Fetter Lane, London EC4P 4EE, pp.101-102
[6] M.T.Bassuoni, M.L.Nehdi: Resistance of self-consolidation concrete to sulfuric acid attack with
consecutive pH reduction, Cement and Concrete Research 37(2007), pp1070-1084