Clarification of Frost Damage Mechanism Based on Mesoscale ...
Transcript of Clarification of Frost Damage Mechanism Based on Mesoscale ...
Faculty of Engineering
Division of Built Environment
Laboratory of Engineering
for Maintenance System
Hokkaido University
Clarification of Frost Damage Mechanism Based on Mesoscale Deformation and Temperature
and Moisture Change
EVDON LUZANO SICAT, M2
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Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Contents
Experimental Methods and Results B
C
Overview of the Study A
Initial Findings
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Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Overview
Freeze-thaw Deterioration
Concrete, like other highly divided porous media, has the ability to absorb and retain moisture. This characteristic has an important consequence since unprotected concrete structures in contact with water are usually susceptible to frost damage.
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Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Overview
Research Objective: To clarify the effect of temperature history and moisture
conditions on concrete that are under the effect of freezing and thawing actions by developing a material model in mesoscale.
Important Facts in FTC (Freezing Thawing Cycle)
1. Volume of water expands by 9% when converted to ice
2. Thermal expansion of ice is higher than mortar (or concrete)
3. The freezing point of water in pores gets lower as their size gets smaller
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Structural and Material Performance Evaluation of Frost Damaged RC Members Laboratory of Engineering for
Maintenance System
These pores are the
remnant of the original
water filled spaces of
fresh concrete mix.
These pores are larger
than the gel pores. The
smaller the capillary
size the lower the
freezing temperature.
(pore size 0.02 – 10 μm)
Consists of a system of very fine pores within the dense packing of cement hydration products. The radii of these pores are very small. Water present in this class of pores seldom freezes under usual freezing conditions of concrete use. (pore size 0.0005 – 0.01 μm)
The sizes of these air bubbles are very much larger than the other two classes of pores. Normally the capillary pores are separated from the air bubbles by layers of cement hydration products with associated gel pores. (recommended at 50 μm)
Pore Structure
Gel Pores Capillary
Pores Entrained-
air
Three Kinds of Pores in Concrete
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Structural and Material Performance Evaluation of Frost Damaged RC Members Laboratory of Engineering for
Maintenance System
Pore Structure
Freezing Temperature vs. Pore Radius
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Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Experimental Methods
Water Curing for 2 Months
Cutting of Specimens
40 x 40 x 2mm
Oven drying for 24 Hours to
Determine Dried Weight
Attaching of Strain Gauges
Water Curing Until Mass is
Constant
Dried Specimen (RH 0%)
100 % Saturated
20% - 50% Saturated
80% - 90% Saturated
SE
AL
ED
Casting and Molding
40 x 40 x 160mm
FT
C
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Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Experimental Methods
LOGO
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Experimental Methods
Experimental Set-up
Specimens
Data logger
PC
Environmental Chamber
Temperature sensor Specimen support
Quartz Strains
-30
030
60
90120
150
180
210240
270
300330
360
390420
450
480
-30 -20 -10 0 10 20
Temperature(ºC )
Str
ain
(με
)
Actua l Quartz Stra in(Deformation)Output Stra in GaugeReading
Aluminum Strains
-830
-730
-630
-530
-430
-330
-230
-130
-30
-30 -20 -10 0 10 20
Temperature(ºC )
Str
ain
(με
)
Actua l A luminum Stra in(Deformation)
Output Stra in GaugeReading
Quartz Strains
-30
030
60
90120
150
180
210240
270
300330
360
390420
450
480
-30 -20 -10 0 10 20
Temperature(ºC )
Str
ain
(με
)
Actua l Quartz Stra in(Deformation)Output Stra in GaugeReading
Aluminum Strains
-830
-730
-630
-530
-430
-330
-230
-130
-30
-30 -20 -10 0 10 20
Temperature(ºC )
Str
ain
(με
)
Actua l A luminum Stra in(Deformation)
Output Stra in GaugeReading
10 °C
-28 °C
0.25°C/min
Temperature History (5/20 cycles)
2.5 h 2.5 h 2.53 h 2.53 h
LOGO Experimental Methods
Moisture Condition Moisture Content
(g/cc)
Relative Humidity Specimens per
Condition
Absolutely Dry - 0% 3 sets
100% Saturated (Set A) 0.228 100% 3 sets
92% Saturated 0.208 99% 3 sets
68.4% Saturated 0.152 80% 3 sets
100% Saturated (Set B) 0.289 100% 2 sets
85% Saturated 0.206 89% 2 sets
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
Moisture Conditions
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-400
-350
-300
-250
-200
-150
-100
-50
0
50
0 500 1000 1500 2000 2500 3000 3500
Temperature
Strain
Dry Mortar - Strain (µ)
Time (minutes)
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-250
-150
-50
50
150
250
350
450
550
650
750
850
950
1050
1150
1250
0 500 1000 1500 2000 2500 3000 3500
Temperature
Average SaturatedMortar Strain
100% Saturated Mortar (Set A) - Strain (µ)
Time (minutes)
-100
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
0 500 1000 1500 2000 2500 3000 3500
Temperature
Average Saturated MortarStrain less Thermal Strains
100% Saturated Mortar (Set A) less Thermal Strains - Strain (µ)
Time (minutes)
-50
50
150
250
350
450
550
650
750
850
950
1250 1450 1650 1850
Temperature
Steady MaxTempMax to -7.3
-7.3 to -9.9
-9.9 to -28(minimum)Steady MinTemp (-28)Min to -9.7
-9.7 to 0
Strain (µ) at 3rd Cycle
Time (minutes)
ice
Water
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-100
0
100
200
300
400
500
0 2000 4000 6000 8000 10000 12000
Temperature
93% Average Saturated MortarStrains less Thermal Strains
FTC Strain Diagram less Thermal Strain - 93% Saturated Mortar Strain (µ)
Time (minutes)
-400
-300
-200
-100
0
100
200
300
400
500
0 2000 4000 6000 8000 10000 12000
Temperature
FTC Strain Diagram - 93% Saturated Mortar
Time (minutes)
-50
0
50
100
150
200
1198 1398 1598 1798 1998
Temperature
Max Steady Temp
Max to 0
0 to -6.6
-6.6 to -7.8
-7.8 to -15.6
-15.6 to -28.5
-28.5 steady temp (-28.1)
-28.1 to -6
-6 to 0
0 to max (9.4)
max steady temp
Strain (µ) at 3rd Cycle
Time (minutes)
water
ice
Water flow
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-400
-300
-200
-100
0
100
200
300
400
500
0 500 1000 1500 2000 2500 3000 3500
Temperature
100% SaturatedMortar Set B
100% Saturated Mortar Set B - Strain
Time (minutes)
-400
-200
0
200
400
600
800
1000
0 500 1000 1500 2000 2500 3000 3500
Temperature
100% Saturated MortarSet B
100% Saturated Set B Mortar Less Thermal Strains - Strain (μ)
Time (minutes)
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-400
-300
-200
-100
0
100
200
300
400
0 500 1000 1500 2000 2500 3000 3500
Temperature
89% Saturated Mortar
89% Saturated Mortar - Strain (μ)
Time (minutes)
-400
-300
-200
-100
0
100
200
300
400
500
0 500 1000 1500 2000 2500 3000 3500
Temperature
89% Saturated Mortar
89% Saturated Mortar less Thermal Strains - Strain
Time (minutes)
LOGO Experimental Results
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change Laboratory of Engineering for
Maintenance System
-450
-350
-250
-150
-50
50
0 500 1000 1500 2000 2500 3000 3500
Time (minute)
68.4% Saturated Mortar Strains - Strain (µ)
Temperature (˚C)
Strain
-100
-50
0
50
100
0 500 1000 1500 2000 2500 3000 3500
Time (minute)
68.4% Saturated Mortar Less Thermal Strains - Strain (µ)
Temperature (˚C)
Strain
water
ice
LOGO Findings
It is evident that the degree of saturation dictates the behavior of concrete mortar under FTC cycles. The level and variation in deformation of mortar specimens depends on the amount of moisture.
The deformation of mortar specimens caused by the effect of moisture can be observed after the thermal expansion of mortar is removed.
The expansion or tensile strain was not caused during the freezing process for test specimens having saturation condition of 92% and below.
Though the expansion was not evident during the freezing process for test specimens having saturation condition of 92% and below, a residual strain resulted at the end of the FTC. However if the thermal expansion/contraction strain of mortar is removed, the behavior of moisture causes a slight expansion strain at the freezing temperature, this is due to the expansion of water as it forms to ice. The level of the resulting residual strain is dependent on the amount of moisture present on the specimens. The higher the moisture content the higher is the resulting expansion and residual strain.
For test specimens having full saturation, higher expansions were observed during the freezing process. As the number of cycles increased so is the amount of expansion at every FTC even though moisture was not supplied.
Supercooling was marked for all test specimens with moisture content, the level of supercooling and behavior of mortar after the supercooling is dependent on the amount of moisture present in the specimens. For mortar specimens with 100% saturation, after the supercooling moisture behavior continued to exhibit positive pressure while specimens having 92% saturation and below shrinkage was observed after the supercooling.
The dry mortar specimens show a constant behavior during the entire FTC process. This constant behavior is the product of the absence of moisture in the test specimens.
The results presented prove that the presence of moisture in concrete specimens or
structures can alter its structural integrity once subjected in a FTC even for low moisture
content specimens.
Clarification of Frost Damage Mechanism based on Mesoscale Deformation and Temperature and Moisture Change
Laboratory of Engineering for Maintenance System
Faculty of Engineering
Division of Built Environment
Laboratory of Engineering
for Maintenance System
Hokkaido University
C l i c k t o e d i t c o m p a n y s l o g a n .
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