Transcript Wet Shortcrete Performance

Wet Shotcrete Performance
– Laboratory Test, Methods and influencing Factors in Practice
Dr. Peter Boos
HeidelbergCement, Zentrallabor HC Nord, Ennigerloh
Dr. Martina Dietermann
HeidelbergCement, Entwicklung und Anwendung, Leimen
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
Shotcrete, high performance product consisting of …
Cement
+ aggregates +
water
+
addition
+ admixture
+
non-alkaline accelerator
compressive strength [MPa]
Requirements on wet shotcrete
100
J3
10
J2
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
compressive strength [MPa]
Requirements on wet shotcrete
100
10
Assessment of accelerated
solidification by using the
HC pull-off test
J3
J2
J1
1
> J2
0.1
0.01
0.01
0.1
1
time [h]
10
100
compressive strength [MPa]
Requirements on wet shotcrete
100
J3
10
J2
J1
1
0.1
0.01
0.01
Assessment of early strength
develop-ment by using the shotcrete
rig
0.1
1
time [h]
10
100
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
HeidelbergCement pull-off test
dissolver
dissolver axis
beaker
Cement paste
vertically positioned axis
electromagnetic force
HeidelbergCement pull-off test
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
Laboratory shotcrete rig
Film
Recipes for the laboratory shotcrete rig
B1
B2
B3
B4
Cement
[kg/m³]
450
450
400
400
Fly ash
[kg/m³]
-
-
70
90
Limestone
[kg/m³]
150
150
-
-
Water
[kg/m³]
203
225
214
218
(w/c)eq
[-]
0.45
0.50
0.50
0.50
Plasticizer
[M.-% v. Z.]
2.0
1.0
1.5
1.0
Compressive strength [MPa]
Results
100
B2 (450/150)
10
J3
B3 (400/70)
J2
B4 (400/90)
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
Compressive strength [MPa]
Results
100
Practise
10
J3
Lab-test B2
J2
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
Influencing factors in practice
fresh concrete
temperature
???
w/c-factor
???
ambienttemperature
???
Influence of w/c-factor and fresh concrete temperature
accelerator demand
HC-pull-off test [M.-%]
14
12
10
8
6
4
2
w/c = 0.40
w/c = 0.50
w/c = 0.55
0
14
16
18
temperature [°C]
20
compressive strength [MPa]
Influence of fresh concrete temperature
100
TB = 20 °C
10
J3
TB = 26 °C
J2
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
compressive strength [MPa]
Influence of the ambient temperature
100
TAir
°C
L ==107°C
10
J3
TAir
20°C
°C
L ==20
? J2
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
Influence of the ambient temperature
20
temperature [°C]
temp.air
temp.concrete
15
10
5
0
0
2
4
6
8
10
12
time [h]
14
16
18
20
22
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
Compressive strength [MPa]
Optimized cement for shotcrete application
100
before optimization
10
J3
after optimization
J2
J1
1
0.1
0.01
0.01
0.1
1
time [h]
10
100
Agenda
 Wet shotcrete
 HeidelbergCement pull-off test
 Laboratory shotcrete rig
 Influencing factors in practice
 Optimized cement for shotcrete
application
 Summary
Summary
 Accelerator efficacy of cement-accelerator combination can be
tested by using the new HC pull-off test
 The following early strength development can be reliably tested by
using the HC shotcrete rig
 Essential external influences on shotcrete performance are:

Solidification: w/c-factor

Further strength development: ambient temperature
 Optimized cement-accelerator combination show solidification
between J2 and J3 and are gaining - even at low ambient air
temperature - continuously strength.