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B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Experimental setup: 250 mm “thick”
cylinders, diameter 150 mm
Curing temperatures Relative humidity,
RH at a depth of 20% of the slab thickness
Weight
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Parameters: Water-cement ratio, 0.38, 0.43 and 0.55 Sealed or water curing at 8°C, 20°C and
30°C, 1st month 20°C 60 % RH after 1 month, some
exposed to wind, some sealed RH measured at 1, 1½, 2, 3 and 6
months
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Effect of maturity on strength:
0
20
40
60
80
100
0 5000 10000 15000 20000
Maturity (°C·h)
Str
eng
th (
1 m
on
th,M
Pa)
w/c= 0.38 w/c= 0.43
w/c= 0.55
8 °C 30 °C
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Temperature effect on self-desiccation:
80
85
90
95
0,35 0,40 0,45 0,50 0,55
Water-cement ratio, w/c
RH
at
self
-des
icca
tio
n (
1 m
on
th,%
) 8 °C
30 °C
averages of three values
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Self-desiccation vs. strength :
80
85
90
95
0 20 40 60 80 100Strength (1 month,MPa)
RH
at
self
-des
icca
tio
n
(1 m
on
th,%
)
w/c= 0.38 w/c= 0.43 w/c= 0.55
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Effect of w/c and water curing on drying:
80
85
90
95
0,35 0,40 0,45 0,50 0,55Water-cement ratio, w/c
RH
, 2
mo
nth
s (s
eale
d+
RH
=60
%,1
m
on
th,%
)
Sealed 3 weeks, 30 °C, plus 1 week water curing
Sealed 1 month, 30 °C
Sealed 28d. at +30C, then dried 28d. at 60 % RH
Sealed 21d. at +30C, 7d. in water, then dried 28d. at 60 % RH
Sealed 28d. at +30C
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Effect of wind on drying, various w/c:
80
85
90
95
0,35 0,40 0,45 0,50 0,55Water-cement ratio, w/c
RH
(se
aled
1
mo
nth
+R
H=
60%
1 m
on
th,%
)
Without windWith wind
Sealed 28d. at +20C, then dried 28d. at 60 % RH
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Effect of w/c and temperature on drying:
80
85
90
95
0,35 0,40 0,45 0,50 0,55Water-cement ratio, w/c
RH
(se
lf-d
esic
cati
on
1
mo
nth
+R
H=
60%
, 1
mo
nth
.,%
)
Sealed 1 month, 8 °C Sealed 1 month, 30 °C
+8°C
+30°CSealed 28d. at: (then dried 28d. at +20°60%RH)
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
RH of concrete with w/c = 0.38:
75
80
85
90
95
100
10 100 1000Age (days)
RH
at
w/c
=0.
38 (
20 °
C,%
)
Age (days)
In water
+30°C
+8°C
dried
sealed
+20°C
Sealed
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
RH of concrete with w/c = 0.43:
75
80
85
90
95
100
10 100 1000Age (days)
RH
at
w/c
=0.
43 (
20 °
C,%
)
Age (days)
+8°C
+30°C sealed
In water
dried
sealed
dried
+20°C
Sealed
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
RH of concrete with w/c = 0.55:
75
80
85
90
95
100
10 100 1000
RH
at
w/c
=0.
55 (
20 °
C,%
)
Age (days)
In water
wind
+20°C
Sealed+8°C
+30°C
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Summary and conclusions, 1: 27 specimens 150 mm in diameter, 250
mm in length with w/c = 0.38, 0.43, 0.55. Effects of heating, sealing, water and wind 28-day strength 20% higher after curing at
8 °C compared to 30 °C. Self-desiccation was more pronounced
after curing at 8 °C than at 30 °C, at the same age!
1 week of water curing gave 4% higher RH for low w/c =0.38 and for w/c =0.55.
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF CONCRETE
Summary and conclusions, 2: Wind of 4 m/s had no influence on the
drying, except possibly some for w/c =0.55.
The maturity concept could not be applied to strength or to self-desiccation.
Probable explanation: Micro & pore structure at low temperature curing became finer.
B Persson, LTH Building Materials, University of Lund, Lund, Sweden
ON THE TEMPERATURE EFFECT ON SELF-DESICCATION OF
CONCRETE
RH [%]0 100
W [kg/m3]
W0
Wn
We
RHself
RH [%]0 100
W [kg/m3]
W0
Wn
We
RHself
T1
Tcur<T
1
wn
RH
