Achieving Durable Concrete Concrete Mixtures · Design a concrete control plan for a 8 ftby 10...
Transcript of Achieving Durable Concrete Concrete Mixtures · Design a concrete control plan for a 8 ftby 10...
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DEPARTMENT OR UNIT NAME. DELETE FROM MASTER SLIDE IF N/A
ConcreteWorks Software For Iowa Use
Thermal Cracking
Picture courtesy of J.C. Liu, TxDOT
Achieving Durable Concrete
DurableConcrete
Concrete MixturesInfinite number of combinations of:• Aggregate type & quantity• Type & amount of cement• SCM use• Admixtures
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Quality concrete Multi-variate problem – rules of thumb can be inaccurate or unconservative
Preplanning Engineer – Best during design Contractor – Best during bidding
Required by specification
Why do we model temperature and stress?Why do we model temperature and stress?
Why is the bread surface cut before baking?
Self-Generated Restraint
Temperature Prediction
Tem
pe
ratu
re
Time
Heat of Hydration
Environmental Cycle
Heat Transfer
Tem
pe
ratu
re
Time
Surface
Core
≤ ΔT ?
Material FactorsCementitious Types/Composition
Cementitious FinenessCementitious ContentChemical Admixtures
w/cmFresh TemperatureAggregate Types
Construction FactorsElement Geometry/Size
InsulationForm PropertiesCuring Methods
Surface ColorCooling Pipes
EnvironmentAir Temperature
Wind SpeedRelative Humidity
Cloud CoverSolar Radiation
SoilWater Submersion
Heat Transfer
Generated Heat
Conducted Heat to soil
Solar Radiation and Radiation from Atmosphere
Convection to/from surface
Irradiation from Footing
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Heat Diffusion Equation
Generated Heat
Conducted Heat to soil
Solar Radiation and Radiation from Atmosphere
Convection to/from surface
Irradiation from Footing
T=temperaturek=thermal conductivityQH=heat generationρ=densityCp=specific heatT=time 𝑑
𝑑𝑥𝑘 ·
𝑑𝑇𝑑𝑥
𝑑𝑑𝑦
𝑘 ·𝑑𝑇𝑑𝑦
𝑑𝑑𝑧
𝑘 ·𝑑𝑇𝑑𝑧
𝑄 𝜌 · 𝐶 ·𝑑𝑇𝑑𝑡
Estimate Max Temperature
Schmidt Method
ConcreteWorks
Proprietary software (Finite Element Analysis)
Temperature Prediction Methods
Incr
eas
ing
Co
mp
lexi
ty
(Schindler, 2002)
Heat Evolved at Each Time Step
cr
ae
eecuh TTR
Et
ttWHtQ 11exp)()(
From Isothermal Calorimetry
From Literature
From Semi-Adiabatic Calorimetry
Role of Temperature in Hydration
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Temperature Sensitivity Example
Effect of temperature on bacteria growth in milk
Reaction Rate (S. Arrhenius, 1889) Where k = rate of reaction A = constant (=0) R = Universal gas constant (8.314) T = reference temperature Ea = Activation Energy
Arrhenius Equation
RTEAk a lnln
Temperature Sensitivity of Cement Reaction
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 10 20 30 40 50 60 70 80 90 100
Paste age (hours)
Deg
ree
of H
ydra
tion
5°C
15°C
23°C
38°C
60°C
y = -3538.3x + 8.5932R2 = 0.981
-5.5
-4.5
-3.5
-2.5
-1.5
0.0028 0.0030 0.0032 0.0034 0.0036 0.0038
ln(k
)
1/Temperature (1/k)
De
gre
e o
f Re
acti
on
Time from Mixing (hrs)
0
10
20
30
40
50
60
1 10 100 1000
Concrete Age (hours)
Adi
abat
ic T
empe
ratu
re R
ise
(°C
)0
12
24
36
48
60
72
84
96
108
Adi
abat
ic T
empe
ratu
re R
ise
(°F)
10ºC (50ºF)
20ºC (68ºF)
30ºC (86ºF)
Cementitious Content = 564 lb/yd3 (325 kg/m3)
40ºC (104ºF)
Type I CementC3S = 61.0C2S = 15.6C3A = 9.6C4AF = 6.0Blaine = 391 m2/kg
Effects of Curing Temperature on Adiabatic Temperature Rise
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(Schindler, 2002)
Heat Evolved at Each Time Step
cr
ae
eecuh TTR
Et
ttWHtQ 11exp)()(
From Isothermal Calorimetry
From Literature
From Semi-Adiabatic Calorimetry
0
10
20
30
40
50
60
70
32
50
68
86
104
122
140
158
0 24 48 72 96 120
Tem
pera
ture
(°C
)
Tem
pera
ture
(°F)
Time from Mixing (Hrs)
Cement Only
40% Class C Fly Ash
40% Class F Fly Ash
Adiabatic or Semi-Adiabatic Calorimetry
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1 10 100 1000 10000 100000
Time (hours)
Degr
ee o
f Hyd
ratio
n
au = 0.900
au = 0.690
au = 0.500
e
ue tt exp*)(
–Degree of Hydration
Increasing
Figure Courtesy of Jonathan Poole
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
1 10 100 1000 10000 100000
Time (hours)
Deg
ree
of H
ydra
tion
t = 12.000
t = 26.774
t = 40.000
–Time Parameter
Increasing
Figure Courtesy of Jonathan Poole
e
ue tt exp*)(
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0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
1 10 100 1000 10000 100000
Time (hours)
Deg
ree
of H
ydra
tion
b = 1.250
b = 0.851
b = 0.450
e
ue tt exp*)(
–Slope Parameter
Increasing
Figure Courtesy of Jonathan Poole
Ea Trends – From 116x5 Isothermal tests
u, , , Hu Trends – From Semi-Adiabatic Data – 204 Semi-Adiabatic Tests
Validation performed using data from Schidler (2005), Ghe Li (2006), and field sites – 58 Semi-Adiabatic Tests
Variability of test methods is quantified – 63 Semi-Adiabatic Tests.
A brief overview of the trends seen in the study is shown next.
Model for Hydration Built From:
Variable Range of Tests Effect on Effect on Effect on u Fly Ash
(%Replacement) 15-55%
Fly Ash (CaO%) 0.7-28.9% CaO Varies
GGBF slag 30-70% Large Small Varies
Silica Fume 5-10% None None Small
LRWR 0.22-0.29% Varies Small Varies
WRRET 0.18-0.53% Large Large Large
MRWR 0.34-0.74% Large Small Varies
HRWR 0.78-1.25% None Small Large
PCHRWR 0.27-0.68% None Small Large
ACCL 0.74-2.23% Small None Varies
AEA 0.04-0.09% None None None
Variable Range of Tests Effect on Effect on Effect on u
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Increasing w/c 0.32-0.68 None None Large
Placement Temp 15-38 °C (50-100 °F) None None None
Increase Cement Fineness 350-540 m2/kg Small Small Varies
Variable Range of Tests Effect on Effect on Effect on u Proportions
Click checkboxes to use an SCM
Proportions
Don’t forget to enter CaOcontent of fly ashes
Check when admixtures used.
Heat Diffusion Equation
Generated Heat
Conducted Heat to soil
Solar Radiation and Radiation from Atmosphere
Convection to/from surface
Irradiation from Footing
T=temperaturek=thermal conductivityQH=heat generationρ=densityCp=specific heatT=time 𝑑
𝑑𝑥𝑘 ·
𝑑𝑇𝑑𝑥
𝑑𝑑𝑦
𝑘 ·𝑑𝑇𝑑𝑦
𝑑𝑑𝑧
𝑘 ·𝑑𝑇𝑑𝑧
𝑄 𝜌 · 𝐶 ·𝑑𝑇𝑑𝑡
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AggregatesMaterial Properties Input Screen
• Concrete thermal properties based on aggregate combination selected
• Can input your own thermal properties by checking box (for example, to use lightweight aggregate)
Aggregate TypeCoarse Aggregate Concrete CTERiver Rock 10.5 με/°CLimestone 6.6 με/°C
INVAR SIDE BAR
CROSSHEAD
Figures from Whigham 2005
Aggregates
Material
Coefficient of Thermal Expansion values used in ConcreteWorks (/°C)
Coefficient of Thermal Expansion from Emanuel and
Hulsey, 1977(/°C)
Hardened Cement Paste 10.8 10.8Limestone Aggregate 3.5 3.5 - 6Siliceous River Gravel and Sand 11 11 – 12.5Granite Aggregate 7.5 6.5 – 8.5Dolomitic Limestone Aggregate 7 7 - 10
pfaca
ppfafacaca
cteh VVVVVV
Construction Inputs
Default is use air temperature at placement
Options: steel, wood, and insulated steel formwork
*If insulated steel forms used, form insulation value appears
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ConcreteWorks Geometry: ColumnsHorizontal CrossSection Assumedfor RectangularColumn
ConcreteWorks Geometry: Footings
Verticalcross-sectionmodeledin 2-D
footing
Subbase Material
Density (kg/m3)
Thermal Conductivity (W/m/K)
Specific Heat (J/kg/K) Reference
Clay 1460 1.3 880
Incropera and Dewitt, 2002
Granite 2630 2.79 775Limestone 2320 2.15 810Marble 2680 2.8 830Quartzite 2640 5.38 1105Sandstone 2150 2.9 745Sand 1515 0.27 800Top Soil 2050 0.52 1840Concrete* - - -
Foundation Thermal Properties
*Concrete is assumed to have the same thermal properties of the concrete used on the footing, with a degree of hydration equal to 0.6.
ConcreteWorks Geometry: Soil on Sides of Footing
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Bent Cap
Vertical cross sectionmodeled in 2-d rectangularbent cap
T-shaped Bent Caps
Circular Column/ Drilled Shaft Mechanical PropertiesCheck to calculate stresses – can be slow, not recommended for more than 4-5 days of analysis
Maturity-Strength Relationship Parameters
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Environment Inputs (Weather)Weather data based on 30 year average values
Click here to manually change values
Service Life Modeling
Used for corrosion service life model inputs
Thermocouple Points
Allows the user to select where sensors would be placed to give realistic estimate of values they would measure
TxDOT (original software development) & IDOT for providing funding for this work
Acknowledgements
Go Gators!
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Design a concrete control plan for a 8 ft by 10 ft column placed in Ames in August 2020 to meet IDOT standards.
Next, determine any changes that would be needed to place the same column in January, 2021 in Ames.
*Pay attention to the difference it makes where the temperature sensor is placed
Problems to Work Out After Lunch Design a control plan for concrete footing that is 20 ft by 30 ft by 8 ft
thick in Des Moines in March. Use limestone subbase. What difference do you get between 1D and 2D analysis?
What about with a 10 ft wide footing – what difference do you get between a 1D and 2D analysis?
Problems to Work Out After Lunch
You want to place a concrete footing that is 30 ft by 20 ft by 6 ft thick. It is August in Des Moines, and you expect a storm after 2 days to lower the high temperature to 60°F and the low temperature on day 2 to 45°F. Design a system that will still meet IDOT standards.
Problems to Work Out After Lunch