When Carbon
Reduction and
Constructability clash
- Who is responsible
for the fallout?
Kevin MacDonald
Beton Consulting Engineers
University of Wisconsin Stout
Prescription vs. Performance
• US lagging behind Europe / Canada in code
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development
I.e. CSA A23.1 class C1 exposure
Economic advantage of “how” is removed
Innovation is stifled
Often meeting the prescription can result in
undesirable, unintended consequences
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Obstacles
 We
are developing new technologies and new
materials
 New processes and new construction
methods
 Doing so not to improve construction or
performance – to reduce / eliminate
emissions and reduce energy needs
 History tells us that there will be problems
and they will be discovered in practice.
Pantheon
Slump
Design and Control
7
 2.
The Contractor shall designate a 3”
slump range. The slump shall be kept
consistent during the entire placement. If a
spread range is specified a Visual Stability
Index (VSI) of 1 or less is required according
to ASTM C1610.
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Case Studies
Coloured Concrete Issues
 The
color of the cement has an influence
 As pozzolans increase – they change the
‘base’ color
Colored Concrete Issue
 Warning
on the color card
 Still a problem
 unhappy customer
 Know what is going to happen – It will affect
the color
Great River Energy
Platinum LEED 45 percent
reduction in cement content
 Flyash
replacement of 60 percent
 Total cementitious content increased
 Net reduction 45 percent
 Change
in just superplasticizer = Disaster
Winter Concrete
AET 4060
 RCP
at 84 days 490 Coulombs passed
 Setting Time 4:30 Initial Set
 Air Void System



Air Content 5.5 percent
Spacing Factor 0.008 in
Specific Surface 600 in2 /in3
 Shrinkage
0.005 percent at 28 days
 Strength Gain
Strength Gain AET 4060
5000
4500
Strength, psi
4000
3500
3000
2500
2000
1500
1000
500
0
1
10
Age, Days
100
Lessons Applied
Extreme Example
82 lb OPC remainder of material is
recycled
Cement Content below 550 lb
All aggregate was recycled
All water was reclaimed
Typical Mixtures - Bridges
Strength Strength
28-Days 56-Days
3,000
3,300
3,900
4,200
3,100
3,600
4,700
5,400
6,300
7,200
3,500
4,000
4,300
5,000
3,500
4,000
5,200
6,000
7,000
8,000
Strength
90-Days
4,000
4,500
5,000
5,500
4,000
4,400
6,000
6,500
8,000
8,600
Cement Slag Fly Ash Silica Total
St. Gen. Holcim Portage Fume Cem.
80
360
90
0
530
324
0
216
0
540
90
360
90
0
540
372
0
248
0
620
84
375
101
0
560
232
116
232
0
580
90
402
108
0
600
294
147
294
0
735
120
320
190
30 660
332
166
332
0
830
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I 35 W St. Anthony Falls Bridge
 All
concrete in foundation and substructure
is High Pozzolan Content
 Conventional cementitious contents – less
than 625 lb per cubic yard
Case Study
 Patio
for a Restaurant in Wisconsin
 Stamped Concrete with Broadcast color
 Architect required high pozzolanic
replacement 50 percent flyash
 Concrete placed late in year
Freeze-Thaw Resistance
 Freeze
thaw resistance is imbued by air
entrainment
 Pozzolans do not change this



low permeability
ASTM C666 testing
Very high class C – may be detrimental secondary
crystallization
LEED Credits
 Materials
& Resources
During both the construction and operations
phases, buildings generate a lot of waste and use
large quantities of materials and resources. The
Materials & Resources category encourages the
selection of sustainably grown, harvested,
produced and transported products and
materials. It promotes waste reduction as well as
reuse and recycling, and it particularly rewards
the reduction of waste at a product’s source
Drying Period
 Water
in concrete can fill pores that once
dried cannot be refilled
 So
concrete may be more saturated before
drying than after immersion following drying
Modified Pore Structure
60 %
Hydratio
n
OPC
Capillary Pores
Intruded Volume
Gel pores
OPC +
GGBFS
0.001
10
0.01
0.1
Pore diameter, μm
1
Modified Pore Structure
60 %
Hydratio
n
3
Days
OPC
Capillary Pores
Intruded Volume
Gel pores
OPC +
GGBFS
28
days
0.001
10
0.01
0.1
Pore diameter, μm
1
Scaling Resistance
 Making
the skin of concrete – because
concrete beauty is skin deep
HASTINGS BRIDGE
Hastings bridge’s flaking concrete
not unsafe, MnDOT says
The concrete surface of the new U.S. 61 bridge in
Hastings is flaking or “scaling,” but the issue does
not pose any safety issues, the Minnesota
Department of Transportation said.
 “It’s not visually appealing, but the bridge is safe,”
said Steve Kordosky, bridge project manager for
MnDOT.
 To determine what caused the scaling, the agency
did visual inspections and took core samples,
which are at a laboratory, Kordosky said.
 The $130 million bridge is under warranty and
MnDOT will fix the problem later this year, he said

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Conclusions : Responsibilities
 In
a mixed specification world we are
concerned about unclear responsibility
 Setting
 Strength Gain
 Shrinkage
 Durability Testing
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Conclusions
 Concrete
is rapidly changing – codes are not
(cannot)
 We need to reduce or eliminate the clinker
content of our concrete.
 We can currently use high volume
replacement with pozzolan
 We are on the cusp of using materials that
would require massive infrastructure
investment (Plants, Equipment, People)
 Construction and Design methods will likely
change as we adopt new materials
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