Process Control of the Rheology of Self-Compacting ... Reference Target value after 15 minutes:...
Transcript of Process Control of the Rheology of Self-Compacting ... Reference Target value after 15 minutes:...
Process Control of the Rheology of Self-Compacting
Concrete Based on Cusum Control Charts
Wolfram Schmidt BAM Federal Institute for Materials Research and Testing, Berlin
Prozesssteuerung der Rheologie von selbstverdichtenden Betonen anhand von Kusum-Kontrollkarten
2 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2014
Introduction
3 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Introduction
Concrete today
• Regarding performance or other specifications of concrete, there are hardly no limitations today.
• Design criteria can be very versatile.
• The challenge „Mix Design“ has become an exciting challenge,
• but the complexity of the system makes it prone to scatter.
Cement Water Aggregates
Additions Admixtures
Colour Ductility
Sustain- ability
Durability
Perme-ability
Cement content
Strength
Flow properties
CONCRETE
4 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Introduction
Reasons for quality scatter in concrete production
Cement undergoes scatter
Set retarder may alter
Fineness
Chemistry (Fuels / Raw materials / Kiln temperature)
Fines, Sand, and aggregates
Particle size distribution and powder content
Surface properties
Humidity
Chemical admixtures
Precursers are often purchased globally depending upon price.
Water
5 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Introduction
Reasons for quality scatter in concrete production
Staff
Equipment
Handling
Supply chains
Timing
Post-processing
…
6 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Introduction
Complexity of modern flowable concrete types
• Multi-phase-system • Effects occur in multiple
scale dimensions. • Time effects
The concept of one mix-design does not fit in with the requirements of modern flowable concrete! Mixtures have to be adjustable!
For flexibility, production has to be controlled efficiently.
7 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Introduction
Reasons to set up a functioning quality control tool
Safety aspects
Standards demand for a steady quality control to make sure that the concrete is conforming with the standards.
Customers may demand quality control in order to make sure that they receive the expected quality.
For everything related to public safety, it is important to make sure that the demanded safety level is achieved.
Cost aspects
Functioning quality control mechanisms help saving money.
Producers may want to show their quality control to customers as a selling point.
Knowledge aspects
Producers may want to understand their parameters and how they affect the process.
8 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Challenges in assessing processes
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Challenges in assessing processes
Example
10 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Challenges in assessing processes
Example
What to do now?
?
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Challenges in assessing processes
Example
Case 1
Case 2
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Challenges in assessing processes
„Under-control“
Case 1: Intervention required
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Challenges in assessing processes
„Under-control“
Case 1: Intervention required No Intervention = „under-control“
after intervention
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Challenges in assessing processes
„Over-control“
Case 2: No intervention required
15 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Challenges in assessing processes
„Over-control“
Case 2: No intervention required Intervention = „over-control“
after intervention
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Challenges in assessing processes
Example
Decision rules required
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Challenges in assessing processes
Process control
A good process control should
indicate processes running out of control early
and should avoid that actions are taken too early.
It is thus a compromise between „over-control“ and „under-control“.
Observing process values along a time axis (so called Shewhart charts) are a simple tool but not efficient in detecting systematic changes quickly.
It is difficult to find clear decision rules.
Cusum control charts are much more efficient.
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Cusum control charts
19 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum control charts
Introduction of CUSUM charts
Observing the technical data of a production process
Has a slow reaction time.
Does not detect systematic errors easily.
Does not locate easily where/when the error occurred.
CUSUM were developed in the 1950‘s by E. S.Page for the quality control of continuous manufacturing processes.
The aim was to generate a system with higher detection sensititivity for small systematic changes.
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Cusum control charts
Introduction of CUSUM charts
Cusum was recently incorporated into EN 206 for the conformity of concrete.
However, cusum is a process control tool, not a conformity assessment tool.
It has been used in concrete production efficiently in UK, South Africa, Australia for the production control.
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Cusum control charts
Introduction of CUSUM charts
CUSUM does not observe production data but the deviation of production data from a target value.
C(n) = fci − fctan1
Principle:
Set target value.
Calculate difference between each production value and its target value.
Sum up these values chronologically.
The following observations can be made:
Horizontal trend Process is running as required
Upward drift Production is higher than target
Downward drift Production is lower than target
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Cusum control charts
CUSUM vs. steady process data control
CUSUM observes the slope rather than the ordinate
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Cusum control charts
CUSUM vs. steady process data control
Advantages of CUSUM:
More vivid illustration
Higher efficiency
Clearly indicates, where the process has changed
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Cusum control charts
CUSUM vs. steady process data control
Possible disadvantages of CUSUM:
Relatively unknown method. Needs training/education.
Higher computational effort.
Interpretation is more difficult.
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Cusum control charts
Sample scenario: Concrete production
New equipment
Compensation of process improvement
New sand provider
1. attempt to compensate reduced performance
2. attempt to compensate reduced performance
Old sand provider Christmas
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Cusum control charts
The V-mask concept
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The V-mask concept
Decision making with CUSUM
CUSUM observes the slope of the curve:
Horizontal slope OK!
Upward drift Production above target
Downward drift Production below target
Curve trends are not always easily identifiable.
If differences are small, the slope may be to small to be identified easily
Increasing standard deviation increase the scatter of the CUSUM
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The V-mask concept
Decision making with CUSUM
Target: 45 s = 1
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The V-mask concept
Decision making with CUSUM
Target: 45 s = 1
Target: 45 s = 4
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The V-mask concept
Decision making with CUSUM
Target: 45 s = 4
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The V-mask concept
Decision making with CUSUM
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The V-mask concept
Geometry of the V-mask
The geometry of theV-mask should depend on the standard deviation
The lead point can be put on any process value of the CUSUM
The half mask height is a measure of the reliability of the detection.
The slope is a measure of the size of change to be detected.
Lead point
h s
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The V-mask concept
h = 5
f = ½
The general purpose, standard, truncated V-mask
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The V-mask concept
As long as the CUSUM runs between the limbs of the mask there is no reason to interfere
this avoids „over-control“
Interpretation of the V-mask
0
20
40
60
80
100
120
140
160
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Strength too high
-160
-140
-120
-100
-80
-60
-40
-20
0
20
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Strength too low
-60
-40
-20
0
20
40
60
80
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Normal processProcess in control Process out of control Process out of control
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The V-mask concept
Crossing limbs indicates that the process is out of control
Interpretation of the V-mask
0
20
40
60
80
100
120
140
160
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Strength too high
-160
-140
-120
-100
-80
-60
-40
-20
0
20
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Strength too low
-60
-40
-20
0
20
40
60
80
0 5 10 15 20 25 30 35
CU
SUM
[M
Pa]
Sequential single value
Normal processProcess in control Process out of control Process out of control
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Using CUSUM and V-mask to control the fresh concrete properties of SCC
Experimental
37 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Aim of the study
Changes in the rheology of self-compacting concrete can depend upon multiple factors.
Typically, it is not easily possible to identify the origin of changes in rheology:
Different cement quality/age?
Superplasticizer?
Water content of aggregates?
Fillers?
….
Is CUSUM a feasible method to maintain a steady slump flow regardless of the influencing factor, based only on:
the addition of superplasticizer (PCE), when too small, and
the addition of stabilising agent (Starch), when too wide?
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Cusum for control of rheology
Reference mix, Target consistence sF = 243 mm
sF = 165 mm
sF = 236 mm
sF = 282 mm
sF = 230 mm
PCE
Increased flowability Reduced flowability
STA
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Cusum for control of rheology
Reference mixture composition
Spec. Gravity [-] Mass/m³ [kg/m³] Vol./m³ [l/m³]
OPC (CEM I 42.5 R) 3.125 458.0 146.6
Limestone filler 2.735 369.7 135.2
Water 1.0 259.0 259.0
PCE superplasticizer 1.07 8.2
Sand 0.1/0.5 2.60 298.5 114.8
Sand 0.5/1.0 2.60 298.5 114.8
Sand 1.0/2.0 2.60 298.5 114.8
Sand 2.0/4.0 2.60 298.5 114.8
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Cusum for control of rheology
Variations: Effects that increase the slump flow
Manipulation Specification
Reference Target value after 15 minutes: 237.7 mm
More water +10% of water
More coarse sand +50% sand 2.0/4.0 and -50% sand 0.1/0.5
Less cement -10% of cement
Less limestone filler -10% of limestone filler
Addition of stabilising agent required to achieve target value of 237.7 mm
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Cusum for control of rheology
Variations: Effects that reduce the slump flow
Manipulation Specification
Reference Target value after 15 minutes: 237.7 mm
Less water -10% of water
Crushed sand Coarse quartz sand fraction replaced by crushed sand
Gypsum addition +0.35% of cement
More fine sand +50% sand 0.1/0.5 and -50% sand 2.0/4.0
More cement +10% of cement
More limestone filler +10% of limestone filler
Addition of extra superplasticizer required to achieve target value of 237.7 mm
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Pro
du
ctio
n d
ata
[MPa
]
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Cusum for control of rheology
Scenario
Manipulation that simulates production scatter
Manipulation active, no counter action taken
Manipulation finished
Normal production
Normal production
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Pro
du
ctio
n d
ata
for
slu
mp
flo
w [
mm
]
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Cusum for control of rheology
Scenario for V-mask observation
Manipulation that simulates production scatter
Manipulation detected and counter action taken
Manipulation active and counter action active
Manipulation finished but counter action still active
Counter action finished: normal production
Normal production
-400
-200
0
200
400
600
800
1000
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
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Cusum for control of rheology
Scenario: Cusum without and with application of V-mask
With application of V-mask (action taken upon detection)
Without application of V-mask (no counter action)
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Cusum for control of rheology
Scenario
9,3
7,7
3,2%
without V-mask
0,3%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
238,4
7,5
0,7
237,7
245,4
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-250
-200
-150
-100
-50
0
50
100
150
200
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
With application of V-mask control
(correction upon V-mask indication)
Without application of V-mask control
(no correction)
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Cusum for control of rheology
Experimental
Reference mixture: Mean value and standard deviation from 5 repetitions.
Manipulated mixtures: Mean value and standard deviations from 3 repetitions.
Simulation of production data according to scenario described before:
Based on normally distributed random values
with the mean values and standard deviations from the experimental investigations.
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Cusum for control of rheology
Experimental
Prediction of counter actions:
Experimental determination of manipulated samples:
+0%; +0.2%; +0.4% superplasticizer
+0%; 0.03%; 0.06% stabilising agent
Simplified assumption: Linear correlation:
200
210
220
230
240
250
260
0 0,2 0,4 0,6
Slu
mp
flo
w [
mm
]
Supplementary PCE [% of cement]
160
170
180
190
200
210
220
230
240
250
260
0 0,02 0,04 0,06 0,08
Slu
mp
flo
w [
mm
]
Addition of stabilising agent [% of water]
-150
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
48 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Experimental
Prediction of flow when manipulation is stopped but counteraction still active:
Experimental determination of manipulated samples:
+0%; +0.2%; +0.4% superplasticizer
+0%; 0.03%; 0.06% stabilising agent
Simplified assumption: Linear correlation:
140
160
180
200
220
240
260
0 0,02 0,04 0,06 0,08
Slu
mp
flo
w [
mm
]
Addition of stabilising agent [% of water]
230,0
235,0
240,0
245,0
250,0
255,0
260,0
265,0
270,0
275,0
280,0
0 0,2 0,4 0,6
Slu
mp
flo
w [
mm
]
Addition of stabilising agent [% of water]
-150
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
49 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
The V-mask concept
h = 5
f = ½
Experimental
50 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Using CUSUM and V-mask to control the fresh concrete properties of SCC
Results and discussion
51 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Extra water
-200
-150
-100
-50
0
50
100
150
200
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
8,5
6,2
2,6%
without V-mask
0,4%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
238,8
7,0
1,1
237,7
243,9
52 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Higher content of coarse aggregate
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
9,9
7,6
3,2%
without V-mask
0,6%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
239,2
7,1
1,5
237,7
245,3
53 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Lower cement content
-100
-50
0
50
100
150
200
250
300
0 10 20 30 40 50 60 70 80 90 100 110 120Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
5,2
15,5
6,5%
without V-mask
0,7%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
239,4
9,0
1,7
237,7
253,2
54 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Less limestone filler
-200
-100
0
100
200
300
400
500
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
12,9
37,0
15,6%
without V-mask
1,6%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
241,6
12,5
3,9
237,7
274,7
55 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Less water
-400
-300
-200
-100
0
100
200
300
400
500
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
9,0
-20,8
-8,7%
without V-mask
-1,1%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
235,1
9,2
-2,6
237,7
216,9
56 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Crushed sand
-2000
0
2000
4000
6000
8000
10000
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
Deviation from target [%]
with applied V-mask
237,7
224,5
39,4
-13,2
237,7
121,6
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
38,7
-116,1
-48,9%
without V-mask
-5,6%
57 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Extra gypsum
-400
-300
-200
-100
0
100
200
300
400
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
Deviation from target [%]
with applied V-mask
237,7
236,0
9,7
-1,7
237,7
215,8
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
9,1
-21,9
-9,2%
without V-mask
-0,7%
58 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Higher content of fine sand
-500
-400
-300
-200
-100
0
100
200
300
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
15,3
-34,4
-14,5%
without V-mask
-1,3%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
234,7
14,4
-3,0
237,7
203,3
59 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Higher cement content
-350
-300
-250
-200
-150
-100
-50
0
50
100
150
200
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
7,2
-20,4
-8,6%
without V-mask
-0,8%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
235,9
10,6
-1,8
237,7
217,3
60 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Results: Extra limestone filler
-400
-350
-300
-250
-200
-150
-100
-50
0
50
100
150
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
14,9
-27,7
-11,6%
without V-mask
-0,9%
Target value after 15 min. [mm]
Mean value [mm]
Standard deviation [mm]
Deviation from target [mm]
Deviation from target [%]
with applied V-mask
237,7
235,5
11,7
-2,2
237,7
210,0
61 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Discussion
In all cases, the V-mask was able to immediately detect systematic effects that negatively affected the production.
The counteractions successfully created stable processes on target:
Additon of supplementary PCE, when slump flow decreased.
Addition of stabilising agent, when slump flow increased.
In all cases the production mean could be maintained close to the target value and the standard deviation of the production was lower than without detection of the systematic error.
The V-mask could also immediately indicate when the systematic production influence ended and standard production could be continued.
62 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Discussion
Nevertheless: often a „simple“ Shewhart chart would have indicated the same.
However, particularly at small changes, cusum is stronger.
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-400
-300
-200
-100
0
100
200
300
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-250
-200
-150
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
Gypsum addition
Water addition
63 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Cusum for control of rheology
Discussion
Example: 3% deviation from target:
Example: 6% deviation from target:
Example: 9% deviation from target:
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-200
-150
-100
-50
0
50
100
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-300
-250
-200
-150
-100
-50
0
50
100
150
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
200
210
220
230
240
250
260
270
280
290
0 10 20 30 40 50 60 70 80 90 100 110 120
Pro
du
ctio
n, t
arge
t va
lue:
23
7.7
mm
[m
m]
-350
-300
-250
-200
-150
-100
-50
0
50
100
150
0 10 20 30 40 50 60 70 80 90 100 110 120
Cu
sum
fo
r sl
um
p f
low
val
ue
[mm
] (t
arge
t =
23
7.7
mm
)
64 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Conclusions
65 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
Conclusions
Investigations on the use of cusum control charts in combination with a standard V-mask for the production control of the fresh concrete properties of SCC were conducted.
In case of a higher slump flow, stabilising agent was added to achieve target slump flow diameter.
In case of a smaller slump flow, supplementary superplasticizer was added to achieve target slump flow diameter.
The cusum system in combination with a standard V-mask identified in all cases systematic effects that caused deviations from standard production.
Different from reading process values (Shewhart chart) the cusum system is much more sensitive and identifies changes immediately.
Cusum in combination with a V-mask ist therefore a strong tool to improve the robustness of the casting of flowable concretes.
66 "Rheologische Messungen an Baustoffen“ 24. Workshop und Kolloquium , Regensburg 2015
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