U of A_Cement Based CompositesPRATUL

8/2/2019 U of A_Cement Based CompositesPRATUL

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Correlating Water Permeabilitywith Ultra-Sonic Pulse Velocity in

Cement Based Composites under

Compression

Meghdad Hoseini & Vivek Bindiganavile

University of Alberta, Edmonton, Canada

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Contents

Introduction

Background

Effect of mechanical stress on permeabilityand ultrasonic wave velocity of concrete

Experimental Program

Results and discussions Concluding Remarks

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Introduction

Deterioration of concrete structures is a serious problem

mainly due to the ingress of aggressive agents into concrete

which leads to the corrosion of reinforcements

Water is the most significant fluid that flows through concrete

and it is the chief agent for soluble aggressive ions that cause

the chemical degradation of concrete

This ingress depends largely on the number, size , distribution

and interconnectivity of the pores and cracks in concrete.

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How Serious Is It?

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Transport Mechanisms(1)

1- PermeabilityTransport of fluids through concrete due to

pressure gradient

Darcys Law (Steady State Condition): Permeability Coefficient (K)

2- Diffusion

Transport of fluids through concrete due to ionicconcentration gradient

Ficks second law: Diffusion Coefficient (Dc)

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Transport Mechanisms(2)3- Absorption

Transport of fluids through concrete due to moisture gradient

4- Migration

Transport of fluids through concrete due to electrical potential gradient

5-Capillary Suction

Transport of fluids through concrete due to action of surface tension

6- Combined Mechanisms

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Steady state condition

Steady state refers to the condition where the

fluid properties such as temperature, pressure

and velocity at any single point in the system do

not change over time

One of the most significant properties of a steady

state flow system is the system constant massflow rate

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Effect of Stress on Permeability(1)

Concrete structures are subjected to differenttypes of distress (mechanical, thermal andchemical)

The applied load promotes crack growth andinterconnectivity of the cracks and in turnincreases permeability of concrete

Permeability in concrete affects the available

oxygen and moisture around the reinforcementand thus quickens the rate of reinforcementcorrosion

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Transport properties, fracture mechanisms,

effect of temperature variation and corrosion

of reinforcement of concrete has been widely

studied separately in the past

Several standard techniques and test methods

have been standardized to measure the

permeability of concrete independent ofstress

Effect of Stress on Permeability (2)

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Very few studies have been done on the

simultaneous effect of mechanical stress on

transport properties of reinforced concrete

which structures are faced in reality

There is no standard test method to evaluate

the permeability of concrete under stress

Effect of Stress on Permeability (3)

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Important parameters

Effect of load type

Effect of load level

Effect of loading history

Effect of crack dimensions

Effect of concrete mix design

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Summary of Test Methods(Hoseini, Bindiganavile & Banthia, Cement & Concrete Composites, 2009)

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Ultrasonic Wave Velocity

Very useful to relate permeability

measurements to a NDT (Non Destructive

Test).

Ultrasonic wave propagation in concrete is

dependent on the extent of microcracks

Studies exist that relate the ultrasonic velocity

to concrete microstructure (porosity,

permeability)

Again, very limited data for concrete under

stress 13


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Experimental Program

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Year 1 of Project:

Development of the Permeability Cell(1)

Adapted from permeability cell developed at

the University of British Columbia:

- N. Banthia, A. Biparva, S. Mindess, Permeability of

Concrete Under Stress, Cement & Concrete Research, Vol. 35,

2005, pp. 1651-1655

Improvement at the University of Alberta:

The system now monitors the onset of steady

state condition

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Measuring

Device

Computer

Measuring

Device

Computer

Measuring

Device

Computer

Measuring

Device

Computer

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Steady State Condition

Steady State Condition

Defined as: in any two

consecutive time intervals,

the weight of collected

water in the flask should bethe same, or practically,

with the difference less

than 5% of previously

recorded value.

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0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300 350

WeightDiffe

rence

Time (min)


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Measuring Wave Velocity(1)

Measuring longitudinal

ultrasonic wave velocity

with a commercially

available meterdesigned for concrete

On cube specimens

150mm*150mm

At load levels of 0%,

25%, 50%, 75% & 90%

of ultimate load

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Measuring Wave Velocity(2)

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Mix Designs

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Material Proportion (kg/m3)

Plain Mortar Fibre Reinforced

Mortar

Mortar Type S 400 400

Cement type GU ----------- -----------

Fine Aggregate 1200 1200

Coarse Aggregate ----------- --------------

Water 200 200

HRWRA 4 6

Polypropylene Fibre 0 2.25


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Load levels

Load levels: 0, 25%, 50%, 75% & 90% of

ultimate load

Ultrasonic wave velocities were also

performed on the same load levels as above

for each specimen

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Results

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Variation of Permeability by Changing Load

Levels (Mortar)

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1

10

100

1000

0 10 20 30 40 50 60 70 80 90

Permeability(K)

1E-13

Load Level (% of Ultimate load)

Fibre Mortar(average)

Plain Mortar (average)

Fiber Mortar

Plain Mortar


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Variation of Ultrasonic Pulse Velocity by

Changing Load Levels

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3100

3200

3300

3400

3500

3600

3700

0 10 20 30 40 50 60 70 80 90 100

UltrasonicVelo

city(m/s)

Load Level (% of ultimate load)

SSD

Tpe S

Tpe S+PP


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Variation of Ultrasonic Wave Velocity by

Changing Load Levels

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2500

2600

2700

2800

2900

3000

3100

3200

3300

3400

0 10 20 30 40 50 60 70 80 90 100

Velocity(m

/s)

Load Level(% of ultimate load)

Oven Dried (24h)

Type S

Type S&PP


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Effect of

Moisture onUPV

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3100

3200

3300

3400

3500

3600

3700

0 20 40 60 80 100

Velocity(m/s)

Load Level (% of Ultimate Load)

Plain Mortar

SSD

OD

250 0

270 0

290 0

31 0 0

330 0

350 0

370 0

0 20 40 60 80 100

Ve

locity(m/s)

Load Level (% of Ultimate Load)

Fibre Reinforced Mortar

SSD

OD


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Correlating Water Permeability

with Ultrasonic Pulse Velocity

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K = 10.893e-0.009V

R = 0.892

K = 0.0008e-0.005V

0

2E-11

4E-11

6E-11

8E-11

1E-10

2900 3100 3300 3500 3700

Permeability,k,(m/s)

UWV (m/s)

Shkolnik et al.(1997)

Present Study


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Conclusions(1) Under compression, the water permeability of cement

based mortars maybe evaluated after achieving

equilibrium in flow. The permeability coefficient is

sensitive to the applied compressive stress beyond a

certain threshold value, which corresponds to 20% ofthe compressive strength in plain mortars and 30% of

the strength in polypropylene fibre reinforced mortars.

The ultrasonic pulse velocity for cement based mortars

in compression is sensitive to the applied stress.

However, the threshold value lies significantly higher

than for permeability coefficients.31


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Conclusions(2) Oven dried specimens register lower ultrasonic

velocity compared to those that are saturated surface

dry. In addition, the sensitivity to the compressive

stress was greater under SSD condition in plain

mortars, due to the stress corrosion in watersaturated pores

An empirical correlation exists between the

coefficient of water permeability and the velocity of

ultrasonic pulses through cement based mortars

under compression

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Work in Progress:

Effect of Mix Design

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3100

3300

3500

3700

3900

4100

4300

4500

4700

4900

0 20 40 60 80 100

UPV(m

/s)

Stress Level (% of Ultimate Stress)

SSD

fc=20 MPa

fc=50 MPa


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Effect of Matrix Strength on

Permeability under Compressive Stress

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0.1

1

10

100

1000

0 20 40 60 80 100

Permeability(K)1E-13

Load Level (% of Ultimate load)

fc=20 MPa

fc=50 MPa


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Thank you for your attention

Acknowledgements

CTEP

Cement Association of Canada

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