Session 10
Purdue Research
Updates
Using Internal
Curing in Concrete
Bridge Decks
Road School
March 9th, 2011
Slide 1 of 31
Purdue University
School of Civil Engineering
Update in Research Study on
Using Internal Curing
in Concrete Bridge Decks
Developed for Discussion with the Road School by:
Carmelo Di Bella, John Schlitter, Igor De
La Varga Nathan Phares and
Jason Weiss
March 9th, 2011
Road School
March 9th, 2011
Slide 2 of 31
Outline
• Difference between external and internal
curing
• Importance of Internal curing
• Benefits of internal curing
• Possible improvements in terms of service
life and CO2 emission reduction
• Conclusion
Road School
March 9th, 2011
Slide 3 of 31
Outline
• Difference between external and internal
curing
• Importance of Internal curing
• Benefits of internal curing
• Possible improvements in terms of service
life and CO2 emission reduction.
• Conclusion
Road School
March 9th, 2011
Slide 4 of 31
What Is external Curing?
• External curing
Bloomington, 2010
Supply of water to the concrete can be
accomplished by ponding, spraying, or by
use of saturated coverings.
Road School
March 9th, 2011
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What Is Internal Curing?
• Internal Curing
Haydite LWA
Road School
March 9th, 2011
SAP
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What is Internal Curing
• ACI “Supplying water throughout a freshly
placed cementitious mixture suing
reservoirs, via prewetted Lightweight
aggregate, that readily release water as
needed for hydration or to replace moisture
lost through evaporation or self desiccation”
• Hiding Water In LWA to increase hydration
and strength while reducing transport,
shrinkage, and cracking
Road School
March 9th, 2011
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What Is Internal Curing?
Road School
March 9th, 2011
Slide 8 of 31
Outline
• Difference between external and internal
curing
• Importance of Internal curing
• Benefits of internal curing
• Possible improvements in terms of service
life and CO2 emission reduction
• Conclusion
Road School
March 9th, 2011
Slide 9 of 31
Fundamental Volume Change
• Le Chatelier 1850-1936
• Chemical Shrinkage: The
apparent volume of the
cement paste may
increase but there is a
substantial decrease in its
absolute volume.
=
+
Road School
March 9th, 2011
Slide 10 of 31
Concept – LWA Supplies Water
• Water stays in
LWA until the
time that this
under pressure
develops
• At that point
water would be
drawn out of
bigger pores in
LWA in a perfect
world
Road School
March 9th, 2011
Slide 11 of 31
IC Mixture Proportion – How much
water does the system want?
• LWA: water reservoirs that
release water at the
appropriate time (after set)
• Hypothesis: All Chemical
Shrinkage water is replaced
• Bentz (1999) equation
Road School
March 9th, 2011
Slide 12 of 31
Outline
• Difference between external and internal
curing
• Importance of Internal curing
• Benefits of internal curing
• Possible improvements in terms of service
life and CO2 emission reduction
• Conclusion
Road School
March 9th, 2011
Slide 13 of 31
Degree of Hydration at 72 h
(Heat / Maximum theoretical heat)
Internal Curing Increases
Hydration
0.7
Internal Curing
Sealed
0.6
0.5
0.4
0.25
0.30
0.35
0.40
0.45
0.50
w/c
Castro 2010
Road School
March 9th, 2011
Slide 14 of 31
Relative Humidity
Relative Humidity (%)
100
96
92
88
LWA Mortar 23.7%
LWA Mortar 11.9%
Plain Mortar (0.0% LWA)
84
80
0
24
48
72
96
120
144
168
Time after mixing (h)
Castro 2010
Road School
March 9th, 2011
Slide 15 of 31
Applications
• Texas – Pavement Construction
• NYDOT – 10+ Decks with IC
– Reviewed and walked these decks
– One crack in the negative region on a very wide
bridge with a high skew
– No problems reported
– Additional Cost ($10 /yd3)
• IN-LTAP – 1 with IC, 1 conventional
– No Problems reported,
• VADOT – Bridge Deck
Road School
March 9th, 2011
Slide 16 of 31
LTAP Project
• To Evaluate Internal Curing in Two Bridges
(With Internal Curing and Without)
• To Document with Local Materials
• To Aide in Understanding What May Be
Needed from Specification and What May
Be Needed in A Change of Process
• Overall – Improve Service Life Performance
for Limited Cost by Being More Efficient
Road School
March 9th, 2011
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Location
• Two Bridges Near One Another
• Similar Exposure/Traffic
• Wanted to Monitor Long Term Performance
Road School
March 9th, 2011
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Conventional Bridge
Road School
March 9th, 2011
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Typical Construction
Road School
March 9th, 2011
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Internally Cured Deck
Road School
March 9th, 2011
Slide 21 of 31
Findings of the IC Project
• Early on (up to 5
days) similar
strength
• At 28 days
Internal curing
increases
strength
(Increased
Hydration)
Road School
March 9th, 2011
Slide 22 of 31
Findings of the IC Project
• At 28 days
similar chloride
resistance
• At 91 Days 25%
more resistance
to chloride
ingress
(Increased
Hydration)
Road School
March 9th, 2011
Slide 23 of 31
An Interesting Aside
• INDOT Class C – 5.5 k-Ohm/cm (90 d)
• With Internal Curing – 7.0 k-Ohm/cm (90 d)
• NYDOT Bridge Deck – 32 k-Ohm/cm (90 d)
• There is room for Indiana to reconsider the
designs using to increase resistance to
chlorides and increase service life
Road School
March 9th, 2011
Slide 24 of 31
Outline
• Difference between external and internal
curing
• Importance of Internal curing
• Benefits of internal curing
• Possible improvements in terms of service
life and CO2 emission reduction
• Conclusion
Road School
March 9th, 2011
Slide 25 of 31
Road School
March 9th, 2011
Slide 26 of 31
Road School
March 9th, 2011
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Current State FHWA/INDOT
• Goal is to reduce the clinker content of
concrete used in transportation structures
• Class C concrete
bridge requires
390 kg/m3 of
cementitous
• Current limit of
20-25% fly ash
Columbus Indiana
Road School
March 9th, 2011
Slide 28 of 31
From FHWA/DOT Perspective
• w/c – 0.42 and w/c -0.3 - 40% ash have
equivalent 1 day strength but have a 40%
reduction in CO2 per yd3 of concrete
• w/c – 0.42 and w/c -0.3 - 60% ash have
equivalent 7 day strength but have a 60%
reduction in CO2 per yd3 of concrete
Road School
March 9th, 2011
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Impact of HVFA on Microstructure
De LA Varga 2011
Road School
March 9th, 2011
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Conclusion
• Showing Benefits (reduced cracking slowed
chloride ingress, similar strength)
• Uses cement more efficiently – increases
degree of hydration
• Enables ‘greener’ concrete as OPC can be
replaced (limestone, ash, slag)
• Increases ‘reserve capacity’ for
temperature effects during construction
• Reduces fluid transport which can extend
service life giving more bang for the buck
Road School
March 9th, 2011
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