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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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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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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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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Maintenance System


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Maintenance System


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


Maintenance System

Moisture Conditions

LOGO Experimental Results


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)



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



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



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)



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)



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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Clarification of Frost Damage Mechanism Based on Mesoscale