frost resistance and nano-structure change of c-s-h of
TRANSCRIPT
Frost resistance and nano-structure
change of C-S-H of concrete
subjected dry-wet cycles
2010.11.11 in Dalian, China
1
Yukio HAMA Muroran Institute of Technology
Simulation model for durability design
Permeability
Performance prediction system
Mechanism of frost deterioration
Mixture Materials
Neutralization
1. Introduction
2
Weathering condition
Pore structureDiagnosis
technique
Equivalent cycles to ASTM C666 A
Temperature Humidity
Frost damage
Evaluation of environmental condition
Moisture in concrete
Simulation model for durability design
Permeability
Performance prediction system
Mechanism of frost deterioration
Mixture Materials
Neutralization
1. Introduction
3
Weathering condition
Pore structureDiagnosis
technique
Equivalent cycles to ASTM C666 A
Temperature Humidity
Frost damage
Evaluation of environmental condition
Moisture in concrete
2. Degradation of Frost Resistance by Aging
Outline of experimentConcrete Specimens : Total 43 kinds
High Fluidity Concrete : 24 kinds
(W/B=32〜50%, Air content=2 and 4.5%)
High Strength Concrete : 7 kinds
(W/C=28〜37%, Air content=1〜5%)
Normal Strength Concrete : 12 kinds
4
Normal Strength Concrete : 12 kinds
(W/C=45〜55%, Air content=2〜6%)
Curing condition before freeze/thaw test
a. 2 weeks in water
b. Outdoor exposure (exposure period : 7 to 12 years)
Freezing and Thawing Test : ASTM C666 A method
60
80
100HPC
HSC
NSC
Durability factors before and after outdoor exposure
2. Degradation of Frost Resistance by Aging
Dura
bil
ity
fac
tor
(Aft
er e
xp
osu
re)
5
0
20
40
60
0 20 40 60 80 100
Durability factor
(Before exposure : 2 weeks in water)
Dura
bil
ity
fac
tor
(Aft
er e
xp
osu
re)
Durability factor
(Before exposure:2weeks in water)
60
80
100
HPC
HSC
NSC
After exposure
60
80
100
Relationship between air content and durability factor
2. Degradation of Frost Resistance by Aging
Dura
bil
ity
fac
tor
Dura
bil
ity
fac
tor
6
0
20
40
0 1 2 3 4 5 6 7
Air content (%)
0
20
40
0 1 2 3 4 5 6 7
Air content (%)
HPC
HSC
NSC
Before exposure
Dura
bil
ity
fac
tor
Dura
bil
ity
fac
tor
Air content (%) Air content (%)
2. Degradation of Frost Resistance by Aging
The frost resistance of non-AE HPC is often evaluated to be
excellent when the drying condition is approx. 20C.
In the actual outdoor environment,
However
7
In the actual outdoor environment,
the frost resistance may be degraded by aging.
Why
micro-cracks ?
pore structure ?
nanostructure in C-S-H ?
10-6 10-310-9 10-0
nm µm mm m
Frost
resistanceMicro
cracksPore
structuresNanostructuresCIF
2. Degradation of Frost Resistance by Aging
8
Degradation Mechanism of Frost Resistance by Aging
Adolphs & Setzer
structures CIFMicroscope
MIP
Under water weighing
NMR,
H2O sorption
ESW model
Nanostructures of CSH Pore structures Micro cracks
3. Effects of Drying and Wetting Cycles
W/C Air s/a
Unit weight
(kg/m3) SP AE
(%) (%) W C S G (C×%) (C×%)
2N 0.25 1 39.3 175 700 623 968 1.3 1*
2A 0.25 4 36.1 175 700 543 968 1.3 0.2*
5N 0.5 1 48.9 175 350 919 968 0.6 0
5A 0.5 4 46.6 175 350 839 968 0.6 0.4
Outline of experiment
Mixture of Concrete
5A 0.5 4 46.6 175 350 839 968 0.6 0.4
*:Air reduce agent
9
Air Spacing factor* Slump Slump Flow Compressive Strength
(%) (µm) (cm) (mm) at 14days (MPa)
2N 0.8 728 - 670×705 93.1
2A 4.1 323 - 770×730 87.7
5N 1.8 741 11.5 - 41.5
5A 3.1 373 19.2 - 68.5
* : ASTM C 457 The linear traverse method
Basic Properties of Concrete
Curing condition
Water curing Air curing or Dry-wet cycles
I 2 weeks at 20oC Air curing for 3months at 20
oC
Curing Conditions before Freeze / Thaw (CIF Test)
3. Effects of Drying and Wetting Cycles
10
M 2 weeks at 20oC 12 dry-wet cycles of air curing for 5 days at 50
oC
and water curing for 2days at 20oC
S 2 weeks at 20oC 12 dry-wet cycles of air curing for 5 days at 80
oC
and water curing for 2days at 20oC
0
20
40
60
80
100
120
RDM (%)
5N-I5N-M5N-S
0
20
40
60
80
100
120
RDM (%)
5A-I5A-M5A-S
Change of RDM with freeze-thaw test (CIF test)
3. Effects of Drying and Wetting Cycles
11
0
0 20 40 60
Number of freeze/thaw cycles
0
0 20 40 60
Number of freeze/thaw cycles
0
20
40
60
80
100
120
0 20 40 60
RDM (%)
Number of freeze/thaw cycles
2N-I2N-M2N-S
0
20
40
60
80
100
120
0 20 40 60
RDM (%)
Number of freeze/thaw cycles
2A-I2A-M2A-S
0
20
40
60
80
100
120
RDM (%)
5N-I5N-M5N-S
0
20
40
60
80
100
120RDM (%)
5A-I5A-M5A-S
Relationship between RDM and water uptake
3. Effects of Drying and Wetting Cycles
12
-1.0 -0.5 0.0 0.5 1.0
Water uptake (%)
0
-1.0 -0.5 0.0 0.5 1.0Water uptake (%)
0
20
40
60
80
100
120
-1.0 -0.5 0.0 0.5 1.0
RDM (%)
Water uptake (%)
2N-I2N-M2N-S
0
20
40
60
80
100
120
-1.0 -0.5 0.0 0.5 1.0
RDM (%)
Water uptake (%)
2A-I2A-M2A-S
2000
2500
3000
surface scaling ( g/m
2)
I
M
curing condition
64668
Surface scaling by freeze-thaw test (CIF test)
I M S
3. Effects of Drying and Wetting Cycles
13
0
500
1000
1500
2000
5N 5A 2N 2A
surface scaling ( g/m
kind of concrete
M
S
Specimens after CIF test (5N)
Crack observation by the microscope
The number of micro-cracks crossed on traverse line was counted under a microscope at
50 times magnification modified ASTM C457 (Linear traverse method)
250
300
350
Degree of cracking
I M S
curing condition
3. Effects of Drying and Wetting Cycles
0
50
100
150
200
250
5N 5A 2N 2A
Degree of cracking
(point/m)
Concrete type
I M S
14
0.00
0.01
0.02
0.03
0.04
0.05
0.06
pore volume (cc/g) 5N-I
5N-M
5N-S
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Pore volume (cc/g) 5A-I
5A-M
5A-S
Total pore volume by MIP
3. Effects of Drying and Wetting Cycles
15
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.001 0.01 0.1 1 10 100 1000
Pore volume (cc/g)
Pore diameter ( µm)
2N-I
2N-M
2N-S
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.001 0.01 0.1 1 10 100 1000
pore volume (cc/g)
Pore diameter (µm)
2A-I
2A-M
2A-S
0.001 0.01 0.1 1 10 100 1000
pore diameter (µm)0.001 0.01 0.1 1 10 100 1000
Pore diameter (µm)
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.001 0.01 0.1 1 10 100 1000
Pore volume (cc/g)
5N-I
5N-M
5N-S
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.001 0.01 0.1 1 10 100 1000
Pore volume (cc/g)
5A-I5A-M5A-S
Pore size distribution by MIP
3. Effects of Drying and Wetting Cycles
16
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.001 0.01 0.1 1 10 100 1000
pore volume (cc/g)
Pore diameter (µm)
2N-I
2N-M
2N-S
0.001 0.01 0.1 1 10 100 1000
Pore diameter (µm)
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.001 0.01 0.1 1 10 100 1000
Pore volume (cc/g)
pore diameter (µm)
2A-I
2A-M
2A-S
0.001 0.01 0.1 1 10 100 1000
Pore diameter (µm)
Drying and wetting
Micro-cracks developed at aggregate-matrix interfaces.
Water uptake during freeze-thaw cycles increased.
3. Effects of Drying and Wetting Cycles
Micro-cracks developed at aggregate-matrix interfaces.
Pore structure became coarser.
Why ?
17
Experiment procedure
Water
20°C 4w35W20
40 mm
Cement Paste (OPC,W/C=0.35)
Sample name
Dry Wet
80 mm
20°C 1d
4. Frost Resistance and Nano-structure Change of C-S-H
18
Water
20°C 2w
Air
30°C 5d
Air
50°C 5d
Air
50°C 4w
Water
20°C 2d
Water
20°C 2d
4 cycles35DW30
35DW50
35D50
160 mm
40 mm
4 cycles
Dry Wet
Test methods
Item Method
Cracking during environmental
changes
RDM
(flexural vibration methods)
Frost resistanceRILEM CIF test
(RILEM TC 176-IDC, 2004)
Mercury Intrusion Porosimetry (MIP)
4. Frost Resistance and Nano-structure Change of C-S-H
19
Pore size distributionMercury Intrusion Porosimetry (MIP)
(Micromeritics Auto-pore 9200)
Total pore volume and
true densityUnder-water weighing
Specific surface area
(BET,ESW)
H2O sorption isotherm
(BEL Japan, BELSORP 18 PLUS-T)
Silicate anion structure29Si NMR MAS
(Bruker, Biospin Avance 400)
60
80
100
120
RD
M (%) 35W20
35DW3035DW5060
80
100
120
RD
M (%) 35W20
35DW3035DW50
Micro-cracks during environmental changesMicro-cracks during environmental changes
Micro-cracks !
4. Frost Resistance and Nano-structure Change of C-S-H
20
0
20
40
0 4 8 12 16 20 24 28
Test duration of environmntal change(days)
RD
M
35DW5035D50
Dry D Wet W W WD D D
0
20
40
0 4 8 12 16 20 24 28
Test duration of environmntal change(days)
RD
M
35DW5035D50
Dry D Wet W W WD D D
Micro-cracks !
SpecimenMicro-
cracks
Frost
resistance
35W20 No cracks Excellent
35DW30 Cracks Excellent
35DW50 Cracks Poor
-10
-8
-6
-4
-2
0
2
4
-7 0 7 14 21 28Test duration (days)
Wa
ter
up
tak
e r
ate
(%)
35W2035DW3035DW5035D50
Capillary
suction
Freezing
& Thawing
-10
-8
-6
-4
-2
0
2
4
-7 0 7 14 21 28Test duration (days)
Wa
ter
up
tak
e r
ate
(%)
35W2035DW3035DW5035D50
Capillary
suction
Freezing
& Thawing
Water uptakeWater uptake Micro-ice-lens pump 4. Frost Resistance and Nano-structure Change of C-S-H
21
35D50 Cracks Poor
0
20
40
60
80
100
120
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56Number of freeze/thaw cycles
RD
M (%)
35W2035DW3035DW5035D50
0
20
40
60
80
100
120
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56Number of freeze/thaw cycles
RD
M (%)
35W2035DW3035DW5035D50
Test duration (days)Test duration (days)
RDMRDM
Micro-cracks
Frost damage
Micro structure ?
0.00
0.02
0.04
0.06
0.08
0.10
1 10 100 1000 10000 100000
Cu
mu
lati
ve p
ore
vo
lum
e (
cm
3/g
)
35W20
35DW30
35DW50
35D50
0.00
0.02
0.04
0.06
0.08
0.10
1 10 100 1000 10000 100000
Cu
mu
lati
ve p
ore
vo
lum
e (
cm
3/g
)
35W20
35DW30
35DW50
35D50
Total pore volume by MIP (8nm ≤ D)
35W2035W20 < 35DW3035DW30 < 35DW5035DW50 < 35D5035D5035W2035W20 < 35DW3035DW30 < 35DW5035DW50 < 35D5035D50
4. Frost Resistance and Nano-structure Change of C-S-H
22
1 10 100 1000 10000 100000
Pore diameter (nm)
0.00
0.05
0.10
0.15
1 10 100 1000 10000 100000
Pore diameter (nm)
dV
/dlo
gD
(cm
3/g
·µm
)
1 10 100 1000 10000 100000
Pore diameter (nm)
0.00
0.05
0.10
0.15
1 10 100 1000 10000 100000
Pore diameter (nm)
dV
/dlo
gD
(cm
3/g
·µm
)
Peak diameter
10nm 100nm
Coarsening pore structure
Dry/Wet or Dry
35W2035W20 < 35DW3035DW30 < 35DW5035DW50 < 35D5035D5035W2035W20 < 35DW3035DW30 < 35DW5035DW50 < 35D5035D50
Specimen
Apparent
density
ρap (g/cm3)
Apparent
specific
volume
vap (cm3/g)
True
density
ρtr (g/cm3)
True specific
volume
vtr (cm3/g)
Total pore
volume
Vtotal (cm3/g)
35W20 1.72 0.581 2.34 0.427 0.154
35DW30 1.71 0.583 2.41 0.415 0.168
35DW50 1.76 0.568 2.50 0.400 0.169
35D50 1.79 0.560 2.56 0.390 0.169
0.60.6 Dry/Wet or Dry
4. Frost Resistance and Nano-structure Change of C-S-H
23
0.0
0.2
0.4
0.6
35W20 35DW30 35DW50 35D50
Specimens
Vo
lum
e o
f p
ore
or
soil
d (
cm3/g
)
(Vtotal - VHg):
d < 8 nm *1
VHg:
d > 8nm *2
vtr: True
specific volume
of C-S-H in
hcp *3
Po
reS
oli
d
0.0
0.2
0.4
0.6
35W20 35DW30 35DW50 35D50
Specimens
Vo
lum
e o
f p
ore
or
soil
d (
cm3/g
)
(Vtotal - VHg):
d < 8 nm *1
VHg:
d > 8nm *2
vtr: True
specific volume
of C-S-H in
hcp *3
Po
reS
oli
d
by MIP
Dry/Wet or Dry
make denser C-S-H
shrunk!
coarsening pore
structure
nanostructure?
Kamada 、1996
20
40
60
80
100
120
CIF耐久性指数
W/C=0.35
W/C=0.55
35W20 (CIF耐久性指数108)
35DW30 (99)
35D50 (22)35DW50 (15)
0.02(cc/g)
0.02(cc/g)
4. Frost Resistance and Nano-structure Change of C-S-H
24
0
20
0 0.02 0.04 0.06 0.08 0.1 0.12
細孔直径40~2000nmの細孔量(cc/g)
35D50 (22)35DW50 (15)
55W20 (14)55DW30 (10)
55DW50 (6)
Kamada 、1996
Change of micro structure
by W/C and age
Change of micro structure
by W/C and age
Change of micro structure
by drying and wetting
Change of micro structure
by drying and wetting
Degradation of frost resistance In this study
29Si MAS NMR
O
O
SiO44- tetrahedron
Q0
Q3
Q1
un-hydrated
cement
silicate anion silicate anion chain
Q1Q2
Bridging structure
4. Frost Resistance and Nano-structure Change of C-S-H
25
SSSSiiii O
O
O
Qn: number of coordination
Q1 Q1
Q3
Qn
Q3
Q1
Q1
Q2
dimer
n = 0 - 4Q2
Q1 Q1Q2
chain
0%
50%
100%
35W20 35DW30 35DW50 35D50
Rel
ativ
e p
eak
in
ten
sity
(%
)
Q0
Q1
Q2P
Q2CaSilicate anion structure of C-S-H (Klur et al.1998)
Ca Ca Ca Ca Ca
H+Q1 Q2CaQ2p
Ca Ca Ca Ca Ca
Ca2+ Q2i
Q2Ca; -85ppmQ2i; -84ppmQ2p; -82ppm
CaO layer
Silicate chain
Q1; -79ppm
4. Frost Resistance and Nano-structure Change of C-S-H
26
35W20 35DW30 35DW50 35D50
-120-100-60
(ppm)
-80
Q1
39.6
-79.5
Q2p
19.5
-82.1
Q2Ca
22.0%
-85.5 ppm
Q0
18.9
-72.6
35W20
-120-100-60
(ppm)
-80
Q1
45.0
-80.0
Q2p
18.8
-83.6
Q2Ca
23.8%
-86.5 ppm
Q0
12.3
-72.7
35DW30
-120-100-60
(ppm)
-80
Q1
34.6
-80.1
Q2p
20.0
-83.3
Q2Ca
31.2%
-86.4 ppm
Q0
14.2
-72.9
35DW50
-120-100-60
(ppm)
-80
Q1
15.8
-79.5
Q2p
16.4
-81.8
Q2Ca
55.9%
-85.5 ppm
Q0
11.9
-73.2
35D50
Q2Ca
2Ca2i2p1
Dry/Wet or Dry at 50°C
Polymerization of C-S-HPolymerization of C-S-HCa Ca Ca Ca
Q1
Q2Ca
Q2p
Ca Ca CaCa Ca Ca
Q1
Q2Ca
Q2p
29Si NMR & Pore
0.05
0.10
0.15
0.20
Po
re v
olu
me
(cm
3/g
)
35W20
35DW5035DW30 35D50
Vtotal : under water weighing
VHg : M I P (8nm ≤D)
0.05
0.10
0.15
0.20
Po
re v
olu
me
(cm
3/g
)
35W20
35DW5035DW30 35D50
Vtotal : under water weighing
VHg : M I P (8nm ≤D)
2.2
2.3
2.4
2.5
2.6
2.7
Tru
e d
ensi
ty o
f C
-S-H
in
hcp
,
ρtr
(g
/cm
3)
35W20
35DW50
35DW30
35D50
ρtr = 1/vtr
(a)
2.2
2.3
2.4
2.5
2.6
2.7
Tru
e d
ensi
ty o
f C
-S-H
in
hcp
,
ρtr
(g
/cm
3)
35W20
35DW50
35DW30
35D50
ρtr = 1/vtr
(a)
4. Frost Resistance and Nano-structure Change of C-S-H
27
0.00
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
0.00
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
Polymerization of C-S-H
Coarsening pore of 8nm≤ D
Shrinkage or aggregation
2.2
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
0.35
0.40
0.45
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
Tru
e sp
ecif
ic v
olu
me
of
C-S
-H
in h
cp ,
vtr
(cm
3/g
)
35W20
35DW50
35DW30
35D50
vtr = 1/ρtr
(b)
2.2
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
0.35
0.40
0.45
30 40 50 60 70 80
Relative peak intensity of Q2total by 29
Si MAS NMR
Tru
e sp
ecif
ic v
olu
me
of
C-S
-H
in h
cp ,
vtr
(cm
3/g
)
35W20
35DW50
35DW30
35D50
vtr = 1/ρtr
(b)
H2O sorption isotherm
2
4
6
8
ad
sorb
ed,
nad
s (m
mo
l/g
)
35W2035DW3035DW5035D50
2
4
6
8
ad
sorb
ed,
nad
s (m
mo
l/g
)
35W2035DW3035DW5035D50 Dry/Wet or Dry
decrease of H2O
adsorbed
4. Frost Resistance and Nano-structure Change of C-S-H
28
0
0 0.2 0.4 0.6 0.8 1
Relative pressure (P/Ps)
H2O
0
0 0.2 0.4 0.6 0.8 1
Relative pressure (P/Ps)
H2O
further analysis by ESW model (Adolphs & Setzer, 1996)
ESW Φ (Excess Surface Work)
adsorbed
-6
0
0 2 4 6 8
H2O adsorbed nads (mmol/g)E
SW
Φ (
J/g
)
35W2035DW3035DW5035D50
(a)
n mono
-6
0
0 2 4 6 8
H2O adsorbed nads (mmol/g)E
SW
Φ (
J/g
)
35W2035DW3035DW5035D50
(a)
n mono
S1: at mono-layer
S2: at multi-layer
Sn: specific surface area calculated from reciprocal slope
ESW model
4. Frost Resistance and Nano-structure Change of C-S-H
29
4
6
8
10
0 2 4 6 8H2O adsorbed, nads (mmol/g)
ln|∆
µ|
35W2035DW30
35DW5035D50
(b)
mono-layer multi-layer
S2
S1
-12
mono
4
6
8
10
0 2 4 6 8H2O adsorbed, nads (mmol/g)
ln|∆
µ|
35W2035DW30
35DW5035D50
(b)
mono-layer multi-layer
S2
S1
-12
mono
Dry/Wet or Dry
decrease of S2
layered structure
100
150
Sp
ecif
ic s
urf
ace
area
by
O)
(m2/g
)
S1100
150
Sp
ecif
ic s
urf
ace
area
by
O)
(m2/g
)
S1
polymerization & Sn
4. Frost Resistance and Nano-structure Change of C-S-H
30
0
50
30 40 50 60 70 80 9029
Si MAS NMR Q2 total peak
Sp
ecif
ic s
urf
ace
area
by
ES
W (
H2O
) (m
S2
0
50
30 40 50 60 70 80 9029
Si MAS NMR Q2 total peak
Sp
ecif
ic s
urf
ace
area
by
ES
W (
H2O
) (m
S2
35W20(20℃水中)
基本ユニット
表4-4より,
(Q2Ca+Q2i)/Q1=1
重合度 = 4
(a)
Globule
シリケートアニオン鎖
Q1 Q2Ca
CaO層
0.73nm
(Jennings8), 2000 より一部転記)
LD C-S-H
LD C-S-HGlobule
Globule
【【【【Before Drying】】】】
JenningsJennings
4. Frost Resistance and Nano-structure Change of C-S-H
31
約6 nm
Q1 Q2CaQ2i
r ≒ 1 nm
Globule
N2吸着,
毛細管凝縮可約20 nm
層状構造を持たない
Jennings’s Colloid ModelJennings’s Colloid Model
Results of NMRResults of NMR
Modified Colloid Model
considering
Nanostructure of C-S-H
Modified Colloid Model
considering
Nanostructure of C-S-H
35D50(50℃乾燥)
表4-4より,
(Q2Ca+Q2i)/Q1=4.5
重合度 = 11
(b)
重合で形成されたGlobule
重合で形成された基本ユニット
重合後のC-S-Hの概念図
0.73nm
重合で形成されたLD C-S-H
Coarsening
pore structure
Coarsening
pore structure
Development
layered structure
Development
layered structure
【【【【After Drying】】】】
4. Frost Resistance and Nano-structure Change of C-S-H
32
約4 nm
N2吸着による
毛細管凝縮なし。水銀圧入可 約20 nm
層状構造
b軸
a軸
Modified Colloid Model considering Drying EffectModified Colloid Model considering Drying Effect
Polymerization
of C-S-H
Polymerization
of C-S-H
Coarsening pore
structure
Coarsening pore
structure
Polymerization
of C-S-H
Polymerization
of C-S-H
Development
layered structure
Development
layered structure
Dry/Wet or Dry (Aging)
Development layered structure
Polymerization of C-S-H
4. Frost Resistance and Nano-structure Change of C-S-H
33
Shrinkage or Aggregation of C-S-H
Coarsening pore structure
Degradation of frost resistance
5. Conclusions
1. Drying and wetting cycles or drying deteriorated the frost resistance .
2. The deterioration of frost resistance is attributed to coarsening of the pore structure and not to micro-crack formation.
3. The true density of the C-S-H in HCP became denser by drying-wetting cycles or drying, that is to say the C-S-H shrunk, that correlates to the coarsening the pore structure.
34
4. 29Si-NMR shows that polymerizations of silicate anion structures of C-S-H in HCP progress with drying-wetting or drying.
5. The ESW model for H2O sorption isotherm shows that the specific surface area at multi-layer decreases with polymerizations.
6. The deterioration of frost resistance of HSC after outdoor exposure is probably affected by the change in nanostructure of C-S-H in HCP subjected to drying condition.